Electric power-assisted steering device for motor vehicle

The invention relates to a steering device according to the Preamble of claim 1, as described in particular for Motor vehicles usable.

Compared with conventional steering devices with mechanical Coupling between the steering angle setting device and the Steering angle adjusting device lacks the steering devices non-mechanical coupling of these two bodies on a direct mechanical transmission of a Retroactivity moment the steering angle adjusting device to the Steering angle setting means.

To this the driver usual feedback information for the steering devices with non-mechanical coupling of the steering angle setting device maintain and steering angle adjusting device, it is known, a reaction-torque-generating device to the to couple the steering shaft. Thus, in the published patent application DE 42 41 849 A1 describes a steering system for vehicles or ships with a Steering wheel with associated steering shaft and thus electrically coupled steering angle adjusting device is disclosed wherein the steering shaft by a moment load unit with a velocity and / or adjustable operator dependent can be the reaction torque applied.

In the unpublished DE 195 39 101 C1 is a Steering apparatus of the aforementioned type is described in which the reaction-torque-generating device one hand Return spring arrangement and on the other hand one to the steering shaft coupled motor comprises. The return spring arrangement is in one embodiment of two transversely to the steering shaft arranged coil springs and a lying therebetween Driver plate, which via a gear to the steering shaft is coupled. In a further example is a to Steering shaft coaxial piston-cylinder unit is provided, whose U- shaped piston surrounding a steering shaft Helical compression spring against a rotationally fixed to the steering shaft fitting backdrop is pressed. In its opposite End limited the piston together with the cylinder a with a pressure fluid filled working space.

The invention is the technical problem of providing a novel, in terms reaction torque generation and compact structure optimized steering apparatus of the mentioned type.

The invention solves this problem by providing a A steering apparatus comprising the features of claim 1 or the sixth

In the steering apparatus according to claim 1 includes the transmission, that the mechanical feedback-torque-generating device coupling to the steering shaft, a steering shaft pinion and with this coupled rack for the piston rod at least one axially movable guided in a cylinder Flask is used, which together with the piston rod Driver unit forms over which the linear elastic deflectable element is coupled to the transmission. These Gear design allows a compact design of Complex of steering angle setting device and mechanically reaction-torque-generating device and the setting any desired ratio. In Motor vehicles with adjustable steering wheel, the compact Construction of this complex has the advantage that it in the footwell Pivoting not a pivotally mounted steering shaft significantly narrows. In addition, this allows the transmission Setting a growing reaction torque even at beyond 360 ° continuous steering angle amounts.

In is a further developed according to claim 2 steering device the mechanical feedback-torque-generating device compact and symmetrically positioned transversely to the steering shaft, wherein a Rack as a common piston rod for two opposing pistons used, of which, depending on the steering direction, ie, depending on whether the steering shaft in one or the other Rotation is deflected from its central position, always straight one is driven by the rack movement.

In a further developed according to claim 3 steering device includes mechanically-interacting torque-generating Means two housed in a cylinder, against each extending the helical compression spring as the linear elastically deflectable element is supported. In other Configuration is here according to claim 4 of the cylinder with the Steering shaft parallel longitudinal axis arranged adjacent to the steering shaft, what the required installation space keeps low angles to the steering shaft.

In is a further developed according to claim 5 steering device as a coupling element between the rack and a respective piston Spring stop element provided that a torsionally flexible replace coupling between a steering wheel and the steering shaft and can help to reduce noise.

In the steering apparatus according to claim 6, the gear unit includes one with the steering shaft rotatably coupled eccentric, against the outer circumference of a front end of a piston rod of rests in a cylinder axially movable piston guided, the together with the piston rod, the driving unit for the Coupling of at least linearly elastically deflectable a Element to the gear forms. By suitable choice of the form the eccentric disc and the transmission ratio can be the desired transfer characteristic between the Steering shaft rotary motion and the linear motion of the linear Set elastically deflectable element.

In a further developed according to claim 7 steering device limited the piston in the cylinder at least one with a Pressure fluid filled working space. By appropriate Pressure fluid, in this apparatus, a additive to the elastic force of the linear elastic deflectable Element reinforcing or weakening supervening pressure force be generated to a desired adjust the reaction torque characteristic.

In is a further developed according to claim 8 steering device additionally an electrically feedback-torque-generating Means provided with a motor, especially the so is designed so that the reaction torque generated overall in a low speed range of the respective constant Change in steering angle and in a high speed range constant a respective increase in the steering angle amount counteracts. This results in that the driver at low Speeds when the steering wheel in the direction Straight ahead a of amount approximately equal large steering torque must exert like greater the steering lock while an automatic in the high speed range Steering return is supported in the straight-ahead position.

Preferred embodiments of the invention are shown in Drawings and are described below. In the figures:

<b>Fig.</b> 1 is a schematic block diagram representation of a Steering apparatus for an automobile with an electronic Coupling between a steering angle setting device and a steering angle adjusting device and with a feedback-moment generating device,

<b>Fig.</b> 2 is a longitudinal sectional view of a Steering angle setting means transversely grown, feedback-torque generating double cylinder piston means

<b>Fig.</b> 3 is a longitudinal sectional view of a Steering angle setting means transversely grown, reaction-torque-generating cylinder double piston means

<b>Fig.</b> 4 is a sectional view taken along line IV-IV of <b>Fig.</b> 3,

<b>Fig.</b> 5 is a longitudinal sectional view of a Steering angle setting device with longitudinally grown, reaction-torque-generating cylinder double piston device and

<b>Fig.</b> 6 is a schematic sectional view of a Steering angle setting means transversely grown, reaction-torque-producing piston-cylinder device with Exzenterscheibengetriebe.

<b>Fig.</b> 1 shows an overview of a steering apparatus for a Automobile with non-mechanical, electrical coupling of Steering angle setting means and steering angle adjusting device. The Steering angle setting device comprises a steering wheel (<b>1</b>) With a coupled steering shaft (<b>2</b>) And a complex (<b>3</b>) To produce a reaction torque to the steering shaft (<b>2</b>). The Steering angle adjusting device comprises a servo-hydraulic (<b>4</b>) and an associated piston-cylinder power unit (<b>5</b>), To which a Steering Gear (<b>6</b>) For the vehicle front wheels (<b>7</b>a, <b>7</b>b) is coupled. The conventional steering column as mechanical Connection of steering shaft steering column tube and steering gear (<b>6</b>) deleted. Instead, the information about the respective is Steering shaft rotational position of an electronic control unit (<b>8th</b>) transmitted, which the servo-hydraulic (<b>4</b>) Terminating the associated steering angle, ie here the wheel angle of Front wheels (<b>7</b>a, <b>7</b>b) controls. Further from the control unit (<b>8th</b>) Required information input you are of a Sensor unit (<b>9</b>) Supplied to the measuring signals of different Sensing elements receives as a sensor (<b>10</b>) For measuring the Steering wheel angle, a sensor (<b>11</b>) For measuring the Steering wheel torque, a wheel angle sensor (<b>12</b>) And a wheel speed sensor (<b>13</b>). While for the other, mentioned Components a common, conventional structure are chosen can, is in more detail below in various, according to the invention Realizations of the steering angle setting device, while in particular of the complex (<b>3</b>) The reaction torque generation received.

<b>Fig.</b> 2 shows a first embodiment to this effect. The steering wheel (<b>1</b>) Flows via the steering shaft (<b>2</b>) In a housing (<b>14</b>) By means of a fixed bearing (<b>15</b>) And two movable bearings (<b>16</b>. <b>17</b>) fixed. Over a certain length, the steering shaft is a pinion (<b>2</b>a) designed, with which a transverse to the steering shaft Rack (<b>18</b>) Cooperates. The rack (<b>18</b>) Is in Guide channels of two with respect to the steering shaft (<b>2</b>) opposite, U-shaped piston (<b>19</b>a, <b>19</b>b) performed, the turn in two with respect to the steering shaft (<b>2</b>) opposing cylinders (<b>20</b>a, <b>20</b>b) transverse to the steering shaft (<b>2</b>) are axially guided. Here are the two pistons (<b>19</b>a, <b>19</b>b) of a respective helical compression spring (<b>21</b>a, <b>21</b>b) on the one hand via one rubber plate (<b>22</b>) at the Cylinder base and the other hand against a piston shoulder supported, in the direction of a respectively associated stop (<b>23</b>) in the immediate vicinity of the steering shaft (<b>2</b>) Pressed.

There is thus a movement coupling-type fit between Rack (<b>18</b>) And the respective piston (<b>19</b>a, <b>19</b>b) only at a steering angle from the central position shown by to the right or to the left, ie, in a steering wheel left remains the in <b>Fig.</b> 2 left piston (<b>19</b>a) in its Starting position on the associated stop (<b>23</b>), While the other Piston (<b>19</b>b) of the rack (<b>18</b>) Against the force of associated helical pressure spring (<b>21</b>b) is moved. The same applies with reversed roles of the two pistons (<b>19</b>a, <b>19</b>b) for a Steering wheel to the right. The respective stop (<b>23</b>) stationary piston simultaneously serves for guiding the rack (<b>18</b>). In order to the center position, that is, the straight-ahead position of the Steering, the transition between the two pistons (<b>19</b>a, <b>19</b>b) takes place not too hard, is located in each flask (<b>19</b>a, <b>19</b>b) a transverse hole (<b>24</b>) That a dangerous release of air just before the stop of the guide in the piston (<b>19</b>a, <b>19</b>b) prevented. This measure reduces the control effort to the steering wheel center position around.

In addition to this passive, mechanical feedback-moment generating Device is a more active, electrically reaction-torque-generating device provided that a Electric motor (<b>25</b>) Which via a worm on a positively to the steering shaft (<b>2</b>) Connected gear (<b>26</b>) is coupled. The electric motor may be in the four-quadrant Operating be operated and can therefore at any, adjusted steering angle setpoint driving and braking Retroactivity moments on the steering wheel (<b>1</b>) to create. Of Furthermore, in <b>Fig.</b> 2 still at an end cover (<b>27</b>) subsequent steering shaft angle sensor (<b>28</b>) Represented, which the rotational position of the steering shaft (<b>2</b>) Absolute and incremental detected.

During operation of the steering device for the electric motor (<b>25</b>) Different depending on the vehicle speed, to be produced Retroactivity moments on the steering shaft (<b>2</b>), And thus the steering wheel (<b>1</b>) Set, while the mechanically reaction-torque-generating device naturally a linear generated by the steering angle amount dependent reaction torque, the for example in the steering wheel center position 3 Nm and in a adopted, maximum steering angle amount of approximately 550 ° 5 Nm is. At low speeds is now the Electric motor (<b>25</b>) Operated so that the by it together with the mechanical feedback-moment generating device supplied Total reaction torque independently of the steering wheel angle a has constant value of z. B. 3 Nm and in each case the direction the steering wheel angle change is opposite. This means, that towards greater steering wheel angle values ​​of the electric motor (<b>25</b>) An acting towards smaller steering wheel angle amounts Reaction torque generated linearly from zero in the Steering wheel center position until -2Nm at the maximum steering wheel angle increases. In restoring the steering wheel movement compensates for the Electric motor (<b>25</b>) In addition, the reaction torque of mechanical means so that a constant in this case, acting in the direction of larger steering wheel angle amounts Reaction torque of -3Nm arises. These increases the from Electric motor (<b>25</b>) Delivered reaction torque of -6Nm in Steering wheel center position until -8Nm at the maximum steering angle.

In the high speeds, however, is a consistent overall reaction torque of, for example, 5 Nm set independently of the steering wheel rotation. To this end, compensates for the electric motor (<b>25</b>) In a with increasing Steering wheel angle amount decreasing dimensions the effect of mechanical feedback-moment generating means by which he generated torque of z. B. 2 Nm in the steering wheel center position linearly on null drops at the maximum steering angle. Depending on requirements, , a gradual transition of these two, for the respective Speed ​​range particularly advantageous Reaction torque characteristics in its intermediate speed range provided.

In the <b>Fig.</b> 3 and 4 is a second example of a combined, mechanically and electrically non-reactive moment generating Means for a steering apparatus according to type of <b>Fig.</b> 1 shown. The means of suitable bearings in a housing (<b>29</b>) guided steering shaft (<b>30</b>) Is again in a certain section designed as a pinion with which a transversely to the steering shaft (<b>30</b>) tooth rail (<b>31</b>) Cooperates, by a thrust piece (<b>32</b>) Which extends via a compression spring (<b>33</b>) On the housing (<b>29</b>) supported, is pressed onto the steering shaft pinion. Over a Gear coupling (<b>34</b>) Is a sensor (<b>35</b>) For measuring the Steering shaft rotational position docked. With, for example, of<b>Fig.</b> 2 analog coupling is the shaft of a feedback-moment generating electric motor via a worm (<b>36</b>) And a worm wheel (<b>37</b>) With the steering shaft (<b>30</b>) connected, wherein the electric motor described herein, as in all other Examples adapted-self-locking.

The mechanical feedback-torque-generating device includes mirror symmetry in this embodiment, two Within a cylinder (<b>38</b>) Arranged, U-shaped flask (<b>39</b>a, <b>39</b>b) the intermediate from a single Helical compression spring (<b>40</b>) Are forced apart. Of the cylinder (<b>38</b>) Is on a side of the steering shaft (<b>30</b>) With transversely arranged lying same longitudinal axis, on the opposite side a receiving sleeve (<b>41</b>) sufficient Length is provided to the each side the projecting part of the rack (<b>31</b>) Record.

The rack (<b>31</b>) Is a common piston rod in both Piston (<b>39</b>a, <b>39</b>b) coupled with them in the <b>Fig.</b> 4 right Piston (<b>39</b>b) with the interposition of a guide tube (<b>42</b>) crosses and with an annular shoulder about an interposed Ring spring (<b>43</b>) Plastic axially against the piston head to Conditioning comes. From there the rack occurs (<b>31</b>) with a thinner bolt section of the piston head and extending up through the bottom of the other piston (<b>39</b>a) through, where It ends with an end portion of larger diameter, in turn, of a setting sleeve (<b>44</b>) Is guided on the outside of the the associated piston (<b>39</b>a) slides. The rack (<b>31</b>) comes with an annular shoulder its end portion on a more annular spring (<b>45</b>) Plastic against the bottom of this piston (<b>39</b>a) to invest. The adjustment sleeve (<b>44</b>) Is in the cylinder (<b>38</b>) Screwed with her by changing axial position of the bias of the helical compression spring (<b>40</b>) is adjustable. A plastic ring (<b>46</b>) Between adjusting sleeve (<b>44</b>) And an associated piston (<b>39</b>a) prevents hard Serving these two steel components and thus serves to Noise attenuation.

In a rack movement <b>Fig.</b> 4 to the right remains the right piston (<b>39</b>b) in its initial position, while the left Piston (<b>39</b>a) of the rack (<b>31</b>) Compressing the Helical compression spring (<b>40</b>) Is taken. Analog remains at a rack leftward movement of the left piston (<b>39</b>a) in its initial position, while the right piston (<b>39</b>b) against the Force of the helical compression spring (<b>40</b>) Is shifted to the left. The plastic spring washers (<b>43</b>. <b>45</b>) Between the rack (<b>31</b>) and each piston crown have on the one hand Noise reduction function and, secondly, they provide a steep, but not jump in Characteristic of the generated by this facility Retroactivity torque depending on the steering angle. With This feature allows the two spring rings (<b>43</b>. <b>45</b>) a flexible coupling between the steering wheel and steering shaft (<b>30</b>) replace.

The reaction torque generation can in setting up the <b>Fig.</b> 3 and 4 additionally by a pressure fluid circuit with a liquid or gaseous pressure fluid can be influenced. To this end, includes the cylinder (<b>38</b>) A first hydraulic fluid port (<b>47</b>), Which in one of the adjustment sleeve (<b>44</b>) On the one hand and the left piston (<b>39</b>a) on the other hand limited, first pressurized fluid space (<b>48</b>) Opens, and a second pressure fluid port (<b>49</b>) of in a one hand from the guide tube (<b>42</b>) And on the other hand from the right piston (<b>39</b>b) limited, the second working chamber (<b>50</b>) opens. A pressure fluid of the respective Working space (<b>48</b>. <b>50</b>) Has a counter to the force of Helical compression spring (<b>40</b>) Acting pressure force on the respective piston (<b>39</b>a, <b>39</b>b) the result so that the piston (<b>39</b>a, <b>39</b>b) only a reduced to the pressing force Reaction torque-on the rack (<b>31</b>) Exerts. When the Pressure fluid pressure force exerted on the piston (<b>39</b>a, <b>39</b>b) Force of the helical compression spring (<b>40</b>) Exceeds moves respective piston (<b>39</b>a, <b>39</b>b) counter to the elastic force of the Helical compression spring (<b>40</b>), Whereby the rack movement in the direction corresponding to a predetermined length any reaction torque of the helical compression spring (<b>40</b>) is kept free, while at the same time Reaction torque for the opposite rack and so that the steering wheel movement to the value of the force exerted by the pressurized fluid Compressive force increases.

Incidentally corresponds the operation of this device that of <b>Fig.</b> 2, to which reference may be made, with the Modification that now in addition to the feedback-moment generating motor of the pressure fluid circuit to Adjustment of each desired reaction torque and in particular the desired depending on the situation Kompen organization of Pressure force of the helical compression spring (<b>40</b>) can be used.

The other, in <b>Fig.</b> 5 embodiment shown corresponds in its mode of action as regards the reaction torque generation on the steering wheel (<b>1</b>) Completely the arrangement of <b>Fig.</b> 3 and 4, differs from this, however, in the positioning of its components. In particular, the device includes from <b>Fig.</b> 5 a cylinder (<b>51</b>) Mirror symmetry with two in arranged and axially movable piston guided (<b>52</b>a, <b>52</b>b) of a helical compression spring (<b>53</b>) Pushed apart will. Further, here again, a pressure fluid circuit according to the example of <b>Fig.</b> 3 and 4 are provided to in addition, the reaction torque characteristic in the desired Way to influence. In addition to the respective pistons (<b>52</b>a, <b>52</b>b) is a respective guide (<b>62</b>a, <b>62</b>b) as an axial limitation the associated pressure fluid workspace. Characteristically, However, in this apparatus, the cylinder (<b>51</b>) In addition to the turn in suitable bearings (<b>54</b>. <b>55</b>) Mounted steering shaft (<b>2</b>) positioned parallel to this longitudinal axis. correspondingly is also a common piston rod for the two pistons (<b>52</b>a, <b>52</b>b) acting rack (<b>56</b>) Parallel laterally next the steering shaft (<b>2</b>). The coupling of the rack (<b>56</b>) done via a gearbox with an intermediate shaft (<b>57</b>), On the rotationally fixed Firstly, a with the rack (<b>56</b>) Cooperating pinion (<b>58</b>) And on the other hand, a bevel gear (<b>59</b>) Sit playing with a rotationally fixed to the steering shaft (<b>2</b>) Seated bevel (<b>60</b>) Meshes. The serving as active reaction-torque-generating device Electric motor (<b>25</b>) Is in the apparatus of <b>Fig.</b> 5 via a Another gear transmission (<b>61</b>) To the steering shaft (<b>2</b>) Coupled. As from <b>Fig.</b> to identify 5, this design requires the feedback-moment generating complex particularly little space transversely to the steering shaft (<b>2</b>).

In <b>Fig.</b> 6 is shown an embodiment in which the Driving unit not shown in the examples described above a rack coupling but a Exzenterscheibenkopplung includes. More specifically, in this steering apparatus for Coupling a mechanical feedback-moment generating Means a transmission with a parallel and adjacent to the steering shaft (<b>2</b>) Lying intermediate shaft provided rotatably on the one gear (<b>63</b>) Which is formed with a pinion as Steering shaft portion engages, and an eccentric (<b>64</b>) sit. Against the outer periphery of the eccentric disc (<b>64</b>) lies a piston rod (<b>65</b>) Via a rotatable roll (<b>66</b>) Meshing to, wherein a notch (<b>67</b>) On the outer periphery of the eccentric (<b>64</b>) A latching wheel center position defined. The piston rod (<b>65</b>) Forms in integrated design with its other end (<b>68</b>) In a cylinder (<b>69</b>) guided piston, in which a sealing ring seal (<b>70</b>) is embedded. On the outside of the cylinder (<b>69</b>) Of a Helical compression spring (<b>71</b>) Surrounded, on the one hand against him a Zylinderbodenflansch (<b>72</b>) And on the other hand against a plunger flange (<b>73</b>) Is supported and in this way Piston rod (<b>65</b>) Against the Exzenterscheibenaußenumfang presses.

The eccentric (<b>64</b>) Pushes the piston rod (<b>65</b>) in both Steering directions symmetrically at from 0 ° to 180 ° rising Exzenterscheibendrehwinkel increasingly against the force of Helical compression spring (<b>71</b>) Back, which according to a rising reaction torque by the compression coil spring (<b>71</b>) Results. Due to the under-setting interpretation of Transmission corresponds to half a Exzenterscheibendrehung significantly larger angle of rotation of the steering shaft (<b>2</b>) coupled steering wheel, for example, over 500 °, which is a sensitive reaction torque setting to fit the Steering wheel angle, as in the above embodiments allows. In addition, the can of this institution producible reaction torque again by a pressure fluid circuit be affected, including the cylinder base a Pressure fluid passage (<b>74</b>) To the cylinder (<b>69</b>) And with the piston rod (<b>65</b>) Integrated formed piston (<b>68</b>) bounded workspace (<b>75</b>) is provided. A Overpressurization this working space (<b>75</b>) Causes here a gain of the feedback torque by the pressure force same direction as the force of the helical compression spring (<b>71</b>) on the Piston rod (<b>65</b>) Acts. Instead of the arrangement shown, the Piston rod (<b>65</b>) Transversely to the steering shaft (<b>2</b>) comes of course, a parallel positioning in Consideration, including the gear z. B. by a bevel gear in the style of <b>Fig.</b> 5 may be modified.

show The embodiments described that the Steering apparatus according to the invention comprises means for Reaction torque generation for a mechanically from the Steering angle adjusting device decoupled Steering angle setting device comprises at which a advantageous reaction torque characteristic can be adjusted and the very compact with a small space requirement in mounted steering shaft area. This is, for example, adjustable steering wheel assemblies in motor vehicles advantageous wherein with the steering shaft and the reaction-torque-generating complex is pivoted.