Steering column comprising an adaptive energy absorption device for a motor vehicle

A steering column with an inner casing tube rotatably mounts a steering shaft. An outer casing unit is connected to a vehicle chassis and the inner casing tube is displaceably received therein and configured to be axially fixable. An energy absorption device is operatively disposed between the casing tube and the casing unit and in which part of the energy arising in the event of a crash is absorbed when the casing tube is telescopically displaced in relation to the casing unit. The energy absorption device is configured to adapt the absorbed energy to the circumstances of the crash event.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Stage Entry of International Patent Application Serial Number PCT/EP2017/076612, filed Oct. 18, 2017, which claims priority to German Patent Application No. DE 10 2016 220 531.5, filed Oct. 19, 2016, the entire contents of both of which are incorporated herein by reference.

FIELD

The present disclosure generally relates to a steering column for a motor vehicle.

BACKGROUND

A steering column in which a strip-shaped deformation element is pulled though a brake having a constricted portion and on account thereof is deformed is known from DE 10 2011 015 140 A1. Part of the energy arising in the event of a crash is absorbed herein and used for the deformation of the deformation element. It is a disadvantage of this solution that an adaptation of the amount of energy to be absorbed to the varying conditions of the respective crash event such as, for example, the vehicle speed, the mass of the vehicle driver, or whether or not the vehicle driver is belted up, is not possible.

Thus a need exists for a steering column having an energy absorption device such that the quantity of energy to be absorbed in the crash event can be adapted to the prevailing circumstances. Furthermore, the adaptive energy absorption device is to have only a minor requirement in terms of installation space.

DETAILED DESCRIPTION

The invention relates to a steering column for a motor vehicle, having an inner casing tube which rotatably mounts a steering shaft, and an outer casing unit which is capable of being connected to the vehicle chassis and in which the inner casing tube is received so as to be displaceable and fixed in the axial direction; having an energy absorption device which is operatively disposed between the casing tube and the casing unit and in which part of the energy arising in the event of a crash is capable of being absorbed when the casing tube is telescopically displaced in relation to the casing unit.

The solution according to the invention provides that the energy absorption device comprises at least two deformation strips which are fastened to the casing tube and on which in each case one deformation slide which is connected to the casing unit and which encompasses and jams the external narrow sides of the respective deformation strip is disposed, in that said deformation slide deforms the respective deformation strip when the deformation strip in the crash event is displaced in the axial direction relative to the deformation slide, and in that a connection between a first deformation slide and the casing unit, or between the first deformation element and a second deformation element, is capable of being coupled or decoupled by means of a switching device.

On account of the measure according to the invention that a deformation slide is capable of being coupled or decoupled by means of a switching device, in the crash event, in the case of a coupled switching device both deformation strips can be deformed, or in the case of a decoupled switching device only the second deformation strip can be deformed. More energy is absorbed in the deformation of both deformation strips than in the case of only the second deformation strip being deformed. On account thereof, the energy absorbed in the crash event can be adapted to the circumstances of the crash, for example to the weight of the driver impacting the steering wheel, or to the circumstance of whether the driver is or is not belted up.

In one preferred embodiment the switching device is a pyrotechnical switch. Said pyrotechnical switch may or may not be triggered in the crash event. Pyrotechnical switches require only a small installation space and switch very rapidly. Alternatively, it is likewise conceivable and possible that a solenoid is used as the switching device.

One advantageous design embodiment of the invention furthermore provides that the deformation slides are connected to the outer casing unit by way of a rack plate, wherein an arrestor element provided with teeth is connected to the outer casing unit by way of a tightening device which pushes the arrestor element against the rack plate so as to in the travelling operation fix the latter in an immovable manner on the casing unit such that a displacement of the casing tube in relation to the casing unit in the crash event is possible only by activating the energy absorption device. This assembly requires particularly little installation space.

The arrestor element being pushed against the rack plate is to be understood that the arrestor element and the rack plate are mutually engaged. To this end, it is not necessary for a force to pre-tension the arrestor element in the direction of the rack plate.

The tightening device can preferably comprise a first lifting disk and a second lifting disk, wherein the first lifting disk is connected in a rotationally fixed manner to an activation lever and a tensioning bolt and interacts with the second lifting disk, wherein in a rotation of the first lifting disk in relation to the second lifting disk by means of the activation lever a clamping stroke is provided in the direction of the tensioning axis. The second lifting disk is coupled to the arrestor part. The first lifting disk preferably comprises a cam portion. The second lifting disk preferably comprises a cam track contour which can interact with the cam portion.

The tightening device by means of an activation lever is either tightened or released, also referred to as the fixing position and the releasing position. In the released state (releasing position) of the tightening device, the casing tube can be telescoped in relation to the casing unit, on the one hand. In the tensioned state (fixing position), the casing tube is blocked in relation to the casing unit such that a displacement of the casing tube in relation to the casing unit is possible only when a force which exceeds a predetermined breakaway force is introduced into the steering shaft. In other words, in the crash event the casing tube can telescope into the casing unit while energy is absorbed by the energy absorption device. The tightening device in the normal operation is in the fixing position in which the adaptation of the steering shaft position, that is to say the adjustment of the casing tube in relation to the casing unit, is prevented.

In one embodiment, as an alternative to a manual adjustment, it is possible that the casing tube and the casing unit are capable of being mutually telescoped by means of a motorized drive. The fixing capability of the casing tube in the relation to the casing unit is implemented by the standstill of the motorized drive, and in one advantageous embodiment is implemented by a self-locking gear mechanism. The invention in terms of the required installation space is further improved when the deformation strips are disposed on top of one another, wherein a second deformation strip that lies closer to the casing tube is preferably configured so as to be wider than the first deformation strip that is disposed on the second deformation strip, wherein the second deformation slide that is disposed on the second deformation strip is preferably wider than the first deformation slide that is disposed on the first deformation strip, such that said second deformation slide encompasses both deformation strips but jams only the second deformation strip, and wherein the first deformation slide encompasses and jams only the first deformation strip.

In the case of this construction mode, both deformation strips are disposed on the same side of the casing tube and said two deformation strips require slightly more installation space than an energy absorption device having a single deformation strip. Nevertheless, when the switching device is coupled, the first deformation slide deforms only the first deformation strip, and the second deformation slide deforms only the second deformation strip. The two deformation slides can preferably be disposed behind one another in the axial direction. In the crash event, either both deformation slides are pulled over both deformation strips, or only the second deformation slide is pulled over the second deformation strip when the switching device has previously been decoupled. The first deformation strip remains in a non-deformed state.

The deformation strips are advantageously held at a mutual spacing by spacers and in the radial direction are fixed between the casing tube and the rack plate. This prevents any bending of the deformation strips and any slipping of the latter from the respective deformation slides, and guarantees uninterrupted functioning when one or both of the deformation strips is/are deformed.

The spacers are advantageously disposed on the second deformation strip. Said spacers can thus be assembled conjointly with the second deformation strips in one single operative step. In an advantageous design embodiment the spacers are disposed both on the upper side of the second deformation strip that faces the first deformation strip as well as on the lower side of the second deformation strip that faces the casing tube. The second deformation tube herein is not only held and guided at a spacing in relation to the first deformation strip but also in relation to the casing tube. In one advantageous embodiment that is simple to produce, the spacers are designed as studs or a web, and are molded in the second deformation strip.

In one advantageous refinement the deformation strip and the spacers are a single-piece integral component.

A steering column according to the invention, in which an inner casing tube1is mounted in an outer casing unit2so as to be longitudinally displaceable in the axial direction3is shown inFIG. 1. A steering shaft4is rotatably mounted in the casing tube1, a steering wheel (not shown) being able to be assembled on the end5of said steering shaft4that faces the driver of the motor vehicle. The casing unit2is capable of being connected to the vehicle chassis (not shown) by way of a holder6. The holder6is capable of being fixed to the vehicle chassis by means of fastening means, while the casing unit2is mounted so as to be pivotable in the vertical direction7in relation to the holder6.

The holder6for the pivotable mounting is provided with two clamping jaws8which encompass the casing unit2and which have vertical slots9configured as elongate bores. The casing unit2comprises a fastening portion201which is capable of being connected to the vehicle chassis and is elastically deformed by an adjustment in the vertical direction7. A tightening device10is provided with a tensioning bolt11which passes through the vertical slots9of the clamping jaws8and through two bores13of the casing unit2. The tightening device10comprises a first lifting disk101, configured as a cam disk, and a second lifting disk102, configured as a cam track disk, wherein the second lifting disk has a cam track103. The first lifting disk101is connected in a rotationally fixed manner to an activation lever12and the tensioning bolt11. The tightening device10, by means of the activation lever12, is either tightened or released in that the first lifting disk101in relation to the second lifting disk102is rotated about the axis of the tensioning bolt11. In the released state (releasing position) of the tightening device10, the casing tube1can be displaced in the axial direction3in relation to the casing unit2, on the one hand, and the casing unit2can be pivoted in the vertical direction7in relation to the holder6, on the other hand. On account thereof, a longitudinal adjustment of the steering wheel in the axial direction3and a height adjustment of the steering wheel in the vertical direction7are enabled. In the tightened state (fixing position) of the tightening device10, the casing tube1is tightly clamped in the casing unit2and the casing unit2is also tightly clamped in the holder6such that the steering column is fixed and a height adjustment or longitudinal adjustment of the steering wheel is no longer possible.

As can best be seen inFIG. 2, the casing tube1is provided with a rack plate14that is aligned in the axial direction3. An arrestor element15which is capable of being pushed against the rack plate14by the tightening device10and which is operatively connected to the second lifting disk102is likewise provided with teeth. When the arrestor element15in the tightened state of the tightening device10is pressed against the rack plate14, the teeth of the arrestor element15mesh with the teeth of the rack plate14such that the rack plate14is fixed so as to be immovable in relation to the holder6. A displacement of the rack plate14in relation to the holder6in the axial direction3is no longer possible in this instance.

In order for the casing tube1in the normal operation of the vehicle to be displaced in the axial direction3in relation to the casing unit2, the tightening device10has to be released by way of the activation lever12, that is to say transferred from the fixing position to the releasing position, wherein the arrestor element15is raised from the rack plate14and a displacement of the rack plate14in the axial direction3in relation to the arrestor element15is possible. The arrestor element15per se cannot be displaced in the axial direction in relation to the holder6and the casing unit2, since the tensioning bolt11is prevented from such a displacement by the vertical slots9.

However, the tensioning bolt11can be displaced in the vertical direction7in the vertical slots9. On account thereof, the casing unit2, conjointly with the casing tube1disposed therein, is pivoted in the vertical direction7. The tightening device10, conjointly with the tensioning bolt11, the activation lever12, and the arrestor element15is also pivoted collectively with the casing tube1and the casing unit2in the vertical direction7such that arrestor element15at all times remains in the region of the rack plate14.

As can best be seen inFIGS. 3 to 6, two deformation strips16,17which are aligned in the axial direction3are disposed on the casing tube1, wherein a first deformation strip16is disposed on top of the second deformation strip17. The second deformation strip17is disposed directly on the surface of the casing tube1. For fastening to the casing tube1, the latter is provided with fastening elements18which protrude beyond the surface of the casing tube1and through corresponding openings19at the ends of the deformation strips16,17.

The rack plate14, at the end20thereof that lies in the travel direction of the vehicle, is connected to two deformation slides21,22, wherein a first deformation slide21is capable of being decoupled. A coupling rail23connects the end20of the rack plate14to the two deformation slides21,22, wherein the connection of the rack plate14to the second deformation slide22is fixed and inseparable, and the connection to the first deformation slide21is designed so as to be capable of being decoupled. The rack plate14and the second deformation slide22are configured as a single-part integral component. The rack plate14and the second deformation slide22can be configured as a formed component or else as a sintered component. A clamping spring141serves as a downholding element and, on the side facing away from the first deformation slide22, fastens the rack plate14to the second deformation strip17such that any radial raising of the rack plate14in the crash event is prevented. The coupling of the first deformation slide21to the coupling rail23is performed by means of a coupling bolt24(seeFIG. 6) which is capable of being introduced into a bore25of the first deformation slide21. A pyrotechnical switch27is fastened by means of a fastening bolt28in a bore26of the coupling rail23. The coupling bolt24in the normal case protrudes through the bore25of the first deformation slide21. The coupling bolt24can be pulled out of the bore25of the first deformation slide21by activating the pyrotechnical switch27, such that the first deformation slide21is decoupled from the coupling rail23. For example, when the driver in the crash event impacts the steering wheel, very high forces in the travel direction, which in the case of a closed tightening device10can cause a displacement of the casing tube1in the axial direction3in relation to the casing unit2, act on the steering wheel and thus on the steering shaft4and the casing tube1. Since the rack plate14by way of the arrestor element15, by means of the tightening device10, is connected in an immovable manner to the casing unit2, said rack plate14cannot move in the axial direction3. The same applies to the second deformation slide22which is non-releasably connected to the rack plate14, and also applies to the first deformation slide21when the latter by way of the pyrotechnical switch27and the coupling bolt24is connected to the coupling rail23. When the casing tube1in the crash event is forcibly displaced by a high force in the axial direction3in relation to the casing unit2, said casing tube1entrains the two deformation strips16,17which are fixedly connected to the casing tube1. On the other hand, since the two deformation slides21,22cannot be displaced in relation to the casing unit2, said two deformation slides21,22are pulled over the associated deformation strips16,17and herein deform the latter. The deformation energy that has to be generated for the deformation of the deformation strips16,17is thus absorbed from the kinetic energy. The casing tube1, and the impacting driver by way of the steering shaft4and the steering wheel, herein are decelerated to the extent that kinetic energy is absorbed in both deformation strips16,17.

When other circumstances, for example because the driver is secured by the safety belt, that is to say is belted up, arise in the crash event, the impact of the driver on the steering wheel will thus be less hard, and less energy will have to be absorbed by the energy absorption device. In this case, the pyrotechnical switch27which pulls the coupling bolt24out of the bore25of the first deformation slide21is activated. When the casing tube1in this case is again displaced by the forces arising in the crash event in the axial direction3in relation to the casing unit2, the decoupled first deformation slide21is not moved in relation to the first deformation strip16but remains at the position assumed by said deformation slide21prior to the crash. Only the second deformation slide22which is non-releasably connected to the coupling rail23and the rack plate14is pulled over the second deformation strip17. This situation is illustrated inFIG. 9.

In this case, only the second deformation strip17is thus deformed; the first deformation strip16remains non-deformed. Less deformation energy is required for the deformation of a single deformation strip17than in the other case in which two deformation strips16,17have to be deformed. Therefore, the deformation of a single deformation strip17also absorbs less kinetic energy than the deformation of two deformation strips16,17. The activation of the pyrotechnical switch27prior to the displacement of the casing tube1in relation to the casing unit2consequently leads to less kinetic energy being absorbed by the energy absorption device according to the invention in the displacement in the axial direction3than in the case without the activation of the pyrotechnical switch27. The kinetic energy absorbed in the crash event can therefore be adapted to the respective prevailing circumstances of the crash event.

The adaptive energy absorption device according to the invention requires only very little installation space because the deformation strips16,17and the rack plate14are disposed directly on top of one another on the same side of the surface of the casing tube1. In order for the first deformation slide21to deform only the first deformation strip16, and for the second deformation slide22to deform only the second deformation strip17, the second deformation strip that lies closer to the casing tube1transverse to the axial direction3is designed so as to be wider than the first deformation strip16. The first deformation slide21by way of the short flanks thereof comprises only the first deformation strip16. The short flanks of the first deformation slide21herein jam the narrow sides of the first deformation strip16such that said narrow sides deform the first deformation strip16as soon as the first deformation slide21is pulled in the axial direction3over the first deformation strip16. The first deformation slide21comprises bolt-type protrusions211which interact with the narrow sides of the deformation strip16and deform the latter in the case of a relative movement. The protrusions211are mutually spaced apart, wherein the spacing between the protrusions211is less than the width of the deformation strip16, that is to say the width of the narrow sides of the deformation strip17. The bolt-type protrusions211comprise a radiused surface.

The second deformation slide22, transversely to the axial direction3, is designed so as to be wider, and the longer flanks thereof reach the wider second deformation strip17lying below the first deformation strip16such that the second deformation slide22by way of the longer flanks thereof jams the narrow sides of the second deformation strip17so firmly that said second deformation slide22deforms the second deformation strip17as soon as the second deformation slide22is pulled over the second deformation strip17.

The second deformation slide22herein also comprises the first deformation strip16. However, since the second deformation slide22is wider than the first deformation slide21, the flanks of the second deformation slide22do not embrace the narrow sides of the first deformation strip16. The first deformation strip16is therefore not deformed when the second deformation slide22is pulled in the axial direction3over the former.

The second deformation slide22comprises a first pair of bolt-type protrusions221and a second pair of bolt-type protrusions222, said bolt-type protrusions221,222interacting with the narrow sides of the deformation strip17and deforming the latter. The protrusions221, and the protrusions222, respectively, are mutually spaced apart, wherein the spacing between the protrusions221, and the protrusions222, respectively, is less than the width of the deformation strip17, that is to say the width of the narrow sides of the deformation strip17. The bolt-type protrusions221and the bolt-type protrusions222comprise a radiused surface. It can be provided that the mutual spacing of the second protrusions222is less than, equal to, or larger than the mutual spacing of the first protrusions221. The crash properties can be set in terms of construction on account thereof.

As can be seen inFIG. 10, it is possible that the second deformation strip17in an alternative embodiment is in each case provided with studs31on the lower side29of said deformation strip17that faces the casing tube1as well as on the upper side30of said deformation strip17that faces the first deformation strip16, said studs31serving as spacers. On account of this measure it is possible for the two deformation strips16,17to be disposed directly on top of one another on the casing tube1. This enables a particularly compact construction mode. It is ensured by the studs31that the deformation strips are not bent in such a manner that said deformation strips slip out of the respective deformation slides. Moreover, space for the deformations of the narrow sides of the deformation strips16,17is thus made available such that mutual impediments of the functions of said deformation strips16,17are avoided.

The invention permits a particularly compact construction mode which is associated with lower production costs and nevertheless guarantees a reliable functioning of the energy absorption device in both switching states.

LIST OF REFERENCE SIGNS