Rear axle steering and rear axle of a vehicle and vehicle

Abstract

The invention relates to a rear axle steering system of a vehicle comprising: a central actuator for the translational displacement of a rack which is connected to two wheels of the rear axle via a tie rod and which causes a change in the steering angle of these wheels; the rear axle steering system comprising at least one sensor unit for detecting a change in the position of the rack; the sensor unit comprising a sensor transmitter and a sensor, the sensor unit being arranged such that the change in position and / or the position of the rack is measurable outside the rack itself.

Description

The invention relates to a rear axle steering system for a vehicle according to claim 1. For the prior art, reference is made, by way of example, to DE 10 2013 203 188 A1. Rear-axle steering has long been established in passenger cars. With rear-axle steering, the turning of the rear wheels directly influences the vehicle's dynamics. This offers advantages in many driving situations. Rear-axle steering is used in some cars to improve driving dynamics and, in particular, to enable efficient driving and thus greater driving comfort during maneuvering and parking at low speeds. To execute the corresponding steering commands, hydraulic or electromechanical actuators can be used, just as with front-axle steering. For example, an active rear-axle steering system similar to that on the front axle (rack and pinion steering, etc.) can be used, which adjusts both rear wheels via tie rods. In this variant, a central actuator is located in the middle of the vehicle's rear axle, steering both rear wheels. DE 10 2013 203 188 A1 provides an example of an active rear-axle steering system with a central actuator. Achieving higher rear-wheel steering angles, particularly in vehicles with driven rear axles and relatively long wheelbases, presents a challenge. The trend towards larger steering angles means that the rear-axle steering system, especially in the lateral direction, requires increasingly more installation space. This, in turn, can lead to problems with the track rod length and thus with the vehicle's kinematic design. In addition to their width, the deflection travel of guides, actuators, and sensors mounted on the rack must also be accommodated. This creates a conflict between limiting the available installation space in the lateral direction and achieving high steering angles. The purpose of the invention is to resolve the aforementioned conflict of objectives as far as possible. The solution to the problem is achieved by a rear axle steering system of a vehicle with the features of claim 1, a rear axle of a vehicle with the features of dependent claim 7, and a vehicle with the features of dependent claim 10. Advantageous embodiments and further developments are the subject of the dependent claims. An active rear axle steering system for a vehicle, designed in particular as a rack and pinion steering system, is proposed. The rear axle steering system comprises a central actuator for the translational displacement of a rack (also known as a steering linkage). The rack itself is connected to at least two (opposite) rear wheels of the rear axle via tie rods (also known as track rods) and, during translational movement, causes a change in the steering angle of these rear wheels. A translational or axial displacement of the rack thus results in a steering movement of the at least two rear wheels. When installed in the vehicle or rear axle, the rack is positioned at least approximately in the transverse direction of the vehicle, which is why a translational movement is essentially a movement in the transverse direction of the vehicle. A rack according to the invention does not necessarily have to comprise "teeth" driven by a gear. Instead, a rack according to the invention is a device that is translationally movable or driven and thus moves a left and right track control arm. The actuator can be controlled electromechanically or electromotorically. The actuator is firmly connected to the body or vehicle structure via a housing, in particular designed as a steering gear housing. The rear axle steering system includes at least one sensor unit for detecting a change in position or the position of the rack. The sensor unit is particularly preferably designed as a displacement sensor or position sensor to detect the translational movement of the rack and to measure the corresponding steering angle. The sensor unit comprises a sensor transmitter as a moving element and a sensor as a measuring element. It is provided that the sensor unit is arranged in such a way that the change in position or the position of the rack outside the rack can be mapped and measured. This arrangement of the sensor unit enables indirect measurement of the rack travel, rack position, or rack position change. The rack travel, position, or position change can thus be measured outside the rack itself, eliminating the need for additional path or distance in the vehicle's transverse direction for the sensor unit. This largely resolves the aforementioned conflict between available installation space in the vehicle's transverse direction and the simultaneous design and implementation of high steering angles (or comparatively large rack travels). It is particularly preferred that the sensor transmitter of the sensor unit is arranged outside the rack itself. For the purposes of this invention, an arrangement outside the rack means that the sensor is not directly connected to the rack and therefore no additional installation space in the transverse direction of the vehicle needs to be provided for the sensor in the length of the rack. Thus, the width of the sensor unit and the deflection paths no longer need to be provided within the rack or the installation space for the rack. In this case, the sensor is in particular connected to a component or represents a component that maps the rack travel in the same way as the rack itself. In an advantageous embodiment of the invention, each tie rod is connected to the rack at one end via tie rod receptacles. The tie rod receptacle accommodates the tie rod described above, which connects the rack to the wheel carrier or the vehicle wheel. A tie rod receptacle can, for example, be in the form of a clevis and is rigidly connected to a rack end. Preferably, the sensor is arranged on or integrated into at least one of the tie rod receptacles. Particularly preferably, a sensor is arranged on or integrated into each of the tie rod receptacles. Thus, for example, a tie rod end, in particular a clevis, can represent the sensor itself, or the sensor can be attached or connected to it accordingly. The sensor of the sensor unit is preferably arranged on the vehicle structure or body, or on a component fixed to the vehicle structure or body. Particularly preferably, the sensor is connected to the housing of the actuator (for example, the steering gear housing) or to an axle carrier, especially a rear axle carrier (for example, elastically mounted to the body), of the vehicle. The entire sensor unit is thus arranged independently of the dimensional chain "tie rod to tie rod" and the geometric design, in particular the installation space of the rear axle steering in the transverse direction of the vehicle, can thus be selected independently of the sensor unit. On an axle where a rack is connected to the vehicle wheels via a tie rod, a sensor is preferably arranged at each tie rod mounting point. Likewise, each sensor is preferably assigned a vehicle-mounted or body-mounted sensor. The sensor unit can function as an inductive, capacitive, or optical sensor, or as a Hall sensor. It is also possible to use ultrasonic, potentiometric, or other sensor technologies. For example, the sensor generator is designed to create a magnetic field, and the sensor is designed to detect the magnetic field. The sensor can, for example, include at least one Hall sensor. The sensor generator can, for example, include at least one permanent magnet. Furthermore, a rear axle of a vehicle (in particular a two-track vehicle) with rear axle steering, configured according to any one of claims 1 to 6, is proposed. A vehicle with a rear axle, configured according to any one of claims 7 to 9, is also proposed. The rear axle comprises a rear axle carrier as well as several wheel-guiding control arms that are attached to the rear axle carrier. The rear axle carrier itself comprises at least one cross member, which is aligned at least approximately in the transverse direction of the vehicle, and at least two longitudinal members, each of which is aligned at least approximately in the longitudinal direction of the vehicle. Particularly preferably, the rear axle also includes an electric motor drive unit suspended in the rear axle carrier for the wheels of the rear axle (and preferably for all wheels of the vehicle). Especially when installing an electric motor drive unit in the vehicle or on the rear axle, the installation space (particularly the possible leeway in the linkage lengths) is severely limited, which is why a rear axle steering system according to the invention with less installation space requirement in the transverse direction of the vehicle is particularly advantageous here. The central actuator of the rear axle steering is preferably positioned at least approximately on the vehicle's longitudinal axis. The housing of the rear axle steering actuator is preferably connected to at least one crossmember or to a vehicle body. The crossmember to which the actuator housing is preferably connected is further preferably located behind the wheel center of the rear wheels, acting in the transverse direction of the vehicle, when viewed in the direction of travel. The rear axle steering system according to the invention allows for a freer design of the control arm lengths, in particular the length of the tie rod, which is why, for example, the tie rod can meet the kinematic requirements of the rear axle despite high adjustable steering angles and thus high rack travel (especially from approx. 30 mm rack travel) thanks to the rear axle steering system. The maximum rack travel of an exemplary rear axle steering system is preferably at least 20 mm. Particularly preferably, the maximum rack travel is in the range of 24 mm to 35 mm. Furthermore, the rear axle or rear axle steering is preferably designed in such a way that steering angles of at least 7 degrees are possible. The wheels of the rear axle are particularly preferably driven or can be driven by a suitable drive unit, in particular an electric motor drive unit. These and other features are evident not only from the claims and the description but also from the drawings, wherein the individual features may be realized individually or in combination in one embodiment of the invention and may represent advantageous and, in themselves, protectable embodiments for which protection is claimed here. The invention will now be explained in more detail using an exemplary embodiment, with the accompanying Fig. 1 showing a schematic view of part of a rear axle steering system of a vehicle. Fig. 2 shows an exemplary rear axle in a schematic view including the part of the rear axle steering system from Fig. 1. All features described in more detail may be essential to the invention. Fig. 1 shows part of an active rear-axle steering system of a vehicle, in particular a passenger car. The rear-axle steering system comprises a central actuator 1 for the translational displacement of a rack 2. As can be seen in Fig. 2, the rack 2 is connected to two wheels of the rear axle via a tie rod 3 each. The tie rods 3 are each rigidly connected to a rack end via tie rod mounts 7 (in particular, fork arms). A translational movement of the rack 2 (in the longitudinal direction when installed in the vehicle) initiated by the actuator causes a change in the steering angle of the two wheels 4 via the two tie rods 3. The rear axle steering system further comprises a sensor unit with a sensor 5 and a sensor transmitter 6 for detecting a change in position or the position of the rack 2 and for measuring the rack travel or for measuring and / or calculating and / or estimating a steering angle of the rear axle steering system. The sensor unit is arranged or mounted on the rear axle or the rear axle steering system in such a way that the change in position or the position of the rack can be measured outside the rack itself. For this purpose, in this specific example, a sensor transmitter 6 of a sensor unit is arranged on or integrated into each tie rod end 7. Furthermore, a corresponding sensor 5 of a sensor unit is arranged on the body- or vehicle-structure-mounted housing of the actuator 1 (not shown in detail). Each sensor transmitter 6 represents the element to be measured.The component is represented by a sensor 5, while a corresponding sensor 5 is the measuring element or component. This arrangement of the sensor unit outside the rack 2 itself enables the rack travel to be mapped or measured without requiring additional installation space in the transverse direction Q of the vehicle or along the longitudinal axis A of the rack for the sensor unit itself or for the deflection paths with the sensor unit. Instead, the sensor unit is spatially displaced outside the rack 2, which offers significantly greater design freedom for the rear axle and its kinematics, particularly for achieving high steering angles at the rear axle. As can be seen in Fig. 2, a preferred rear axle comprises a rear axle carrier with two longitudinal members 8 (viewed when installed in the vehicle) oriented in the longitudinal direction L of the vehicle, and in this case, three cross members 9 (also viewed when installed in the vehicle) oriented at least approximately in the transverse direction Q of the vehicle, which connect the two longitudinal members 8 to each other. Several wheel-guiding links 10 connect the rear axle carrier to each wheel 4 (only indicated). The rear axle steering, or in particular the housing of the actuator 1, is connected at least approximately centrally to the rearmost cross member 9 when viewed in the direction of travel F of the vehicle. The rear axle steering is thus arranged, when viewed in the direction of travel, behind a wheel center M of the rear wheels 4 that acts in the transverse direction Q of the vehicle. A steering movement of the wheels 4 is initiated by a translational movement of the rack 2 (in the installed state in the vehicle at least approximately in the transverse direction Q of the vehicle), via a respective tie rod 3 to the respective wheel 4. Particularly preferably, an electric motor drive unit (not shown) is suspended on the rear axle shown in Fig. 2 for at least partial drive of the vehicle or the vehicle wheels 4. Such a drive unit is further preferably connected between the two front cross members 9 on the rear axle carrier (viewed in the direction of vehicle travel F). Particularly preferably, the wheels 4 of the rear axle are even driven, in particular by the electric motor drive unit. Especially when such an electric motor drive unit is arranged on the rear axle, the available installation space is particularly limited, especially in the transverse direction Q of the vehicle. A "narrowing" or saving of the installation space in the transverse direction Q of the rear axle steering, as made possible by the invention shown here, facilitates orThis even makes it possible to achieve high steering angles while allowing for largely unrestricted freedom in the design of the axle kinematics and steering linkage. QUOTES INCLUDED IN THE DESCRIPTION This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature DE 10 2013 203 188 A1 [0001, 0003]

Claims

Rear axle steering of a vehicle comprising: a central actuator (1) for the translational displacement of a rack (2) which is connected to two wheels (4) of the rear axle via a tie rod (3) and causes a change in the steering angle of these wheels (4); the rear axle steering comprising at least one sensor unit for detecting a change in position of the rack (2); the sensor unit comprising a sensor transmitter (&) and a sensor (5); the sensor unit being arranged such that the change in position and / or the position of the rack (2) can be measured and / or displayed outside the rack (2) itself. Rear axle steering according to claim 1, wherein the sensor transmitter (6) of the sensor unit is arranged outside the rack (2). Rear axle steering according to claim 1 or 2, wherein a respective tie rod (3) is connected to the rack (2) at one end via tie rod receptacles (7) and wherein the sensor transmitter (6) is arranged on at least one of the tie rod receptacles (7) and / or is integrated into the tie rod receptacle (7). Rear axle steering according to one of the preceding claims, wherein the sensor (5) of the sensor unit is arranged on the vehicle body and / or on a component fixed to the vehicle body. Rear axle steering according to one of claims 3 to 4, wherein a sensor transmitter (6) is arranged on each of the two tie rod mounts (7) and a corresponding sensor (5) is arranged on the vehicle body side and / or body side. Rear axle steering according to one of the preceding claims, wherein the sensor unit is an inductively and / or capacitively and / or optically acting sensor unit. Rear axle of a vehicle with a rear axle steering system designed according to one of claims 1 to 6, comprising a rear axle carrier and several wheel-guiding control arms (10) supported on the rear axle carrier, wherein the rear axle carrier comprises at least one cross member (9) which is aligned at least approximately in the transverse direction (Q) of the vehicle and at least two longitudinal members (8) which are each aligned at least approximately in the longitudinal direction (L) of the vehicle. Rear axle according to claim 7, comprising an electric motor drive unit suspended in the rear axle carrier for at least partial drive of the vehicle. Rear axle according to one of the preceding claims 7 or 8, wherein the housing of the actuator (1) of the rear axle steering is connected to the at least one cross member (9) and / or to a vehicle body and wherein this cross member (9) is arranged behind a wheel center (M) of the rear wheels (4) acting in the vehicle direction (F) when viewed in the direction of travel (F). Vehicle with a rear axle designed according to one of claims 7 to 9.

Images