Method for producing a spindle drive of a steer-by-wire steering system and steer-by-wire steering system

Abstract

The invention relates to a method (500) for producing a spindle drive (13) of a steer-by-wire steering system (1) for a motor vehicle with a steerable front and / or rear axle, wherein the spindle drive (13) is produced at least from a translationally displacable spindle (5), a spindle nut (6) mounted in a stationary manner (6) and at least one bearing sleeve (30, 31, 130, 131, 150), wherein the at least one bearing sleeve (30, 31, 130, 131, 150) is provided as a bearing and connection component of the spindle (5). According to the invention, the at least one bearing sleeve (30, 31, 130, 131, 150) is produced in a preproduction step (510) at least partially from a fibre-plastic composite, wherein the bearing sleeve, in a first step (520) of assembling the spindle drive (13), is indirectly or directly joined to the spindle (5) in an integral and / or force-fitting and / or form-fitting manner.

Description

[0001] Method for producing a spindle drive of a steer-by-wire steering system and steer-by-wire steering system

[0002] The invention relates to a method for producing a spindle drive of a steer-by-wire steering system for a motor vehicle with a steerable front and / or rear axle as well as an actuator and a steer-by-wire steering system according to the preambles of the independent claims.

[0003] A steer-by-wire steering system according to DE 102014 206 934 A1 is known from the prior art. This system is connected to the vehicle body and acts centrally on both wheels or wheel carriers of a vehicle axle to change the wheel steering angle. Bearing sleeves made of solid round bars are provided to extend a spindle of a spindle drive.

[0004] DE 10 2019 213 979 A1 discloses the construction of bearing sleeves made of steel tubular components in order to reduce weight in steer-by-wire steering systems. By extending the spindle using a bearing sleeve made of tubular components as a semi-finished product, a steer-by-wire steering system can be adapted to the available installation space in the area of ​​an axle of the respective vehicle.

[0005] The invention aims to provide an alternative manufacturing and design for a steer-by-wire steering system with the objective of further reducing the weight. Furthermore, it should be possible to adapt the steer-by-wire steering system with minimal effort, depending on the available installation space on a vehicle axle.

[0006] The invention relates to the aspect of extending a spindle or spindle drive with a significantly reduced weight compared to known steer-by-wire steering systems. For this purpose, a method for producing a spindle drive for a steer-by-wire steering system, as well as an actuator and a steer-by-wire steering system according to the independent patent claims, are specified. Preferred embodiments are specified in the subclaims. According to a first aspect, the invention relates to a method for producing a spindle drive for a steer-by-wire steering system for a motor vehicle with a steerable front and / or rear axle. The spindle drive is manufactured from at least one spindle that can be displaced translationally or axially along its longitudinal axis, a stationary spindle nut, and at least one bearing sleeve for extending and supporting the spindle in a housing of the steer-by-wire steering system.

[0007] The spindle is provided for changing the steering angle of at least one wheel on a vehicle axle by displacement. By means of a movement thread formed by an external thread of the spindle and an internal thread of the spindle nut, an axial displacement of the spindle is carried out by rotating the spindle nut, preferably by indirect or direct rotary drive using an electric motor. For this purpose, at least one bearing sleeve is provided on at least one end of the spindle as a bearing and connecting component between the axially displaceable spindle and the wheel carrier or wheel to be steered. The bearing sleeve thus forms an extension of the spindle. The spindle is designed as a solid component which is manufactured from a semi-finished product such as round steel. For this purpose, a round steel is manufactured into a spindle by forming, for example by rolling and / or machining, such as turning and / or milling.The spindle is given an external thread which, depending on its pitch and the desired axial adjustment range, is preferably created by rollers. To enable low-friction and as quiet as possible operation of the steering, both the spindle nut and the spindle are manufactured to close tolerances and are therefore precision components. In terms of weight, it is advantageous to make the spindle as short as possible in terms of its axial extension and with the smallest possible diameter, preferably 10 to 20 mm. The spindle length depends on the intended use and the adjustment range required by the steer-by-wire steering. For a single actuator acting on each wheel, the spindle is preferably around 100 to 140 mm long. For a central actuator acting on both wheels on an axle, a length of around 190 to 300 mm is preferable. The transmission of the steering movement to the wheel carriers and thus the wheels and the guide and / or the maintenance of the set wheel steering angle, if necessary.The task of steer-by-wire steering using actuators is to achieve this by interposing control arms or a steering linkage. However, this is not achieved directly by coupling joint forks to the ends of the spindle. Instead, bearing sleeves are installed between the joint forks and the spindle ends as an extension of the spindle, which simultaneously ensure the bearing and guidance of the spindle in the steering housing along its longitudinal axis. By extending the spindle with bearing sleeves, the required overall length of the spindle drive for the respective steer-by-wire steering system can be achieved.

[0008] A steer-by-wire steering system preferably has at least a two-part housing which has a parting plane that is approximately orthogonal to the longitudinal axis of the spindle. The housing requires the most space in the area of ​​the movement thread. This is determined, for example, by the diameter of the spindle nut and also by the drive, e.g. a drive motor arranged parallel to the longitudinal axis of the spindle and a transmission, e.g. a necessary belt drive. If the available space is limited, for example in vehicles with a transmission or electric drive that is usually close to the axle and centrally arranged, the steer-by-wire steering system cannot be arranged centrally between the wheels. In this case, the steering system and its housing must be arranged very off-center in the area of ​​the parting plane, i.e. close to the wheels.This results in one end of the spindle being positioned relatively close to the wheel, while the opposite end is relatively far away from the opposite wheel. A relatively long spindle extension must be provided to bridge the gap between this wheel, which is further away from the parting plane of the housing. If a central steer-by-wire steering system were simply positioned off-center and the distance between the joint fork and the distant wheel or wheel carrier were bridged by a link, this would disadvantageously result in different positioning movements on the left and right wheels of the axle to be steered. This is due to kinematic reasons, and the differences in the wheel steering angles are so great that a uniform change in the wheel steering angles to an acceptable extent is not feasible.For this reason, the respective extension of the spindle must be selected so that the joint forks at the end of the bearing sleeve are each the same distance from the respective wheel carrier or wheel. For a centrally located steer-by-wire steering system, for example, bearing sleeves of approximately the same length would have to be selected. The extension of the spindle using the bearing sleeves is therefore related to the weight of the entire steer-by-wire steering system. Steering systems are usually subject to high tensile and compressive forces in the form of longitudinal and transverse forces of up to 15 kN during operation or in the event of misuse loads of up to approximately 50 kN (e.g. when driving onto a curb, etc.). Surprisingly, it has been found that these forces, which act on the steering of an axle in a motor vehicle from the wheels or wheel carriers at least via the bearing sleeves onto the spindle, can also be absorbed by a bearing sleeve made of fiber-plastic composite.It has been shown that a fiber-reinforced plastic composite component in the form of a bearing sleeve, preferably with a cylindrical design, is suitable for introducing, absorbing, and transmitting the aforementioned longitudinal and transverse forces. Bearing sleeves designed in this way are approximately 50% lighter than steel bearing sleeves of the same length.

[0009] According to the invention, it is therefore proposed to manufacture the bearing sleeve at least partially, preferably entirely, from a fiber-plastic composite, preferably with a wall thickness of 2 to 5 mm, preferably 3 to 4 mm. With regard to the manufacture of the spindle drive, the bearing sleeve is manufactured in a prefabrication step.

[0010] Depending on the design requirements regarding the expected tensile and compressive forces from the axle to be steered or the steer-by-wire steering system for a motor vehicle, a sleeve component with the appropriate length, wall thickness and diameter can be manufactured to suit.

[0011] In a first step of assembly of the spindle drive, the bearing sleeve is joined to the spindle directly or indirectly in a materially and / or non-positively and / or form-fitting manner. The ends of the spindle preferably have an external thread. Using this external thread, the spindle is screwed into the bearing sleeve's internal thread during assembly. This results in a form-fitting connection and, when subjected to the appropriate torque during assembly, also a force-fitting connection. This connection can be additionally secured in a materially bonded manner using an adhesive, such as threadlocker. Alternatively, only a materially bonded connection between the spindle and the bearing sleeve can be provided. The spindle extended in this way is screwed into the spindle nut in further assembly steps, and the spindle drive is installed in the housing of the steer-by-wire steering system.This means that the weight of a conventional steer-by-wire steering system in a car, designed as a central actuator, can be reduced by approximately 1000g.

[0012] Preferably, in the prefabrication step, at least one sleeve component is manufactured by at least the following steps: a) producing a textile semi-finished product b) pre-forming and creating a blank c) manufacturing the sleeve component. In step a), a textile semi-finished product can first be created from yarns and so-called rovings (also known as bundles, strands or multifilament yarns) made of parallel arranged filaments (also known as continuous fibers), which can, for example, be a flat woven fabric. A cylindrical sleeve component can be formed from this flat fabric using a cylindrical mold or a dome in step b). At the ends or on the front side, a widening in the sense of reinforcement, a contour or a thread can preferably be formed, as will be explained below. A combination is also possible, e.g.the sleeve can be widened outwards at the end and a contour or a thread or a suitable combination thereof can be formed on the inside. As an alternative to flat weaving, a cylindrical multi-part winding core can be used in steps a) and b). A blank for the intended sleeve component can be created around this winding core using the yarn and rovings. In this case, a round, preferably cylindrical semi-finished product is created in contrast to a flat semi-finished product, which may save a work step because a sleeve component can be formed straight away. The multi-part winding core can be provided with circumferential or axially running engravings so that so-called bandages and / or axial reinforcements are introduced or woven into the fabric made from the yarns and rovings for the bearing sleeve, which consists entirely or partially of the sleeve component.For this purpose, the multi-part winding core can have shaped segments, particularly at its ends, to create an inner contour or a thread. Bearing sleeves made of fiber-plastic composite can be designed with a conical widening at the end specifically to absorb transverse forces, which are primarily introduced from a wheel carrier indirectly via control arms or steering rods or directly via a joint fork into the ends of a bearing sleeve. With such intended contours or contour connections, the positive connection is created between approximately axially oriented fiber layers that follow the contours on the component surface, e.g. on the inner wall of the sleeve component. To prevent the contours from failing, the contours must be stiffened. For this purpose, expanders or inner tangential fiber layers can be introduced during production of the semi-finished product. In a final prefabrication step, the sleeve component is heated to a temperature of 150 °C with the addition of resin and, if necessary,The material is infiltrated using a mold and, if necessary, under pressure (air) or vacuum, and then consolidated. If necessary, the bearing sleeve can be subsequently machined. In a preferred design, machining is not required, thus resulting in further cost advantages.

[0013] In a preferred embodiment of the prefabrication for forming the bearing sleeve, a thread is formed on at least one end of the sleeve component in step b) and / or c). In order to be able to screw the spindle with its end-side external thread into the bearing sleeve, the thread is preferably designed as an internal thread in the prefabrication process in order to be able to carry out the form-fitting and force-fitting joining with the spindle in the assembly step. During the formation of the thread, the aforementioned bandages and / or axial reinforcements in the fabric made of the yarns and rovings are also introduced into the location of the sleeve component at which the thread is formed. The form fit is also created here for the contours for the thread to be formed between approximately axially oriented fiber layers that follow the thread contours on the component surface, e.g. on the inner wall of the sleeve component. In order to prevent failure of the contours, e.g.in the form of a thread as a result of the very high flank pressures, the contours must be stiffened, for which purpose expansion bodies or inner tangential fiber layers can be introduced during production of the sleeve component. In order to mount a joint fork on the opposite end of the bearing sleeve, the joint fork is screwed into the internal thread of the bearing sleeve in a later assembly step using a screw bolt with an external thread. This results in a simple option for joining the spindle to the bearing sleeve without any additional components using a bearing sleeve made exclusively from a fiber-plastic composite. In a further embodiment of the prefabrication for forming the bearing sleeve, a contour is formed on the sleeve component in step b) and / or c) at least at one end. The contour can be, for example,These are radially inward-projecting and axially adjacent projections that can interact in a form-fitting manner with a connecting component. As previously mentioned, bandages and / or axial reinforcements and / or shaped segments can also be incorporated into the fabric made from the yarns and rovings in step b) and / or c) in the area of ​​the contours to be formed. To prevent failure of the contours, e.g., in the form of an inner contour, the contours must also be stiffened here. For this purpose, expansion bodies or inner tangential fiber layers can also be introduced during the production of the sleeve component.

[0014] Preferably, in the step of prefabrication of the bearing sleeve, at least one insert is inserted into the sleeve component in step b) and / or c). The insert can be made of steel, preferably 30MnB4, for example. The insert can have an external thread and is screwed into the aforementioned internal thread at the end of the sleeve component of the bearing sleeve made of fiber-plastic composite and, if necessary, held there by means of a locking device, preferably by means of an adhesive, preferably a locking varnish. Alternatively, the insert can have an external contour, e.g. projections projecting radially outwards. For example, during the formation of an internal contour in the aforementioned steps, the insert can be inserted into the sleeve component and held there in a form-fitting manner. In another prefabrication step, in addition to the external thread or the external contour, an internal thread, e.g. by machining, is created on the insert.This internal thread allows the spindle to be screwed into the insert with its fastening thread during assembly. This creates an indirect connection between the bearing sleeve and the spindle.

[0015] Alternatively, the end of the spindle can also be non-positively connected to the insert, for example by means of an interference fit, preferably by shrinking the insert. Additionally or alternatively, the screw connection or the aforementioned non-positive connection can be secured by a material fit, for example by gluing. Alternatively, the end of the spindle can be connected to the end of the spindle by a material fit, preferably by gluing. The bearing sleeve can be designed such that a thread, as described above, is formed at one end and an insert, as described above, is inserted at the opposite end of the bearing sleeve. This allows for a variety of options for joining the spindle to the bearing sleeve. The same applies to connecting a joint fork to the spindle, for example by means of a screw bolt.

[0016] In a further embodiment, it is conceivable that, to produce the bearing sleeve, a first sleeve component can be manufactured with another prefabricated sleeve component made of fiber-plastic composite during prefabrication. In a further prefabrication step, the bearing sleeves can preferably be joined by a material fit, a force fit, and / or a form fit.

[0017] A steer-by-wire steering system can be designed as a type of modular system, so that many identical parts are used, e.g. spindle, spindle nut, belt drive, electric motor and, for example, the housing or parts of the housing. To apply the steer-by-wire steering system to different vehicles, it may be necessary, for example, that - to put it very simply - only the length of the steer-by-wire steering system needs to be adjusted. In addition to the already mentioned option of producing a bearing sleeve with the appropriate length, a bearing sleeve with a standard length can also be manufactured, e.g. 800 mm. This standard length forms the aforementioned first sleeve component. Depending on the required length of the steer-by-wire steering system, a further sleeve component is provided, which is prefabricated with the first component to form a bearing sleeve of the required length. This can result in further cost advantages.If the sleeve components are provided with inserts at one end, the sleeve components are preferably joined together at their opposite ends, facing away from the inserts, in particular by means of a material bond, preferably by adhesive bonding. It is also possible to prefabricate a bearing sleeve as a semi-finished product, e.g., 1000 mm in length. This semi-finished product is cut to length depending on the required length for the installation space.

[0018] CFRP (carbon fiber reinforced plastic) or GFRP (glass fiber reinforced plastic) are preferably used as materials for bearing sleeves made of fiber-reinforced plastic in the prefabrication step (510). These materials are suitable in terms of their strength for the tensile and compressive forces due to the expected longitudinal and transverse forces in steer-by-wire steering systems or steering systems in a motor vehicle, as mentioned above, both in normal operation and with abuse loads.

[0019] The invention can be used for both a so-called individual actuator and a central actuator, also called an actuator. If the steer-by-wire steering system is designed as an individual actuator, this individual actuator on an axle can be used to change the steering angle on one wheel. For an axle with a left wheel and a right wheel, two individual actuators are therefore preferably used. With a single actuator, preferably only one bearing sleeve is required at one end of the spindle. In this case, the aforementioned articulated fork is indirectly connected to one end of the spindle by means of the bearing sleeve. With a central actuator, which acts on both wheel carriers or wheels of an axle simultaneously for steering, a bearing sleeve is preferably arranged at each end of the spindle, and an articulated fork is connected to the spindle at each end with the bearing sleeves. The articulated fork serves to provide an articulated connection, at least indirectly, to a wheel carrier.By moving the spindle in the manner of a steering rod, the steering angle of the wheel or wheels on an axle can be changed.

[0020] As already mentioned above, the bearing sleeves ensure that the spindle is supported and guided along its longitudinal axis relative to the housing. The bearing sleeves are supported and guided by slide bushings that are embedded, preferably pressed into, the housing of the steer-by-wire steering system. For this purpose, a corresponding bearing seat is provided in the housing for the slide bushings, and once pressed in, a permanent positive and non-positive connection is created. The smooth-walled outer skin of the bearing sleeve made of fiber-plastic composite can be used as a slide bearing surface without further processing. There is no need for a separate slide bearing surface, thus offering another advantage over steel bearing sleeves.

[0021] According to a further aspect, the invention relates to a steer-by-wire steering system for a motor vehicle for maintaining and changing a wheel steering angle, comprising a housing and a spindle drive accommodated therein, with a spindle nut fixed to the housing and a spindle that can be moved axially relative to the housing. The spindle drive is manufactured in one or more parts from a fiber-plastic composite according to the aforementioned method in one or more steps. At least one end of the spindle is connected directly or indirectly to a bearing sleeve, as in one of the aforementioned steps or embodiments, and is mounted displaceably relative to the housing by means of the bearing sleeve. If the stationary spindle nut with its internal thread is rotationally driven, for example by an electric motor, the spindle, whose external thread engages the spindle nut, is displaced along its longitudinal axis.

[0022] Preferred embodiments of the invention are described below with reference to the drawings. They show:

[0023] Fig. 1 shows a steer-by-wire steering system with spindle drive. State of the art,

[0024] Fig. 2 a steer-by-wire steering system designed with spindle drive according to the invention

[0025] Fig. 3 a detailed view of a version of the spindle drive

[0026] Fig. 4 a detailed view of another version of the spindle drive

[0027] Fig. 5 a detailed view of another version of the spindle drive

[0028] Fig. 6 a flow chart regarding the procedure

[0029] Fig. 1 shows a schematic plan view of a rear axle 300 according to the prior art with steerable wheels 17r, 18r, which are rotatably mounted on wheel carriers 17, 18. The vehicle moves forward in the direction of travel F. The steerable wheels 17r, 18r are steered by means of an actuator 20 in the form of a central actuator of a steer-by-wire steering system 1, which has a two-part housing 12 with a left housing part 121 and a right housing part 12r. The housing parts 121, 12r are connected to one another along a parting plane ET formed orthogonal to the longitudinal axis s of the spindle 5. In the region of the spindle nut 6, the spindle 5 has a thread formed as an external thread 5a, which engages with a corresponding internal thread 6a of the spindle nut 6 and thus forms a movement thread.When the spindle nut 6 rotates by an electric motor 7, the spindle 5, which is prevented from rotating in a manner not shown, performs a translational movement (in the drawing) to the right or left along its longitudinal axis s. This movement is transmitted to forks 3, 4 via bearing sleeves 30, 31. The forks 3, 4 transmit this movement to the control arms 14, 15, which are pivotably coupled to the wheel carriers 17, 18, which can pivot about their vertical axes. In this way, the wheels 17r, 18r are steerable.

[0030] If there is only limited installation space available in the area of ​​the vehicle center (indicated by the longitudinal axis m) on a steered axle, an assembly such as actuator 20, 120 of a steer-by-wire steering system 1 must be arranged or constructed in such a way that installation into the existing axle concept or the available installation space is possible without expensive modifications to the vehicle at the installation location in the area of ​​axle 300. Due to the diameter of the spindle drive 13 with the drive wheel 6t pressed onto the spindle nut 6, the housing 12 has the largest diameter of the entire actuator 20, 120 of the steer-by-wire steering system 1 in the area of ​​the parting plane Er. In addition, the installation space required for the flange-mounted electric motor 7 comes into play, which in the illustration shown is arranged behind the right-hand housing part 12r. In Fig.1 and 2, a drive unit 200 of the axle is shown schematically in dashed lines, which extends around the longitudinal axis m of the vehicle (not shown) in the region of the rear part of the vehicle. With respect to the longitudinal axis of the spindle 5, which coincides with the longitudinal axis s, the spindle drive 13 and thus also the parting plane Er are arranged significantly off-center. The arrangement shown here requires that the spindle 5 is extended by means of a first bearing sleeve 30. The bearing sleeve 30 consists of the left sleeve end 30I and the right sleeve end 30r and an intermediate extension 30v in the form of a tubular body made of steel. On the other side of the spindle (on the left in the drawing), a bearing sleeve 31 is also designed as a left sleeve end 311 and a right sleeve end 31r. Here, however, due to its proximity to the wheel, the bearing sleeve 31 is designed only as a short bearing sleeve 31 without an extension.Both bearing sleeves 30, 31 are made of steel and have joints 31f, 30fi, 30f2. The bearing sleeve 31 shown on the left is manufactured in such a way that the left sleeve end 311 is first produced as an extruded part by cold forming. The right sleeve end 31r is a turned part made of high-strength steel. The two sleeve ends 311, 31r are permanently joined together by friction welding in the area of ​​the joint 31f to form a one-piece bearing sleeve 31. In the area of ​​its outer end, i.e. facing away from the joint, the bearing sleeve 31 is guided and supported radially in the housing part 121 by means of sliding bushes 11b, 31b. The bearing sleeve 30 inserted on the other side between the end of the spindle 5 and the fork 4, in contrast, was manufactured from three parts.In analogy to the previously explained bearing sleeve 31, a short left sleeve end 30I, which is connected to the spindle 5 and was manufactured as a turned part, has also been manufactured here. On the opposite side, a short sleeve end 30r is shown, which was manufactured as an extruded part, i.e. by forming. Between these sleeve ends 30I, 30r, an extension 30v in the form of a tubular body is arranged. The connection between the sleeve ends 30I, 30r and the tubular body 30v was also carried out by friction welding, analogous to the bearing sleeve 31. The friction welds were carried out at the joints shown as 30fi, 30f2. The bearing sleeve 30 is guided and mounted radially in the housing part 12r in the area of ​​its outer end, i.e. facing away from the joint, by means of sliding bushes 10b, 30b. Due to the extension of the spindle 5 by means of the bearing sleeve 30 orThe 30v tubular body allows for a lighter extension compared to a solid round rod, as is common with other steer-by-wire actuators. This allows for longer distances to be bridged when the limited space available on a vehicle axle makes this necessary.

[0031] Fig. 2 shows the invention in an embodiment based on the schematically shown rear axle 300 analogous to Figure 1, wherein components with the same reference numerals are largely not explained again here. To extend the spindle 5, bearing sleeves 130, 131 are also used in the inventive embodiment according to Figure 2. In order to significantly reduce the weight of the actuator 120, the bearing sleeves 130, 131 are not made of steel, but of a fiber-plastic composite. Materials such as GRP or CFRP are suitable for this purpose. It has been shown that bearing sleeves 30, 31 according to the embodiment according to Figure 1 have a weight approximately twice as high as the bearing sleeves 130, 131 according to the invention made of a fiber-plastic composite. In an actuator 120 of a steer-by-wire steering system 100 according to the invention, which extends over almost the entire vehicle width, approximately 1000 g of weight can thus be saved in a simple manner.

[0032] A bearing sleeve 131 is inserted into the left housing part 121, which has an internal thread 131g at each of its front ends 1311, 131r. This internal thread was created during the prefabrication of the bearing sleeve 131, so that the bearing sleeve 131 is exclusively a fiber-plastic composite component. One end of the spindle 5 can thus be easily screwed firmly to the right sleeve end 131r of the bearing sleeve 131 during assembly of the spindle drive 13 or actuator 120. The fork 3 is screwed to the left sleeve end 1311 of the bearing sleeve 131 in a rotationally fixed manner by means of a screw bolt 40. Advantageously, the threads do not have to be cut into the ends of the bearing sleeve, as is the case with the steel bearing sleeves 30, 31.In a further embodiment of a bearing sleeve, the bearing sleeve 130 is formed, which is inserted in the right-hand housing part 12r for extension between the spindle 5 and the fork 4. At each of the left sleeve ends 1301 and the right sleeve end 130r, an insert 130e is integrally bonded into the bearing sleeve 130 by means of adhesive. The insert 130e is preferably made of metal, preferably steel. During prefabrication of the bearing sleeve, the insert can be designed as a common part with an internal thread, so that an identical component can advantageously be used for both ends of the bearing sleeve 130. Such a common part can enormously reduce unit costs in the production of an actuator through economies of scale.

[0033] Fig. 3 shows a schematic detailed view according to III of Figure 2. In this exemplary embodiment, a sleeve end 1301 of the bearing sleeve 130 is shown, which is indirectly joined to the end of the spindle 5. At the end face or at the sleeve end 1301, a steel insert 130e is integrally bonded to the sleeve component by adhesive to form a bearing sleeve 130. The spindle 5 has an external thread 5a and its end is firmly screwed into the internal thread 131g of the insert 130e. The spindle 5 is mounted by means of the bearing sleeve 130 within the sliding bushing 30b relative to the housing (not shown).

[0034] Fig. 4 shows a schematic detailed view according to IV of Figure 2. In this exemplary embodiment, a thread 131g is provided as an internal thread on the front side of the sleeve end 1311 of the bearing sleeve 130, which thread was formed in step (510) of the prefabrication of the bearing sleeve 130 in step b) and / or c). The fork 3 is positively and non-positively connected to the sleeve end 1311 of the bearing sleeve 130 by means of a screw bolt 40. For this purpose, the screw bolt 40 has a conventional thread 40g in the form of a metric external thread, which was screwed to the thread 131g. The threads are not shown to scale here - the illustration serves to clarify and does not show a typical pitch of a thread for such fastenings. This results in a firm connection between fork 3 and spindle 5, which is screwed at its other end to the bearing sleeve 130 in the same way (according to Figure 2 in the right housing part 12r).

[0035] Fig. 5 shows a further exemplary embodiment with an insert 52e at the end of the bearing sleeve 150. In this exemplary embodiment, the bearing sleeve 150 has an inner contour 51i at its front end. The insert 52e engages positively with its outer contour 52a in the inner contour 51i. The inner contour 51i is formed in step 510 of the prefabrication of the bearing sleeve 150 in steps a) and / or b) and / or c). The joint fork 3 is firmly screwed to the insert 52e by means of a screw bolt 50, which has an internal thread as shown. This results in a sufficiently strong and resilient connection between the joint fork 3 and the bearing sleeve 150 and thus also to the spindle 5 (not shown here) for the forces or tensile and compressive stresses occurring in the area of ​​a vehicle steering system.

[0036] Fig. 6 shows a flow diagram schematically a method 500 for producing a spindle drive 13 of a steer-by-wire steering system for a motor vehicle with a steerable front and / or rear axle. In a prefabrication step 510, a bearing sleeve 30, 31, 130, 131, 150 is manufactured. This is formed from at least one sleeve component made of a fiber-plastic composite. The sleeve component is manufactured by at least the following steps: a) manufacturing a textile semi-finished product b) preforming and creating a blank c) manufacturing the sleeve component. In step a), a textile semi-finished product is first created from yarns and so-called rovings, which can, for example, be a flat woven fabric. A cylindrical sleeve component can be formed from this flat fabric by means of a cylindrical mold or a mandrel in step b). Alternatively, a cylindrical multi-part winding core can be used in steps a) and b).A blank for the intended sleeve component can be created around this winding core using the yarn and rovings. This creates a round semi-finished product as opposed to a flat semi-finished product. The multi-part winding core can be provided with circumferential engravings so that so-called bandages 45 and / or axial reinforcements 47 can be incorporated into the fabric of the yarns and / or rovings for the bearing sleeve, which consists entirely or partially of the sleeve component. For this purpose, the multi-part winding core can have shaped segments, particularly at its ends, for creating an inner contour or a thread.

[0037] In steering systems, high tensile and compressive forces of 15 kN are to be expected during operation or under misuse loads of 50 kN (e.g., driving onto a curb, etc.). In order to withstand these high forces, fiber-plastic composite components, in this case a bearing sleeve 130 in the form of a cylindrical fiber composite sleeve component, e.g., at the sleeve end 1301, are designed with a conical widening 130k (see Fig. 4). Following this principle, an aforementioned thread 131g can also be formed. With such intended contours or contour connections, the positive connection arises between approximately axially oriented fiber layers 47, which follow the conical or thread contours on the component surface, e.g., on the inner wall of the bearing sleeve 130. In order to avoid failure of the contours, e.g. in the form of a 131 g thread, due to the very high flank pressures, the contours must be stiffened, for which purpose expansion bodies orinner tangential fiber layers are introduced during the production of the semi-finished product. In a final prefabrication step, the sleeve component is infiltrated with the addition of resin and, if necessary, by using a molding tool and finally consolidated. The above-mentioned exemplary embodiments show that the bearing sleeve can certainly be made exclusively from a fiber-plastic composite in accordance with the load. So-called inserts (52e, 130e) made of a metallic material, e.g. steel, preferably 30MnB4, can also be combined with the sleeve component to form a bearing sleeve. Such a mixed construction can be designed as described above in relation to Figures 3 and 5. For this purpose, an insert can be joined to the fiber-plastic composite component (sleeve component) in a material-to-material manner, preferably by means of adhesive bonding in a step 530 after the production of the fiber-plastic composite component (sleeve component).Also, during the forming in step 510 or in an additional step 520, such an insert can be joined, e.g., in a form-fitting manner, preferably by screwing, to the sleeve component to form a bearing sleeve.

[0038] Manufacturing is easy even with long spindle drives, with the cylindrical shape of the sleeve component or bearing sleeve being particularly advantageous for load introduction due to the longitudinal and transverse forces prevalent in steering systems. Thus, an existing steer-by-wire steering system can be easily and significantly reduced in weight using a bearing sleeve made of fiber-plastic composite compared to a bearing sleeve made of steel. The available installation space does not need to be adapted. The bearing sleeve can be easily produced to the required lengths during prefabrication. The weight optimization required in modern vehicles is advantageously possible with a steer-by-wire steering system using the inventive design of a bearing sleeve made of a fiber-plastic composite.

[0039] Reference symbol Steer-by-wire steering Joint fork Joint fork Spindle a External thread Spindle nut a Internal thread t Drive wheel Electric motor Spindle end (right) Spindle end (left) 0b Sliding bush 1 b Sliding bush 2 Housing 21 Left housing part 2r Right housing part 3 Spindle drive 4 Link 5 Link 7 Wheel carrier 7r Steerable wheel 8 Wheel carrier 8r Steerable wheel 0 Actuator 0 Bearing sleeve 0b Sliding bush 0I Sleeve end 0r Sleeve end 0v Extension, tubular body 0fi Joint 0f2 Joint 1 Bearing sleeve 1 b Sliding bush 1f Joint 11 Sleeve end 1 r Sleeve end 0 Screw bolt 0g Thread Screw bolt 1 Thread 5 Bandages 7 Axial reinforcements, axially oriented fiber layers 0 Screw bolt 2e Insert 2a Outer contour 1 i Inner contour

[0040] 100 steer-by-wire steering

[0041] 120 Actuator

[0042] 130 bearing sleeve

[0043] 130e insert

[0044] 1301 sleeve end

[0045] 130r case end

[0046] 130k conical expansion

[0047] 131 bearing sleeve

[0048] 131g thread

[0049] 1311 sleeve end

[0050] 131 r sleeve end

[0051] 150 bearing sleeve

[0052] 200 drive unit

[0053] 300 axle, rear axle

[0054] 500 Process for manufacturing a spindle drive

[0055] 510 Step of prefabrication with steps a), b), c)

[0056] 520 Step of prefabrication 530 Step of prefabrication s Longitudinal axis

[0057] F Direction of travel

[0058] ET parting plane housing m longitudinal axis

Claims

Patent claims 1 . Method (500) for producing a spindle drive (13) of a steer-by-wire steering system (1) for a motor vehicle with a steerable front and / or rear axle, wherein the spindle drive (13) is manufactured from at least one translationally displaceable spindle (5), a stationary spindle nut (6) and at least one bearing sleeve (30, 31, 130, 131, 150), wherein the at least one bearing sleeve (30, 31, 130, 131, 150) is provided as a bearing and connecting component of the spindle (5), characterized in that the at least one bearing sleeve (30, 31, 130, 131, 150) is produced at least partially from a fiber-plastic composite in a prefabrication step (510), wherein the bearing sleeve is is joined directly or indirectly in a material and / or force-fitting and / or form-fitting manner to the spindle (5).

2. Method for producing a spindle drive (13) of a steer-by-wire steering system 1 according to claim 1, characterized in that in the prefabrication step (510), the bearing sleeve (30, 31, 130, 131, 150) is manufactured from a sleeve component made of a fiber-plastic composite, at least by means of the steps a) manufacturing a textile semi-finished product b) preforming and creating a blank c) manufacturing the sleeve component to a bearing sleeve 3. Method for producing a spindle drive (13) of a steer-by-wire steering system 1 according to claim 2, characterized in that, in order to form the bearing sleeve, the sleeve component is formed in step b) and / or c) of the prefabrication at at least one end as a thread (131g), preferably formed as an internal thread, in order to be able to carry out the joining with the spindle in step 520.

4. Method for producing a spindle drive (13) of a steer-by-wire steering system 1 according to claim 2 or 3, characterized in that, in order to form the bearing sleeve, the sleeve component in step b) and / or c) is fixed to at least one end is formed as a contour, preferably formed as an inner contour.

5. A method for producing a spindle drive (13) of a steer-by-wire steering system 1 according to one of claims 2 to 4, characterized in that in step (510) of prefabrication of the bearing sleeve (30, 31, 130, 131, 150) in the sleeve component in step b) and / or c), at least one insert (52e, 130e) is inserted for indirect material and / or force-fitting and / or form-fitting joining of the bearing sleeve (30, 31, 130, 131, 150) to the spindle (5), wherein the insert (52e, 130e) is connected to the sleeve component in a form-fitting and / or force-fitting and / or material-fitting manner.

6. Method for producing a spindle drive (13) of a steer-by-wire steering system 1 according to one of the preceding claims, characterized in that for producing the bearing sleeve (30, 31, 130, 131, 150) a first sleeve component is joined to at least one further prefabricated sleeve component in a material and / or force-fitting and / or form-fitting manner.

7. A method for producing a spindle drive (13) of a steer-by-wire steering system (1) according to claim 6, characterized in that the sleeve components are joined, in particular with the ends or end faces facing away from the inserts (52e, 130e).

8. Method for producing a spindle drive (13) of a steer-by-wire steering system 1 according to one of the preceding claims, characterized in that for the production of the bearing sleeve (30, 31, 130, 131, 150) in step (510) of prefabrication, preferably CFRP or GFRP are used as materials for the fiber-plastic composite.

9. Steer-by-wire steering system 1 for a motor vehicle for maintaining and changing a wheel steering angle on at least one axle (300), with a housing (12) and a spindle drive (13) accommodated therein, comprising a spindle nut (6) arranged stationary in the housing and a spindle nut (6) axially opposite the Housing (12) displaceable spindle (5), wherein at least one end of the spindle (5) is connected to a bearing sleeve (30, 31, 130, 131, 150) and is mounted displaceably relative to the housing (12) by means of the bearing sleeve (30, 31, 130, 131, 150), characterized in that the bearing sleeve (30, 31, 130, 131, 150) is formed at least in one part from a fiber-plastic composite, and the spindle drive (13) is produced according to a method according to one of the preceding claims.

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