STEERING COLUMN FOR A MOTOR VEHICLE

Description

State of the art

[0001] The invention relates to a motor-adjustable steering column for a motor vehicle, comprising a support unit which can be attached to a vehicle body and which holds an adjusting unit in which a steering spindle is mounted rotatably about a longitudinal axis, and comprising an adjusting drive which is connected to the support unit and to the adjusting unit and by which the adjusting unit can be adjusted relative to the support unit, wherein the adjusting drive has a threaded spindle engaging in a spindle nut and a drive unit by which the threaded spindle can be driven in rotation relative to the spindle nut, wherein the adjusting unit has a casing unit in which a casing tube in which the steering spindle is mounted is accommodated so as to be telescopically adjustable in the direction of the longitudinal axis, and the adjusting drive for longitudinal adjustment is effectively arranged between the casing unit and the casing tube, wherein the gear unit is attached to the casing unit,and a relatively translationally movable part of the spindle drive is connected to the casing tube.

[0002] Steering columns for motor vehicles have a steering shaft with a steering spindle. At the rear end in the direction of travel, closest to the driver, a steering wheel is attached to which the driver can initiate steering commands. The steering spindle is mounted so that it can rotate about its longitudinal axis in an actuating unit which is held on the vehicle body by a support unit. The length can be adjusted because an inner casing tube of the actuating unit, also referred to as the casing tube for short, is held in a casing unit connected to the support unit, also referred to as a guide box, outer casing tube or box swing arm, so that it can be moved telescopically in the direction of the longitudinal axis. Height can be adjusted because the actuating unit, or a casing unit supporting it, is pivotably mounted on the support unit. The adjustment of the actuating unit in terms of length or height is possible via the control unit.Height direction allows the adjustment of an ergonomically comfortable steering wheel position relative to the driver's position in the operating position, also known as the driving or operating position, in which manual steering intervention can take place.

[0003] It is known in the art to provide a motorized adjustment drive with a drive unit for adjusting the actuating unit relative to the support unit. The drive unit comprises an electric servomotor connected - usually via a gear - to a spindle drive comprising a threaded spindle screwed into a spindle nut. The drive unit drives the threaded spindle and the spindle nut in rotation relative to one another about the threaded spindle axis, whereby they can be moved translationally towards or away from one another depending on the direction of rotation. In one embodiment, a so-called rotary spindle drive, the threaded spindle can be driven in rotation about its threaded spindle axis by the drive unit, which is fixedly connected to the actuating unit or the support unit, and engages the spindle nut, which is fixedly attached to the support unit or the actuating unit with respect to rotation about the threaded spindle axis.In the direction of the threaded spindle axis, the threaded spindle rests on the support unit or the adjusting unit, and the spindle nut rests on the adjusting unit or the support unit, so that a rotary drive of the threaded spindle causes a translational adjustment of the support unit and the adjusting unit relative to each other. In an alternative embodiment, known as a plunger spindle drive, the threaded spindle is non-rotatably coupled to the support unit or the adjusting unit with respect to rotation about its threaded spindle axis, and the spindle nut is rotatable but fixed in the direction of the threaded spindle axis and mounted on the adjusting unit or the support unit.As in the first embodiment, the threaded spindle rests on the support unit or the adjusting unit in the direction of the threaded spindle axis, and the spindle nut rests on the adjusting unit or the support unit, respectively, so that the threaded spindle can be translated by the drive unit in the direction of the threaded spindle axis. In both embodiments, the spindle drive forms a motorized adjustment drive acting between the support unit and the adjusting unit, allowing the adjusting unit to be adjusted relative to the support unit.

[0004] In order to realize a longitudinal adjustment of the actuating unit in the direction of the longitudinal axis of the steering spindle, a spindle drive of an adjustment drive can be arranged between the casing tube of the actuating unit and a casing unit which receives it in an axially longitudinally displaceable manner and which is connected to the support unit, and wherein the threaded spindle axis can be aligned substantially parallel to the longitudinal axis.

[0005] For height adjustment, a spindle drive can be arranged between the support unit and a vertically pivoting actuator mounted on it. Motorized longitudinal and height adjustment can be implemented on a steering column individually or in combination.

[0006] In the prior art, DE 195 24 196 C1 describes a steering column in which the drive unit of an adjustment drive including drive motor, gear and spindle nut is attached to the casing unit, and the threaded spindle engages a casing tube of the adjustment unit which is telescopically adjustable relative thereto.

[0007] A similar arrangement is known from DE 10 2011 083 190 A1, in which the drive unit formed by the drive motor and gear is also attached to the casing unit connected to the support unit.

[0008] A disadvantage of the known designs is the relatively large installation space required for the adjustment drive in the area of ​​the actuating unit, which limits the design options for adaptation to the installation space available in the vehicle.

[0009] A steering column of the type mentioned above is known from EP 2 822 836 B1. The transmission of the drive torque of the adjustment drive is disadvantageous.

[0010] From EP 0705754 A1 a motor-adjustable steering column is known which discloses the features in the preamble of claim 1.

[0011] In view of the problems explained above, it is an object of the present invention to enable an improved transmission of the drive torque. Description of the invention

[0012] This object is achieved according to the invention by a steering column having the features of claim 1. Advantageous further developments emerge from the subclaims. According to the invention, in a motor-adjustable steering column for a motor vehicle, comprising a support unit which can be attached to a vehicle body and which holds an adjusting unit in which a steering spindle is mounted so as to be rotatable about a longitudinal axis, and comprising an adjusting drive which is connected to the support unit and to the adjusting unit and by which the adjusting unit is adjustable relative to the support unit, wherein the adjusting drive has a threaded spindle engaging in a spindle nut and a drive unit by which the threaded spindle is rotatably driven relative to the spindle nut, wherein the adjusting unit has a casing unit in which a casing tube in which the steering spindle is mounted is accommodated so as to be telescopically adjustable in the direction of the longitudinal axis,and the adjustment drive for longitudinal adjustment is effectively arranged between the casing unit and the casing tube, wherein the gear unit is attached to the casing unit, and a part of the spindle drive that is translationally movable relative thereto is connected to the casing tube, provided that the drive unit is connected via a flexible drive connection to a gear unit that is spatially displaceable relative to the drive unit.

[0013] In contrast to the prior art, in which the gear is rigidly and spatially immovably attached to the drive unit, the invention separates the drive unit and the gear unit spatially and structurally from one another. The drive unit forms a first assembly, which may include the drive motor and optionally a gear, and the gear unit forms a separate second assembly, which may include a gear wheel connected to the spindle nut or the threaded spindle and further gear elements. To transmit the drive torque, the invention uses a spatially movable, flexible drive connection between the output of the drive unit and the input of the gear unit.The drive connection comprises a torque transmission means which is designed to be spatially flexible and movable in such a way that a change in the spatial orientation between the drive unit and the transmission unit can be compensated by linear displacements and / or tilting in space.

[0014] An advantage of the invention arises from the fact that the separate gear unit has significantly smaller dimensions than the drive unit in the prior art. Therefore, the gear unit can be mounted, for example, on the support unit or the associated casing unit even in tight spaces and with limited local installation space. By appropriately designing the length and path of the drive connection, the drive unit can be positioned at a spatial distance from the gear unit according to the invention. Preferably, the placement can take place in a spatially less critical area within the installation space. This results in greater design freedom, and the available installation space can be better utilized.

[0015] It is possible for the gear unit to be movable synchronously with the actuator unit. During adjustment, the actuator unit is spatially displaced relative to the body-mounted support unit. The gear unit can be spatially fixed relative to the actuator unit, for example, through a direct or indirect connection to the actuator unit, so that it moves synchronously with the actuator unit during adjustment.

[0016] Further advantages result from the fact that the drive connection is spatially variable and can transmit torque independently of a defined, aligned alignment of the drive and transmission units. This simplifies assembly and increases operational reliability. Furthermore, it is possible to mount the drive unit and transmission unit on functional parts that are moved relative to each other during operation of the steering column, for example, when adjusting the steering column or in the event of a crash, in which the steering column is compressed by high external forces. Furthermore, an adjustment drive can advantageously be designed modularly.For example, differently designed drive unit types, for example, with different drive torques or speeds, can be combined with gear units specifically adapted for specific applications, which, for example, have different gear ratios or are designed for submersible or rotary spindle drives. The drive connection can also be adapted to the specific application, for example, with regard to length, diameter, bending radius or flexibility, transmittable torque and permissible speed, and the like.

[0017] The gear unit preferably has a gear unit housing in which the gear wheel is at least partially accommodated, wherein the drive unit has a drive unit housing in which at least one component of the drive motor is at least partially accommodated, wherein the gear unit housing and the drive unit housing are spaced apart from one another, in particular such that the gear unit housing and the drive unit housing are non-contacting, i.e., do not contact one another. The distance between the gear unit housing and the drive unit housing is preferably at least 1 cm.

[0018] The drive motor preferably comprises a stator as a first component and a rotor rotatable thereto as a second component.

[0019] To implement the flexible drive connection, shaft arrangements can be used that can compensate for spatial and / or angular misalignment, for example cardan shafts that can have misalignment-compensating couplings, such as Oldham couplings, universal joints or constant velocity joints, and / or splined shafts or other connections for length compensation.

[0020] An advantageous embodiment is for the flexible drive connection to have a flexible shaft. The torque-transmitting element is an elongated, freely bendable shaft core, for example, in the form of a coil spring made of spring steel wire similar to a speedometer shaft. The shaft core is connected to the drive unit on the output side and to the transmission unit on the input side via suitable connecting flanges, for example, using a polygonal profile, preferably a square profile. To protect against external influences, the shaft core can be enclosed in a freely bendable shaft tube. Flexible shafts can be manufactured in various lengths with little effort. This allows for easy adaptation to specific applications and different steering column designs.

[0021] The gear unit can preferably comprise a gear wheel that is non-rotatably connected to the spindle nut or the threaded spindle and can be driven in rotation by the drive connection. In a submersible spindle drive, a gear wheel designed as a spur, bevel, or worm gear can be rotationally connected to the spindle nut, into which the threaded spindle engages and which is supported axially, i.e. in the direction of the threaded spindle axis, on the gear unit. Preferably, the threaded spindle plunges completely through the spindle nut in the direction of the threaded spindle axis, so that it protrudes from the spindle nut on both sides. During adjustment, the rotatingly driven spindle nut is moved in one or the opposite direction on the stationary threaded spindle, depending on the direction of rotation. In a rotary spindle drive, the threaded spindle is rotationally connected to the gear wheel and axially supported in the gear unit.

[0022] Alternatively, it is possible for the threaded spindle or spindle nut in the gear unit to be directly connected to the drive connection in a rotationally locked manner.

[0023] The gear unit can also accommodate at least one intermediate gear, which meshes with the gear wheel and is rotationally connected to the drive connection, or at least can be driven rotationally by the drive connection. The intermediate gear can be designed, for example, as a spur or bevel gear, or as a worm gear.

[0024] If necessary, additional transmission elements can be mounted in the transmission unit, for example intermediate shafts or gears, clutches or the like.

[0025] An advantageous development is that the gear unit comprises a multi-stage gear unit, i.e., at least a two-stage gear unit. Because the gear unit has at least two gear stages, a high gear ratio can be easily and reliably achieved. This can be designed for torque- and force-optimized transmission and conversion of the drive torque introduced into the gear unit from the drive unit on the input side into the relative linear adjustment movement of the support and actuating units.

[0026] Preferably, at least two gear stages comprise different gear types. For example, one gear stage may comprise a toothed gear, such as a spur gear, and a second gear stage may comprise a worm gear or a spindle drive with a threaded spindle engaging a spindle nut. The use of different gear types allows for optimized adaptation to the required transmission characteristics, dimensions, weight, and other operating requirements.

[0027] Preferably, all gear stages can be housed in a common gear housing. Housing a multi-stage, at least two-stage, gear unit in a single gear housing enables a compact, space-optimized, and efficient design.

[0028] A common gear housing preferably provides a housing space sealed to the outside, in which all or at least several gear stages can be arranged. This allows for the formation of a protected, lubricant-filled, sealed gear arrangement that is essentially maintenance-free or at least low-maintenance over its operating life.

[0029] The transmission housing can preferably be constructed in multiple parts, whereby, for example, after the gear stages have been inserted, two or more sub-housings are joined together using detachable or non-detachable connections. The number of sub-housings or housing parts can be optimized for production, for example, depending on the transmission types used and the like.

[0030] The drive unit preferably comprises a drive motor, to which the drive connection is connected on the output side. It is possible for the motor shaft, which is coupled to the rotor, to be rotationally coupled to the drive connection in the drive unit, so that, for example, the shaft core of a flexible shaft is driven at the speed of the drive motor. An advantageous embodiment is for the drive unit to have a reduction gear, to which the drive motor is coupled on the input side and to which the drive connection is coupled on the output side.

[0031] By selecting the reduction ratio of a reduction gear of the drive unit and the gear ratio realized in the gear unit between the drive connection and the spindle nut or threaded spindle, the torque and speed to be transmitted by the drive connection can be specified and adapted to the respective application.

[0032] The drive unit may comprise a drive housing. The drive motor may be integrated into the drive housing or fixed to it, for example by means of a

[0033] Flange connection. Furthermore, a reduction gear can be implemented in the drive housing between the drive motor and the drive connection, for example, a worm gear with a worm connected to the motor shaft, which meshes with a worm wheel connected in a rotationally fixed manner to the shaft core of the drive connection.

[0034] The gear unit can have a gear housing that is structurally separate from the drive unit. The flexible drive connection according to the invention, for example a flexible shaft, extends between the drive housing and the gear housing. A gear wheel, which is connected to the spindle nut or the threaded spindle, can be rotatable about the spindle axis but axially fixed in place in the gear housing. An intermediate gear that meshes with the gear wheel and is connected to the drive connection, preferably to the shaft core, can also be mounted in the gear housing. Furthermore, it is possible for the gear unit to have fastening means for connection to the support unit and / or the actuating unit. The fastening means can be attached to or formed on the gear housing, or interact with it.

[0035] The actuating unit can be provided with a casing unit in which a casing tube, also referred to as the inner casing tube, in which the steering spindle is mounted, is accommodated so as to be telescopically adjustable in the direction of the longitudinal axis. The casing unit is connected to the support unit and is supported against it in the direction of the longitudinal axis. The casing tube is telescopically adjustable relative to the casing unit for longitudinal adjustment.

[0036] In order to effectively implement an adjustment drive according to the invention for longitudinal adjustment between the jacket unit and the jacket tube, the gear unit can preferably be attached to the jacket unit, and the part of the spindle drive that can be moved translationally relative to it can be connected to the jacket tube. As a result, the jacket tube, as part of the adjustment unit, is adjustable relative to the support unit, which supports the jacket unit against the body in the direction of the longitudinal axis.

[0037] An advantageous embodiment of the invention provides that an energy absorption device is arranged between the gear unit and the support unit.

[0038] An energy absorption device serves to increase occupant safety in the event of a crash. In the event of a crash, a body impacting the steering wheel exerts a large force on the actuating unit, which acts on the spindle drive of the longitudinal adjustment device in the direction of the threaded spindle axis. This so-called crash force is transferred to the support unit via the spindle drive. An energy absorption device, such as that described in DE 195 24 196 C1 cited above, which is arranged between the actuating unit and the support unit, can achieve a controlled dissipation of kinetic energy in the event of a crash. In this case, the kinetic energy can be absorbed and converted into friction and / or deformation energy when the drive unit is displaced relative to the support unit, or relative to the associated casing unit, as a result of the crash force.Preferably, a defined, progressive energy absorption takes place along the displacement path of the steering column, which essentially corresponds to the adjustment path of the adjustment drive, in accordance with a predetermined energy absorption characteristic.

[0039] According to the invention, in the event of a crash, the adjustment drive is not displaced as a whole relative to the support unit, as in the prior art, or as in other known embodiments, such as DE 10 2011 083 190 A1, also mentioned above, where only the threaded spindle or spindle nut is displaced, but rather only the separate gear unit is moved relative to the support unit. The energy absorption device integrated between the gear unit and the support unit ensures energy absorption according to a predetermined energy absorption characteristic along a predetermined displacement path of the gear unit relative to the support unit, which is also referred to as the crash path.

[0040] To absorb energy along the longitudinal axis, an energy absorption device is formed between the casing unit and the gear unit. A crash force exerted by the casing tube via the threaded spindle onto the gear unit causes the gear unit to move along a crash path along the casing unit, absorbing kinetic energy.

[0041] Advantages compared to a drive unit that moves in the event of a crash are the lower moving mass and the smaller spatial area traversed by the transmission unit on the crash path.

[0042] Thanks to the flexible drive connection, the movement of the transmission unit relative to the drive unit is not noticeably affected in the event of a crash.

[0043] The energy absorption device can have at least one energy absorption element that is plastically deformable when the gear unit moves in the direction of the threaded spindle relative to the support unit. An energy absorption element, also known as a crash element, is arranged as a deformation element in the force flow of the crash force occurring in the event of a crash in the connection between the gear unit and the support unit; in the case of an adjustment drive for longitudinal adjustment, preferably between the gear unit and the casing unit. This converts the kinetic energy introduced between the casing unit and the gear unit into plastic deformation of an energy absorption element over a predetermined deformation path. This results in a deceleration that is uniformed over the deformation path or a structurally predetermined deceleration.

[0044] In the energy absorption device, a slotted hole, a so-called crash slot, can be plastically expanded along its length for energy absorption by a deformation element, such as a mandrel that is oversized relative to the crash slot, that moves along it in the event of a crash. In alternative designs, a deformation element can, for example, have a bending tab that is continuously plastically bent over a displacement path of the actuating unit relative to the support unit, or as a tear tab that is severed by the relative movement in the event of a crash, or a combined bending and tear tab. Energy absorption can also occur in other ways, for example, by machining a crash element with a moving chisel or the like.

[0045] In an advantageous embodiment, the gear unit has a deformation member, of which an energy absorption element is plastically deformable upon movement of the gear unit relative to the support unit. The deformation member can comprise a mandrel protruding from the gear element, for example on the outside of the gear housing, which extends into a crash slot elongated in the direction of the spindle axis. The mandrel is wider in cross-section than the crash slot, which is fixed relative to the support unit, and is formed, for example, in an energy absorption element fixed to the casing unit. Alternatively, the gear unit can have a type of anvil, through which an energy absorption element is plastically compressed or stretched in the event of a crash. It is also conceivable for the deformation member to have a through-opening through which a deformation strip is pulled under plastic deformation in the event of a crash.

[0046] It is advantageous for the energy absorption device to have a guide device along which the transmission unit can slide in the event of a crash. The guide device can comprise, for example, a rail, such as an elongated U-profile, which can be attached to the casing unit parallel to the longitudinal axis and in which the transmission unit is held during normal operation and can slide in the event of a crash.

[0047] An energy absorption element can be formed between the gear unit and the guide device. For example, the gear unit can have a protruding pin on a gear housing that engages a crash slot formed in a U-shaped profile. The pin has multiple functions: to hold the gear unit during normal operation, to guide it in the event of a crash, and to absorb energy through plastic expansion.

[0048] It can further be provided that the energy absorption device has a switching device, of which at least one energy absorption element can be coupled or uncoupled between the transmission unit and the support unit. The switching device can reduce or increase the energy absorption capacity, the so-called crash level, as needed. For this purpose, one or more energy absorption elements can be coupled or uncoupled between the transmission unit and the support unit, and thus activated or deactivated, using a switching element, which, for example, comprises a pyroelectric actuator, a so-called pyroswitch.For example, an energy absorption device may include several mandrels that can be selectively brought into or out of engagement with one or more crash slots by means of a pyroswitch, or mandrels with different cross-sections can be activated or deactivated for different widening of a crash slot.

[0049] A predetermined breaking element can be arranged between the gear unit and the support unit. This element can be designed, for example, as a shear pin and fixes the gear unit relative to the support unit during normal operation. Only when a high force threshold is exceeded, which only occurs in the event of a crash, does the predetermined breaking element break, allowing the relative movement of the gear unit and support unit, and the energy absorption device is activated. Description of the drawings

[0050] Advantageous embodiments of the invention are explained in more detail below with reference to the drawings. In detail: Figure 1 shows a steering column according to the invention in a schematic perspective view, Figure 2 shows the steering column according to Figure 1 in a schematic perspective view from the opposite side, Figure 3 the steering column according to Figure 1 in a schematic perspective view from below, Figure 4 a detailed view of the gear unit of the steering column according to Figure 1 in open position, Figure 5the steering column according to Figure 1 in a schematic perspective view in partially exploded state, Figure 6 the steering column according to Figure 1 in a plan view in normal operating condition, Figure 7 the steering column according to Figure 6 in plan view in the state after a crash (crash state), Figure 8 an enlarged detailed view as in Figure 6the energy absorption device in a second embodiment in the normal operating state, Figure 9 an enlarged detailed view as in Figure 6 the energy absorption device in a third embodiment in the normal operating state, Figure 10 a view of the energy absorption device according to Figure 9 after a crash (crash condition), Figure 11 an enlarged detailed view as in Figure 6 the energy absorption device in a fourth embodiment in the normal operating state, Figure 12 a schematic longitudinal section through an energy absorption device in an alternative embodiment. Embodiments of the invention

[0051] In the various figures, identical parts are always provided with the same reference symbols and are therefore usually named or mentioned only once.

[0052] Figures 1, 2 and 3show a steering column 1 according to the invention in schematic perspective views from above diagonally to the left ( Figure 1 ) or diagonally to the right ( Figure 2 ) or from below ( Figure 3 ) to the rear end, seen in the direction of travel of a vehicle not shown.

[0053] The steering column 1 comprises a support unit 2, which can be attached to a vehicle body (not shown) via mounting holes 21. The support unit 2 supports an actuating unit 3, in which a steering spindle 31 is mounted for rotation about a longitudinal axis L. The actuating unit 3 is supported on the support unit 2 in the direction of the longitudinal axis L. At the rear end, relative to the direction of travel, the steering spindle 31 is provided with a mounting portion 32 for attaching a steering wheel (not shown here).

[0054] The adjusting unit 3 has a casing unit 33 which is pivotably mounted relative to the support unit 2 so that the fastening section 32 can be adjusted in a height direction H for height adjustment.

[0055] In the jacket unit 33, a jacket tube 34 - also referred to as inner jacket tube or inner jacket tube - is axially telescopically adjustable in the longitudinal direction, ie in the direction of the longitudinal axis L, in order to realize a longitudinal adjustment, as indicated by the double arrow.

[0056] For longitudinal adjustment, an adjustment drive 4 according to the invention is provided, which comprises a drive unit 41 and a gear unit 42, which are spatially separated from one another and connected to one another via a flexible drive connection in the form of a flexible shaft 43.

[0057] The drive unit 41 comprises an electric motor 411, which is flanged on the input side to a reduction gear 412. On the output side, the rotatable shaft core of the flexible shaft 43 is coupled to the reduction gear 412. The drive unit 41 is attached to the casing unit 33 and is thus firmly connected to the support unit 2, at least in the direction of the longitudinal axis L.

[0058] The gear unit 42 has a gear housing 421, which in the view of Figure 4 is partially omitted to allow a view of the interior.

[0059] The adjustment drive 4 is designed as a so-called submersible spindle drive, with a threaded spindle 44 which extends with its spindle axis S parallel to the longitudinal axis L and which is connected to the casing tube 34 in a manner secured against relative rotation to the longitudinal axis L.

[0060] The threaded spindle 44 is screwed into a spindle nut 45, which is coaxially connected to a gear wheel 46, which is mounted in the gear unit 42 so as to be rotatable about the spindle axis S. The spindle thread, not shown in detail, can also be formed in the gear wheel 46, whereby the spindle nut 45 is integrated therewith.

[0061] An intermediate gear 47 has a toothing corresponding to the gear wheel 46 and is mounted in the gear unit 42 so that it meshes with the gear wheel 46. The intermediate gear 47 is rotationally coupled to the flexible shaft 43.

[0062] Between the gear unit 42 and the casing unit 33, an energy absorption device 5 is arranged, the functional elements of which are shown in the illustration of Figure 5 can be seen, in which the spindle drive including gear unit 42 and threaded spindle 44 is shown schematically exploded transversely to the longitudinal axis L.

[0063] The energy absorption device 5 comprises an elongated, U-shaped guide profile 51, which is fixed parallel to the longitudinal axis L laterally to the support unit 2 by means of screws. As shown in the Figures 1 , 3 and 4 As can be seen, the gear unit 42 is held between the U-legs of the guide profile 51.

[0064] For the actual energy absorption, the guide profile 51 has elongated crash slots 52 in the direction of the longitudinal axis L. A deformation element in the form of a mandrel 53 is inserted into each of the crash slots 52, as shown in the detailed view of Figure 6 and 8 is clearly visible.

[0065] Each mandrel 53 has a cross-section with a width that is greater than the slot width of the corresponding crash slot 52.

[0066] In the normal operating state, ie before a crash has occurred, the mandrel 53 is located at the rear end of the crash slot 52, as shown in Figure 6 shown.

[0067] Between the gear unit 42 and the casing unit 33, a predetermined breaking element in the form of a shear bolt 54 can be arranged, which is positively fixed through a fastening opening 422 in the gear housing 421 in a corresponding opening 512 in the guide profile 51.

[0068] If, in the event of a crash, a large crash force F acts forwards on the steering spindle 31 in the direction of the longitudinal axis, as in Figure 6 As shown, this is transmitted to the gear unit 42 via the casing tube 34 and the threaded spindle 44 supported thereon, the spindle nut 45 and the gear wheel 46. If the crash force F exceeds a predetermined limit, the shear bolt 54 breaks. The crash force F then moves the gear unit 42 along the guide profile 51, as shown in Figure 7indicated by the arrow on the gear unit 42. The casing tube 34, the steering spindle 31, the threaded spindle 44, and the gear unit 42 move relative to the guide profile 51, the casing unit 33, and the drive unit 41, absorbing energy.

[0069] Due to the relative movement in the event of a crash, the mandrel 53 is moved along the crash slot 52, whereby the latter is progressively expanded plastically while absorbing kinetic energy. The expanded section 52a is in Figure 7 recognizable.

[0070] As from Figures 6 and 7As can be seen, the drive unit 41 remains in its position relative to the casing unit 33 and the support unit 2. The relative movement in the event of a crash causes a deformation and thus a deflection of the flexible shaft 43, whereby the relative movement of the gear unit 42 for energy absorption is practically unaffected. In the event of a crash, the gear unit 42 is thus displaceable relative to the drive unit 41.

[0071] Figure 8 shows a second embodiment in which the crash slot 52 tapers in a wedge shape toward its front end 52b—to the right in the drawing. As a result, in the event of a crash, the deformation energy required for expansion increases along the crash path of the transmission unit 42 relative to the casing unit 33, thus realizing a progressive energy absorption characteristic. The crash slot 52 has side walls, which preferably taper in a wedge shape at an angle of less than or equal to 10°.

[0072] In the Figures 9 and 10 A third embodiment is shown, which has two adjacent crash slots 52 in one leg of the U-profile 51. While the outer edges of the two slots 52 run parallel, the inner edges define a web 55 which converges towards the rear in a wedge shape and which is plastically deformed in the widened section 52a after a crash, as shown in Figure 10 shown. Two mandrels 53 are provided, which are spaced apart from each other and between which the web 55 is arranged. In the event of a crash, the mandrels 53 move relative to the web 55 of the guide profile 51, whereby this web 55 is moved through the mandrels 53 and is plastically deformed in the process. This is particularly well suited to Figure 10 removable, in which a section of the web 55 is deformed.

[0073] The Figure 11 The fourth embodiment shown differs from that shown in Figure 8shown embodiment in that an additional, second mandrel 56 is provided, which has a smaller cross-section than the first mandrel 53. Because the first mandrel 53 can be selectively removed from the crash slot 52 by means of a pyrotechnic actuator (not shown), only the second mandrel 56 is then active. Due to its smaller cross-section, less deformation work is required to pass through the crash slot 52. In this way, a lower crash level can be set by deactivating the first mandrel 53. This allows two different crash levels to be created in a simple manner.

[0074] Figure 12shows a schematic longitudinal section through the energy absorption device 5. This shows that an additional or alternative energy absorption element in the form of a bending strip 57 can be arranged between the gear unit 42 and the casing unit 33. With an input-side leg 571, the bending strip 57 is suspended in the direction of the spindle axis S behind a driver 423 formed on the gear unit 42. The other, output-side leg 572 is connected to the first leg 571 via a substantially U-shaped bend 573 and is supported in the direction of the longitudinal axis L against an abutment 513 on the guide profile 51 or the casing unit 33.

[0075] If, in the event of a crash, the transmission unit 42 is displaced forward relative to the casing unit 33 in the direction of the longitudinal axis L—to the right in the drawing—a continuous plastic deformation of the leg 572 occurs in the then continuous bend 573. This also continuously absorbs crash energy. The dimensions of the leg 572 can vary along the longitudinal extent of the leg 572.

[0076] The energy absorption device 5 may alternatively or in combination comprise different arrangements of bending strips 57, mandrels 53, 56 engaging in crash slots 52 and other energy absorption devices which enable absorption of kinetic energy by conversion into deformation and friction.

[0077] For height adjustment, a second adjustment drive 7 can be provided, which is Figure 2can be seen, and in the example shown is designed as a conventional rotary spindle drive. The translationally displaceable spindle nut 71, into which a rotatably driven threaded spindle 72 engages, is articulated to an adjusting lever 73, which is inserted between the casing unit 33 and the support unit 2 so as to be pivotable in the vertical direction H. In contrast to the drawing, the adjusting drive 7 can, in principle, also be designed like the first adjusting drive 4 according to the invention. List of reference symbols

[0078] 1Steering column 2Support unit 21Mounting holes 3Adjusting unit 31Steering spindle 32Mounting section 33Sleeve unit 34Sleeve tube 4Adjustment drive 41Drive unit 411Motor 412Reduction gear 42Gear unit 421Gear housing 422Mounting opening 423Drive element 43Flexible shaft 44, 72Threaded spindle 45, 71Spindle nut 46Gear wheel 47Idler gear 5Energy absorption device 51Guide profile 512Opening 513Abutment 52Crash slot 52aFlared section 52bFront end 53, 56Mandrel 54Shear bolt 55Web 57Flexible strip 571Leg 572Leg 573Bend 7Adjustment drive 73Adjustment lever LLongitudinal axis HHeight direction SSpindle axis FCrash force

Claims

1. Motor-adjustable steering column (1) for a motor vehicle, comprising a support unit (2) which can be attached to a vehicle body and by which an adjusting unit (3) is held, in which a steering spindle (31) is mounted rotatably about a longitudinal axis (L), and comprising an adjusting drive (4) which is connected to the support unit (2) and to the adjusting unit (3), and by which the adjusting unit (3) can be adjusted relative to the support unit (2), the adjusting drive (4) having a threaded spindle (44) engaging in a spindle nut (45) and a drive unit (41), by which the threaded spindle (44) can be driven in rotation relative to the spindle nut (45), the adjusting unit (3) having a casing unit (33) in which a casing tube (34), in which the steering spindle (31) is mounted, is accommodated so as to be adjustable telescopically in the direction of the longitudinal axis (L), and the adjusting drive (4) for longitudinal adjustment is effectively arranged between the casing unit (33) and the casing tube (34), a gear unit (42) being attached to the casing unit (33), and a part (44) of the spindle drive which can be moved in translation relative thereto being connected to the casing tube (34), characterized in in that the drive unit (41) is connected via a flexible drive connection (43) to the gear unit (42) which can be displaced spatially relative to the drive unit (41).

2. Steering column according to claim 1, characterized in that the flexible drive connection comprises a flexible shaft (43).

3. Steering column according to one of the preceding claims, characterized in that the gear unit (42) comprises a gear wheel (46) which is non-rotatably connected to the spindle nut (45) or the threaded spindle (44) and can be driven in rotation by the drive connection (43).

4. Steering column according to one of the preceding claims, characterized in that the drive unit (41) comprises a drive motor (411) to which the drive connection (43) is connected on the output side.

5. Steering column according to one of the preceding claims, characterized in that an energy absorption device (5) is arranged between the transmission unit (42) and the support unit (2).

6. Steering column according to claim 5, characterized in that the energy absorption device (5) has at least one energy absorption element (51, 52) which can be plastically deformed relative to the support unit (4) when the transmission unit (42) is moved in the direction of the axis of the threaded spindle (44).

7. Steering column according to claim 6, characterized in that the transmission unit (42) has a deformation member (53, 56, 423), of which an energy absorption element (51, 52) can be plastically deformed during a movement of the transmission unit (42) relative to the support unit (2).

8. Steering column according to one of claims 5 to 7, characterized in that the energy absorption device (5) has a switching device from which at least one energy absorption element (52) can be coupled or uncoupled between the transmission unit (42) and the support unit (2).

9. Steering column according to one of the preceding claims, characterized in that a predetermined breaking element (54) is arranged between the transmission unit (42) and the support unit (2).