Steering spindle provided for mounting on a body part of a motor vehicle

A profile steering spindle of a motor vehicle has a telescopic profile piece, which can be displaced in the axial direction by an adjusting tube, and into which project a first profile piece close to the steering wheel and a second profile piece remote from the steering wheel, intended for retaining a steering wheel. During axial displacements, the second profile piece remote from the steering wheel can be displaced relative to the telescopic profile piece by an adjusting tube without expenditure of force. The first profile piece close to the steering wheel is connected to the telescopic profile piece by means of bending lugs. If the driver of the motor vehicle strikes the steering wheel, the bending lugs are held by the telescopic profile piece, and the first profile piece close to the steering wheel is torn. The kinetic energy is thereby absorbed.

FIELD AND BACKGROUND OF THE INVENTION 
The invention relates to a steering spindle provided for mounting on a body 
part of a motor vehicle and intended for a steering device, having a 
telescopic first profile piece, which encloses a first profile piece at 
least in one end region, and a shock-absorbing member for absorbing 
kinetic energy during a movement of the first profile piece relative to 
the telescopic first profile piece. 
Such steering spindles are often used in modern motor vehicles and are thus 
known. The shock-absorbing member, in the event of the motor vehicle 
crashing, serves to convert kinetic energy between the telescopic first 
profile piece and the first profile piece into plastic deformation. In 
this way, in particular if the head of the driver strikes the steering 
wheel, head injuries are kept especially slight. A disadvantage of the 
known steering spindle is that the steering wheel in the case of this 
steering spindle cannot be shifted into a desired position by the driver. 
The possibility of pushing the first profile piece into the telescopic 
profile piece in order to adjust the steering wheel could be considered. 
In this case, however, the shock-absorbing member is likewise adjusted or 
deformed, so that the manual adjustment turns out to be very sluggish. 
Furthermore, due to this design, no intended force characteristic can be 
produced during the absorption of the kinetic energy by the 
shock-absorbing member in the event of a crash. 
The problem addressed by the invention is to design a steering spindle of 
the foregoing type in such a way that a steering wheel, with this steering 
spindle, can be shifted as simply as possible into a desired position by 
the driver and that the shock-absorbing member, in the event of a crash, 
absorbs the kinetic energy irrespective of the position of the steering 
wheel. 
SUMMARY OF THE INVENTION 
This problem is solved according to the invention in that a second profile 
piece displaceable in the axial direction relative to the telescopic 
profile piece by an adjusting device is arranged on that side of the 
telescopic profile piece which is remote from the first profile piece. 
Either the first profile piece is connected to a steering wheel and the 
second profile piece is connected to a steering mechanism or the first 
profile piece is connected to a steering mechanism and the second profile 
piece is connected to a steering wheel. 
By this design, the steering spindle, in the event of a crash and during 
the manual adjustment, can be telescoped at points which are spatially 
separate from one another. In the event of the motor vehicle crashing, the 
kinetic energy, as in the known steering spindle, is absorbed uniformly by 
the shock-absorbing member by a displacement of the first profile piece. 
During a manual adjustment of the steering wheel, the telescopic profile 
piece is displaced relative to the second profile piece. Therefore 
different force characteristics can be provided in a simple manner during 
the manual adjustment and the displacement caused by the crash. A further 
advantage of this design is provided by the fact that the steering spindle 
according to the invention consists of few components, which are simple to 
produce and in addition can be preassembled outside the motor vehicle. As 
a result, the steering spindle according to the invention is especially 
cost-effective. 
In an advantageous development of the invention, the adjusting device is to 
be of especially simple design if it has an adjusting tube which supports 
the telescopic profile piece and can be secured to the body part in an 
intended position. 
The shock-absorbing member, in the event of a crash, has a constant force 
characteristic as a function of the travel of the first profile piece 
relative to the telescopic profile piece if it has at least one tear 
strip, which is made in first piece with the first profile piece and is 
fastened at one end to the telescopic profile piece. In the event of the 
motor vehicle crashing, the tear strips tear the first profile piece, so 
that the latter can penetrate into the telescopic profile piece. In the 
process, the kinetic energy is absorbed by the tearing of the first 
profile piece. In this case, the force which is required to tear the first 
profile piece is constant over virtually the entire travel of the first 
profile piece. 
In another advantageous development of the invention, the shock-absorbing 
member can be installed in an especially simple manner if the ends of the 
tear strips are designed as bending lugs penetrating into recesses of the 
telescopic profile piece. To assemble the steering spindle, the bending 
lugs can be bent into the recesses in a simple manner. In the event of the 
motor vehicle crashing, the ends are held in the recess in a 
positive-locking and/or frictional manner. 
In another advantageous development of the invention, forces which occur 
during normal operation of the motor vehicle are absorbed without 
deformation or tearing of the shock-absorbing member if the 
shock-absorbing member has a shearing pin passing through the first 
profile piece and the telescopic profile piece. Such shearing pins are 
commonly used in engineering and can be calculated very accurately for an 
intended shearing force. In the event of the motor vehicle crashing, the 
shearing pins shear off, so that the shock-absorbing member can 
subsequently absorb the kinetic energy. 
The shock-absorbing member could be arranged, for example, on a profile 
piece remote from the steering wheel. However, this results in a very 
large number of components being arranged on the steering wheel, a factor 
which leads to a high mass moment of inertia of the steering wheel. A high 
mass moment of inertia of the steering wheel leads to a high risk of 
injury if the head of the driver strikes the steering wheel. In another 
advantageous development of the invention, the mass moment of inertia of 
the steering wheel can be kept especially small if the shock-absorbing 
member is arranged on the profile piece close to the steering wheel. 
In order to transmit torque, the profile pieces and the telescopic profile 
piece must have mutually positive-locking connections. The profile pieces 
could each be designed as a splined shaft and engage in a positive-locking 
manner in a corresponding internal tooth system of the telescopic profile 
piece. However, in another advantageous development of the invention, the 
profile pieces and the telescopic profile piece are especially 
cost-effective if the profile pieces and the telescopic profile piece in 
each case have a hexagonal cross section in adjacent regions. 
In another advantageous development of the invention, the steering wheel 
can be adjusted manually in its position by simple rotation of the 
adjusting tube if the adjusting tube has an external thread interacting 
with a nut intended for fastening to the body part. Of course, an 
individual bolt having a contour corresponding to the external thread is 
also suitable as the nut. 
In another advantageous development of the invention, the adjusting tube is 
held automatically in its position after the position of the steering 
wheel has been set if the adjusting tube can be rotated by worm gearing. 
Due to the self-locking of the worm gearing, a locking device, to be 
arranged separately, for the adjusting tube can generally be dispensed 
with. 
The worm gearing could be adjusted, for example, by means of a crank. 
However, this results in the steering spindle according to the invention 
having especially large dimensions. Furthermore, this design requires the 
arrangement of the adjusting tube and the telescopic profile piece in a 
position especially close to the steering wheel or complicated laying of a 
crankshaft of the crank. In another advantageous development of the 
invention, the adjusting tube and the telescopic profile piece can be 
arranged at virtually any point in the steering spindle if the worm 
gearing can be driven by an electric motor intended for fastening to the 
body part. 
In another advantageous development of the invention, the steering wheel 
can be shifted especially quickly into an intended position if the 
adjusting device has a clamping socket, which is intended for fastening to 
the body part, encloses the adjusting tube or the telescopic profile piece 
and has an actuating element selectively opening or closing the clamping 
socket. Due to this design, the steering wheel can be displaced into the 
intended position in a simple manner after the clamping socket has been 
opened. The clamping socket is then closed. The steering wheel is thereby 
held in its intended position in a frictional manner. 
In another advantageous development of the invention, the profile piece 
having the shock-absorbing member is reliably guided in the telescopic 
profile piece in the event of a crash if sliding bearings for the axial 
guidance of the profile piece are arranged between the telescopic profile 
piece and the profile piece which is displaced in the event of a crash. In 
this way, canting of the one profile piece in the telescopic profile piece 
is avoided in the event of a crash. 
In another advantageous development of the invention, kinetic energy which 
occurs in the event of a crash can be converted into frictional heat in a 
simple manner if the sliding bearings are designed to produce intended 
friction during a relative movement between the first profile piece and 
the telescopic profile piece. In this way, virtually any force 
characteristic can be produced during the relative movement between the 
first profile piece and the telescopic profile piece. Due to this design, 
the steering spindle according to the invention can also be produced in an 
especially cost-effective manner.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a steering spindle, according to the invention, of a motor 
vehicle, the steering spindle having an adjusting device 2, which has an 
adjusting tube 1. The adjusting tube 1 accommodates a telescopic profile 
piece 3 of hexagonal design at its outer end. A profile piece 4 close to 
the steering wheel and a profile piece 5 remote from the steering wheel 
project into the telescopic profile piece 3. The profile piece 4 close to 
the steering wheel has at its free end a multiple-tooth connecting piece 6 
for connection of a steering wheel (not shown). The profile piece 5 remote 
from the steering wheel has at its free end a connecting piece 7 for 
connection to a universal joint of a steering mechanism. The adjusting 
device 2 has an external thread 9, which is arranged on the adjusting tube 
1 and meshes with a fixed nut 8, and a worm wheel 11 of worm gearing 12, 
the worm wheel 11 being drivable by means of an electric motor 10. The 
adjusting tube 1 is thereby rotated and moved by the fixed nut 8 in the 
axial direction. 
FIG. 2 shows the steering spindle according to the invention from FIG. 1 in 
a sectional representation. Bearings 13, 14 for the telescopic profile 
piece 3 are arranged in the adjusting tube 1, one of the bearings 13 being 
preloaded by a spring 15 in order to compensate for length tolerances. The 
two profile pieces 4, 5 have a hexagonal cross section (another polygonal 
cross section, e.g. quadrilateral, is also conceivable, the telescopic 
profile piece then being designed accordingly) and are connected to the 
telescopic profile piece 3 in a rotationally locked manner. The profile 
piece 5 remote from the steering wheel can be displaced axially relative 
to the telescopic profile piece 3 in a rotationally locked manner. The 
profile piece 5 remote from the steering wheel can be displaced axially 
relative to the telescopic profile piece 3, whereas the profile piece 4 
close to the steering wheel is fastened to the telescopic profile piece 3 
by means of a plurality of tear strips 16, 17, the ends of which are 
designed as bending lugs 18, 19 and penetrate into recesses 20, 21 of the 
telescopic profile piece 3. Furthermore, sliding bearings 22 are arranged 
between the telescopic profile piece 3 and the profile piece 4 close to 
the steering wheel. Due to this design, torque is transmitted from the 
profile piece 4 close to the steering wheel to the profile piece 5 remote 
from the steering wheel, while the adjusting tube 1 is stationary due to 
the self-locking of the worm gearing 12. 
During rotation of the adjusting tube 1, the telescopic profile piece 3 is 
displaced in the axial direction and performs a movement relative to the 
profile piece 5 remote from the steering wheel. In this way, the distance 
between the two profile pieces 4, 5 and thus the position of the 
multiple-tooth connecting piece 6 retaining the steering wheel can be 
manually adjusted. If, in the event of the motor vehicle crashing, a large 
force is exerted on the profile piece 4 close to the steering wheel, for 
examples by the head of the driver striking the steering wheel, the 
bending lugs 18, 19 of the tear strips are held in place in the recesses 
20, 21 of the telescopic profile piece 3, while the profile piece 4 close 
to the steering wheel moves in the direction of the profile piece 5 remote 
from the steering wheel. In this way, the tear strips 16, 17 tear the 
profile piece 4 close to the steering wheel, as a result of which some of 
the kinetic energy is absorbed. During this movement, the profile piece 4 
close to the steering wheel is guided by the sliding bearings 22. 
FIG. 3 shows a further embodiment of the steering spindle according to the 
invention in a schematic representation. In this case, an adjusting device 
23 has an adjusting screw 24 with a left-hand thread 25 and a right-hand 
thread 26 for the manual displacement of a profile piece 27 close the 
steering wheel relative to a telescopic profile piece 28. A profile piece 
29 remote from the steering wheel is inserted in that end of the 
telescopic profile piece 28 which is remote from the profile piece 27 
close to the steering wheel. The profile piece 29 remote from the steering 
wheel is held in the depicted position by sliding bearings 30, 31 and a 
shearing pin 32. The shearing pin 32 serves to absorb forces which occur 
during normal operation of the motor vehicle and to break in the event of 
the motor vehicle crashing. After the shearing pin 32 has broken, the 
profile piece 29 remote from the steering wheel can move into the 
telescopic profile piece 28, in the course of which it is guided by the 
sliding bearings 30, 31. In the process, the sliding bearings 30, 31 
produce friction, which dampens the movement. 
FIG. 4 shows a further embodiment of the steering spindle according to the 
invention, in which a telescopic profile piece 33 is held in the depicted 
position by an adjusting device 39 having a clamping socket 34 mounted 
opposite a fixed body part. The clamping socket 34 can be opened and 
closed by means of a lever 35. When the clamping socket 34 is open, the 
telescopic profile piece 33 can be easily displaced in the axial direction 
relative to a profile piece 40 remote from the steering wheel. A profile 
piece 38 close to the steering wheel moves along with it in the process, 
this profile piece 38 being fastened to the telescopic profile piece 33 by 
bending lugs 36, 37. When the clamping socket 34 is closed, in order to 
displace the profile piece 38 close to the steering wheel as in the case 
of the steering spindle from FIGS. 1 and 2, a high expenditure of force is 
required to tear the profile piece 38 close to the steering wheel.