DE102019119128A1 - Steering gear for a motor vehicle - Google Patents

Abstract

The invention relates to a steering gear (1) for a motor vehicle, with a steering rod (2) which has rack teeth (2.3, 2.5), and a worm shaft (4, 11) which is rotatable about a worm axis (S, S ') and which with the rack toothing (2.3, 2.5) interacts to move the handlebar (2) relative to a housing (20) along a handlebar axis (L) of the handlebar (2). In order to provide a reliable and efficient steering gear with a motor drive, the invention provides that the worm shaft (4, 11) is coupled to a drive shaft (5, 12) of a motor unit (6, 13) in such a way that it can be rotated relative to the Drive shaft (5, 12) is at least limited.

Description

The invention relates to a steering gear for a motor vehicle with the features of the preamble of claim 1.

A rack and pinion steering is normally used in steering gears of conventional motor vehicles, in particular of passenger cars. A pinion shaft that is rotated by the steering wheel interacts with a rack that acts as a steering rod directly or indirectly - via external tie rods - on the steering levers of the wheels. The rack is pressed against the pinion of the pinion shaft via a spring-loaded pressure piece. Both the pinion shaft and the rack are arranged at least partially within a steering gear housing in which they are guided so that they can rotate or move. As a rule, the steering movement exerted by the driver is supported by a servomotor. One possibility is that the rack is connected to a threaded spindle or formed in one piece with it, the servomotor driving a spindle nut via a drive belt, which cooperates with the threaded spindle. The rotation of the spindle nut is converted into a translation of the handlebar by the interaction of the internal and external threads. Another possibility is to drive a worm wheel, which is fixedly attached to the pinion shaft in a rotationally fixed manner, via a worm shaft which is coupled to a servomotor. In the former solution, the drive belts are usually made of materials such as nylon or rubber. In the latter solution, the worm shaft and / or worm wheel are normally made of plastic. Therefore, both solutions are not very robust and a mechanical failure of a component usually leads to a complete failure of the steering assistance. Furthermore, transmission systems are known in the prior art in which a plurality of transmission stages are usually provided, which significantly impairs the efficiency.

Apart from classic power steering systems, there are also known steer-by-wire systems in which there is no direct power transmission from the steering wheel to the steering gear, i.e. these two systems are mechanically decoupled. The same can apply to autonomous driving systems in which a steering wheel is omitted or, if necessary, provided in addition. In principle, similar drives can be used in such driving systems as in power steering systems, but with the main difference that a failure of the power transmission would not only lead to a loss of steering assistance, but also to a complete loss of the vehicle's steerability.

The JP H01-168568 A discloses a steering gear for a rear axle of a motor vehicle. A drive wheel of a hypoid gear is connected to a shaft of an electric motor. The ring gear of the hypoid gear is in turn connected in a rotationally fixed manner to a worm shaft that interacts with a rack that acts as a steering rod on the steering levers of the wheels on both sides. The rack has helical teeth that run at an angle of less than 10 ° to the longitudinal axis of the rack. The worm shaft has a helix angle that is smaller than the angle of the helical teeth. The angle between the shaft axis and a plane perpendicular to the handlebar axis of the rack is equal to the difference between the helix angle and the helix angle.

The US 2016/0362130 A1 shows a method for characterizing a sliding friction state in an electrically assisted steering system with a rack, a toothed gear, which is arranged at one end of a steering shaft in meshing engagement with the rack, a steering motor, and a drive mechanism that provides a steering input to the steering system via the steering motor electrically assisted. A torsion bar and an inertia plate are connected to the steering shaft and a periodic steering control signal is transmitted from a controller to a rotary actuator while the steering motor and drive mechanism assist the steering input, thereby causing the steering shaft to rotate, via the torsion bar and inertia plate a calibrated range of steering angles. Displacement of the rack from a center position via a linear actuator is measured, an axial force is applied to the rack, and a steering torque output along the steering shaft is measured.

The US 7 900 890 B2 Fig. 3 shows a worm-rack-and-pinion type gear unit. A toothed rack has a curved side section that forms an ellipsoidal surface. This interacts with the turns of a worm shaft, which has a frustoconical body. The worm shaft is coupled to a motor, the rotary movement of which is converted into a linear movement of the rack. The gear unit is designed to be self-locking.

The US 2014/0041957 A1 discloses a power steering system with a steering shaft arranged along a steering shaft axis. A servo drive shaft defines a drive shaft axis and is arranged in a plane essentially perpendicular to the steering shaft axis. The servo drive shaft is opposed to the vehicle body by a first bearing assembly and a second bearing assembly supported. A worm shaft on the servo drive shaft cooperates with a worm wheel on the steering shaft. The first bearing assembly is designed as an eccentric bearing bush.

In view of the state of the art shown, the provision of a reliable and efficient steering gear, in which the steering action is at least motor-assisted, still offers room for improvement.

The invention is based on the object of providing a reliable and efficient steering gear with a motor drive.

According to the invention, the object is achieved by a steering gear having the features of claim 1, the subclaims relating to advantageous embodiments of the invention.

It should be pointed out that the features and measures listed individually in the following description can be combined with one another in any technically meaningful manner and show further embodiments of the invention. The description additionally characterizes and specifies the invention, particularly in connection with the figures.

The invention provides a steering gear for a motor vehicle. The motor vehicle can be, for example, a car or a truck. The steering gear is of course used to steer at least one vehicle wheel, whereby a force for steering this vehicle wheel can be transmitted through the steering gear and possibly increased or reduced by a translation or reduction.

The steering gear has a handlebar. The handlebar is provided to transmit a force for steering the at least one vehicle wheel, for which purpose it can normally be connected directly or indirectly to a steering lever in the assembled state. It has rack teeth. Under certain circumstances, a section of the handlebar can be designed as a rack, i.e. the rack teeth can be designed in one piece with the handlebar. Preferably, the handlebar is made in one piece, typically made of metal, for example steel.

The steering gear can in particular be part of a steer-by-wire system or an autonomous steering system, in both cases therefore belong to a system in which there is no mechanical power transmission from a steering wheel to the vehicle wheels. In this case, the handlebar does not have any teeth that interact with a pinion that, for example, transmits a force from the steering wheel. Alternatively, however, such a toothing can also be provided if the steering gear is part of a power steering system.

Furthermore, the steering gear has a worm shaft which can be driven about a worm axis and which interacts with the rack teeth in order to move the handlebar relative to a housing along the handlebar axis. While the steering rod has the rack teeth, the worm shaft has a turn (or a worm thread) designed to engage with the rack teeth. The worm shaft can be driven around a screw axis, i.e. it can be driven by a motor. In the operating state, the worm shaft is coupled to a motor, usually an electric motor, which drives it so that it rotates around the worm axis. This screw axis normally forms the central axis of the screw shaft. Due to the interaction of the worm shaft with the rack teeth, the rotational movement of the worm shaft is converted into a displacement (i.e. a translational movement) of the steering rod along the steering rod axis. The handlebar axis can in particular coincide with the Y-axis (transverse axis) of the vehicle.

In the broadest sense, the housing forms a type of frame or base on which the parts of the steering gear mentioned here and possibly other components are mounted. As a rule, the housing completely or partially surrounds at least some of these parts. It is usually composed of several interconnected parts. When assembling the motor vehicle, it can be connected to the chassis of the vehicle together with parts of the steering gear as a pre-assembled assembly.

According to the invention, the worm shaft is coupled to a drive shaft of a motor unit in such a way that rotatability with respect to the drive shaft is at least limited. The motor unit is usually a single motor, in particular an electric motor. The drive shaft is coupled to or firmly connected to the rotor of the motor unit. Under certain circumstances it can also be viewed as part of the rotor. By coupling the worm shaft to the drive shaft, the rotatability of the worm shaft with respect to the drive shaft is at least limited. In particular, the coupling can be non-rotatable or non-rotatable, ie the rotatability can be completely prevented. However, it would also be possible to rotate, for example due to an elastic connection. Such rotatability is limited, for example to a few degrees. Thus, the rotary movement of the worm shaft is immediate, without any further gear stages Coupled rotary movement of the motor unit. There are therefore no unnecessary frictional losses, which ensures high efficiency of the gear unit. There is also no need for a drive belt. As will be explained in the following, the essential components of the gear unit can be implemented in a robust manner, which makes a loss of power transmission from the motor unit to the handlebar unlikely.

Usually the steering rod and the worm shaft are preloaded against each other. That is, in the operating state, a preload acts on the steering rod in the direction of the worm shaft and / or a preload acts on the worm shaft in the direction of the steering rod. The preload can improve the engagement between the worm shaft and the rack toothing and, for example, production tolerances or temperature-related deformations can be compensated for. Normally, a spring element is provided which directly or indirectly acts on the steering rod or the worm shaft with the preload. In particular, a pressure piece can act under prestress on the steering rod towards the worm shaft and have a guide section for the steering rod. Such a pressure piece is normally biased by a spring element and is mounted in the housing together with this spring element.

The coupling of the drive shaft and the worm shaft can be implemented in different ways. For example, it would be compatible with this that the connection, viewed in isolation, allows a slight axial displacement (that is, in the direction of the drive shaft). It would also be conceivable that the worm shaft and the drive shaft are connected to one another via a universal joint or a coupling. The worm shaft can optionally also be rigidly connected to the drive shaft. That is, it can be detachably connected to the drive shaft, for example by a screw connection, or non-detachable, for example by welding, soldering or gluing. In addition, it is possible that the worm shaft is manufactured in one piece with the drive shaft, for example in such a way that both elements are manufactured from one piece by primary molding or by machining. According to a preferred embodiment, the worm shaft is connected to the drive shaft by an elastic coupling element. With such a coupling element, on the one hand, positioning errors between the worm shaft and drive shaft can be compensated for, and on the other hand, the transmission of noises and vibrations can be reduced. In general, the presence of an elastic coupling element can lead to the fact that the coupling of the worm shaft to the drive shaft is not completely rotationally fixed, but rather that both elements can be slightly rotated relative to one another. However, this does not normally limit the function of the steering gear or does not limit it to any significant extent.

In terms of a robust, long-lasting design of the steering gear, it is preferred that the rack teeth and the worm shaft are made of metal, in particular steel. This is in contrast, for example, to worm gear drives, which are often made of plastic parts in the power steering in the prior art. As already mentioned above, the rack teeth can be formed in one piece with the handlebar, both parts of course being made of the same metal. Various metals can be used, with steel basically representing an advantageous compromise with regard to the mechanical properties on the one hand and the material and processing costs on the other. Under certain circumstances, however, alloys of aluminum, copper or other metals could also be used.

In particular, the worm shaft can be cylindrical. That is, the radius of the turns of the worm shaft is constant along its entire length. If the rack teeth run in one plane, the axis of rotation of the worm shaft runs in the same plane in this embodiment. The maximum possible tooth engagement is achieved by a cylindrical configuration, which is associated with low local loads. This in turn reduces wear. Alternatively, a conical or truncated cylinder design of the worm shaft would also be conceivable, in which the radius of the turns decreases along the worm shaft. In this case the worm axis runs at an angle to the rack toothing plane.

Normally the worm axis is not parallel to the handlebar axis. The alignment of the rack teeth is determined on the one hand by the helix angle of the worm shaft and on the other hand by the angle of attack between the worm axis and the steering rod axis. Particularly in the case of a cylindrical design of the worm shaft, the latter angle of attack must normally have a certain minimum amount, for example so that the motor unit can be arranged offset to the steering rod. In principle, it would be conceivable that the angle of attack between the worm axis and the steering rod axis on the one hand and the pitch angle of the worm shaft on the other hand compensate each other so that the rack teeth are straight, i.e. all the teeth are perpendicular to the steering rod axis. Usually, however, the rack teeth are designed as helical teeth. Ie the individual teeth run in one Angle to the handlebar axis that is different from 90 °.

A helix angle of the helical toothing is preferably at most 45 °. In this context, the helix angle is measured relative to a plane that runs perpendicular to the handlebar axis and is referred to here as the transverse bar plane. More preferably, the helix angle can be at most 30 ° or at most 20 °. Since the power transmission between the worm shaft and the rack teeth is predominantly perpendicular to the flank line or head line of the teeth of the rack teeth, a comparatively small helix angle is advantageous. In general, the helix angle can be selected taking into account various aspects, namely the efficiency, the necessary gear ratio and the available installation space. As a rule, the choice of a certain helix angle represents a compromise in this regard.

Furthermore, it is preferred that an angle of attack between the worm axis and the handlebar axis is at most 60 °. Furthermore, the angle of attack can be at most 50 ° or at most 40 °. In the case of a cylindrical worm shaft, this angle of incidence normally corresponds to the sum of the helix angle of the helical toothing and the helix angle of the worm shaft. In this respect, the limitation of the above-mentioned helix angle is connected to a certain extent with a limitation of the angle of attack. This is particularly true since the helix angle of the worm shaft cannot be chosen to be arbitrarily large.

The possible uses of the steering gear according to the invention are different. For example, a handlebar can be designed to steer two wheels. The handlebar has two end sections, each of which is designed for direct or indirect connection to a steering lever of a vehicle wheel. This means that when the handlebar is shifted in the direction of the handlebar axis, both wheels are steered at the same time. The rack teeth of the handlebar are arranged between the end sections, for example in the middle. Depending on the arrangement of other vehicle components and the available installation space, the rack teeth could also be arranged offset relative to the center of the steering rod. Alternatively, the handlebar can also be designed to steer exactly one wheel. Accordingly, the handlebar is only designed for connection to a steering lever. Overall, in this case two steering rods are provided for two wheels arranged on different sides of the vehicle, each of which is designed to steer one wheel each. A single motor unit must be comparatively powerful and designed to steer two wheels, which can be problematic with regard to the installation space, while a lower motor power, combined with a smaller size, is sufficient to steer a single wheel.

According to a development of the invention, the steering gear can have two motor units and two worm shafts, each of which is coupled to a drive shaft of a motor unit and interacts with a rack toothing of the handlebar. In other words, in this embodiment, the force or power required to move the handlebar is generated by two separate motor units. It goes without saying that these two motor units can be controlled via a higher-level control unit in such a way that they interact to drive the handlebar. Each of the motor units has a drive shaft to each of which a worm shaft is coupled. The coupling at least limits the rotatability of the respective worm shaft with respect to the associated drive shaft. In particular, the coupling can be non-rotatable or non-rotatable. Each worm shaft in turn interacts with at least one rack toothing of the steering rod. The preferred configurations described above with regard to the worm shaft and the rack teeth can be used in a corresponding manner, in particular, on both worm shafts and the respectively assigned rack teeth. In this context, the most varied of configurations are possible. For example, the handlebar could have a single rack tooth system, the worm shafts interacting with sections of the rack teeth that are offset from one another in the direction of the handlebar axis. Alternatively, the handlebar can have two separate toothed rack teeth. On the one hand, these can be offset from one another along the handlebar axis. Alternatively or additionally, it would also be conceivable, for example, for the rack teeth to be offset tangentially to one another with respect to the handlebar axis. For example, they could be formed on opposite sides of the handlebar. In this case the worm shafts are arranged on opposite sides of the handlebar. The steering rod is thus to a certain extent enclosed between the worm shafts, which is why, for example, a spring-loaded pressure piece can be dispensed with. A wide variety of design options are available, with the two rack teeth being able to be inclined in different directions with respect to the transverse plane of the rod, in particular in the case of helical teeth. This allows the worm shafts to act in the direction of the steering rod axis Forces reinforce each other, while forces acting perpendicular to the handlebar axis or torques resulting therefrom cancel each other out. In this way, for example, bearings can be relieved, by means of which the steering rod is mounted relative to the housing.

As already described above, the transmission unit according to the invention is particularly suitable for steer-by-wire systems or autonomous steering systems. However, the application is not limited to this. Rather, the gear unit can also be used as part of a power steering system. In a corresponding embodiment, a pinion shaft, which is provided for the torque-transmitting connection with a steering wheel, interacts with the handlebar. When installed, the pinion shaft is connected to the steering wheel to transmit torque, i.e. there is a mechanical, torque-transmitting connection. In principle, the driver can directly exert a steering force on the pinion shaft and thus on the handlebar via the steering wheel, the steering force being supported by the action of the (at least one) motor unit, the worm shaft and the rack teeth. The corresponding pinion shaft carries a pinion in a known manner, which is normally designed as a gear with straight teeth or possibly also with helical teeth. This in turn is combined with an associated rack toothing which is formed on the handlebar. As a rule, this is an additional rack toothing that is optimized for interaction with the pinion, while the above-mentioned rack toothing is optimized for interaction with the worm shaft. However, it cannot be ruled out that both the pinion and the worm shaft could interact with different sections of one and the same rack toothing.

• 1 eine Draufsicht eines Teils eines erfindungsgemäßen Lenkgetriebes gemäß einer ersten Ausführungsform;
• 2 eine Draufsicht des Lenkgetriebes aus 1;
• 3 eine Draufsicht eines erfindungsgemäßen Lenkgetriebes gemäß einer zweiten Ausführungsform;
• 4 eine Draufsicht eines erfindungsgemäßen Lenkgetriebes gemäß einer dritten Ausführungsform;
• 5 eine Draufsicht eines erfindungsgemäßen Lenkgetriebes gemäß einer vierten Ausführungsform; sowie
• 6 eine Draufsicht eines erfindungsgemäßen Lenkgetriebes gemäß einer fünften Ausführungsform.

Further advantageous details and effects of the invention are explained in more detail below on the basis of different exemplary embodiments shown in the figures. It shows

• 1 a plan view of part of a steering gear according to the invention according to a first embodiment;
• 2 a top view of the steering gear 1 ;
• 3 a plan view of a steering gear according to the invention according to a second embodiment;
• 4th a plan view of a steering gear according to the invention according to a third embodiment;
• 5 a plan view of a steering gear according to the invention according to a fourth embodiment; such as
• 6th a plan view of a steering gear according to the invention according to a fifth embodiment.

In the different figures, the same parts are always provided with the same reference numerals, which is why they are usually only described once.

1 and 2 show a first embodiment of a steering gear according to the invention 1 for a car, where 1 a plan view of part of the steering gear 1 and 2 a top view of the entire steering gear 1 shows. The steering gear 1 is part of a steer-by-wire system or an autonomous steering system, so that there is no mechanical power transmission from a steering wheel of the vehicle to the wheels. In the figures, the X-axis and Y-axis of the vehicle are in accordance with the intended installation position of the steering gear 1 drawn.

The steering gear has a handlebar 2 on, which extends along a handlebar axis L. extends along this opposite a (in 2 schematically shown) housing 20th is movable. Wheel-side end sections 2.1 , 2.2 the handlebar 2 are with steering levers 15th connected, via which the alignment of (not shown) vehicle wheels is influenced. The handlebar 2 also has rack and pinion teeth 2.3 on which is integral with the rest of the handlebar 2 is made of steel. A worm shaft 4th works with the rack teeth 2.3 together, making the handlebar 2 along the handlebar axis L. opposite the housing 20th is movable. The handlebar can be used to improve the engagement 2 and the worm shaft 4th be biased against one another in a manner not shown here. The worm shaft 4th is around a screw axis S. rotatable by a drive shaft 5 an electric motor 6th is given. The latter is outside the case 20th arranged, but could alternatively also be arranged within the same. For storage opposite the housing 20th are two pivot bearings shown schematically 7th intended. The worm shaft 4th is twist-proof with the drive shaft 5 connected and can also be made in one piece with this, for example from steel. Alternatively, however, a coupling element (shown here very schematically by a dashed contour) can also be used 3 to connect the worm shaft 4th with the drive shaft 5 be provided, which can be at least partially elastic. In this way, position deviations can be compensated and the transmission of noise or vibrations can be suppressed. In the other figures is the coupling element 3 omitted for the sake of clarity, but it can be supplemented in any of the embodiments shown.

As in 1 is recognizable, is the rack teeth 2.3 designed as helical teeth and has a helix angle α opposite one to the steering shaft axis L. vertical bar transverse plane Q on. The helix angle α is, however, smaller than 45 °, in the present example approx. 20 °. In this and the following exemplary embodiments, the screw axis runs S. each within the XY plane of the vehicle. Alternatively, the screw axis could S. also have any other orientation, since in contrast to, for example, a pinion shaft of a conventional steering gear, no mechanical connection to a steering wheel is necessary. An angle of attack β the screw axis S. opposite the handlebar axis L. is significantly smaller than 60 °, in the present example approx. 30 °.

1 and 2 show an embodiment of a steering gear 1 intended for a steer-by-wire system or an autonomous steering system. There is no mechanical connection to the handlebar 2 on a steering wheel. The electric motor 6th is controlled in the case of a steer-by-wire system as a function of the angle of a steering wheel determined by sensors or by specifications of a control unit of an autonomous steering system.

3 shows a second embodiment of a steering gear according to the invention 1 , which is also intended for a steer-by-wire system or an autonomous steering system. In this case the handlebar is 2 however, intended for steering a single vehicle wheel, which is why only one end section 2.1 with a steering lever 15th connected is. It goes without saying that a corresponding, for example, mirror-symmetrical steering gear for the opposite vehicle wheel 1 is provided. The fact that in this embodiment the electric motor 6th only has to provide the driving force for steering an individual vehicle wheel, it can be designed to be less powerful and therefore smaller. Of course, the illustrated embodiment also enables the steering angles of the two vehicle wheels to be set differently, if this is considered advantageous.

4th shows a third embodiment of a steering gear according to the invention 1 which largely coincides with the in 1 and 2 embodiment shown is identical and will not be explained again. However, the steering gear shown is 1 designed as a power steering system, with the steering rod 2 a second rack toothing 2.4 has, with which a pinion 8 which is coupled to a pinion shaft 9 engages. This is through at least one pivot bearing 10 rotatable on the housing 20th stored and mechanically coupled to a steering wheel in a manner not shown here. A set steering angle of the steering wheel can be read out via sensors, after which a control unit controls the electric motor 6th can control according to the determined steering angle to a supporting drive force on the handlebar 2 exercise. In the embodiment shown, the pinion shaft 9 runs parallel to the X-axis, but could also have a different course, for example also outside the XY plane.

5 shows a fourth embodiment of a steering gear according to the invention 1 . In contrast to the first exemplary embodiment, there are two worm shafts 4th , 11 provided with two separate rack teeth 2.3 , 2.5 work together. The second worm shaft 11 is with a drive shaft 12 a second electric motor 13th connected and via pivot bearings 14th around a second screw axis S ' rotatably mounted. The helix angle of the second rack teeth 2.5 corresponds to the amount of the first rack toothing 2.3 , however, are the rack teeth 2.3 , 2.5 in different directions against the bar transverse planes Q inclined. Also the angle of attack of the two screw axes S. , S ' opposite the handlebar axis L. are equal in amount, but opposite. When operating the two electric motors 6th , 13th add up in the direction of the handlebar axis L. Forces acting on the steering rod via the two worm shafts 4th , 11 on the rack teeth 2.3 , 2.5 be exercised. The forces that also occur transversely to the handlebar axis L. however, cancel each other out, which may reduce the load on the handlebar 2 reduced as well as their storage on the housing 20th simplified. In addition, each of the electric motors has the necessary drive power 6th , 13th naturally less than with a single electric motor 6th , 13th , which enables a smaller and space-saving design.

6th shows a fifth embodiment of a steering gear according to the invention 1 . In this embodiment, too, there are two worm shafts 4th , 11 provided, but on opposite sides of the handlebar 2 are arranged. Accordingly, in addition to the in 6th visible first rack teeth 2.3 a second, in 6th concealed, rack teeth on the opposite side of the handlebar 2 educated. This can also have a helix angle the amount of which is that of the first rack toothing 2.3 corresponds, the second rack teeth, however, opposite to the first rack teeth 2.3 is inclined. As in 5 can thereby transversely to the handlebar axis L. acting forces compensate each other. As the handlebar 2 in a way between the worm shafts 4th , 11 is included, can also be dispensed with a pressure piece to the handlebar 2 against one of the worm shafts 4th , 11 pre-tension.

List of reference symbols

1

Steering gear

2

Handlebar

2.1, 2.2

End section

2.3, 2.4, 2.5

Rack teeth

3

Coupling element

4, 11

Worm shaft

5, 12

drive shaft

6, 13

Electric motor

7, 10, 14

Pivot bearing

15th

Steering lever

20th

casing

L.

Steering rod axis

Q

Bar transverse plane

S, S '

Spindle axis

X

X axis

Y

Y axis

α

Helix angle

β

Angle of attack

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• JP H01168568 A [0004]
• US 2016/0362130 A1 [0005]
• US 7900890 B2 [0006]
• US 2014/0041957 A1 [0007]

Claims (10)

Steering gear (1) for a motor vehicle, with a steering rod (2) which has rack teeth (2.3, 2.5), and a worm shaft (4, 11) which can be driven about a worm axis (S, S ') and which is connected to the rack teeth (2.3 , 2.5) cooperates to move the handlebar (2) relative to a housing (20) along a handlebar axis (L) of the handlebar (2), characterized in that the worm shaft (4, 11) is connected to a drive shaft (5, 12) a motor unit (6, 13) is coupled so that the rotatability relative to the drive shaft (5, 12) is at least limited. Steering gear according to Claim 1 , characterized in that the worm shaft (4, 11) is connected to the drive shaft (5, 12) by an elastic coupling element (3). Steering gear according to one of the preceding claims, characterized in that the rack teeth (2.3, 2.5) and the worm shaft (4, 11) are made of metal, in particular steel. Steering gear according to Claim 3 , characterized in that the worm shaft (4, 11) is cylindrical. Steering gear according to Claim 3 , characterized in that the rack teeth (2.3, 2.5) are designed as helical teeth. Steering gear according to one of the preceding claims, characterized in that a helix angle (a) of the helical toothing is at most 45 °. Steering gear according to Claim 4 or 5 , characterized in that an angle of attack (β) between the screw axis (S, S ') and the handlebar axis (L) is at most 60 °. Steering gear according to one of the preceding claims, characterized in that a handlebar (2) is designed to steer two wheels, or to steer precisely one wheel. Steering gear according to one of the preceding claims, characterized in that it has two motor units (6, 13) and two worm shafts (4, 11), each of which is coupled to a drive shaft (5, 12) of a motor unit (6, 13) and interacts with a rack toothing (2.3, 2.5) of the steering rod (2). Steering gear according to one of the preceding claims, characterized in that a pinion shaft (9), which is provided for the torque-transmitting connection with a steering wheel, interacts with the steering rod (2).

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