Gear wheel for an adjustment drive, adjustment drive for a steering column and steering column for a motor vehicle

Abstract

Gear wheel for an adjustment drive (2), which has a gear ring (30) which is mounted coaxially on the outside on a core element (31) which has an axial through-opening (311) in which a threaded element (33) is mounted, which has an axially continuous internal thread (32) with at least one helically rotating thread tooth (321), wherein the threaded element (33) is formed from a plastic as a plastic injection-molded part, which is injection-molded onto the core element (31) on an inner wall of the through-opening (311), characterized by that a crash support section (36) is formed in the through opening (311), in which at least one support element (37) projects from the core element (31) into a thread tooth (321).

Description

State of the art

[0001] The invention relates to a gear wheel for an adjustment drive, which comprises a gear ring that is mounted coaxially on the outside of a core element, which has an axial through-opening in which a threaded element is mounted, which has an axially continuous internal thread with at least one helically extending thread tooth. The threaded element is formed from a plastic as a plastic injection-molded part that is molded onto the core element on an inner wall of the through-opening. An adjustment drive with a gear wheel, and a steering column for a motor vehicle having an adjustment drive, are also subject of the invention.

[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 for the driver to initiate steering commands. The steering spindle is mounted so that it can rotate about its longitudinal axis in a casing tube of an actuating unit which is held on the vehicle body by a support unit. Because the actuating unit has at least one casing tube which can be telescopically moved in the direction of the longitudinal axis in a casing unit connected to the support unit, also referred to as a guide box or box swing arm, the steering wheel can be adjusted longitudinally relative to the body. Height adjustment can be achieved by pivoting the actuating unit or a casing unit receiving it on the support unit. The adjustment of the actuating unit in the longitudinal or vertical directions is possible via a...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] In motor-adjustable steering columns, it is known to provide a motorized adjustment drive with a drive unit comprising an electric drive motor that drives a spindle drive with a threaded spindle screwed into an internal thread of a spindle nut. The drive unit drives the threaded spindle and the spindle nut to rotate relative to one another about the threaded spindle axis, or spindle axis for short, whereby the threaded spindle and the spindle nut can be moved translationally towards or away from one another in the direction of the threaded spindle axis, depending on the direction of rotation. The threaded spindle and the spindle nut are supported in the direction of the spindle axis on parts of the steering column that are adjustable relative to one another, for example on a casing unit and a support unit, or on casing tubes of a casing unit that are telescopic in the axial direction.

[0004] The spindle drive is driven by the drive unit via a gear wheel that rotates around its axis, which is identical to the threaded spindle axis and is rotationally coupled to the spindle nut. In the generic design, the internal thread of the spindle nut is integrated into the gear wheel.

[0005] A generic gear wheel has a core element that carries a gear ring on the outside and forms, for example, a worm wheel with teeth into which a worm driven by a drive motor engages to form a reduction gear. The internal thread can be formed in the core element, as described, for example, in the generic US Pat. No. 4,967,618 A. Alternatively, it is known for a metal core element to have the gear ring on the outside and an axial through-opening on the inside into which a threaded bushing is inserted as a threaded element, as known, for example, from DE 38 86 900 T2. The disadvantage of this is that this known threaded element must first be manufactured separately as a separate component and then joined and fixed to the core element. The required precise fit requires a correspondingly high manufacturing effort.The assembly in the core element, where deformation or misalignment of the threaded element must be avoided as much as possible, and the material and / or form-fitting fixation result in additional assembly effort. The joint can also impair the load-bearing capacity and durability of the gear wheel. Manufacturing the threaded element as an injection-molded plastic part is described in DE 10 2014 101 995 A1.

[0006] In view of the problems explained above, it is an object of the present invention to provide an improved gear wheel which has a higher load capacity and durability. Description of the invention

[0007] This object is achieved according to the invention by a gear wheel having the features of claim 1, as well as by an adjustment drive according to claim 9 and a steering column according to claim 10. Advantageous further developments emerge from the subclaims.

[0008] The terms used to designate the internal thread follow DIN 2244. In particular, the thread tooth refers to the material-filled part of the thread delimited by mutually inclined screw surfaces, and the thread gap or thread groove refers to the material-free part of the thread delimited by mutually inclined screw surfaces.

[0009] In a generic gear wheel, the threaded element is made of a plastic as a plastic injection-molded part, which is injection-molded onto the core element on an inner wall of the through opening.

[0010] By using the plastic injection molding process, it is possible to precisely form the threaded element, including the internal thread, in a single production step of an integrated manufacturing process, while simultaneously creating a particularly durable, material-fit and, if necessary, form-fitting joint with the core element. This reduces manufacturing and assembly costs compared to the state of the art, while simultaneously increasing durability and resilience.

[0011] The threaded element is injected into the core element. For this purpose, the core element is prepared and positioned in an injection mold of a plastic injection molding machine. The molten plastic is injected into a mold cavity between a threaded core of the injection mold and the inner wall of the through-hole. This creates a material bond between the plastic and the inner wall. After the plastic has solidified, the threaded core is removed from the mold, and the internal thread of the threaded element formed from the plastic is positioned and oriented precisely coaxially in the core element. The additional manufacturing and assembly steps required in the prior art can be eliminated. This reduces the manufacturing and assembly effort.

[0012] According to the invention, a crash support section is formed in the through-opening, in which at least one support element projects from the core element into a thread tooth. The support element is preferably formed integrally with the core element, which preferably consists of a mechanically stressable material, preferably steel. The at least one circumferential thread tooth of the internal thread is thus at least partially formed by the core element. The support element forms, in a sense, a thread tooth core. In other words, the core element in the crash support section has a part of the internal thread which is at least partially - preferably on the thread flanks - coated with the plastic or enclosed by the plastic. As a result, the thread element is positively supported on the core element in the region of the thread via the support element with respect to stress in the axial direction.

[0013] Additional surface textures, elevations, depressions, or similar form-fitting elements can be formed in the inner wall, creating a permanent, positive connection between the plastic of the threaded element and the core element. For example, targeted roughening of the surface of certain areas of the inner wall can also be performed to optimize the adhesive effect.

[0014] It is advantageous for the through-opening to have at least one smooth, cylindrical positioning section. The positioning section, also referred to as the movement region, extends over an axial section of the through-opening. The inner wall there is designed as a smooth, coaxial inner cylinder. The constant inner diameter in the positioning section is larger than the outer diameter of the internal thread. As a result, the wall thickness of the threaded element, measured radially between the diameter of the internal thread and the inner wall, is constant in the circumferential direction and over the length of the positioning section. The smooth inner wall ensures that no irregular collapse of the plastic injection-molded part occurs during cooling during the injection molding process, whereby the internal thread of the threaded element is formed dimensionally accurate in the region of the positioning section.In addition, potentially harmful stresses due to shrinkage during solidification are largely avoided.

[0015] It can be provided that an undercut connecting section is formed in the through-opening. Such a connecting section can, for example, be in the form of a groove-shaped depression formed radially from the inside into the through-opening and at least partially surrounding it. Because the inner diameter in the connecting section is larger than in the other sections, in particular the positioning section, the plastic material injected into the connecting section forms a positive-locking element that acts in the axial direction between the core element and the threaded element. This ensures that, after the plastic has solidified, the threaded element is fixed in the through-opening and connected to the core element in a material-to-material and positive-locking manner.Preferably, the connecting section may also have a smooth cylindrical inner wall, whereby potentially harmful deformations or stresses due to collapse or distortion during solidification can be largely avoided.

[0016] Preferably, a connecting section is arranged at a distance from the end face of the core element and borders on a positioning section via a circumferential, radially inwardly projecting step.

[0017] In an assembled adjustment drive, the core element with a support element projects within the thread tooth into the helical thread gap of a screwed-in threaded spindle. If, in the event of a crash, i.e. during a vehicle collision, for example due to an object impacting the steering wheel, an extremely high axial force is exerted on the adjustment drive, this so-called crash force acts axially in the direction of the threaded spindle axis between the internal thread and the threaded spindle. The thread teeth of the internal and external threads are subjected to correspondingly high shear stress. The load acting on the plastic thread tooth of the threaded element is positively absorbed by the support element of the crash support section and transferred to the casing unit via the core element.The support element forms a reinforcing or reinforcement element which prevents the thread tooth from shearing off and thus the threaded spindle from slipping through the internal thread in the event of a crash.

[0018] A support element can extend from the core element to the thread crest of the thread tooth on the inner diameter of the internal thread, and can be overmolded with plastic on the thread flanks. This enables a deep positive engagement with the external thread of a screwed-in threaded spindle, achieving a high support effect in the axial direction. At least the thread flanks, with the plastic surface of the plastic overmold, are in contact with the external thread flanks of the threaded spindle, which is usually made of a metallic material, preferably steel, thus ensuring smooth and low-friction adjustment.

[0019] The crash support section can be arranged in one end region of the through-opening, and the positioning section in the other, opposite end region. This creates a spatial and functional separation.

[0020] It can be provided that at least in a part of the crash support section, the internal thread has an enlarged core diameter. Due to the support element protruding at least partially into the thread tooth, the thread element has less elastic deformability there due to the higher strength of the core element than in an area in which at least the thread tooth and a circumferential area supporting it are made entirely of plastic. For example, the internal thread has greater radial elasticity in a positioning section and / or a connecting section described above. As a result, the thread can be screwed onto the external thread of the threaded spindle with little or no play, whereby play-free yet smooth running of the adjustment drive can be achieved.In the crash support section, the thread is inherently more rigid due to the support element, making it less flexible and potentially stiffer under changing operating conditions, such as temperature fluctuations. This is effectively prevented by an enlarged core diameter of the internal thread, which results in greater thread play.

[0021] The core element can preferably be made of a high-strength material that is at least higher than the strength of the plastic of the threaded element. Preferably, the core element can be made of a metallic material, for example, steel, and the threaded element can be made of a thermoplastic, injection-moldable plastic, for example, polypropylene (PP), polyoxymethylene (POM), or the like.

[0022] The gear ring can be injection-molded from a plastic material onto the outside of the core element. This also allows a material-to-material and / or form-fitting toothing, for example a worm gear, to be formed using the plastic injection-molding process and connected to the core element in the same production step. In the connection area with the gear ring, additional surface textures, elevations, depressions, projections, or similar form-fitting elements can be formed on the core element, which are embedded in the plastic of the gear ring, thus creating an additional, permanent form-fitting connection with the core element. For example, the surface on the outer circumference of the core element can also be deliberately roughened to optimize the adhesive effect.

[0023] The thermoplastic material used can be individually adapted to the stresses expected on the threaded element and the gear ring during operation. This allows for the use of different plastics with different material properties if required. Alternatively, it is conceivable to use the same plastic material to enable more efficient production.

[0024] It can be provided that the core element has molded-in bearing rings. The bearing rings form axial bearing surfaces arranged axially on both sides of the gear wheel, which preferably have raceways for rolling elements, for example ball raceways of ball bearings. Rolling elements are arranged between these ball raceways and corresponding ball raceways in axially or diagonally opposite outer bearing surfaces that are fixed in the gear housing of the drive unit. This forms a bearing arrangement in which the gear wheel is supported in the axial direction between two thrust bearings, each of which consists of a bearing surface, an outer bearing surface, and the rolling elements arranged between them. A particular advantage here is that the high forces occurring in the event of a crash are reliably transmitted from the crash support section via the core element and the bearing surfaces.In addition, efficient production is possible and high operational reliability and functionality are guaranteed.

[0025] In an adjustment drive for a motor-adjustable steering column for a motor vehicle, comprising a gear wheel, a threaded spindle engaging an internal thread of the gear wheel, and a drive unit by which the gear wheel can be driven in rotation relative to the threaded spindle, the gear wheel can be designed according to the previously described embodiments of the invention. The drive unit has, for example, a gear element that meshes with the gear ring, such as a worm. The use of a gear wheel according to the invention enables more efficient production and offers increased operational reliability, particularly under high loads and in the event of a crash.

[0026] It is advantageous that, in a motor-adjustable steering column for a motor vehicle, comprising an adjustment drive arranged between a support unit connectable to the body and a casing unit rotatably receiving a steering spindle and / or between casing tubes of a casing unit that are axially telescopically adjustable relative to one another and support the steering spindle, the adjustment drive is designed with a gear wheel according to the invention, as described above. This enables more efficient production and increased operational reliability, particularly under high loads and in the event of a crash. Description of the drawings

[0027] Advantageous embodiments of the invention are explained in more detail below with reference to the drawings. In detail: Fig. 1 a schematic perspective view of a steering column with a motorized adjustment, Fig. 2 an adjustment drive of the steering column according to Fig. 1 in exploded view, Fig. 3 shows an arrangement of a gear wheel according to the invention in an adjusting drive with engaging threaded spindle in a perspective view, Fig. 4 the order pursuant to Fig. 3 with cutaway gear wheel, Fig. 5 a longitudinal section through an arrangement according to Fig. 3 or Fig. 4, Fig. 6 a schematic exploded view of the arrangement according to Fig. 3, Fig. 4 or Fig. 5, Fig. 7 a further schematic exploded view of the arrangement according to Fig. 3, Fig. 4, Fig. 5, Fig. 6 without sprocket, Fig. 8 a longitudinal section through a bearing arrangement of an adjustment drive according to Fig. 1 or Fig. 2, Fig. 9 an enlarged detailed view Fig. 5. Embodiments of the invention

[0028] In the various figures, identical parts are always provided with the same reference symbols and are therefore usually named or mentioned only once.

[0029] Fig. 1 shows a steering column 1, which has a support unit 10 connectable to the body of a motor vehicle (not shown here), on which an adjusting unit 16 is adjustably mounted, specifically in the longitudinal direction L and in the vertical direction H, as indicated by the double arrows. The support unit 10 comprises a bracket 100, which can be attached to the chassis of the motor vehicle, for example, via mounting holes 102.

[0030] The actuating unit 16 comprises a casing tube 12 in which a steering spindle 14 is rotatably mounted. A steering wheel (not shown here) can be attached to the steering-wheel-side end 141 of the steering spindle 14. The steering spindle 14 serves to transmit a steering torque applied by a driver via the steering wheel to the steering spindle 14 in a known manner to a steerable wheel (not shown here). The steering spindle 14 can transmit the steering movement from the steering wheel to the steerable wheel via a steering gear, optionally with the aid of a power assist.

[0031] In one variant, the steering movement of the steering spindle 14 can also be sensed by a sensor, for example, electrically, electronically, or magnetically, and fed into a controller, which, with the aid of a steering device, pivots the steerable wheel to represent the steering movement. Such systems are known as steer-by-wire steering systems.

[0032] The jacket tube 12 is held displaceably in a jacket unit 104 in the longitudinal direction L, which is the longitudinal adjustment direction, wherein the longitudinal direction L extends in the axial direction of the steering spindle 14. By adjusting the jacket tube 12 relative to the jacket unit 104, a longitudinal adjustment of the steering spindle 14 and thus of the steering wheel (not shown) can be achieved to adapt the position of the steering wheel to the seating position of a driver of the motor vehicle.

[0033] The casing unit 104 is pivotably attached to a bracket 100 and can be pivoted about a pivot axis 106 relative to the bracket 100. Adjustability of the adjusting unit 16 in a height direction H, i.e., the height adjustment direction oriented substantially perpendicular to the longitudinal direction L, is enabled by the fact that the casing tube 12 is held on the bracket 100 via a pivot mechanism 18. This results in pivotability of the casing tube 12 and the steering spindle 14 relative to the support unit 10 and in particular relative to the bracket 100 about the pivot axis 106 such that a height adjustment of the steering wheel (not shown here but arranged on the steering spindle 14) is also achieved, in order to also adapt the position of the steering wheel to the driver's seating position in this way.

[0034] In the exemplary embodiment, a separate adjustment drive 2, 2' is provided for each of the two adjustment directions, each with a separate spindle drive comprising a threaded spindle 4, 4', and a gear wheel 3.

[0035] An adjustment drive 2 is provided, by which the actuating unit 16 can be adjusted relative to the support unit 10 in the longitudinal direction L. The adjustment drive 2 comprises a threaded spindle 4 having an external thread 42 and connected via a fastening element 107, which is designed as a hinge pin, to the linkage lever 120, which is connected to the casing tube 12. The linkage lever 120 is displaceably guided in a slot 110 in the casing unit 104 such that a displacement of the linkage lever 120 relative to the casing unit 104 leads to a displacement of the actuating unit 16 relative to the support unit 10 in the longitudinal direction L.

[0036] The threaded spindle 4 is held on the linkage lever 120 via a coupling element 6, which is designed as a joint head 43, and extends with its spindle axis S in the longitudinal direction L. The threaded spindle 4 engages with its external thread 42 in an internal thread 32 of a gear wheel 3, i.e. is screwed therein. The gear wheel 3 is rotatable, but is mounted in a gear housing 25 in a stationary manner in the longitudinal direction L with respect to the casing unit 104, so that a rotation of the gear wheel 3 leads to an axial movement of the threaded spindle 4 relative to the gear wheel 3 in the direction of the spindle axis S. In other words, a rotation of the gear wheel 3 causes a relative movement between the casing tube 12 and the casing unit 104 such that an adjustment of the position of the actuating unit 16 relative to the support unit 10 is effected.

[0037] The adjustment drive 2 further comprises a drive motor 20, on whose output shaft 24 a worm 22 is arranged. The worm 22 engages with the toothing 30 of the gear wheel 3, which is designed as a worm wheel. The gear wheel 3 is rotatably mounted in a bearing 23 in the gear housing 25 about the spindle axis S. The rotational axis of the worm 22 and the spindle axis S of the gear wheel 3 are perpendicular to each other, as is known per se from worm gears.

[0038] Accordingly, by rotating the output shaft 24 of the drive motor 20, the gear wheel 3 can be rotated, whereby a longitudinal adjustment of the actuating unit 16 in the longitudinal direction L relative to the casing unit 104 and thus a longitudinal displacement of the actuating unit 16 relative to the support unit 10 takes place.

[0039] Fig. Figure 2 shows an exploded view of the adjustment drive 2. The threaded spindle 4 is clearly visible, with the coupling element 6 firmly attached to one end. At the other end, a stop element 7 made of plastic is firmly attached to the threaded spindle 4. The stop element 7 is fixed to the threaded spindle 4 by partial plastic deformations in the form of recesses 71, which are introduced by hot or warm caulking. Alternatively, the stop element 7 can also be made of a metallic material, which is fixed to the threaded spindle by partial plastic deformations.

[0040] Fig. 3, Fig. 4 and Fig. 5 show the spindle drive of an adjustment drive 2 formed by the gear wheel 3 and the threaded spindle 4 engaging therein, as for example in Fig. 1 and Fig. 2 shown. Fig. 9 shows an enlarged section of the longitudinal section along the spindle axis S of Fig. 5 through the gear wheel 3. In Fig. 6 and Fig. 7 the gear wheel 3 is shown schematically exploded.

[0041] In the sectional views of Fig. 4, Fig. 5 and Fig. 9 shows that the gear wheel 3 has a core element 31, which is preferably made of steel. An internal thread 32 is formed in a threaded element 33, which is coaxially fixed in an axial through-opening 311 of the core element 31. The threaded element 33 is made of a thermoplastic material and is injected into the core element 31 using a plastic injection molding process.

[0042] In the example, the internal thread 32 is designed as a single-start thread and therefore has a helically rotating thread tooth 321 which engages in a rotating thread gap 421 of the external thread 42 of the threaded spindle 4.

[0043] In the example, the gearing is formed by a gear ring 30 made of thermoplastic material, which is injection-molded onto the outside of the core element 31 using a plastic injection molding process. To create a particularly resilient positive connection, the core element 31 has positive locking elements 301 on its outer circumference in the form of grooves or projections that are embedded in the plastic of the gear ring 30.

[0044] In the through-opening 311, the core element 31 has a positioning section 34 in which the inner wall is cylindrical and smooth. The inner diameter of the through-opening 311, which corresponds to the outer diameter of the threaded element 33, is larger in the positioning section 34 than the outer diameter of the internal thread 32. The plastic injected into the positioning section 34 adheres firmly to the cylindrical inner wall, whereby the dimensional accuracy of the thread tooth 321 is ensured by the smooth inner wall and the rotationally symmetrical alignment with the internal thread 32.

[0045] The positioning section 34 is adjacent in the axial direction - in the Fig. 4, Fig. 5 and Fig. 9 right - a connecting section 35. The connecting section 35 has a groove-like recess formed radially from the inside in the through-opening 311, which has an inner diameter that is larger than the positioning section 34 and is therefore undercut. Accordingly, the plastic in the connecting section 35 effects a positive, non-releasable fixation of the threaded element 33 in the core element 31 in the axial direction. The inner wall in the connecting section 35 can also be smooth and cylindrical in the circumferential direction in order to avoid potentially disadvantageous shrinkage and distortion during solidification of the plastic.

[0046] Furthermore, the core element 31 has a crash support section 36, in which a one-piece support element 37 projects radially inward into the thread tooth 321. The support element 37 is designed to run helically around the pitch of the thread 32 and forms a thread projection that tapers conically inward - to the right in the figures. It is clearly visible that the support element 37 radially penetrates the circumferential thread gap 421 of the threaded spindle 42. As a result, it forms a positive connection effective in the axial direction, even if the thread tooth 321, which is formed entirely of plastic in the positioning section 34, is deformed or sheared off due to extremely high loads, such as can occur in the event of a crash. At least partially - preferably on the thread flanks - the thread tooth 321 is also overmolded with plastic in the crash support section 36, as shown in the Fig. 8 and Fig. 9 recognizable.

[0047] In the crash support section 36, the internal thread 32 can have a larger internal diameter relative to the positioning section 34, so that there is a larger radial play in the thread between the threaded spindle 4 and the internal thread 32.

[0048] As shown, the connecting portion 35 may preferably be arranged between the positioning portion 34 and the crash support portion 36.

[0049] Fig. Figure 6 shows a schematic exploded view of the individual elements of the gear wheel 3, which are normally permanently connected to one another. For clarity, the positioning section 34, the connecting section 35, and the crash support section 36 are labeled correspondingly on the threaded element 33 and the core element 31. Fig. 7 shows a further schematic exploded view of the individual elements - but without a gear ring - in particular of the threaded element 33. It can be seen therein that not only the internal thread 32 has a thread tooth 321, but that one or more thread turns made of plastic are formed in the area of the support element 37 on the outside of the crash support section 36.

[0050] On both axial end faces, rotating bearing rings 38 are formed in the core element 31, which form integrally formed raceways for rolling elements, for example balls 8. In a bearing arrangement, as in Fig. As shown in Figure 8, corresponding bearing rings 81 are fixed diagonally opposite the bearing rings 38 to form angular contact thrust bearings in the gear housing 25. Between the ball bearings formed by the bearing rings 38 and 81 together with the balls 8, the gear wheel 3 is supported on both sides by roller bearings. List of reference symbols 1 steering column 10 carrying unit 12 jacket pipe 14 Steering spindle 141 steering wheel end 16 Actuator 18 Swivel mechanism 100 console 102 Mounting hole 104 jacket unit 106 Swivel axis 107 Fastening element 110 slot 120 control levers 181 control lever 182 joint 183 Joint axis 184 Joint axis 2, 2' adjustment drive 20, 20' drive motor 22 snail 23 camps 24 Output shaft 25 Gearbox housing 3 gear wheel 30 Gearing 31 Core element 311 passage opening 32 internal thread 321 thread tooth 33 threaded element 34 Positioning section 35 connecting section 36 Crash support section 37 Support element 38 bearing ring 4, 4' threaded spindle 42 external thread 421 thread gap 43 Rod end 7 Stop element 71 indentations 8 ball 81 Bearing ring

Claims

[1] Gear wheel for an adjustment drive (2), which has a gear ring (30) which is mounted coaxially on the outside on a core element (31) which has an axial through-opening (311) in which a threaded element (33) is mounted, which has an axially continuous internal thread (32) with at least one helically rotating thread tooth (321), wherein the threaded element (33) is formed from a plastic as a plastic injection-molded part, which is injection-molded onto the core element (31) on an inner wall of the through-opening (311), characterized by , that a crash support section (36) is formed in the through opening (311), in which at least one support element (37) projects from the core element (31) into a thread tooth (321). [2] Gear wheel according to claim 1, characterized by that the through opening (311) has at least one smooth, cylindrical positioning section (34). [3] Gear wheel according to claim 1 or 2, characterized by that an undercut connecting section (35) is formed in the through opening (311). [4] Gear wheel according to one of the preceding claims, characterized by that the crash support section (36) is arranged in one end region of the through opening (311), and the positioning section (34) in the other, opposite end region. [5] Gear wheel according to claims 1 to 3, characterized by that a connecting section (35) is arranged between the positioning section (34) and the crash support section (36). [6] Gear wheel according to one of the preceding claims, characterized by that at least in a part of the crash support section (36) the internal thread (32) has an enlarged core diameter. [7] Gear wheel according to one of the preceding claims, characterized bythat the gear ring (30) is injection-molded from a plastic as a plastic injection-molded part on the outside of the core element (31). [8] Gear wheel according to one of the preceding claims, characterized by that the core element (31) has molded-in bearing rings (38). [9] Adjustment drive (2) for a motor-adjustable steering column (1) for a motor vehicle, comprising a gear wheel (3), a threaded spindle (4) engaging in an internal thread (32) of the gear wheel (3) and a drive unit (20) by which the gear wheel (3) can be driven in rotation relative to the threaded spindle (4), characterized in that the gear wheel (3) is designed according to one of claims 1 to 8. [10] Motor-adjustable steering column (1) for a motor vehicle, comprising an adjusting drive (2) which is arranged between a support unit (10) connectable to the body and a casing unit (104) rotatably receiving a steering spindle (14) and / or between casing tubes (12) of a casing unit (104) which are axially telescopically adjustable relative to one another and support the steering spindle (14). characterized by that the adjustment drive (2) is designed according to claim 9.

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