Steering column for motor vehicle

Abstract: A motor vehicle steering column (10), Figure 2, including a tubular lower mast jacket (12) anchored on a vehicle body, a tubular upper mast jacket (14) telescoped inside the tubular lower mast jacket, a plurality of steel spheres (44) interference fitted in an annulus (38) defined at an overlap between the mast jackets, and a plastic ball sleeve (40) in the annulus having pockets (42) loosely receiving respective ones of the steel spheres. The ball sleeve has a plurality of notches (50A,50B) in an edge (46) thereof exposed through an outboard end (22) of the lower mast jacket. An anti-rotation bracket (54) is welded to a stationary mounting bracket (20) attached to the lower mast jacket and includes a plurality of tangs (60A,60B) which project through the outboard end of the lower mast jacket into respective ones of the notches (50A,50B) in the ball sleeve whereby rotation of the ball sleeve about a longitudinal centreline of the steering column is positively foreclosed. With the ball sleeve blocked against rotation, the magnitude of turning moment which must be applied to the upper mast jacket to twist it relative to the lower mast jacket, e.g. to defeat an anti-theft system on the steering column, is sufficient to prevent defeat of the anti-theft system without also causing collateral steering column damage sufficient to render the vehicle undriveable anyway.

Description: Field of the Invention This invention relates to steering columns for motor vehicles, such as defined in the preamble of claim 1 and known for example from US-A-3 815 438. Background of the Invention In a motor vehicle steering column described in United States Patent 3,392,599, issued 16 July 1968 and assigned to the assignee of this invention, steel spheres are interference fitted in an annulus defined between a lower tubular mast jacket anchored to the vehicle body and an upper tubular mast jacket telescopically enveloping the lower tubular mast jacket and attached to the vehicle body through releasable capsules. The spheres roll tracks in the mast jackets during relative telescopic collapse between the mast jackets to absorb energy and are loosely disposed in pockets in a tubular plastic ball sleeve which maintains the relative positions of the spheres as they roll between the mast jackets. United States Patent 3,815,438, issued 11 June 1974 and assigned to the assignee of this invention, describes a similar motor vehicle steering column except that the relationship between the mast jackets is reversed relative to the relationship described in the aforesaid US Patent 3,392,599, i.e. the tubular upper mast jacket is telescoped inside the tubular lower mast jacket. A motor vehicle steering column according to this invention is an improvement relative to the steering column described in the aforesaid US Patent 3,815,438. Summary of the Invention According to the invention, a new and improved motor vehicle steering column including a tubular lower mast jacket anchored on a vehicle body, a tubular upper mast jacket telescoped inside the tubular lower mast jacket, a plurality of steel spheres interference fitted in an annulus defined at an overlap between the mast jackets, and a plastic ball sleeve in the annulus having pockets loosely receiving respective ones of the steel spheres, is characterised by the features defined in the characterising portion of claim 1. In a preferred embodiment of the invention, the ball sleeve has a plurality of notches in an edge thereof exposed through an outboard end of the lower mast jacket. An anti-rotation bracket is welded to a stationary mounting bracket attached to the lower mast jacket and includes a plurality of tangs which project through the outboard end of the lower mast jacket into respective ones of the notches in the ball sleeve whereby rotation of the ball sleeve is positively foreclosed. With the ball sleeve blocked against rotation, the magnitude of turning moment which must be applied to the upper mast jacket to twist it relative to the lower mast jacket, e.g. to defeat an anti-theft system on the steering column, is sufficient to prevent defeat of the anti-theft system without also causing collateral steering column damage sufficient to render the vehicle undriveable anyway. Brief Description of the Drawings Figure 1 is a fragmentary perspective view of a motor vehicle steering column according to this invention; Figure 2 is a fragmentary exploded perspective view of a motor vehicle steering column according to this invention; and Figure 3 is an enlarged sectional view taken generally along the plane indicated by lines 3-3 in Figure 1. Description of a Preferred Embodiment As seen best in Figures 1-2, a motor vehicle steering column 10 according to this invention includes a tubular lower mast jacket 12 and a tubular upper mast jacket 14. A schematically represented inboard bracket 16 is rigidly attached to the lower mast jacket 12 at a corresponding inboard end 18 thereof for anchoring the lower mast jacket on a front wall, not shown, of a passenger compartment of a motor vehicle. An outboard bracket 20 is welded to the lower mast jacket 12 adjacent an outboard end 22 of the latter, Figures 2-3. The outboard bracket 20 is rigidly connected to mounting structure, not shown, on the vehicle body. The tubular upper mast jacket 14 is telescopically received inside the lower mast jacket and includes an inboard end 24 inside the lower mast jacket and an outboard end 26. A schematically represented escutcheon 28 is mounted on the upper mast jacket 14 and conceals apparatus of the steering column including, for example, switches operated by a turn signal lever 30 and by an emergency warning flasher actuator 32. A steering shaft 34 is supported on the upper and lower mast jackets for rotation about a longitudinal centreline 36 of the steering column. A steering wheel, not shown, is mounted on an end of the steering shaft in the usual fashion. An annulus 38, Figure 3, is defined at the overlap between the outboard end 22 of the lower mast jacket and the inboard end 24 of the upper mast jacket. A tubular plastic ball sleeve 40 of the steering column 10 has a plurality of pockets 42 therein each of which loosely holds one of a plurality of substantially identical steel spheres 44. The diameter of each sphere 44 exceeds the wall thickness of the ball sleeve and, by a closely controlled difference, the radial depth of the annulus 38. The ball sleeve 40 has a first circular edge 46 at one end and a second circular edge 48 at the other end each of which is interrupted by a pair of notches 50A-B, 52A-B, respectively, each separated circumferentially by identical angular intervals. As described generically in the aforesaid US Patent 3,392,599, the upper and lower mast jackets 14,12 are assembled by forcing the inboard end 24 of the upper mast jacket 14 into the outboard end 22 of the lower mast jacket 12 with the ball sleeve 40 and the steel spheres 44 therebetween. The ball sleeve 40 can be assembled with edge 48 first or with edge 46 first. As the annulus 38 envelops the spheres 44, the relative longitudinal movement between the upper and lower mast jackets and the degree of interference between the spheres and the mast jackets causes the spheres to roll tracks into the mast jackets. In a fully assembled position of the upper mast jacket 14 relative to the lower mast jacket 12, Figure 1, the ball sleeve 40 is fully shrouded in the annulus 38 with first edge 46 thereof, for example, facing out and exposed through the outboard end 22 of the lower mast jacket 12. After the mast jackets 12,14 are assembled together as described above, an arc-shaped anti-rotation bracket 54 is fitted to the support bracket 20. The anti-rotation bracket has a flat body 56 in a plane perpendicular to the centreline 36, a pair of weld tabs 58A-B, and a pair of tangs 60A - B separated by the same included angle as between the notches 50A-B and 52A-B in the edges 46 and 48, respectively, of the ball sleeve 40. With the ball sleeve oriented angularly about the centreline 36 such that the pair of notches 50A-B in the circular edge 46 are aligned with the tangs 60A-B on the anti-rotation bracket, the bracket is advanced to an installed position, Figure 3, in which the tangs 60A-B seat in corresponding ones of the notches 50A-B and the weld tabs 58A-B seat in a corresponding pair of slots 62A-B in a vertical face 64 of the outboard bracket 20. In the installed position of the anti-rotation bracket, the tangs positively prevent rotation of the ball sleeve about the centreline 36 while freely separating from the notches 50A-B in the direction of the longitudinal centreline 36 so as to not interfere with an energy absorbing telescopic collapse stroke of the upper mast jacket 14 into the lower mast jacket 12. The sides of the notches 50A-B and 52A-B may have a slight taper, e.g., 2 degrees, to achieve zero angular lash relative to the tangs. The anti-rotation bracket 54 is retained on the outboard bracket 20 by welding the tabs 58A-B to the bracket 20 behind the vertical face 64. In steering columns such as described in the aforesaid US patent 3,815,438, where the upper mast jacket is connected to the vehicle body only through the lower mast jacket, some anti-theft systems on the upper mast jacket may be susceptible to defeat by forced rotation or twist of the upper mast jacket relative to the lower mast jacket about the longitudinal centreline of the steering column or by forced longitudinal withdrawal of the upper mast jacket from the lower mast jacket. In such steering columns, where the ball sleeve is unrestrained, twist or withdrawal begins at a turning moment or longitudinal force magnitude sufficient to start the steel spheres rolling between the mast jackets. That magnitude is relatively low because the interference fit between the spheres and the mast jackets is calculated to afford resistance commensurate only with forces sustainable by a human driver during a collapse stroke of the steering column. In the steering column 10, however, with the tangs 60A-B positively preventing rotation of the ball sleeve 40 about the centreline 36, the spheres 44 are effectively prevented from rolling easily between the mast jackets. That is, whereas an unrestrained ball sleeve is simply pulled along by the rolling spheres, the restrained ball sleeve 40 forces the spheres to either skid between the mast jackets or to roll in place in their respective stationary ball sleeve pockets. In either circumstance, the turning moment and/or longitudinal force on the upper mast jacket necessary to initiate cold forming of the mast jackets by the spheres is significantly higher than when the spheres are permitted to roll freely and is high enough, when exceeded, to cause collateral damage to the steering column sufficient to render the vehicle undriveable anyway. Therefore, forcibly twisting or pulling the upper mast jacket 14 will not effectively defeat the anti-theft system on the steering column. While this invention has been described in terms of a preferred embodiment thereof, it will be appreciated that other forms could readily be adapted by one skilled in the art. Accordingly, the scope of this invention is to be considered limited only by the following claims.

Claims: A motor vehicle steering column (10) including a tubular lower mast jacket (12) adapted for rigid attachment to a vehicle body and having an outboard end (22), a tubular upper mast jacket (14) disposed telescopically inside said lower mast jacket and cooperating therewith in defining an annulus (38) at an overlap between an inboard end (24) of said upper mast jacket and said outboard end of said lower mast jacket, a tubular ball sleeve (40) in said annulus having a first circular edge (46) at a first end thereof exposed through said outboard end of said lower mast jacket and a second circular edge (48) at a second end thereof and a plurality of pockets (42) therein, and a plurality of steel spheres (44) loosely received in respective ones of said pockets and interference fit between said upper and said lower mast jackets operative to roll tracks in said upper and said lower mast jackets in an energy absorbing collapse stroke of said steering column during relative telescopic bodily movement between said upper and said lower mast jackets in the direction of a longitudinal centreline (36) of said steering column, characterised in that said steering column includes: an anti-rotation bracket means (20,54) rigidly mounted on said vehicle body, and means (52A-B,60A-B) on said anti-rotation bracket means and on said tubular ball sleeve cooperating in preventing rotation of said ball sleeve about said longitudinal centreline of said steering column while permitting longitudinal bodily movement of said ball sleeve in the direction of said longitudinal centreline during said energy absorbing collapse stroke of said steering column. The motor vehicle steering column recited in claim 1 wherein said anti-rotation bracket means includes: an anti-rotation bracket (54), and means (20,58A-B,62A-B) rigidly mounting said anti-rotation bracket on said lower mast jacket adjacent said outboard end thereof. The motor vehicle steering column recited in claim 2 wherein said means on said anti-rotation bracket means and on said tubular ball sleeve cooperating in preventing rotation of said ball sleeve about said longitudinal centreline of said steering column while permitting bodily movement of said ball sleeve in the direction of said longitudinal centreline includes: means on said ball sleeve defining a first notch (50A) open through said first circular edge (46) of said ball sleeve, and means on said anti-rotation bracket defining a first tang (60A) projecting into said annulus through said outboard end of said lower mast jacket and seating in said first notch. The motor vehicle steering column recited in claim 3 wherein said means on said anti-rotation bracket and on said tubular ball sleeve cooperating in preventing rotation of said ball sleeve about said longitudinal centreline of said steering column while permitting bodily movement of said ball sleeve in the direction of said longitudinal centreline further comprises: means on said ball sleeve defining a second notch (50B) open through said first circular edge (46) of said ball sleeve separated circumferentially from said first notch (50A) by a predetermined included angle, and means on said anti-rotation bracket defining a second tang (60B) separated from said first tang (60A) by said predetermined included angle and projecting into said annulus through said outboard end of said lower mast jacket and seating in said second notch. The motor vehicle steering column recited in claim 4 further comprising: means on said plastic ball sleeve defining a pair of notches (52A,52B) each identical to said first and said second notches (50A,50B) open through said second circular edge (48) and separated circumferentially from each other by said predetermined included angle so that each of said first and said second tangs seats in a corresponding one of said pair of notches when said plastic ball sleeve is disposed in said annulus with said second circular edge exposed through said outboard end of said lower mast jacket.

Inventors: SCHNEIDER DOUGLAS MATTHEW, TUGGLE ROBERT EDWIN, SCHNEIDER, DOUGLAS MATTHEW, TUGGLE, ROBERT EDWIN
Applicants: GEN MOTORS CORP, GENERAL MOTORS CORPORATION
Application year: 1995
Main classification: B62D1
IPC codes: B62D1, B60R25