Steering device for a motor vehicle

[0002] The invention relates to a device for generating a steering signal for controlling an actuating drive for an adjustment of steerable wheels on motor vehicles, in particular passenger vehicles.

[0003] For reasons of safety and comfort, endeavors have been made for some time, apart from the actuation for the horn contact, to arrange more and more devices for actuation of the most varied of vehicle functions (lamp switches, windscreen wipers, window lifters, radio, heating, telephone) directly in the steering wheel, so that the driver is no longer forced to take one hand from the steering wheel to switch on such functions. It is immediately clear that the transmission of electrical signals generated on a rotatable steering wheel to the adjusting members fixedly arranged in the bodywork of the motor vehicle is not without problems, in particular when a plurality of different signals has to be transmitted. Therefore, already fixed or substantially fixed steering devices were proposed, in which the mechanical coupling between steering device and steering linkage has been replaced by a measurement transducer on the steering device and an actuating drive on the steering linkage. With such steering devices, one can dispense with the conventional maximum 2 to 4 revolutions to achieve the maximum steering angle of the wheels and one can limit the actual adjustment distance for the actuation of the steerable wheels to a rotation angle of 30 degrees or less. Thereby, the transmission of a plurality of signals is not a problem, because the actuating devices are either arranged on parts of the steering device which are constructed so as to be fixed relative to the bodywork, or else on parts of the steering device which are only able to be moved by a small rotation angle relative to the bodywork, so that one manages with simple lead loops in order to be able to produce an electrical connection between rotating and fixed parts.

[0004] A mechanical uncoupling and an electrical transmission of the steering command to the steerable wheels is also necessary if one wishes to achieve a driver-independent vehicle stabilizing by means of modern safety systems and in so doing also wishes to influence the adjustment angle of the steerable wheels.

[0005] The development of such steering devices is still at its beginnings and the proposals made hitherto still do not satisfy all requirements.

[0006] The invention provides a steering device which is of simple construction and which, vis-a-vis conventional steering wheels, demands from the driver only little effort to get into the way of it. This is achieved in a device which comprises a non-rotatable frame having an axis of symmetry and curved guiding portions, as well as a pair of handles intended for transmitting actuating forces and being coupled with each other. The handles are mounted on the guiding portions so as to be displaceable in same direction and are able to be displaced along the guiding portions and relative to the axis of symmetry to a limited extent. The device further comprises a measurement transducer for generating one of an electrical and electronic signal for determining a position of the handles relative to the frame.

[0007] The proposed steering device has the advantage that it can readily take the place of conventional steering wheels, without the driver having to assume a completely different steering-and sitting position. The steering commands are also introduced through an accustomed movement of the handles which are coupled with each other, and owing to the comparatively short adjustment distance, no alteration of the position of the hands is necessary as in conventional steering wheels, which is to be regarded as advantageous with regard to safety and comfort.

[0008] FIG. 1 shows a first embodiment of the steering device according to the invention in top view.

[0009] FIGS. 2a,2bshow a second embodiment of the idea of the invention, partially in top view (FIG. 2a) and partially in section (FIG. 2b).

[0010] FIGS. 3ato 3cshow details of the embodiment according to FIG. 1.

[0011] FIGS. 4ato 4dshow details of further embodiments of the idea of the invention.

[0012] The embodiment of the idea of the invention illustrated in FIG. 1 comprises a frame 1 with curved guiding portions in the form of guide rails 1aon and along which a pair of handles 3a,3b,coupled with each other and likewise being curved, are mounted so as to be displaceable along the guiding portions by a limited extent in same direction to the axis of symmetry 2. In the illustrated example embodiment, the guide rails 1aare constructed in the form of circle segments, so that the handles 3a,3bcan perform a circular movement about a point of the axis of symmetry 2 which can also be a central axis. This circular movement corresponds to the usual hand guidance in the case of a rotatable steering wheel, so that the actuation of the steerable wheels does not require any re-acclimatization for the driver. The handles 3a,3beach consist of a lower and an upper shell, merely the lower shell being illustrated in FIG. 1. In the guide rails 1a,slits 1bin the shape of circular arcs are formed, into which a transmission element 14, firmly connected with the handles 3a,3b,engages. This transmission element 14 is connected with a cable 6 which is guided in the frame 1 in a cable guide 15, as in the case of a known Bowden cable. In this way, the two handles 3a,3bare coupled with each other mechanically, and they can therefore automatically only be actuated in same direction. Screw elements 18 or pre-stressed elements, not shown, can be used for tensioning the cable, as are usually in the known Bowden cables.

[0013] The ends of the cable 6 are connected with a transmission element 11, which in turn is fastened to a toothed rack 12 which engages into a toothed wheel 13 cooperating with a measurement transducer 4 for generating an electrical or electronic signal. The parts last mentioned are arranged in a housing 16 which is situated behind a covering 17 which is only partially illustrated.

[0014] With a movement of the handles 3a,3bin same direction, the cable 6 is entrained via the transmission element 14, so that its movement is transferred onto the transmission element 11 and hence finally onto the measurement transducer 4. Through a movement of the handles 3a,3btherefore a signal can be generated for an adjustment member which acts on the steering linkage. Preferably, the signal generated is proportional to the relative displacement between handles and frame. Springs 31 act as a means for automatically returning the handles into the neutral initial position which is illustrated.

[0015] The previously described components are illustrated again in FIGS. 3ato 3c,in which FIG. 3acorresponds substantially to the left-hand part of FIG. 1 and only differs therefrom in that the housing 16, in which the measurement transducer 4, the toothed rack 12 and the toothed wheel 13 are situated, is illustrated closed here. FIGS. 3band 3cshow once again on an enlarged scale the connecting of the cable 6 to the transmission elements 11 and 14 and also the configuration of the slit 1bin the guide rail 1a.Further explanations to FIGS. 3ato care not necessary. FIGS. 2aand 2bshow a second embodiment of the idea of the invention which differs from that according to FIG. 1 merely in that in place of a cable, a band 5 is used and that instead of a cable guide 15 a band guide 15′ is provided. A further difference can be seen in that the band guide 15′ other than the cable guide 15 is provided only in the lower part of the frame 1 and that the transmission elements 11 and 14 are also the slit 1bin the guide rail 1aare designed to the cross-sectional shape of the band. The handles 3aand 3bare in turn constructed as two half shells, of which in FIGS. 2aand 2bonly the lower shells are illustrated. The housing is in turn designated by 16, in which the measurement transducer 4, a toothed rack 12 and a toothed wheel 13 are accommodated. From the sectional illustration according to FIG. 2bit can be seen how the transmission element 11 is connected with the band 5 and that it moves via the toothed rack 12 the toothed wheel 13 and, hence, the measurement transducer 4. In FIG. 2b,a guiding portions illustrated as being turned through 90° into the drawing plane. Alternatively, a toothed belt 29 may also be used instead of the band 5; in that case the toothed rack 12 may be omitted.

[0016] In the embodiment according to FIGS. 4ato c,the mechanical coupling of the handles 3a,3baccording to the embodiments of FIGS. 1 to 3 is replaced by a hydraulic coupling, which comprises a duct system 7, arranged in the frame 1, with piston/cylinder units 8, 9, 10a,10b.The handles 3a,3bare arranged in the guide rail 1aof the frame 1 as in the embodiments hitherto described, so as to be displaceable about a point of the axis of symmetry on a circular arc, reach through a slit 1bin the guide rail 1awith a transmission element 14 and are connected with a piston 8 which engages in the cylinder 9 mounted stationary in the housing and, hence, can bring about a displacement of the hydraulic fluid situated therein. A second piston/cylinder unit 10a,10bis connected with the transmission element 11 which, as in the embodiments described hitherto, moves a measurement transducer 4 via a toothed rack 12 and a toothed wheel 13, the latter components being accommodated in the housing 16 so as to be not visible in the illustration. Parts of a covering are designated by 17, which covers the housing 16.

[0017] In FIGS. 4band 4conce again the connection of the transmission elements 11 and 14 to the pistons 10aand 8 is illustrated, which cooperate with the cylinders 10band 9 and are coupled with each other hydraulically via the duct system 7. Alternatively, the piston 10acould also be mounted stationary in the frame 1 and the cylinder 9 could be coupled with the handle, as can be seen from FIG. 4d.Further, as outlined in FIG. 4b,balls 33 also may fill the duct system 7 and act in a force-transmitting manner.

[0018] In all illustrated example embodiments, the steering movement introduced via the handles 3a,3bis transferred to a centrally arranged measurement transducer, in which the control signal for the actuating drive of the steering linkage is generated. The idea of the invention is of course not limited to these embodiments. It is conceivable for example that the handles 3a,3bare coupled mechanically with each other directly via a rotatable lever 35 as outlined in FIG. 1 and that one measurement transducer each is associated directly to the handles 3a,3b.Thereby, a steering device according to the invention would be provided, which is doubly secured against the failure of a measurement transducer. A greater security with respect to the measurement transducer can, however, of course also be achieved in that two or more centrally arranged measurement transducers are provided (see the second measurement transducer 4′ in FIG. 1), which are actuated as in the embodiments of FIGS. 1 to 4.