Steering column assembly

Abstract

An adjustable steering column assembly has a steering shaft 18 to which a steering member is attachable at one end 20, an elongate housing 16 within which shaft 18 is rotatably mounted about its longi

Description

This invention relates to steering column assemblies, and in particular to steering column assemblies which are adjustable for both rake and reach. It is common for the rake and reach of a steering column to be manually adjustable, to allow the steering coulmn to be positioned comfortably and safely for a driver. It is important for the steering column to be readily unlocked but to be securely locked in place once the positio of the steering column has been adjusted. In addition, it is important the the axial position of the steering column be capable of resisting forces acting in both directions, namely a handling force and a crash force. In accordance with a first aspect of the present invention, an adjustable steering column assembly comprises: a steering shaft configured at one end for attachment of a steering member; an elongate steering shaft housing within which the steering shaft is rotatably mounted about its longitudinal axis; a base member with respect to which the steering shaft housing is slidably mounted and constrained to be displaceable in a reach adjustment direction corresponding to the rotational axis of the steering shaft; a support bracket configured for attachment to a vehicle, the base member being displaceably mounted with respect to the support bracket in a rake adjustment direction; a first securing mechanism for controlling displacement of the steering shaft housing along the reach axis, comprising a reach adjustment rack member mounted on the steering shaft housing, the reach adjustment rack member comprising an elongate slot and first and second racks of teeth on opposite sides of the elongate slot extending in the reach adjustment direction; a pivotally mounted reach adjustment lock member having two rows of teeth complementarily shaped with the teeth of a respective one of the racks in the reach adjustment rack member; a second securing mechanism for controlling the displacement of the base member in the rake adjustment direction, comprising: a rake adjustment rack member fixed with respect to the support bracket, the rake adjustment rack member comprising an elongate slot and first and second racks of teeth on opposite sides of the elongate slot extending in the rake adjustment direction; a pivotally mounted rake adjustment lock member having two rows of teeth complementarily shaped with the teeth of a respective one of the racks in the rake adjustment rack member; and actuating means for simultaneously rotating the lock member of each of the first and second securing mechanisms between a first, locked position in which the first and second rows of teeth of each lock member are engaged with the first and second racks of teeth respectively in the associated rack member and a second, unlocked position in which the first and second rows of teeth of each lock member are disengaged from the first and second racks of teeth in the associated rack member. The present invention is simple in construction and can be assembled from a small number of low cost components. It produces an assembly of compact size and uniform concept, that can be quickly redesigned for any desired concept of column system. The assembly is also capable of withstanding a siginifcant amount of axial load without failure (whether static failure or fatigue failure) nad id highly robust. In addition, the securing mechanisms are selflocking and the higher the applied force, the higher the engagement between the teeth of the locking heads and the teeth of the associated racks. Moreover, the kinematics of lever (effort on the locking lever) is not affected by tooth-on-tooth engagement. The present invention also addresses some of the problems with the design of known reach position lock mechanism was invented taking into consideration two main features. Firstly, after adjustment of the reach and rake, the present invention prevents any further movement of steering wheel. Secondly, the present invention not only transmits and withstands axial load from the rear to the front during a crash event, but also takes into account opposite forces acting from the front to the rear, unlike the conventional designs was not intended to handle this loading condition. According to experience, the opposite force tends to appear, for example, during an explosion of airbag, rear-end collision and when a driver tries to lift himself / herself using a steering wheel. The base member may comprise a tubular portion within which the steering shaft housing is slidably received. The actuating means may comprise an axle. The assembly may comprise a lever for pivoting the axle. The assembly may comprise a cam member mounted on the axle, for adjusting the orientation of a lock member. The assembly may comprise a first cam member mounted on the axle, for adjusting the orientation of the reach adjustment lock member and a second cam member for adjusting the orientation of the rake adjustment lock member. The assembly may comprise first and second pivotally mounted cam followers engaged with the first and second cam members respectively, the first cam follower being constrained to pivot with the reach adjustment lock member and the second cam follower being constrained to pivot with the rake adjustment lock member. The assembly may comprise spring means for biasing each cam follower in a direction which urges the pivotally mounted lock members towards their first, locked positions. The assembly may comprise a mounting member secured to the base member and on which the reach adjustment lock member is pivotally mounted. The assembly may comprise spring means for biasing the pivotally mounted reach adjustment lock member towards its first, locked position. The base member may comprise a recess in which the mounting member is received. The mounting member may comprise a plate. At least one of the pivotally mounted lock members may be mounted on, and may rotate with, the axle. The reach adjustment lock member and the rake adjustment lock member may mounted on, and may rotate with, the axle. The first and second racks of teeth of the rake adjustment rack member may be arcuate. The first and second securing mechanisms may be located on the same side of the reach adjustment axis. The first and second securing mechanisms may be located on opposite sides of the reach adjustment axis. The invention also comprises a vehicle fitted with or comprising a steering column assembly in accordance with the first aspect. By way of example only, specific embodiments of the present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is a perspective view, partly exploded, of a first embodiment of steering column assembly in accordance with the present invention; Figures 2(a) and (b) are perspective views, from above and below respectively, of a manually pivotable locking lever which forms part of the steering column assembly of Figure 1; Figure 3 is a side view of the steering column assembly of Figure 1, showing the rake adjustment mechanism to a larger scale; Figure 4 is a side view of the steering column assembly of Figure 1, shown with a pivotable locking head removed; Figure 5 is a side view of the steering column assembly of Figure 1, shown with a toothed rake adjustment plate removed; Figure 6 is a vertical cross-section through the steering column assembly of Figure 1, showing the reach adjustment mechanism; Figure 7 is a perspective view of a housing which forms part of the steering column assembly of Figure 1; Figure 8 is a perspective view of a steering column receivable in the housing of Figure 7; Figure 9 is an exploded perspective view of a reach lock mechanism which forms part of the steering column assembly of Figure 1; Figure 10 is a side view of the assembled reach lock mechanism of Figure 9; Figures 11(a) and 11(b) are side views of the operating mechanism of the reach lock assembly of a second embodiment of the present invention, which is a modification of the first embodiment, shown respectively in situ and with the other components of the steering column assembly removed, in a locked condition; Figures 12(a) and 12(b) are side views of the operating mechanism of the reach lock assembly of Figure 11, shown respectively in situ and with the other components of the steering column assembly removed, in an unlocked condition; Figure 13 is a perspective view of a third embodiment of steering column assembly in accordance with the present invention, which is a variation of the steering column assembly of Figure 1; Figure 14 is a perspective view of a fourth embodiment of steering column assembly in accordance with the present invention; Figure 15 is a side view of the steering column assembly of Figure 14, with the portion A showing the rake adjustment lock at an enlarged scale; and Figure 16 is a side view of the steering column assembly of Figure 14 with the portion B showing the rake and reach adjustment locks at an enlarged scale. The first embodiment of steering column assembly 10 in accordance with the present invention is shown in Figures 1 to 10, and comprises an elongate housing 12 having a cylindrical internal recess 14 in which a cylindrical steering shaft housing 16 is slidably received. A steering shaft 18 is rotatably mounted within the steering shaft housing 16. The steering shaft 18 projects longitudinally from the steering shaft housing 16 and its free end is splined as shown at 20, for attachment of a steering wheel (not shown). The cylindrical internal recess 14, the steering shaft housing 16 and the steering shaft 18 are all aligned coaxially along a reach adjustment axis X. The steering shaft 18 will normally be formed in a conventional manner from two aligned shaft portions 18a, 18b (shown schematically in Figures 3 and 4) joined together by complementary splined connections to accommodate longitudinal displacement of the outer portion 18a of the steering shaft 18. As best seen in Figure 1, the elongate housing 12 (and the steering shaft housing 16 and steering shaft 18 mounted within it) are pivotally mounted with respect to a mounting bracket 22 mounted transversely with respect to the reach adjustment axis X and which, in use, is secured to a vehicle in which the steering column assembly is to be fitted. As best seen in Figures 1 to4, a rake adjustment locking plate 24 having curved opposite elongate edges 25 and mounted on a locking shaft 25 (to be explained in more detail) is received in a complementarily-shaped arcuate guide slot 26 of a guide plate 28 which is secured to, and extends perpendicularly downwards from, the undersurface of the transverse mounting bracket 22. As best seen in Figure 3, and as will be explained in more detail later, the inclination of the housing 12 (and therefore the rake of the steering column assembly 10) can be fixed in a desired position with respect to the mounting bracket 22 by engaging rows of teeth 29 extending along the curved elongate edges 25 of the locking head 30 with complementarily-shaped rows of teeth 31 of a rake locking plate 32 secured to the bracket 22 and situated laterally outwardly of the guide slot 26. The locking plate 24 is of a generally cuboidal shape, although its longer opposite edges 25 are slightly curved to slide along the curved slot 26 of the guide plate 28, as described previously. The rows of teeth 31 project outwardly from the curved edges 25 and each row of teeth 30 is releasably engageable with the corresponding row of teeth 31 on the edges of the rake locking plate 32. As will be explained, the rake locking plate 24 is pivotable between a locked position shown in Figure 2, in which the rows of teeth 30 of the locking plate 24 are engaged with the teeth 31 of the rake locking plate 32, whereby the inclination (rake) of the elongate housing 12 is fixed with respect to the mounting bracket 22 and an unlocked position pivotally displaced from the orientation shown in Figure 2, in which the teeth 30 of the locking plate 24 are disengaged from the teeth 31 of the rake locking plate 32, which allows the inclination (rake) of the elongate housing 12 to be adjusted with respect to the mounting bracket 22. The locking plate 24 is mounted on the locking shaft 25 which extends perpendicularly to the reach adjustment axis X. A cam member 39 is also mounted on the shaft and can be pivoted between a first, locking position (shown in Figure 1) and a second, unlocked position, by manual pivoting of a dog-legged lever 40 which attached to the shaft 25. In the position of the lever 40 shown in Figure 1, the locking plate 24 is pivoted to a position in which the its teeth 30 are engaged with the respective rows of teeth 31 of the rake locking plate 32, thereby preventing the housing 12 from being pivoted in either direction, and thereby setting the rake angle of the steering column assembly 10. It will be observed that the maximum width of the locking plate 24 between the teeth 30 is greater than the separation of the rows of teeth 31 of the locking plate 32. In this way, when in the locked position shown in Figure 2 the locking plate 24 is “wedged” in place, whereby an attempt to move the housing 12 downwardly with respect to the mounting bracket 22 causes one row of the teeth 30 of the locking plate 24 to engage more firmly with the corresponding row of teeth 31 the locking plate 32 and an attempt to move the housing 12 upwardly with respect to the mounting bracket 22 causes the other row of teeth 30 of the locking plate 24 to engage more firmly with the corresponding row of teeth 31 of the locking plate 32. The lever 40 can be pivoted manually through an angle of approximately 40° from the first extreme position shown in Figure 1 to a second position which causes the pivotally mounted rake locking plate 24 to be pivoted to the unlocked position in which its rows of of teeth 30 on its opposite ends are disengaged from the respective rows of teeth 31 of the rake locking plate 32, thereby allowing the housing 12 to be pivoted with respect to the mounting bracket 22 in order to adjust the rake angle of the steering column assembly. As explained below, operation of the lever 40 also controls the locking and unlocking of a reach locking mechanism 46 shown in Figures 5 to 9. As best seen in Figures 9 and 10, the shaft 25 connected to the lever 40 and to the rake locking plate 24 also carries a cam 44 for controlling the reach locking mechanism 46. As best seen in Figures 2 to 5, the reach locking mechanism 46 comprises a reach adjustment locking plate 50 secured to the exterior of the steering shaft housing 16 at the longitudinally inner end of the housing. The plate 50 comprises an elongate recess 52 whose longitudinal axis is aligned with the reach adjustment axis X and the opposed longitudinally extending inner faces 54, 56 of the elongate recess 52 are each provided with a respective toothed rack portion 58, 60. The locking mechanism 46 also comprises a locking head 66 which is of a generally parallelogram shape and comprises two identical arm portions 66a, 66b arranged on diametrically opposed sides of the rotational axis Y of the locking head. The end of each of the arms 66a, 66b is formed into toothed portions 62, 64 on its opposite shorter edges, engageable with the complementarily-shaped teeth of the rack portions 58, 60 of the plate 50. The locking head 66 is pivotally mounted on a mounting plate 68 by means of a pivot pin 70 passing through the plate into the locking head 66, and the locking head 66 is biased towards engagement with the toothed rack portions 58, 60 by means of a torsion spring 72 which engages a mounting lug 73 on the laterally outer face of the locking head 66 and the mounting plate 68. The mounting plate 68 is mounted in a recess 76 of the elongate housing 12 by means of four identical securing bolts 78. The recess 76 also accommodates the reach adjustment locking plate 50 secured to the exterior of the steering shaft housing 16 as it moves within the housing 12. As seen in Figures 1 to 8, the laterally outer face of the locking head 66 is provided with a further lug 79 having a concave upper face which engages with the cam member 39 which is mounted on the shaft 25. By pivoting the lever 40, the cam member 39 can be pivoted through an angle of approximately 40° between a first extreme position shown in Figure 9, in which the cam 39 engages the lug 79 and a second extreme position in which the cam 44 is rotated to urge the reach locking head 66 to pivot in the anticlockwise direction (as viewed in Figure 9) against the restoring force of the tension spring 82. In the first extreme position, shown in Figure 9, the toothed rack portions 62, 64 of the locking head 66 are engaged in the corresponding toothed rack portions 56, 58 of the reach adjustment locking plate 50, which is secured to the outer surface of the steering shaft housing 16, thereby preventing the steering shaft housing 16 from being displaced in either direction along the reach adjustment axis X, and securing it in position longitudinally. In a similar manner to the rake adjusting mechanism, it will be observed that the maximum width of the reach locking head 66 between the teeth 62, 64 is greater than the separation of the rack portions 58, 60 of the reach locking plate 50. In this way, when in the locked position shown in Figure 9 the locking head 66 is “wedged” or “locked” in place, whereby an attempt to move the steering shaft housing 16 outwardly with respect to the housing 12 causes the teeth 62 of the locking head 66 to engage more firmly with the corresponding rack portion 58 of the locking plate 50 and an attempt to move the steering shaft housing 16 inwardly with respect to the housing 12 causes the teeth 64 of the locking head 66 to engage more firmly with the corresponding rack portion 60 of the locking plate 50. In the second extreme position, the toothed rack portions 62, 64 of the locking head 66 are disengaged from the corresponding toothed rack portions 56, 58 of the reach adjustment locking plate 50, thereby allowing the position of the steering shaft housing 16 to be adjusted in either direction along the reach adjustment axis X to the desired reach position. Therefore, when the lever 40 is in the first extreme position, shown in Figure 1, the shaft 25 is rotated to a position in which, simultaneously, (a) the two rows of teeth 30 on the opposite edges of the pivotally mounted rake locking plate 24 are engaged with the respective rows of teeth 31 of the rake adjustment locking plate 32 and (b) the toothed rack portions 62, 64 of the reach locking head 66 are engaged in the corresponding toothed rack portions 56, 58 of the reach adjustment locking plate 50, thereby simultaneously preventing adjustment of the rake and reach of the steering column assembly 10. By pivoting the lever 40 the other extreme position, as described, the shaft 25 is rotated to a position in which, simultaneously, (a) the two rows of teeth 30 on the opposite edges of the pivotally mounted rake locking plate 24 are disengaged from the respective rows of teeth 31 of the rake adjustment locking plate 32 and (b) the toothed rack portions 62, 64 of the reach locking head 66 are disengaged from the corresponding toothed rack portions 58, 60 of the reach adjustment locking plate 50, thereby allowing simultaneous adjustment of both the rake and reach of the steering column assembly 10. Pivoting the lever 40 back to the first extreme position, shown in Figure 1, locks the selected rake and reach positions of the steering column assembly 10. Securing both the rake and reach of the steering wheel assembly is of particular importance during the deployment of a vehicle airbag following a rear-end collision and during which it is found that a driver tries to lift himself / herself using the steering wheel of the vehicle. A second embodiment of the present invention, which is a modification to the reach adjustment mechanism is shown in Figures 11 and 12. In the modification, the cam 39 described above is replaced with an elongate generally teardrop-shaped cam follower 80 rotatably mounted at its wider end to the same pivot pin 72 to which the locking head 66. The cam follower 80 is biased upwardly (anticlockwise / counterclockwise in Figures 11 and 12) by means of a tension spring 82 extending between a mounting lug 84 on one lateral edge of the cam follower 80 and a mounting pin 86 on the housing 12. The cam follower 80 is located between the mounting plate 68 and an inner wall of the housing 12. The cam follower 80 is engaged by a cam 44 which is mounted on, and rotates with, the shaft 25. By pivoting the lever 40, the cam 44 can be pivoted through an angle of approximately 40° between a first extreme position shown in Figure 11, in which a flat side face 88 of the cam 44 engages the pivotally mounted cam follower 80 and a second extreme position shown in Figure 12 in which a lobe 90 of the cam 44 engages the flat face of the cam follower 80 and pivots the cam follower 80, and the reach locking head 66 which rotates with it, against the restoring force of the tension spring 82. Other than the above, the construction and operation of the second embodiment are identical to the first embodiment and only those features which differ from the first embodiment have been described and illustrated. A third embodiment of the present invention is illustrated in Figure 13. The features of the third embodiment are very similar to those of the first embodiment, and corresponding features are identified by the same reference numerals, increased by 100. The only significant difference from the first embodiment is that the recess 76 in the elongate housing 12 of the first embodiment in which the mounting plate 68 is located is enlarged in the second embodiment to form a larger recess 176 to accommodate known features indicated at 192 and 194 of a proprietary crash system. The features, construction and operation of the second embodiment are otherwise identical to the first embodiment. A fourth embodiment of the present invention is illustrated in Figures 14 to 16 and comprises an elongate housing 212 having a cylindrical internal recess 214 in which a cylindrical steering shaft housing 216 is slidably received. A steering column 218 is rotatably mounted within the steering shaft housing 216. The steering column 218 projects longitudinally from the steering shaft housing 16 and its free end is splined as shown at 220, for attachment of a steering wheel (not shown). The cylindrical internal recess 214, the steering shaft housing 216 and the steering column 218 are all aligned coaxially along a reach adjustment axis X. The elongate housing 212 (and the steering shaft housing 216 and steering column 218 mounted within it) are pivotally mounted with respect to a mounting bracket 222 mounted transversely with respect to the reach adjustment axis X and which, in use, is secured to a vehicle in which the steering column assembly is to be fitted. As for the previous embodiments, the steering assembly has a rake adjustment and locking mechanism 229 and a reach locking mechanism 246 which are operated simultaneously. However, in contrast to the previous embodiments, the rake adjustment and locking mechanism 229 and reach locking mechanism 246 are positioned on opposite sides of the steering column assembly 10. One end of a dog-legged lever 240, is attached to, and rotates with, a shaft 238 extending transversely to the reach adjustment axis X and which simultaneously controls the locking and unlocking of the rake adjustment and locking mechanism 229 and reach locking mechanism 246. As seen in Figures 14 to 16, a roller 224 mounted on the shaft 238 is received in an arcuate guide recess 226 of a guide plate 228 which extends downwards from the undersurface of the transverse mounting bracket 222. As will be explained in more detail later, the inclination of the housing 112 can be fixed in a desired position with respect to the mounting bracket 222 by means of a pivotally mounted rake locking head 230 which is releasably engageable with teeth of a rake locking plate 232. As for the previous embodiments, the rake adjustment and locking mechanism 229 comprises a locking head 230 of a generally parallelogram shape, with toothed portions 233, 234 on its opposite shorter edges, engageable with the complementarily-shaped teeth (only partially visible in Figure 12) of facing curved rack portions 235, 236 formed on opposed inner edges of an elongate arcuate aperture 237 in the rake locking plate 238 extending from the mounting bracket 222 on the opposite side of the assembly 212 from the lever 240. As for the previous embodiments, the rake locking head 230 is pivotable by pivoting the lever 240 between: (a) a locked position shown in Figures 12 to 14 (corresponding to the retracted or uppermost position 240a of the lever 240), in which the teeth 233, 234 of the locking head 230 are engaged with the teeth of the rack portions 235, 236 in the rake locking plate 32, whereby the inclination (rake) of the elongate housing 212 is fixed with respect to the mounting bracket 222 and (b) an unlocked position (corresponding to the extended or lowermost position 240b of the lever 240), in which the teeth 233, 234 of the locking head 230 are disengaged from the teeth of the rack portions 235, 236 of the rake locking plate 232, which allows the inclination (rake) of the elongate housing 212 to be adjusted with respect to the mounting bracket 222. As for the previous embodiments, it will be observed that the maximum width of the locking head 230 between the teeth 233, 234 is greater than the separation of the rack portions 235, 236 of the locking plate 232. In this way, when in the locked position shown in Figures 12 to 14 the locking head 230 is “wedged” in place, whereby an attempt to move the housing 212 downwardly with respect to the mounting bracket 222 causes the teeth 233 of the locking head 230 to engage more firmly with the corresponding rack portion 235 of the locking plate 232 and an attempt to move the housing 212 upwardly with respect to the mounting bracket 222 causes the teeth 234 of the locking head 230 to engage more firmly with the corresponding rack portion 236 of the locking plate 232. As explained in more detail below, operation of the lever 240 also controls the locking and unlocking of the reach locking mechanism 246 shown in Figures 12 to 14. As seen in Figures 14 to 16, the shaft 238 connected to the lever 240 also carries a reach adjustment locking plate 250 which forms part of the reach locking mechanism 246, secured to the exterior of the steering shaft housing 216. The plate 250 comprises an elongate recess 252 whose longitudinal axis is aligned with the reach adjustment axis X and the opposed longitudinally extending inner faces 254, 256 of the elongate recess 252 are each provided with a respective toothed rack portion 258, 260. The toothed rack portions 258, 260 are configured to be releasably engageable with complementarily-shaped toothed portions 262, 264 located at the opposite ends of the elongate pivotally mounted reach locking head 266. The shaft 238 extends perpendicularly to the reach adjustment axis X and as explained previously can be pivoted between a first, locking position (shown in Figures 12 to 14) and a second, unlocked position, by pivoting the dog-legged lever 240, as described above. In the position of the lever 240 shown at 240a, the two sets of teeth 233, 234 on the opposite ends of the rake locking head 230 are engaged with the respective toothed rack portions 235, 236 of the rake locking plate 232, thereby preventing the housing 212 from being pivoted in either direction, and thereby setting the rake angle of the steering column assembly 210. As for the previous embodiments, it will be observed that the maximum width of the reach locking head 266 between the teeth 262, 264 is greater than the separation of the rack portions 258, 260 of the reach locking plate 250. In this way, when in the locked position shown in Figures 12 to 14 the locking head 266 is “wedged” in place, whereby an attempt to move the steering shaft housing 216 outwardly with respect to the housing 212 causes the teeth 262 of the locking head 266 to engage more firmly with the corresponding rack portion 258 of the locking plate 250 and an attempt to move the steering shaft housing 216 inwardly with respect to the housing 212 causes the teeth 264 of the locking head 666 to engage more firmly with the corresponding rack portion 260 of the locking plate 250 The lever 240 can be pivoted through an angle of approximately 40° between the two extreme positions shown in Figure 14, which causes the pivotally mounted rake locking head 230 to be pivoted to the unlocked position in which the two sets of teeth 233, 234 on the opposite ends of the rake locking head 230 are disengaged from the respective toothed rack portions 235, 236 of the rake locking plate 232, thereby allowing the housing 212 to be pivoted with respect to the mounting bracket 222 in order to adjust the rake angle of the steering column assembly. Therefore, when the lever 240 is in the first extreme position, shown in Figure 12, the shaft 238 is rotated to a position in which, simultaneously, (a) the two sets of teeth 233, 234 on the opposite ends of pivotally mounted rake locking head 230 are engaged with the respective toothed rack portions 235, 236 of the rake adjustment locking plate 232 and (b) the toothed rack portions 262, 264 of the reach locking head 266 are engaged in the corresponding toothed rack portions 256, 258 of the reach adjustment locking plate 250, thereby simultaneously preventing adjustment of the rake and reach of the steering column assembly 210. By pivoting the lever 240 the other extreme position, as described, the shaft 238 is rotated to a position in which, simultaneously, (a) the two sets of teeth 233, 234 on the opposite ends of pivotally mounted rake locking head 230 are disengaged from the respective toothed rack portions 235, 236 of the rake adjustment locking plate 232 and (b) the toothed rack portions 262,264 of the reach locking head 66 are disengaged from the corresponding toothed rack portions 258, 260 of the reach adjustment locking plate 250, thereby allowing simultaneous adjustment of both the rake and reach of the steering column assembly 210. Pivoting the lever 240 back to the first extreme position, shown in Figure 12, locks the selected rake and reach positions of the steering column assembly 210. Securing both the rake and reach of the steering wheel assembly is of particular importance during the deployment of a vehicle airbag following a rear-end collision and during which it is found that a driver tries to lift himself / herself using the steering wheel of the vehicle. The invention is not restricted to the details of the foregoing embodiments. For example, the manually operated lever 40, 140, 240 may be replaced with a motor for rotating the shaft 25, 125, 238 in order to lock and unlock the rake and reach locking mechanisms.

Claims

1. An adjustable steering column assembly comprising:a steering shaft configured at one end for attachment of a steering member;an elongate steering shaft housing within which the steering shaft is rotatably mounted about its longitudinal axis;a base member with respect to which the steering shaft housing is slidably mounted and constrained to be displaceable in a reach adjustment direction corresponding to the rotational axis of the steering shaft;a support bracket configured for attachment to a vehicle, the base member being displaceably mounted with respect to the support bracket in a rake adjustment direction;a first securing mechanism for controlling displacement of the steering shaft housing along the reach axis, comprisinga reach adjustment rack member mounted on the steering shaft housing, the reach adjustment rack member comprising an elongate slot and first and second racks of teeth on opposite sides of the elongate slot extending in the reach adjustment direction;a pivotally mounted reach adjustment lock member having two rows of teeth complementarily shaped with the teeth of a respective one of the racks in the reach adjustment rack member;a second securing mechanism for controlling the displacement of the base member in the rake adjustment direction, comprising:a rake adjustment rack member fixed with respect to the support bracket, the rake adjustment rack member comprising an elongate slot and first and second racks of teeth on opposite sides of the elongate slot extending in the rake adjustment direction;a pivotally mounted rake adjustment lock member having two rows of teeth complementarily shaped with the teeth of a respective one of the racks in the rake adjustment rack member;andactuating means for simultaneously rotating the lock member of each of the first and second securing mechanisms between a first, locked position in which the first and second rows of teeth of each lock member are engaged with the first and second racks of teeth respectively in the associated rack member and a second, unlocked position in which the first and second rows of teeth of each lock member are disengaged from the first and second racks of teeth in the associated rack member.

2. An adjustable steering column assembly as claimed in claim 1, wherein the base member comprises a tubular portion within which the steering shaft housing is slidably received.

3. An adjustable steering column assembly as claimed in claim 1 or claim 2, wherein the actuating means comprises an axle.

4. An adjustable steering column assembly as claimed in claim 3, comprising a lever for pivoting the axle.

5. An adjustable steering column assembly as claimed in claim 4, comprising a cam member mounted on the axle, for adjusting the orientation of a lock member.

6. An adjustable steering column assembly as claimed in claim 5, comprising a first cam member mounted on the axle, for adjusting the orientation of the reach adjustment lock member and a second cam member for adjusting the orientation of the rake adjustment lock member.

7. An adjustable steering column assembly as claimed in claim 6, comprising first and second pivotally mounted cam followers engaged with the first and second cam members respectively, the first cam follower being constrained to pivot with the reach adjustment lock member and the second cam follower being constrained to pivot with the rake adjustment lock member.

8. An adjustable steering column assembly as claimed in claim 7, comprising spring means for biasing each cam follower in a direction which urges the pivotally mounted lock members towards their first, locked positions.

9. An adjustable steering column assembly as claimed in any of the preceding claims, comprising a mounting member secured to the base member and on which the reach adjustment lock member is pivotally mounted.

10. An adjustable steering column assembly as claimed in claim 9, comprising spring means for biasing the pivotally mounted reach adjustment lock member towards its first, locked position.

11. An adjustable steering column assembly as claimed in claim 9 or claim 10, wherein the base member comprises a recess in which the mounting member is received.

12. An adjustable steering column assembly as claimed in any of claims 9 to 11, wherein the mounting member comprises a plate.

13. An adjustable steering column assembly as claimed in claim 3 or claim 4, wherein at least one of the pivotally mounted lock members is mounted on, and rotates with, the axle.

14. An adjustable steering column assembly as claimed in claim 13, wherein the reach adjustment lock member and the rake adjustment lock member are mounted on, and rotate with, the axle.

15. An adjustable steering column assembly as claimed in any of the preceding claims, wherein the first and second racks of teeth of the rake adjustment rack member are arcuate.

16. An adjustable steering column assembly as claimed in any of the preceding claims, wherein the first and second securing mechanisms are located on the same side of the reach adjustment axis.

17. An adjustable steering column assembly as claimed in any of claims 1 to 16, wherein the first and second securing mechanisms are located on opposite sides of the reach adjustment axis.

18. A vehicle fitted with or comprising a steering column assembly as claimed in any of the preceding claims.

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