Motor vehicle adjustable telescopic steering column

An adjustable telescopic steering column for motor vehicles has at least one longitudinally adjustable telescopic section which is held in an adjusted position by a locking device. In the event of a crash, the telescopic section is acted upon by an additional holding force by way of a locking part. The locking part is a component which operates independently of the locking device for the adjusted position and, in the operative position, is applied with a frictional connection to the longitudinally adjustable telescopic section.

BACKGROUND AND SUMMARY OF THE INVENTION 
This application claims the priority of 196 17 561.5, the disclosure of 
which is expressly incorporated by reference herein. 
The present invention relates to an adjustable telescopic steering column 
for motor vehicles and, more particularly, to a steering column having at 
least one longitudinally adjustable telescopic section which is held in an 
adjusted position by means of a locking device, and having a locking part 
which causes a holding force in the case of a crash which in a 
frictionally connected manner is applied to the adjustable telescopic 
section. 
DE 29 04 205 C2 describes an adjustable telescopic steering column having 
an adjustable telescopic section held by a clamping device in a position 
which is determined as favorable as a result of a longitudinal and/or 
inclination adjustment. The clamping force required for this purpose is 
introduced by a swivellable operating lever which in a frictionally 
connected manner braces the legs of a bow surrounding the telescopic 
section in a U-shape with the walls of a vehicle-fixed holding part. 
In the event of a crash of the vehicle with an impact by the occupant onto 
the steering wheel, a tilting movement of the known bow takes place and 
thus a tilting of the bow with the telescopic section, whereby an 
additional holding force is to be generated. This swivel movement of the 
bow requires, as a function of the force, a yielding deformation of the 
holding flanges of the bow on the walls of the holding part. The original 
clamping force between the bow and the holding part can no longer, 
however, be reliably obtained. The additional holding force becomes 
possible only with the impact by the occupant on the steering wheel. 
DE 41 18 863 C1 discloses an adjustable telescopic steering column having 
an adjustable telescopic section held in different adjustable longitudinal 
and vertical positions by a clamping force introduced by an operating 
lever frictionally connected between console cheeks on both sides and a 
clamping body holding the telescopic section. In a vehicle crash, this 
clamping body is swivelled by the effect of a traction rope and is tilted 
with the adjustable telescopic section. Thereby, with the traction rope, 
the telescopic steering column can be pulled away from the occupant almost 
without any backlash. The clamping effect by the operating lever, by way 
of a clamping bolt on the console cheeks and the clamping body, is reduced 
by its swivelling. 
EP 0 557 767 B1 describes an adjustable telescopic steering column for 
motor vehicles whose clamping force in the clamping device is intended to 
be improved in a crash by a certain alignment of the adjusting slot in the 
holding part. 
DE 41 18 976 A1, DE 33 00 268 C2, EP 0 058 495 B1 and DE 83 00 261 U 
describe various adjustable telescopic steering columns which have a 
clamping locking system for the position-stable fixing of the telescopic 
sections on one another. This clamping locking system comprises 
vehicle-side and steering-column-side clamping legs which can be braced 
with respect to one another. As a result of the produced static friction, 
the telescopic sections are held on one another in an adjusted 
overlapping. When the vehicle is involved in a crash, this mechanical 
clamping device must be constructed with large clamping surfaces and a 
high bracing force. Otherwise, if its locking effect during the crash were 
discontinued because of the impacting occupant caused the steering wheel 
with its telescopic section to move in to the end stop, the driver would 
be stressed by high impact values in the case of the end stop. 
Another approach for increasing the locking effect consists of constructing 
the clamping surfaces in a form-locking manner, as described in DE 36 19 
125 C1 or DE 32 05 416 A1. A disadvantage in this approach, however, is a 
high-expenditure and difficult adjustability because the clamping surfaces 
are not completely detached from one another in order to maintain a 
certain adjusting resistance. 
DE 33 39 926 C2 and DE 26 57 485 A1 describe safety steering columns having 
partial shafts which are fitted into one another. In the event of a crash, 
these shafts can be pushed further into one another, whereby a corrugated 
spring inserted between their walls is deformed in an energy-converting 
manner. A locking of the partial shafts to one another cannot be achieved 
by way of this corrugated spring. In addition, this energy-reducing 
process cannot be used in a telescopic steering column which permits a 
displacement of the partial shafts with respect to one another during the 
adjusting operation. A corresponding ball element which absorbs energy in 
a crash is also known from EP 0 629 540 A1. 
An object of the present invention is to provide a telescopic steering 
column with an additional holding force for the adjustable telescopic 
section which acts early only in the case of a crash of the motor vehicle. 
This object has been achieved in accordance with the present invention by 
constructing a locking part to act independently of the locking device for 
adjusting the position of the telescopic section. 
The locking device for locking the adjustable telescopic section in the 
position desired for the occupant can be constructed here to be adapted to 
the vehicle with respect to the holding force and the operating comfort. 
Only in the event of a crash, the independently acting locking part will be 
operated early, i.e. before the occupant impacts on the steering wheel, by 
way of the vehicle deceleration. As the result of its additional holding 
force, the locking part ensures the constant position of the 
longitudinally adjustable telescopic section. An influencing of the 
locking device for the adjusted position does not take place in this 
event. 
Operation of the locking part by inertial force permits a simple and 
low-cost movement control. If useful, the locking part can also be changed 
into the operative position by a sensor-controlled adjusting device. A 
mechanical control of the acceleration-dependent operational point in time 
of the locking part can be implemented by a spring which keeps the locking 
part disengaged in a crash until the effect of the correspondingly high 
force takes place. 
A bearing of the locking part on the position-stable telescopic section is 
advantageous for adjustability of the telescopic steering column because 
adjustment of its inclination will then have no influence on the necessary 
path of the locking part into the operative position in that the radial 
distance of the telescopic sections always remains the same. 
The locking part can also be disposed independently of the telescopic 
steering column fixedly on the vehicle body, in which case additional 
possibilities exist for the arrangement of the locking part. 
As a locking part, movable embodiments are suggested in the form of a wedge 
or a sheet metal strip, of a locking ball or a swivel cheek which can all 
be predetermined for an application case in a specific telescopic steering 
column construction. 
The holding force of the locking part can also be adapted to the 
requirements recognized for a crash of the motor vehicle by a frictional 
application and/or a form-locking engagement on the adjustable telescopic 
section. Here, a deformation on the adjustable telescopic section, while 
reducing energy, may be additionally useful during the movement of the 
locking part into the operative position. 
The movement of the locking part into the operative position can be 
transmitted by a toggle lever to another locking part which increasingly 
locks a movement of the adjustable telescopic section into the opposite 
direction or applies an additional holding force.

DETAILED DESCRIPTION OF THE DRAWINGS 
FIG. 1 shows a section of a telescopic steering column 1 whose 
longitudinally adjustable telescopic section 2 can be displaced to a 
telescopic section swivellably linked on the end side and can be locked in 
different positions by a locking device 4. The adjustable telescopic 
section 2 allows a steering spindle 5 with a steering wheel 6 to be moved 
and adjusted to a height position and at a distance suitable to the 
vehicle occupant. 
The locking device 4 has a locking bush 7 so that the adjustable telescopic 
section 2, by way of an oblong hole 8 on the locking bush 7, is adjustably 
guided in its length and by way of an oblong hole 9 on a vehicle 
body-fixed flange 10 extending at an angle thereto is adjustably guided in 
its inclination and is fixed by a clamping device 12 operated with a lever 
11. The clamping device 12 comprises a bolt 13 which is axially moved by 
the swivel movement of the lever 11 and in the process also braces the 
vehicle-body-fixed flange 10 and the locking bush 7 with respect to one 
another as shown in principle in FIG. 2a. 
In addition to the locking device 4 for locking the adjustable telescopic 
section 2 in adjusted positions, the section 2 is held by a locking part 
14 in the event of a crash. This locking part 14, which operates 
independently of the locking device 4 and therefore does not influence the 
latter's holding force, is disposed on the longitudinally displaceable 
telescopic section 2 in the inoperative position A (solid line), and, in a 
crash, is displaced by the acceleration introduced into the telescopic 
steering column in the direction of the interior telescopic section 3 and, 
in the operative position B shown by dot-dash line, is placed in a 
frictional contact. Subsequently, the two telescopic sections 2, 3 are 
held on one another by an additional holding force which only has an 
effect in the event of a crash. Thereby, an unintentional longitudinal 
adjustment of the telescopic section 2 and of the steering wheel 6 is 
avoided. 
The locking part 14 used in the present invention is a sliding wedge 15 
which, in the inoperative position A, is disposed by a step 16 on the 
jacket of the telescopic section 2 and is held by a tension spring 17. The 
acceleration introduced in a crash into the displaceable telescopic 
section 2 causes the sliding wedge 15 to be guided, against the force of 
the tension spring 17, along the slope 18 on the telescopic section 2 in 
the direction of the telescopic section 3 and into frictional contact 
therewith. The tension spring 17 predetermines the force threshold at 
which the locking part 14 is to apply the additional holding force. The 
pressure onto the steering wheel 6, for example, as the result of the 
impact of the occupant onto the steering wheel 6 and onto the telescopic 
section 2, presses the sliding wedge 15 still closer onto the telescopic 
section 3. 
FIG. 2a illustrates a correspondingly acting locking device 4' in which the 
telescopic section 2', together with a steering spindle 5' and the 
steering wheel 6', guided in oblong holes in the longitudinal and 
inclination direction, is longitudinally slidable with respect to the 
telescopic section 3, can be locked in the adjusted position which is 
advantageous for the occupant. The locking bush 7' is tensioned by the 
clamping device 12' with clamping cheeks 19' against the flange 10'. That 
is, the lever 11' is moved by a nose 20' out of an indentation 21', 
whereby the bolt 13' is pulled to the left in the drawing to apply the 
clamping force. 
Holding cheeks 22', which are swivellably disposed, independently of the 
telescopic steering column 1', on the motor-vehicle-body-fixed flange 10', 
are a locking parts 14' which in a motor vehicle crash apply an additional 
holding force on both sides of a web 23' projecting away from the 
longitudinally displaceable telescopic section 2'. 
As illustrated more clearly in FIG. 2b, as a result of the acceleration in 
the driving direction during impact in a crash, the holding cheeks 22' are 
swivelled from the inoperative position A (solid line) determined by the 
tension spring 17' into a frictional contact on the web 23'. During the 
swivelling into this holding operative position B illustrated by a 
dash-dot line, the holding cheeks 22' can be applied in a deforming manner 
to the adjustable telescopic section, in which case the moving energy can 
then also be converted into deforming energy. 
In a further advantageous embodiment within the contemplation of the 
present invention, a locking part similar to the principle of the sliding 
wedge 15 can be a displaceable locking ball or a sheet metal strip which 
is changeable into its locking position by a displaceable mass-produced 
part. Furthermore, the movement of the locking part 14 into the operative 
position B can be transmitted by a toggle lever to another locking part 
which increasingly locks in the opposite direction or increases the 
locking effect. 
Such an additional locking part 14, 14' for a possible crash may also be 
useful for supplementing a mechanically operating locking device 4, 4' as 
well as for an externally operated locking device. The locking part 14, 
14' can also be constructed to be changeable into the operative position 
by a sensor-controlled adjusting device. 
Although the invention has been described and illustrated in detail, it is 
to be clearly understood that the same is by way of illustration and 
example, and is not to be taken by way of limitation. The spirit and scope 
of the present invention are to be limited only by the terms of the 
appended claims.