WO2011058115A2

WO2011058115A2 - Steering comprising an electric motor for steering assistance

Info

Publication number: WO2011058115A2
Application number: PCT/EP2010/067317
Authority: WO
Inventors: Werner M. Bless
Original assignee: Bless Werner M
Priority date: 2009-11-12
Filing date: 2010-11-11
Publication date: 2011-05-19
Also published as: WO2011058115A3; DE102009046648A1

Abstract

According to a first concept of the invention, a steering for a motor vehicle comprises an electric motor (24) for steering assistance and a tie rod (10). The electric motor (24) comprises a rotor (28) coupled to a pinion (16). The tie rod (10) comprises a toothing that engages with the pinion (16). The pinion (16) is connected gearlessly to the rotor (28) of the electric motor (24). According to a second concept, an electric motor assembly is provided in the steering for steering assistance, which acts on the tie rod by means of an actuating element. A measuring device is arranged between the actuating element and the electric motor assembly to measure a force that is applied to the actuating element and a torque that acts on the actuating element.

Description

Steering with an electric motor for steering power assistance

The invention relates to a steering system for a motor vehicle having an electric motor for steering power assistance.

Power steering with electric motor are well known. Thus, DE 39 1 1 088 A1 shows a power steering system which is designed as a rack and pinion steering. A tie rod has two toothed areas. A steering pinion connected to the steering column meshes with one of these areas, while one auxiliary pinion meshes with the other area. The auxiliary power pinion is driven via a reduction gear by an electric motor.

From DE 10 2008 021 591 A1 an electromechanical rack and pinion steering is known. A hollow shaft motor is arranged on a steering column approach and acts via a reduction gear on the steering column approach or a steering pinion.

In general, an important consideration in power steering systems is that forces acting on the wheels of the motor vehicle are appropriately reported back to the driver. For example, the driver should be able to feel clearly on the steering wheel when ruts affect the directional stability of the vehicle. A lack of feedback leads to an unsatisfactory driving impression and can even affect driving safety.

The invention therefore has the object to provide a power steering system for a motor vehicle, which allows for low construction costs a particularly good feedback to the driver of the motor vehicle. The invention is defined by the independent claims. The dependent claims relate to optional features of some embodiments of the invention. According to a first aspect of the invention, the above object is achieved by a rack and pinion steering in which a pinion, which engages in a toothing of the tie rod, is gearless connected to the rotor of an electric motor for power steering assistance. In such embodiments, the electric motor in a de-energized operating state ("free running") affects the movement of the tie rod - and thus the feedback to the driver - not or only slightly. This is because the gearless rotor connected to the pinion is easily rotatable. If, on the other hand, a reduction gear were present, then slight movements of the tie rod by the friction and the breakaway torque of the reduction gear, as well as by the correspondingly translated moment of inertia of the engine, would be significantly hindered.

The term "gearless" is to be understood in the present document in particular that no reduction gear between the electric motor and the pinion is connected. In some embodiments, the electric motor and the pinion directly - for example, via a rigid shaft or even in one piece - connected to each other. However, it can also be provided at least one joint which rotatably connects the electric motor and the pinion each other. Here, the term "rotationally fixed" in the present document includes a direct connection as well as a connection via at least one joint, even if the joint possibly causes a certain rotational angle error.

In some embodiments, the pinion is a steering pinion, which is also gearless - in some embodiments, rotationally fixed or direct - coupled to a steering column. It goes without saying that a connection via shaft pieces and / or joints can also take place here. In these embodiments, furthermore, a torque-measuring device can be coupled between the steering column and the steering pinion, as corresponds to the currently customary arrangement in the case of power steering systems. In other embodiments, however, the pinion is an auxiliary power pinion provided in addition to the steering pinion. In this case, in some embodiments, the entire steering assist assembly of the actual steering gear - which can be configured in a known per se - structurally separate. This results in a particularly high flexibility in the adaptation to a given space.

According to a second aspect of the invention, the above-mentioned object is achieved by a steering system for a motor vehicle in which an electric motor assembly for steering power assistance via an actuating element acts on a tie rod, wherein a measuring device between the actuating element and the electric motor assembly is arranged to one on the actuating element applied force or acting on the actuator torque to measure. In other words, in these embodiments, the measuring device is assigned functionally to the auxiliary power assembly. The otherwise common measuring device on the steering gear can then be omitted in many embodiments or, if it is still provided, lead to improved measurement accuracy or increased redundancy. In some embodiments, the electric motor assembly includes an electric motor and a reduction gear, wherein the measuring device is disposed between the actuating element and the reduction gear. These refinements have the advantage that the measuring path of the measuring device, at least in an electroless operating state ("freewheeling operation") of the electric motor assembly corresponds to a freewheeling region for the tie rod, in which the movement of the tie rod is not or only slightly inhibited.

In some embodiments, the measuring device has at least one spring element and a sensor. The at least one spring element may be, for example, at least one web formed like a spoke in a wheel or at least one web extending between two shaft sections in the axial direction. The actuator may be in different embodiments, a pinion - in particular a steering pinion or an auxiliary power pinion - or a ball nut or have.

Further features, advantages and objects of the invention will become apparent from the accompanying schematic drawings of several embodiments. 1 A and 1 B each show a perspective view of components of a steering system in a first exemplary embodiment,

1 C is a view obliquely from above and front of the first embodiment in a direction normal to the tie rod and normal to steering column,

1 D is a side view of the first embodiment in a direction along the tie rod and normal to the steering column,

2A and 2B are each a perspective view of components of a steering in a second embodiment,

2C is a front view of the second embodiment in a direction normal to the tie rod, Fig. 2D is a side view of the second embodiment in a direction along the tie rod,

3A is a perspective view of a built-in housing steering according to the second embodiment,

3B is a plan view of the embodiment of FIG. 3A in a direction normal to the tie rod, Fig. 3C is a rear view of the embodiment of FIG. 3A in one

4A shows a perspective view of a steering system built into a housing according to a third exemplary embodiment,

4B is a plan view of the embodiment of FIG. 4A in a

Direction normal to the tie rod,

Fig. 4C is a rear view of the embodiment of FIG. 4A in one

Direction normal to the tie rod,

5A is a perspective view of components of a steering in a fourth embodiment,

5B is a plan view of the fourth embodiment in a direction normal to the tie rod, Fig. 5C is a view obliquely from below on the fourth embodiment in a direction normal to the tie rod,

5D is a side view of the fourth embodiment in a direction along the tie rod,

6A is a perspective view of components of a steering in a fifth embodiment,

6B is a plan view of the fifth embodiment in a direction normal to the tie rod, 6C is a front view of the fifth embodiment in a direction normal to the tie rod,

7A is a perspective view of components of a steering in a sixth embodiment,

Fig. 7B is a view obliquely from the top and front of the sixth embodiment in a direction normal to the tie rod and normal to steering column, Fig. 7C is a view obliquely from above and behind the sixth embodiment in a direction along the steering column, in the direction of the driver .

8A is a perspective view of components of a steering in a seventh embodiment,

8B is a view obliquely from above and in front of the seventh embodiment in a direction normal to the tie rod and normal to steering column,

8C is a view obliquely from above and behind on the seventh embodiment in a direction along the steering column,

9A is a perspective view of components of a steering in an eighth embodiment, Fig. 9B is a plan view of the eighth embodiment in a direction normal to the tie rod,

9C is a side view of the eighth embodiment in a direction along the tie rod,

10A and 10B each show a perspective view of components of a steering in a ninth embodiment, 10C is a view obliquely from below and on the front of the ninth embodiment in a direction along the steering column, against the line of sight of the driver,

1 1 A is a sectional view of components of a steering in a tenth embodiment along the center axis of the tie rod, as shown as section A-A in Fig. 1 1 B, Fig. 1 1 B is a cross section of the tenth embodiment,

1 1 C is an enlarged view of the marked in Fig. 1A with the circle C area, Fig. 1 1 D is a side view of the tenth embodiment in a direction normal to the tie rod,

Fig. 1 1 E an exploded view of components of the tenth embodiment, and

Fig. 1 1 F is an enlarged view of the in Fig. 1 1 E marked with the circle F spring package.

1A-1D show a first embodiment in which a tie rod 10 in a region 12, which is located near a steering column (not shown), a toothing 14 has. It is understood that the toothing 14 and the steering pinion 16 can be configured in a variety of different designs. While FIGS. 1A-1D show a simple embodiment of a rack-and-pinion steering system, alternative embodiments provide progressive steering systems, for example according to EP 1 841 635 B1, in which the teeth 14 and the steering pinion 16 are complexly formed and optionally consist of several parts , The steering pinion 16 is connected to a steering shaft part 18 or formed as a toothing on the steering shaft part 18. The steering shaft part 18 is in turn in a conventional manner - for example via a universal joint (not shown) - coupled to the steering column. The steering shaft part 18 has a torque-measuring device 20, which responds to the steering column controlled via the steering torque. In the present embodiment, the torque-measuring device 20 is configured as a tubular portion of the steering shaft portion 18 having cuts 22, between which thin webs of the steering shaft portion 18 extending in the axial direction. These webs bend depending on the

Steering torque, so that the steering pinion 16 facing portion of the steering shaft portion 18 relative to the steering column facing portion rotates. A sensor (not shown) measures the rotation and generates a corresponding measurement signal, which is evaluated by control electronics (not shown).

It is understood that the torque-measuring device 20 may be configured differently in alternative embodiments. For example, the torque-measuring device 20 in a conventional manner have a torsion bar whose rotation caused by the steering torque is scanned by a suitable sensor. In other alternative embodiments, the torque-measuring device 20 may have one or more springs, which are arranged between two sections of the steering shaft part 18.

The sensor (not shown) for sensing the rotation or relative movement produced by the steering torque in the torque measuring device 20 can also be designed in many different ways, for example as a piezo sensor or as an optical sensor or as an electromagnetic sensor that is sensitive to a change the shielding of a permanent magnetic field responds. In the steering system according to the invention, an electric motor 24 is further provided for steering power assistance. In the embodiment of FIGS. 1A-1D, the electric motor 24 is connected directly to the steering pinion 16 via a short shaft 26. Of the Electric motor 24 is configured in the present embodiment as an external rotor. A bell-shaped rotor 28 has an outer magnetic ring 30 and a perforated connecting wheel 32, which connects the magnetic ring 30 with the shaft 26. An annular stator 34 is disposed within the magnet ring 30 and in the present embodiment has an inner stator ring 36 with a plurality of magnet windings 38.

An essential feature of the present embodiment is that the rotor 28 via the shaft 26 - or in alternative embodiments, another connecting piece or a one-piece extension - gearless coupled to the steering pinion 16. This embodiment has the considerable advantage that the electric motor 24 in the freewheeling movement of the tie rod 10 barely opposes resistance and thus excellent feedback of road influences on the steering column - and the steering wheel to the driver - allowed.

It is understood that the electric motor 24 may be configured in different ways. In addition to the design described so far as external rotor configurations are also provided as a pancake or internal rotor. The electric motor 24 may be designed brushless or with brushes, and the magnet windings may be part of the rotor and / or part of the stator. Desirable in many embodiments, a sufficiently high torque with the lowest possible weight and low cost and the smallest possible moment of inertia. It is understood that the electric motor 24 must be suitably dimensioned to afford the desired power steering even without reduction gear. This is achieved in particular by the combination of a relatively large rotor diameter with a relatively small pinion - here the steering pinion 16. For example, in some embodiments, a steering force of about 3,000 N acting laterally on the tie rod 10 may be desirable. If about 1 500 N of these are applied as a manual torque via the steering wheel, approximately 1 500 N remain, which the electric motor 24 must provide. At a typical torque of the electric motor 24 in the range of 9 - 22 Nm, this force is available when the pinion - here the steering pinion 16 - has a radius in the range of 6-15 mm. The torque just mentioned, of the order of 9-22 Nm, may for example be generated by an electric motor 24 having a diameter of approximately 20 cm and 4 cm in height. The electric motor 24 may have, for example, an operating voltage of 12 V or 24 V or 70 V or 200 V or 400 V and a maximum power consumption of 3 kW. Generally, the diameter of the rotor - for example of the rotor 28 - by at least a factor of 5 or 10 or 15 greater than the diameter of the pinion connected to the electric motor 24 - here the steering pinion 16, but in other embodiments also a Hilfskraftritzels - be. In the embodiment shown in Fig. 1 A-1 D, a single pinion - namely the steering pinion 16 - - provided, on which both the manual torque of the driver and the auxiliary torque of the electric motor 24 act. This embodiment is particularly component-saving and therefore inexpensive. In other embodiments, however, separate assemblies for the manual torque and the auxiliary torque are provided, as shown for example in the embodiment of FIG. 2A-2D.

In the embodiment according to FIGS. 2A-2D, the tie rod 10 has two regions 12, 40 with teeth 14, 42. The first region 12 corresponds to the region already described above in connection with FIGS. 1A-1 D, in which the steering pinion (not shown in FIGS. 2A-2D) engages. Separated therefrom, the second region 40 is provided with the toothing 42. An auxiliary power pinion 44 meshes with the toothing 42. The electric motor 24 is connected in the embodiment described here via the shaft 26 with the auxiliary power pinion 44. Again, thus provided by the electric motor 24 auxiliary steering force acts directly - without reduction gear - on the tie rod 10th The embodiment according to FIGS. 2A-2D is somewhat more complicated than the embodiment described above according to FIGS. 1A-1D, but it increases the possibilities of design and construction. In particular, an already existing design of the steering gear can be maintained unchanged, and the power unit can, depending on the available space, at a suitable location along the tie rod 10 and be mounted in a suitable orientation. Because of the relatively large electric motor 24, this more flexible adaptability of the construction to given installation space conditions can represent a considerable advantage. Figs. 3A-3C are external views of the housing-mounted embodiment of Figs. 2A-2D. In particular, the tie rod 12 is in a

Tie rod housing 46, and the electric motor 24 is located in a motor housing 48. Furthermore, a housing 50 for the steering gear - in particular the steering pinion 16 - and the torque-measuring device 20 is provided.

It is understood that various modifications of the embodiments described so far are possible in order to adapt the construction to the available installation space. For example, in the embodiment according to FIGS. 2A-2D, the shaft 26, which connects the rotor 28 of the electric motor 24 to the auxiliary power pinion 44, is relatively short. In particular, in embodiments in which the electric motor 24 is arranged below the tie rod 10, it may be desirable to extend this shaft 26. In this way, a lower center of gravity of the steering - and thus the entire motor vehicle - can be obtained, and the motor housing 48 can be up to a suitable attachment point - e.g. a cross member of the vehicle - be moved.

Such an embodiment is shown in Figs. 4A-4C. The motor housing 48 in this case has an elongated connector 52 to the tie rod housing 46 to receive the extended shaft 26. Since the motor housing 48 in the embodiment according to FIGS. 4A-4C points downwards, a particularly deep center of gravity results. This is especially important for sports and racing vehicles. The conditional by the electric motor 24 weight is usually in racing unproblematic, because racing vehicles usually have balance weights, which can be made correspondingly lighter in a heavy - but mainly advantageous arranged - electric motor 24. 5A-5D show another embodiment in which the rotor 28 of the electric motor 24 is connected to the auxiliary power pinion 44 via a universal joint 54. The occurring universal joint error of the universal joint 54 can be compensated by a suitable motor control of the electric motor 24. In these embodiments, too, a gearless and non-rotatable connection between the rotor 28 and the auxiliary power pinion 44 is used in these embodiments.

The shaft 26 is reduced in the embodiment according to FIGS. 5A-5D to two extensions 56, 58. In further modifications, in addition to the universal joint 54, an elongated shaft 26 (similar to those in FIGS. 4A-4C) and / or further joints and / or further connecting pieces may be provided. In general, in the exemplary embodiments described here, it is only considered important that no or only a slight reduction of the engine torque takes place in order to influence the tie rod 10 as little as possible when the electric motor 24 is freewheeling.

In the embodiments described so far, the torque-measuring device 20 was associated with the steering column and integrated into the steering shaft portion 18 between the steering pinion 16 and the steering column. In the following, embodiments will be described according to a further aspect of the invention, in which a measuring device - which may be configured, for example, as a torque measuring device or as a measuring device for a translational movement - is assigned to the power steering assembly. In these embodiments, an electric motor assembly for power steering is generally provided. This electric motor assembly has in some embodiments, only an electric motor - as described above - on. In other embodiments, however, an electric motor and a reduction gear connected thereto are provided as electric motor assembly. The embodiment according to FIGS. 6A-6C is similar to the embodiment according to FIGS. 2A-2D. In both cases, a tie rod 10 with two toothed portions 12, 40 and correspondingly two teeth 14, 42 are provided. An electric motor assembly 60 designed as a gearless electric motor 24 acts on the toothing 42 of the second region 40 of the tie rod 10 via an actuating element 62-configured here as an auxiliary power pinion 44. The forces or moments occurring between the electric motor assembly 60 and the actuator 62 are measured by a measuring device 64.

In the presently described embodiment, the connecting wheel 32, which connects the outer magnetic ring 30 of the rotor 28 with the shaft 26 and the auxiliary power pinion 44, configured as a measuring device 64 which responds to a torque between the auxiliary power pinion 44 and the outer magnetic ring 30. More specifically, the connecting wheel 32 has a plurality of sector-shaped notches 66, each defining a likewise circular sector-shaped wheel disc section 68. Between the cuts 66 thin, spoke-like webs 70 are formed in the connecting wheel 32. The webs 70 connect an inner hub region 72 to an outer edge region 74 of the connecting wheel 32.

In the unloaded condition shown in Figs. 6A-6C, each ridge 70 is straight and centered between each pair of wheel disc sections 68. On the other hand, if, for example, by a ridge groove, track rod 10 is slightly to the right (in the orientation of Figs. 6A-6C). shifts so designed as auxiliary power pinion 44 actuator 62 slightly rotates counterclockwise. The hub portion 72 and the wheel disc portions 68 follow this rotational movement. Due to the inertia of the rotor 28, however, this does not follow the rotational movement immediately, so that the outer edge region 74 initially remains stationary. The webs 70 therefore bend slightly, and a suitable sensor (not shown) measures the relative rotational movement between the shaft 26 and the hub region 72 on the one hand and the rim 74 and outer magnet ring 30 on the other hand. The maximum bending of the webs 70 is achieved by abutment of the webs 70 on the respectively clockwise adjacent wheel disk sections 68 (in the case of rotation of the hub section 72 in the counterclockwise direction) or by abutment of the webs 70 on the respectively counterclockwise adjacent wheel disk sections 68 (when the hub portion 72 is rotated clockwise). The counteracting a rotation spring force is determined in particular by the width and thickness of the webs 70 and by their number. It will be appreciated that in alternative embodiments, instead of the six webs 70 shown in FIGS. 6A-6C, more or fewer webs may be provided.

The sensor (not shown) for measuring the rotational movement may be configured in different ways, similar to the sensor of the torque measuring device 20 of the embodiments described above. For example, a piezo sensor or an optical sensor or a magnetic sensor or a resistance sensor or a high-frequency distance sensor can be used.

Overall, when the electric motor assembly 60 is idling, the measured value determined by the measuring device 64 thus corresponds to the torque exerted on the actuating element 62 -or in other embodiments, the force exerted on the actuating element 62 -in relation to the mass inertia and the breakaway torque of the electric motor assembly 60 Embodiment of FIG. 6A-6C, this counter-torque is relatively low, because the rotor 28 is directly - in particular gearless - coupled to the actuator 62. However, embodiments are also provided in which the electric motor assembly 60 in addition to the actual electric motor 24 has a reduction gear.

In embodiments with reduction gear, the counter-torque in the currentless operation ("freewheeling") of the electric motor is significantly higher because, firstly, the breakaway torque of the reduction gear has to be overcome and, secondly, the mass inertia of the rotor multiplied by the reduction factor. In these embodiments, it is particularly advantageous to switch the measuring device 64 between the actuating element 62 and the reduction gear of the electric motor assembly 60, because then the rotation angle of the measuring device 64 required for the measurement represents a freewheeling range for the actuating element 62 with very little counter-torque. If, for example, in the embodiment according to FIGS. 6A-6C, the bending region of the webs 70 is 5 ° in each direction until it abuts against the respectively adjacent wheel disk sections 68, an excellent response of ruts or other roadway properties takes place at least when driving straight ahead. For this feedback is namely only an unobstructed movement of the tie rod 10 by a few millimeters or even less than a millimeter (eg a maximum of 4 mm or a maximum of 2 mm) is required. The auxiliary power pinion 44, which can move due to the bending of the webs 70 without movement of the reduction gear and rotor 28 in each direction by 5 °, for example, allows such a displacement of the tie rod 10 readily.

It is understood that the embodiment with an electric motor assembly 60 and a measuring device 64 assigned to this assembly can also be provided in embodiments in which the actuating element 62 is configured not as an auxiliary power pinion 44 but as a steering pinion 16. Such an embodiment, which is a modification of the embodiment of Figs. 1A-1D, is shown in Figs. 7A-7C.

On one of the steering column (not shown) connected to the steering shaft portion 18, the steering pinion 16 is formed as an actuator 62 in the embodiment of FIGS. 7A-7C. The steering pinion 16 is further connected to the electric motor assembly 24 designed as an electric motor assembly 60 via a shaft 26. The shaft 26 has a measuring device 64, which is similar to the torque-measuring device 30 shown in FIG. 1A-1 D is formed, but not Lenksäulenseitig, but between the steering pinion 16 and the electric motor 24 is arranged. It goes without saying that the embodiment according to FIGS. 7A-7C can optionally also be designed with a measuring device 64 integrated in the connecting wheel 32, similar to that shown in FIGS. 6A-6C. Such a configuration is shown in FIGS. 8A-8C. The wheel disk sections 68 are designed to be V-shaped here for material savings, with the legs of the "V" forming stops for limiting the maximum bending of the webs 70.

In a further modification, in the embodiment according to FIGS. 6A-6C, an extended shaft 26 may be provided with a measuring device 64 integrated in the shaft 26, as shown in FIGS. 7A-7C. The connecting wheel 32 then needs to have no bending sections.

As already mentioned, as a modification of the embodiments according to FIGS. 6A-6C, 7A-7C and 8A-8C, the electric motor assembly 60 can be equipped with a sub-reduction gear.

The embodiment of FIGS. 9A-9C is a modification of the embodiment of FIGS. 6A-6C. The electric motor assembly 60 here has an electric motor 24 of any type, which via a reduction gear 76 and a measuring device 64 on the actuator 62 - which is designed here as a power steering pin 44 - acts. The reduction gear 76 may be configured, for example, as a gear with a worm or bevel gear or conical helical gear or crown-gear transmission. In the embodiment of FIGS. 9A-9C, the reduction gear 76 has a bevel gear 80 directly connected to the electric motor 24 and the wheel 78 with a likewise conical toothing. In the wheel 78 -as in the connecting wheel 32 according to FIGS. 6A-6C-a disk with a plurality of spoke-like webs 70 and a plurality of wheel disk sections 68 acting as lateral stops is formed. Similar to the embodiment according to FIGS. 6A-6C, a sensor 71 measures the lateral bending of the webs 70. The measurement result corresponds to that applied by the tie rod 10 to the actuating element 62. controlled torque against the inertia and the breakaway torque of the electric motor assembly 60, so in the present case of the electric motor 24 with the reduction gear 76. Also in the embodiment shown here, it is advantageous, the measuring device 64 functionally between the actuator 62 - which is configured here as auxiliary power pinion 44 - And the reduction gear 76 to switch, so that the loaded only by the restoring force of the webs 70 freewheeling area of the measuring device 64 leads directly to a corresponding freewheeling area of the power steering gear 44.

In a further embodiment variant is similar to one embodiment

Fig. 9A-9C integrated in the steering gear unit. This variant, which in

10A-10C thus corresponds to a combination of the spatial

Arrangement according to FIGS. 8A-8C with an electric motor assembly 60 and a measuring device 64 according to FIGS. 9A-9C. Again, the measuring device 64 is functionally connected between the actuator 62 and the reduction gear 76. The steering shaft part 18 has no torsion elements and thus provides a direct connection between the steering pinion 16 and the control column. In addition to the component savings, this results in a particularly direct steering feel with excellent feedback properties.

Fig. 1 1A-1 1 F show a further embodiment in which the tie rod 10 instead of the toothing 14 has a screw thread 82 for a recirculating ball nut 84. The ball nut 84 is held by two spring assemblies 86, 88 axially floating in a housing 90. The housing 90 has a first and a second part 92, 94 which are fixedly connected to each other. The first part 92 of the housing 90 is provided with a serration 96 for a toothed belt (not shown), via which the housing 90 is driven by an electric motor assembly (not shown). As can be seen in particular from Fig. 1 1 E and 1 1 F, spring tabs 98 of the spring assemblies 86, 88 non-rotatably engage in recesses 100 of the ball nut 84 and (not shown) of the two housing parts 92, 94 a. The ball nut 84 is thus rotationally fixed, but axially floating, held in the housing 90. A rotational movement of the housing 90 is therefore transmitted to the ball nut 84, which in turn pushes the tie rod 10 in the axial direction - depending on the direction of rotation of the ball nut 84 to the right or left -.

The axially resilient spring tabs 98 of the spring packs 86, 88 allow some relative axial movement between the ball nut 84 and the housing 90, which is measured by a sensor (not shown). Within the spring travel, the measured value of the sensor is thus approximately proportional to the force acting axially between the housing 90 and the tie rod 10. Since the measurement takes place in the transverse direction of the vehicle, occurring transverse or gear forces should be taken into account as far as possible for correcting the measured value.

Overall, therefore, in the embodiment of FIG. 1 1 A-1 1 F, the ball nut 84, the actuator 62, while the spring assemblies 86, 88 - together with the sensor, not shown - form the measuring device 64. The electric motor assembly 60 may comprise an electric motor of any type.

A steering system according to the invention with electromotive steering power assistance can be used both for vehicles with internal combustion engine and for electric vehicles. In particular, in electric vehicles, there is the advantage that the electric motor can be fed to the steering power assistance without further energy distribution measures from the same power source as the main drive motor of the vehicle. The reason for this is that strong steering angles, which require strong assistance from the power engine, occur only at low speeds - ie low load on the main drive motor. Conversely, at high load of the main drive motor - ie high speed or high acceleration - no strong steering angle, so that the power motor needs no or at most low power.

The details given in the above description and illustrated in the drawings are not to be considered as limiting the scope of the invention but as examples of some embodiments of the invention. Further modifications will be apparent to those skilled in the art. Thus, in particular features of the embodiments described above can be combined with each other to obtain further embodiments of the invention. Accordingly, the scope of the invention should be defined not by the described embodiments but by the claims and their equivalents.

Claims

1 . Steering for a motor vehicle, with:

an electric motor (24) for steering power assistance, which has a rotor (28) coupled to a pinion (16, 44),

a track rod (10) having a toothing (14, 42), in which the pinion (16, 44) engages,

characterized in that

the pinion (16, 44) is gearless connected to the rotor (28) of the electric motor (24).

2. Steering according to claim 1, characterized in that the pinion (16, 44) and the rotor (28) of the electric motor (24) by at least one shaft (26) and / or at least one joint (54) are rotatably connected to each other.

3. Steering according to claim 1 or claim 2, characterized in that the pinion (16, 44) is a steering pinion (16), which is coupled gearless with a steering column.

4. Steering according to claim 3, characterized in that a torque-measuring device (20) between the steering column and the steering pinion (16) is coupled.

5. Steering according to claim 1 or claim 2, characterized in that the pinion (16, 44) is an auxiliary power pinion (44), and that the steering further comprises a steering pinion (16), in a further toothing (14) of the tie rod (10) intervenes.

6. steering system according to one of claims 1 to 5, characterized in that the diameter of the rotor (28) by a factor of 5 or a factor of 10 or a factor 15 is greater than the diameter of the pinion (16, 44).

7. Steering for a motor vehicle, comprising:

a tie rod (10), and

an electric motor assembly (60) for power steering, which acts via an actuating element (62) on the tie rod (10),

characterized in that

- A measuring device (64) between the actuating element (62) and the electric motor assembly (60) is arranged to measure a force applied to the actuating element (62) or a force acting on the actuating element (62) moment.

8. Steering according to claim 7, characterized in that the electric motor assembly (60) comprises an electric motor (24) and a reduction gear, and that the measuring device (64) between the actuating element (62) and the reduction gear is arranged.

9. Steering according to claim 7 or claim 8, characterized in that the measuring device (64) has at least one spring element (70, 86, 88), and in that a sensor for sensing the deformation of the at least one spring element (70, 86, 88) or an associated movement is provided.

10. Steering according to claim 9, characterized in that the at least one spring element (70, 86, 88) at least one in a wheel (32, 78) spoke-like web (70) or at least one between two shaft sections axially extending web.

1 1. Steering according to one of claims 7 to 10, characterized in that the actuating element (62) is a pinion (16, 44), in particular a steering pinion (16) or an auxiliary power pinion (44).

12. Steering according to claim 1 1, characterized in that the measuring device (64) is adapted to measure a between the pinion (16, 44) and the electric motor assembly (60) acting torque.

13. Steering according to one of claims 7 to 12, characterized in that the actuating element (62) is a ball nut (84).

14. Steering according to one of claims 1 to 6 and one of claims 7 to 13.