WO2006058660A1

WO2006058660A1 - Superimposed steering system

Info

Publication number: WO2006058660A1
Application number: PCT/EP2005/012599
Authority: WO
Inventors: Matthias Gregor; Rainer Kaufmann; Jens Meintschel
Original assignee: Daimlerchrysler Ag
Priority date: 2004-12-01
Filing date: 2005-11-24
Publication date: 2006-06-08
Also published as: DE102004057925A1

Abstract

The invention relates to a steering system for a motor vehicle comprising a steering wheel (1), which is actuated by the driver, a steering gear (11), which converts the rotational displacement of an input shaft (12) into a shifting displacement of a steering tie rod, a cross-drive steering transmission (21), which is located between the steering gear (11) and the steering wheel (1), said transmission having a first ring gear (2a) that interacts with the steering wheel (1) and a second ring gear (2b) that interacts with the input shaft (12) of the steering gear (11), whereby a planetary gear (4) engages with the first and second ring gear (2a, 2b). The steering system is characterised in that the planetary gear (4) extends across the central axis of the ring gears (2a, 2b) and is mounted on an eccentric shaft (5) that is connected to the rotor (7) of an electric motor (6). Said system can be used in motor vehicles, in particular passenger vehicles.

Description

ABOUT STORAGE STEERING

The invention relates to a steering device according to the preamble of claim 1.

From the published patent application DE 101 60 313 A1, a steering device is known, which has a superposition gear designed as a planetary gear. The planetary gear has two ring gears, at least one stage planetary gear wheel mounted on a web and a worm gear which can be driven by an electric motor.

The object of the invention is in contrast to provide a steering device that has a superposition gear with a simpler structure.

This object is achieved by a steering device having the features of claim 1.

The steering device according to the invention is characterized by a planetary gear which extends over the central axis of the ring gears and is mounted on an eccentric shaft connected to a rotor of an electric motor. The number of teeth of the planetary gear is only up to 10%, ie slightly smaller than that of the ring gears. The eccentric shaft has the function of a web which can be driven directly, ie without intermediate gear by an electric motor in an advantageous manner. By energizing the electric motor whose rotor rotates the eccentric shaft, thereby the planetary gear rolls in the first ring gear, the second ring gear rotates relative to the first ring gear and the from Driver adjusted steering angle is superimposed on an additional steering angle.

In a refinement of the invention, the planetary gear designed as a simple planetary gear meshes with the first and second ring gears, wherein the first ring gear and the second ring gear have different profile displacements and numbers of teeth. A simple planetary gear is to be understood as meaning a planetary gear in which the teeth defined by a toothing geometry extend over the entire gear width. In order to enable a meshing of the ring gears of different numbers of teeth with the Einfachplanetenrad, the ring gears have different profile shifts. For example, the second gear may have more teeth by a positive profile displacement relative to the first gear, which has no or a negative profile displacement. In another case, the second gear has fewer teeth than the first gear by a negative profile shift. The structure of the superposition gear with a simple planet and the two hollow wheels takes up little space, is inexpensive to produce and allows high ratios between the eccentric shaft and the second ring gear. The high gear ratio allows the use of a small electric motor and allows exact adjustment of the overlay angle.

In a further embodiment of the invention, the planetary gear is designed as a two toothed regions comprehensive Stufenplanetenrad, wherein a first region with the first ring gear and a second region is in engagement with the second ring gear. At high ratios between the eccentric shaft and the second ring gear, the planetary gear is designed as a stepped planetary gear to avoid interference. For example, in the case of an involute toothing, only involute plank parts may come into engagement. The numbers of teeth of the toothed areas of the stepped planet are about 10% smaller than the meshing with the respective toothed areas ring gears. The study fenplanet enables the display of high ratios between the eccentric shaft and the second ring gear.

In a further embodiment of the invention, the electric motor in a second ring gear and the input shaft of the steering gear interconnecting steering shaft is arranged. The rotor of the electric motor is arranged concentrically with the ring gears. As a result of cramped space conditions between the two ring gears and the planet gear comprehensive gear set and the steering handle, the electric motor in the steering shaft can be arranged in an advantageous manner.

In a further embodiment of the invention, the electric motor in a steering handle and the first ring gear interconnecting steering tube is arranged. The steering tube has a sufficiently large inner diameter for receiving the electric motor. The rotor of the electric motor is arranged concentrically with the ring gears. The example designed as a brushless motor electric motor can be arranged to save space in the steering tube.

In a further embodiment of the invention, the steering handle is connected via a gear stage with the first ring gear. The gear stage includes a gear connected to the steering tube and connected to the first ring gear. A rotational movement of the steering handle or the steering tube is transmitted by combing the gears of the gear stage to the first ring gear. The gear stage can be executed, for example, as a pair of spur gears or as a pair of bevel gears. The gear stage allows an arrangement of the electric motor outside of the steering tube or the steering shaft. The electric motor can thus be stored fixed to the vehicle. The torque on the stator of the electric motor is thus not supported on the steering tube or the steering shaft.

In a further embodiment of the invention occurs between the first and second ring gear on self-locking. The self-locking prevents torque application of the first or second ring gear rolling of the planet gear in the ring gears, d. H . the ring gears and the planet rotate in the block and the speed of the two ring gears is equal.

Further features and combinations of features result from the description and the drawings. Concrete embodiments of the invention are illustrated simplified in the drawings and explained in more detail in the following description. Show it

Fig. 1 is a schematic representation of a steering device according to the invention,

Fig. 2 perspective views of the components of the superposition gearing of FIG. 1 ,

Fig. 3 is a perspective and sectional view of a mounted superposition gearing of FIG. 2,

Fig. 4 shows a variant of the steering device from FIG. 1 and

Fig. 5 another variant of _. Steering device of FIG. l.

Like-acting components in FIGS. 1 to 5 are denoted by the same reference numerals below.

In Fig. 1 shows schematically the structure of a steering device according to the invention with a superposition gear 21. A steering handle 1 in the form of a steering wheel is connected via a steering tube 3 with a first ring gear 2a. A planetary gear 4 is in meshing engagement with the first ring gear 2a and a second ring gear 2b. The planetary gear 4 is designed as a simple planetary gear, d. H . the teeth marked by a tooth geometry extend over the entire gear width. The second ring gear 2b has a different number of teeth from the first ring gear 2a. In order to enable the engagement with the planetary gear 4, the different number of teeth is achieved by a profile shift. This measure familiar to the toothing expert is that a profile reference line of the toothing of the ring gears 2a, 2b is displaced from the pitch circle diameter in the direction of the tip diameter (positive profile displacement) or in the direction of the root diameter (negative profile displacement). In the case of a sufficiently large displacement, more or fewer teeth can be arranged on the ring gears 2a, 2b in comparison to a design without profile displacement, wherein the ring gears 2a, 2b continue to mesh with the planetary gear 4.

The planetary gear 4 is rotatably mounted on an eccentric shaft 5. The eccentric shaft 5 is coupled to a rotor 7 of an electric motor 6 arranged in the steering tube 3. The stator 8 of the electric motor 6 is supported in the steering tube 3. Via a flexible ribbon cable 15, the electric motor 6 is connected to a control unit 14. Alternatively, the electric motor 6 can also be supplied with electrical energy via sliding contacts. The control unit 14 connected to a vehicle dynamics computer, for example via CAN, energizes the electric motor 6 as a function of an additional steering angle requested by the vehicle dynamics computer.

A steering shaft 9 is connected via a flange 10 with the second ring gear 2b. The steering shaft 9 transmits the rotational movement of the second ring gear 2b to an input shaft 12 of a steering gear 11. The steering gear 11 converts the rotational movement of the steering shaft 9 into a sliding movement of tie rods. The tie rods are connected to steerable wheels of the vehicle.

By controlling the electric motor 6, the steering device according to the invention makes it possible to superimpose a further angle on a steering angle predetermined by the driver via the steering wheel 1. In a steering operation without steering angle superimposition, the rotational movement of the steering wheel 1 is transmitted to the planetary gear 4 via the first ring gear 2a. The eccentric shaft 5 stands still, as long as a torque applied to the eccentric shaft 5 can be supported via the electric motor 6. The ratio i _{H2a H2b of} the speeds n _H 2a from the first ring gear 2a to the speed n _H2b to the second ring gear 2b is determined by the number-of-teeth ratio as follows:

- ^Z H2b _ ⁿ H2a ^l H2a_H2b ~ ^'~~'

² HZa ⁿ H2b

wherein the number of teeth of the first ring gear 2a with z _{H2a /} that of the second ring gear 2b is designated Z _H2 b.

The translation iH2a_H2b is equivalent to the gear ratio between the steering wheel 1 and the steering shaft 9.

Preferably, the steering device is designed such that the planetary gear 4 rotates with the ring gears 2a, 2b in the block. This avoids that a projecting on the steering shaft 9 steering torque must be constantly supported by the eccentric shaft 5 and by the electric motor 6. Optionally, a circulation in the block can be ensured by a slight energization of the electric motor 6. Alternatively, a design is to be preferred which, when the first ring gear 2a is driven, provides self-locking to the second ring gear 2b (self-locking gearbox) and thereby ensures block circulation of the two ring gears 2a, 2b. Even in the opposite case, that is, when driving the second ring gear 2b occurs self-locking to the first ring gear 2a. In the self-locking a rolling of the planetary gear 4 in the ring gears 2a, 2b when driving on one of the two ring gears 2a, 2b is not possible.

In case of failure of an electrical component such as the electric motor 6 or the control unit 14, the vehicle is purely mechanically steerable. During a block revolution of the two hollow wheels 2a, 2b, between steering wheel wheel 1 and the steering shaft 9, the translation

one. Since the ring gears 2a, 2b have only small numbers of teeth differences, for example, 1 or 2 teeth, even with stationary eccentric shaft 5, the ratio between the steering wheel 1 and the steering shaft 9 is approximately 1, so that both the stationary and co-rotating eccentric shaft 5, the mechanical steerability is guaranteed. A stationary eccentric shaft 5 is represented by a non-self-locking gear by support on the electric motor 6 and / or an additional locking of the eccentric shaft 5.

To increase, for example, a driving stability or a vehicle agility, the driving dynamics computer predefines an additional steering angle superimposed on the steering angle set by the driver. The control unit 14 energizes the electric motor 6 until the additional steering angle is set. In this case, the tooth engagement point between the planetary gear 4 and the ring gears 2a, 2b is displaced by rotation of the eccentric shaft 5. The planetary gear 4 rotates relative to the eccentric shaft 5 and rolls in the two ring gears 2a, 2b from. Due to the different numbers of teeth of the ring gears 2a, 2b, these rotate relative to each other. The steering shaft 9 rotates upon actuation of the steering wheel 1 due to the revolution of the planetary gear 4 and the two ring gears 2, a rotational movement of the planetary gear 4 on the eccentric axis 5 is superimposed as additional steering angle to the steering shaft 9. A provision of the additional steering angle by turning back the eccentric shaft fifth to the original position.

The translation ig H _2b between the rotational speed n _{E of} the eccentric shaft 5 and the rotational speed n _{H2b of} the second ring gear 2b, which is connected to the steering shaft 9, is determined by the number of teeth z _H 2a and z _H 2b of the first when the first ring gear 2a is stationary and second ring gear 2a, 2b to:

wherein the possible translation range of the arrangement in

10 <I i _E _ _H2b | <l ° 0. Depending on the profile The ratio i _{E H2b is} positive or negative, that is, the second ring gear 2b rotates in the same direction as or opposite to the eccentric shaft 5. If, for example, z _H 2a> ZH2 _b , the second ring gear 2b rotates in the same direction, then z _H 2a <z _H 2 b, the second ring gear 2 b rotates in the opposite direction to the eccentric shaft 5.

2 shows components of the superposition gear 21 of the steering device according to the invention in an exploded view. In the steering tube 3, the stator 8 of the electric motor 6 is arranged. The rotor 7 is mounted in a bearing 15 and drives the eccentric shaft 5 at. A first needle bearing 16 supports the planetary gear 4 on the eccentric shaft 5. The planetary gear 4 engages both in the first ring gear 2a and in the second ring gear 2b. The steering tube 3 has a flange 13 which is connected via screws 19 with the first ring gear 2a. As shown in FIG. 3, the steering shaft 9 has a flange 10, which is mounted via a second needle bearing 17 in a carrier ring 18 preferably integral with the first ring gear 2a. Alternatively, the carrier ring 18 can be connected to the first ring gear 2a, for example, via a material and / or positive connection. The steering shaft flange 10 is also connected via a material and / or a positive connection 20 with the second ring gear 2b. Under a cohesive connection, for example, a welded joint to understand under a positive connection a press connection or a splined connection. The arrangement shown allows a rotation of the first ring gear 2a relative to the second ring gear 2b. Via a screw connection 23, the carrier ring 18 is connected to a closing ring 22 which limits the axial movement of the steering shaft flange 10. An axial emigration of the steering shaft flange 10 from the support ring 18 is thus avoided. The steering shaft flange 10 has a pin bearing a third needle bearing 24. In the assembled state of the superposition gear 21, the third needle bearing 24 is disposed in a bore of the eccentric shaft 5. The eccentric shaft 5 is supported on the journal or on the steering shaft flange 10 from. A deformation of the eccentric shaft 5 under high shear forces is avoided by the support.

4, a variant of the steering device of Fig. 1 is shown. In contrast to the embodiment in Fig.l the steering wheel 1 via a spur gear 27a, 27b comprehensive gear stage 25 is connected to the first ring gear 2a. This arrangement makes it possible to store the stator 8 of the electric motor 6 fixed to the vehicle and to be able to design the steering tube 3 independently of the electric motor 6. The function of the steering device is identical to that of Fig.l.

In an alternative embodiment, not shown, the second ring gear 2b is connected via a gear stage 25 with the steering shaft 9. This is a vehicle-mounted arrangement of the electric motor 8 is possible with an arrangement of the electric motor between the steering gear 11 and superposition gear 21.

In Figure 5, a steering apparatus is shown which compared to the embodiment of Fig.l has a planetary gear 4 designed as Stufenplanetenrad. The Stufenplanetenrad has two teeth 26a, 26b with different numbers of teeth and / or gearing geometries. The use of a stepped planetary gear 4 makes it possible to avoid meshing interference, i. Tooth touches outside the point of engagement, which can occur in the range of 100, in particular at high ratios iE H2b.

By superimposing an additional steering angle, the steering device according to the invention makes it possible to adapt the overall steering ratio, ie the ratio of the change of a steering wheel angle to the change of the average steering angle on the wheel, to different driving situations. For example, when parking due to a small overall translation reaching the maximum Radeinschlagwinkels with a few rotational movements on the steering wheel 1 is possible, however, at high speeds to the Total ratio for safe vehicle handling to be greater than at lower speeds.

The steering gear 11 is designed such that the overall steering ratio assumes a value that allows comfortable parking without steering angle superposition. When driving fast then the total ratio is increased by driving the electric motor 6.

Alternatively, the steering gear 11 may be designed such that the overall ratio assumes a value that allows safe driving at high speeds. During a parking process, the overall ratio is then reduced by driving the electric motor 6. Likewise, the steering gear 11 may also have a total translation, which mediates a good road contact at medium speeds, when parking or fast driving is reduced or increased by driving the electric motor 6, the translation.

Claims

claims

1. steering device for a motor vehicle, with

a driver-operable steering handle (1),

a steering gear (11) which converts the rotational movement of an input shaft (12) connected to the steering handle (1) into a sliding movement of a tie rod,

- One between the steering gear (11) and steering handle (1) arranged superposition gear (21) standing in operative connection with the steering handle (1) first ring gear (2a) and one with the input shaft (12) of the steering gear (11) in operative connection second ring gear (2b), wherein a planetary gear (4) at the same time with the first and second ring gear (2a, 2b) is engaged, characterized in that the planet gear (4) extends over the central axis of the ring gears (2a, 2b) and is mounted on an eccentric shaft (5) connected to a rotor (7) of an electric motor (6).

2. Steering device according to claim I _1, characterized in that running as a simple planetary gear (4) with the first and second ring gear (2 a, 2 b) meshing, wherein the first ring gear (2 a) and the second ring gear (2 b) different profile shifts and have numbers of teeth.

3. Steering device according to claim 1, characterized in that the planetary gear (4) is designed as two toothed areas comprehensive Stufenplanetenrad, wherein a first region with the first ring gear (2a) and a second region with the second ring gear (2b) is engaged.

4. Steering device according to one of claims 1 to 3, characterized in that the electric motor (6) in a second ring gear (2b) and the input shaft (12) of the steering gear connecting steering shaft (9) is arranged.

5. steering device according to one of claims 1 to 3, characterized in that the electric motor (6) in a steering handle (1) and the first ring gear (2a) interconnecting the steering tube (3) is arranged.

6. Steering device according to one of claims 1 to 3, characterized in that the steering handle (1) via a gear stage (25) with the first ring gear (2a) is connected.

7. Steering device according to claim 6, characterized in that the electric motor (6) is arranged fixed to the vehicle.

8. Steering device according to one of claims 1 to 7, characterized in that between the first and second ring gear (2a, 2b) self-locking occurs.