Electromechanical vehicle steering system and method for producing same

Abstract

The invention relates to an electromechanical vehicle steering system (1) comprising a housing (2), an electric motor (3) having an axis of rotation (A), a drop arm (4) having a longitudinal axis (B), wherein the drop arm (4) is arranged in the housing (2) so as to be axially movable in the direction of the longitudinal axis (B) and the longitudinal axis (B) extends in parallel with the axis of rotation (A) of the electric motor (3), and a gearbox mechanism (5) by means of which the electric motor (3) is drivingly coupled to the drop arm (4) in order to translate a rotational movement of the electric motor (3) into a linear movement of the drop arm (4), wherein the gearbox mechanism (5) comprises a toothed belt drive (51) and a ball screw drive (55), wherein a ball screw nut (56) of the ball screw drive (55) is in engagement with the drop arm (4) and supports the drop arm (4) in the housing (2), wherein the ball screw nut (56) is supported on the housing (2) by an adjustable bearing (57), and wherein a toothed belt (54) of the toothed belt drive (51) can be tensioned by the adjustable bearing (57). The drop arm (4) is also supported in the housing (2) by a guide bush (70). The position of the guide bush (70) can be adjusted in the housing (2) radially to the drop arm (4). The invention further relates to a method for producing such a vehicle steering system.

Description

[0001] Description

[0002] Electromechanical vehicle steering and method for producing such a

[0003] The invention relates to an electromechanical vehicle steering system, comprising a housing, an electric motor with a rotational axis, a push rod with a longitudinal axis, wherein the push rod is arranged in the housing so as to be axially movable in the direction of the longitudinal axis and the longitudinal axis runs parallel to the rotational axis of the electric motor, a gear via which the electric motor is drivingly coupled to the push rod in order to translate a rotational movement of the electric motor into a linear movement of the push rod, wherein the gear comprises a toothed belt drive and a ball screw drive, wherein a ball screw nut of the ball screw drive engages with the push rod and supports the push rod in the housing, wherein the ball screw nut is mounted on the housing via an adjustable bearing, and wherein a toothed belt of the toothed belt drive can be tensioned via the adjustable bearing.

[0004] Furthermore, the invention relates to a method for producing such an electromechanical vehicle steering system.

[0005] A generic electromechanical vehicle steering system is known from DE 10 2008 050 248 A1. In this system, a toothed belt drive is coupled via a first, smaller toothed belt pulley to an output shaft of an electric motor and via another, larger toothed belt pulley to a ball screw nut of a ball screw drive, which operatively engages a push rod of the steering system. To adjust the belt pretension, after the toothed belt is placed on the steering belt pulleys, the rack is tilted relative to the steering housing with the ball screw bearing loosened until a predetermined belt pretension, measured during the adjustment process, is reached. The ball screw bearing is then fixed in the determined position on the steering housing. This avoids the need for an additional tensioning and adjustment mechanism on the toothed belt drive. The belt pretension can be adjusted automatically.However, tilting to tension the timing belt can cause tension. In DE 10 2009 037 873 B4, in a modification of DE 102008 050248 A1, it is proposed to first measure the timing belt while applying a specified belt pretension. Then, depending on the measurement result, the center distance between a first timing belt pulley and a bearing unit for a further timing belt pulley is set by adjusting the position of the bearing unit such that a specified timing belt pretension is achieved on the subsequently mounted timing belt. The further timing belt pulley is then mounted on the bearing unit. Only then is the measured timing belt mounted on the timing belt pulleys. This is intended to achieve a high level of adjustment accuracy for the timing belt pretension, since any tolerances in the timing belt are compensated at the end of the process chain.

[0006] Since the timing belt drive is adapted to the specific timing belt being installed during assembly, there is no need for time-consuming preliminary measurements and classification of timing belts and timing belt drives for the purpose of individual assignment.

[0007] A further advantage of the solution of DE 102009 037 873 B4 is that the bearing unit can be attached concealed by the toothed belt drive, in particular a toothed belt pulley. If a toothed belt assigned to the toothed belt drive has been measured, the bearing unit can be adjusted and secured, as well as the toothed belt pulley mounted, in front of or on the bearing unit, before the toothed belt is installed. This increases the design freedom. Furthermore, the bearing unit and the associated pulley can be accommodated very compactly in a housing, for example in a vehicle steering system. Since the toothed belt is measured while applying a specified belt pretension, its stretching behavior is taken into account during assembly, which keeps the variation in the belt pretension particularly low. This is important in series production for a consistent steering feel.However, in the solution proposed in DE 102009 037 873 B4, the timing belt must be mounted in a pre-tensioned state, which is only possible with straight-toothed timing belts, the running characteristics of which are less favorable than those of helical-toothed timing belts.

[0008] Another way to ensure the smallest possible variation in the timing belt pretension force is known from DE 102006 036215 B4. This document describes a method for assembling steering gears with a tensioner-free timing belt drive. This method is based on two timing belt pulleys with a fixed, non-adjustable center distance, which are coupled to each other via a pre-tensioned timing belt. The center distance of the timing belt pulleys is fixed.DE 102006 036215 B4 proposes measuring the actual center distance of the toothed belt pulleys for each steering gear with respect to a tolerance range for the center distance, maintaining toothed belts in several belt classes, with classification based on different lengths and / or widths of the belts, and ensuring that all toothed belts falling into the belt class, in conjunction with the tolerance range for the center distance in the installed state of the toothed belt, result in a toothed belt tension within a specified tolerance range, and selecting a toothed belt from the corresponding belt class for the measured actual center distance and then installing it. However, this procedure is quite complex due to the need to stock a large number of different belts and the required selection process during assembly.

[0009] Another electromechanical vehicle steering system is known from DE 10 2010 034 698 A1. Its assembly is as follows: First, the toothed belt pulleys of the toothed belt drive are mounted, with at least one of the toothed belt pulleys being offset relative to a transmission component. The toothed belt is then loosely placed on the toothed belt pulleys. Then, at least one toothed belt pulley is moved from its offset position to the tensioned position to tension the toothed belt. Finally, the initially offset toothed belt pulley(s) are fixed in the tensioned position. This procedure enables the installation of toothed belts with tooth profiles that, due to their geometry, cannot be pushed axially onto the toothed belts in toothed belt drives with only slightly offset or no offset. At the same time, a defined belt tension can be ensured.To tension the timing belt, the timing belt pulley, which is mounted on a ball screw nut, is rotated relative to the ball screw nut. An eccentric mechanism between a peripheral portion of the ball screw nut and the timing belt pulley enables the aforementioned offset for mounting the timing belt, as well as the subsequent tensioning through relative rotation. However, the manufacture of such an eccentric mechanism is complex.

[0010] A similar design with an eccentric mechanism is known from DE 103 10492 A1, although the eccentric mechanism is located at a different location than in DE 10 2010 034698 A1. According to DE 103 10492 A1, the electric motor and / or the push rod are to be mounted by means of an eccentric such that the center distance between the output shaft and the push rod is variable. In one embodiment, the push rod is accommodated in a ball screw nut, which in turn is supported on an eccentric ring via a rolling bearing. The eccentric ring, in turn, is mounted in a steering housing. By rotating the eccentric ring, a toothed belt of a toothed belt drive can be tensioned.

[0011] The state of the art explained above illustrates the complexity of manufacturing an electromechanical vehicle steering system with a toothed belt drive with regard to ensuring a uniform steering feel in series production.

[0012] The object of the present invention is to provide a technically simple alternative which is suitable for ensuring a uniform steering feel in series production with little effort.

[0013] This object is achieved by an electromechanical vehicle steering system having the features of patent claim 1. The vehicle steering system according to the invention is characterized in particular in that the push rod is further mounted in the housing via a guide bushing and the guide bushing is adjustable in its position radially to the push rod in the housing.

[0014] The adjustable guide bushing within the housing can be used to compensate for tension in the gearbox, particularly in the area of ​​the ball screw drive, which could occur as a result of manufacturing tolerances while maintaining a constant belt pretension.

[0015] Nevertheless, the electromechanical vehicle steering remains simple in terms of both its design and assembly.

[0016] Since the timing belt can be installed in a non-pretensioned state, both straight-toothed and helical-toothed timing belts can be used.

[0017] The inventive solution is particularly suitable for steer-by-wire systems, where gearing on the push rod is no longer required for engagement with a steering pinion. The position of the push rod in the transmission can thus be influenced independently at two points: firstly, by adjusting the position of the ball screw nut and, secondly, by adjusting the position of the additional guide bushing. This allows for particularly high flexibility in compensating for any manufacturing tolerances. Since the latter can be permitted to a greater extent than before, the inventive solution also enables a reduction in manufacturing costs.

[0018] In comparison to electromechanical vehicle steering systems, in which the tensioning of the toothed belt pulley is carried out by adjusting the position of the electric motor, in the solution according to the invention the electric motor can be arranged non-adjustably on or in the housing, thus eliminating the need for a corresponding sealing point.

[0019] Compared to electromechanical vehicle steering systems with a fixed center distance between the electric motor and the push rod, there is no need to measure the required belt length or select a timing belt of the appropriate length.

[0020] Particular embodiments of the invention are the subject of further patent claims.

[0021] For example, the guide bushing can have a plain bearing in which a section of the push rod is axially guided and secured against rotation about its longitudinal axis. In this case, the guide bushing also serves as a torque lock for the push rod.

[0022] According to another particular embodiment, a section with a motor mounting space for the electric motor is attached to the housing or formed integrally therewith, while the electric motor has an output shaft on which a first toothed belt pulley of the toothed belt drive is arranged in a rotationally fixed manner. The electric motor is preferably inserted axially into the motor mounting space from a side opposite the first toothed belt pulley. This further simplifies assembly.

[0023] According to a further special embodiment, the output shaft of the electric motor is rotatably mounted in the housing via a rolling bearing, with an outer ring of the rolling bearing being supported on an inner wall shoulder of the housing. This enables, on the one hand, good support of the toothed belt strand forces and, on the other hand, good accessibility of the toothed belt drive for the assembly of the toothed belt pulley. According to a further special embodiment of the invention, the adjustable bearing comprises a rolling bearing and a bearing clamping device, while an outer ring of the rolling bearing is displaceable radially to the longitudinal axis of the push rod in the housing and can be secured to the housing by means of the bearing clamping device, wherein the bearing clamping device is clamped to the housing radially outside a second toothed belt pulley arranged on the ball screw nut in a rotationally fixed manner. This makes it very easy to adjust the position of the ball screw nut when tightening the toothed belt pulley.The production of eccentric surfaces can be omitted.

[0024] According to another particular embodiment of the invention, the housing integrally forms a section with a gear receiving space, the outer wall of which extends radially around the toothed belt drive. The gear receiving space is closed at the front by a gear cover, which has a through-opening for the push rod. This allows for easy access to the components for the toothed belt drive during assembly. At the same time, the housing structure remains simple.

[0025] The above-mentioned object is further achieved by a method for producing an electromechanical vehicle steering system of the type with an axially parallel arrangement of a push rod and an electric motor according to claim 7. The method is characterized by the following steps, namely:

[0026] - Attaching the electric motor to a push rod housing,

[0027] - Inserting a ball screw nut with a rolling bearing into a gear receiving space of the housing, wherein the ball screw nut is designed to support the push rod,

[0028] - Pre-fixing the rolling bearing to the housing,

[0029] - Arranging toothed belt wheels on an output shaft of the electric motor and on the ball screw nut,

[0030] - loosely placing a timing belt on the mounted timing belt pulleys,

[0031] - Tensioning the timing belt by radially moving the rolling bearing of the ball screw nut and fixing the rolling bearing with the timing belt tensioned, and

[0032] - Providing a guide bushing to guide the connecting rod and radially positioning the guide bushing in the housing according to the position of the ball screw nut's rolling bearing, and securing the guide bushing to the housing. The steps can be performed in the order specified here, but this is not mandatory. Such a process can be implemented manually with minimal effort, and if necessary, automated or semi-automated. In particular, this allows the timing belt tension to be adjusted with high precision despite relatively coarse timing belt tolerances, thus avoiding distortions in the ball screw drive.

[0033] According to a special design of the process, the push rod, together with the ball screw nut and the guide bushing, can be displaced radially in the housing, parallel to the longitudinal axis of the push rod. This makes it particularly easy to prevent the push rod from tilting in the ball screw nut.

[0034] According to another particular embodiment of the method, the electric motor and the ball screw nut are inserted into the housing from opposite sides and in opposite directions.

[0035] According to another special embodiment, the electric motor is inserted into the motor housing with a first toothed belt pulley pre-mounted on an output shaft, with the first toothed belt pulley passing through a bearing point on the housing for the output shaft. The formation of such a subassembly can further simplify assembly.

[0036] One way of implementing the invention is explained in more detail below using an embodiment shown in the drawing. The drawing shows:

[0037] Figure 1 is a longitudinal sectional view of a possible embodiment of an electromechanical vehicle steering system according to the invention.

[0038] The embodiment in Figure 1 shows an electromechanical vehicle steering system 1, which in the present case is designed as an example as a steer-by-wire steering system for a passenger car or light commercial vehicle.

[0039] The electromechanical vehicle steering system 1 comprises a housing 2 and an electric motor 3 with a rotational axis A, a push rod 4 with a longitudinal axis B and a gear 5, via which the electric motor 3 is drivingly coupled to the push rod 4 in order to translate a rotational movement of the electric motor 3 into a linear movement of the push rod 4 in the direction of the longitudinal axis B thereof.

[0040] The push rod 4 is in turn coupled via push rod joints 6 to wheel carriers not shown in detail, so that a linear movement of the push rod 4 along its longitudinal axis B leads to a steering angle of the associated vehicle wheels.

[0041] For this purpose, the push rod 4 is arranged in the housing 2 so as to be axially movable in the direction of the longitudinal axis B. The longitudinal axis B of the push rod 4 runs parallel to the rotational axis A of the electric motor 3.

[0042] The electric motor 3 can be flanged to a portion of the housing 2 that accommodates the push rod 4. It is also possible to arrange the electric motor 3 in a motor receiving space 21 of the housing 2, which is formed by an integral portion 22 of the housing 2.

[0043] In one embodiment, components of the electric motor 3 are provided as a power pack 31, which is mounted directly in the motor housing space 21 of the section 22. In this case, the motor housing is formed by integral wall sections of the housing

[0044] 2 of the push rod 4.

[0045] However, as already mentioned, the section 22 with the motor receiving space 21 can be provided as a separate component and fixedly mounted to the further housing 2 which receives the push rod 4.

[0046] In all cases, the position of the electric motor 3 relative to the housing 2 of the push rod 4 is fixed and cannot be adjusted. The position of the rotational axis A of the electric motor

[0047] 3 is thus fixed. Ideally, if section 22 is formed integrally with the housing 2 of the push rod 4, otherwise required sealing points are eliminated.

[0048] The transmission 5 comprises a toothed belt drive 51 and a ball screw drive 55, which are connected in series in this case.

[0049] The toothed belt drive 51 has a first toothed belt pulley 52, which is non-rotatably coupled to an output shaft 32 of the electric motor 3, as well as a second toothed belt pulley 53 and a toothed belt 54 placed on these toothed belt pulleys 52 and 53. The toothed belt 54 can have a straight toothing or a helical toothing.

[0050] The ball screw drive 55 has a ball screw nut 56 which engages via balls 56a with a corresponding threaded portion 41 of the push rod 4 and supports the push rod 4 in the housing 2.

[0051] For this purpose, the ball screw nut 56 is rotatably mounted in the housing 2 and at the same time secured against axial displacement.

[0052] In the illustrated embodiment, an adjustable bearing 57 is provided for this purpose, which can be designed, for example, as a rolling bearing. An inner ring 58 of the adjustable bearing 57 is fixed to the ball screw nut 56, while an outer ring 59 of the adjustable bearing is fixed to the housing 2.

[0053] To fix the adjustable bearing 57, a bearing clamping device 60 can be provided, by means of which the outer ring 59 of the adjustable bearing 57 is fixed axially and radially relative to the housing 2.

[0054] In this context, it should be noted that the adjustable bearing 57 can be displaced radially to the longitudinal axis B of the push rod 4 before it is fixed to the housing 2 in order to enable the toothed belt 54 to be placed and tensioned.

[0055] The bearing clamping device 60 can be formed, for example, by a retaining disc or a retaining ring, which is clamped axially against the housing 2 by means of threaded bolts 61 or the like, including the adjustable bearing 57.

[0056] The bearing clamping device 60 can preferably be clamped to the housing 2 radially outside the second toothed belt pulley 53, which is arranged in a rotationally fixed manner on the ball screw nut 56. Depending on the design of the bearing clamping device 60, clamping can also take place within the circumference of the second toothed belt pulley 53, for example by providing corresponding through-openings on the latter, which allow access to suitable clamping devices, for example threaded bolts 61. In a modification of this, other fastening mechanisms for securing the outer ring 59 of an adjustable bearing 57 can also be provided. In particular, it is possible to screw the outer ring 59 of the adjustable bearing 57 directly to the housing 2. For this purpose, a corresponding flange can be formed on the outer circumference of the outer ring 59, if necessary.

[0057] Since the production and processing of rolling element steels is generally complex, fastening by means of a bearing clamping device 60 will be preferred.

[0058] As already mentioned, the push rod 4 is mounted on the housing 2 via the ball screw nut 56 and the adjustable bearing 57. The toothed belt 54 of the toothed belt drive 51 is tensioned by radially displacing the adjustable bearing 57 relative to the housing 2, thereby shifting the longitudinal axis B of the push rod 4 relative to the housing 2 and to the rotational axis A of the electric motor 3, and subsequently fixing the adjustable bearing 57 and thus ultimately also the push rod 4 in this position.

[0059] To avoid tension in the ball screw 55, the push rod 4 is further supported in the housing 2 via a guide bushing 70. In other words, in addition to a first bearing point L1 on the ball screw 55, a separate second bearing point L2 for the push rod 4 is provided via the guide bushing 70 within the housing 2.

[0060] In this case, the guide bushing 70 is adjustable in its position radially relative to the push rod 4 in the housing 2. When the toothed belt 54 is tensioned, the position of the push rod 4 in the area of ​​the guide bushing 70 can thus be radially adjusted, for example, to prevent the push rod 4 from tilting in the ball screw drive 55. This has a positive effect in series production, ensuring a consistent steering feel across many vehicle steering systems.

[0061] The guide bush 70 can in particular have a plain bearing in which the push rod 4 is axially guided with a section 42 and is additionally secured against rotation about its longitudinal axis B.

[0062] To facilitate assembly of the electromechanical vehicle steering system, the electric motor 3 can be provided with an output shaft 32, on which the first toothed belt pulley 52 of the toothed belt drive 51 is arranged in a rotationally fixed manner. The electric motor 3 is preferably inserted axially into the motor receiving space 21 from a side opposite the first toothed belt pulley 52.

[0063] In addition, the output shaft 32 of the electric motor 3 can be rotatably mounted in the housing 2 via a rolling bearing 33, wherein an outer ring 34 of this rolling bearing 33 is supported on an inner wall shoulder 23 of the housing 2.

[0064] The rolling bearing 33 of the drive shaft 32 is arranged axially between the electric motor 3 and the first toothed belt wheel 51.

[0065] The rolling bearing 33 of the drive shaft 32 can separate the motor housing 21 from a section 24, preferably formed integrally with the housing 2, with a gear housing 25. The gear 5 with its toothed belt drive 51 and ball screw drive 55 can be arranged in this gear housing 25.

[0066] Preferably, an outer wall of section 24 extends radially around the toothed belt drive 51. The gear receiving space 25 is preferably open at the front over the entire area of ​​the toothed belt drive 51, which allows for very easy assembly of the components of the toothed belt drive 51. After assembly, the gear receiving space 25 can be closed at the front by a gear cover 26, which has a through-opening for the push rod 4.

[0067] In the same way, a motor cover 27 can be provided on the motor receiving space 21, which is mounted after the assembly of the electric motor 3 or a corresponding power pack 31.

[0068] An electromechanical vehicle steering system of the type with axially parallel arrangement of the push rod 4 and the electric motor 3 as described above can be manufactured in the manner explained in more detail below.

[0069] Production involves first attaching the electric motor 3 to the housing 2 of the push rod 4. In particular, this may involve inserting the electric motor 3 or a corresponding power pack 31 into the motor receiving space 21 of the housing 2. If the motor receiving space 21 is provided via a separate housing component, this separate housing component is first fastened to the housing 2 of the push rod 4. Attaching the electric motor 3 may also involve firmly flanging the electric motor 3 to the housing 2 of the push rod 4. The position of the rotational axis A of the electric motor 3 relative to the housing 2 is thus fixed and, as such, cannot be changed.

[0070] Furthermore, the production includes the insertion of the ball screw nut 56 with an adjustable bearing 57, in particular a rolling bearing, into the gear receiving space 25 of the housing 2, wherein the ball screw nut 56, as already explained above, is designed to support the push rod 4.

[0071] The push rod 4 can be installed simultaneously with the ball screw nut 56. However, it is also possible to install the push rod 4 after the ball screw nut 56 has been installed.

[0072] The adjustable bearing 57 or the rolling bearing is then pre-fixed to the housing 2, for example by tack-fastening threaded bolts 61.

[0073] Furthermore, the toothed belt wheels 52 and 53 are arranged on the output shaft 32 of the electric motor 3 and on the ball screw nut 56.

[0074] In particular, the second toothed belt wheel 53 can be mounted on the ball screw nut 56 after the adjustable bearing 57 has been pre-fixed.

[0075] The first toothed belt pulley 52 can already be provided with the assembly of the electric motor 3 on the housing 2, but can also be subsequently attached to the output shaft 32 already mounted on the housing 2.

[0076] If the electric motor 3 is inserted into the motor receiving space 21 with the first toothed belt pulley 52 pre-mounted on the output shaft 32, the first toothed belt pulley 52 can be guided through a bearing point on the housing 2 for the output shaft 32.

[0077] The toothed belt 54 is placed on the mounted toothed belt wheels 52 and 53 when the toothed belt 54 is loose and untensioned. The pre-fixing of the adjustable bearing 57 is adjusted accordingly.

[0078] After the toothed belt 54 is applied, it is tensioned by radially displacing the adjustable bearing 57 of the ball screw nut 56 until the desired toothed belt tension is reached. This shifts the position of the longitudinal axis B of the push rod 4 relative to the housing 2, specifically in the radial direction to the longitudinal axis B.

[0079] The adjustable bearing 57 is then fixed with the toothed belt 54 tensioned, whereby the set toothed belt tension is maintained.

[0080] According to the invention, the guide bushing 70 is also provided on the housing 2 as a second bearing point L2 for guiding the push rod 4. When tensioning the toothed belt 54, the guide bushing 70 can be radially positioned in the housing 2 according to the position of the adjustable bearing 57 of the ball screw nut 56 to avoid tension, and the guide bushing 70 can be fixed to the housing 2.

[0081] When tensioning the toothed belt 54, the push rod 4 with the ball screw nut 56 and the guide bushing 70 in the housing 2 can be displaced radially to the longitudinal axis B of the push rod 4, essentially parallel to it, as indicated in Fig. 1 by double arrows at the bearing points L1 and L2. The displacement occurs transversely or radially to the longitudinal axis B of the push rod 4.

[0082] The electric motor 3 and the ball screw nut 56 can be inserted into the housing 2 from opposite sides and in opposite directions. The corresponding insertion openings of the preferably one-piece housing 2 are then closed by covers 26 and 27. Sealing can be provided between the housing 2 and the tie rod joints 6 using bellows.

[0083] The invention has been explained in more detail above using an exemplary embodiment and further modifications. In particular, individual technical features explained above in the context of further individual features can be implemented independently of these and in combination with further individual features, even if not expressly described, as long as this is technically possible. The invention is therefore expressly not limited to the described exemplary embodiment and the specifically mentioned modifications, but encompasses all embodiments defined by the patent claims. List of reference symbols

[0084] 1 electromechanical vehicle steering

[0085] 2 housings

[0086] 3 electric motor

[0087] 4 push rod

[0088] 5 gearboxes

[0089] 6 Tie rod end

[0090] 21 Engine compartment

[0091] 22 Section of the housing 2

[0092] 23 Interior wall ledge

[0093] 24 Section of the housing 2

[0094] 25 Gearbox mounting space

[0095] 26 Gearbox cover

[0096] 27 Engine cover

[0097] 31 Powerpack

[0098] 32 Output shaft

[0099] 33 rolling bearings

[0100] 34 Outer ring

[0101] 41 threaded section

[0102] Section 42

[0103] 51 Toothed belt drive

[0104] 52 first toothed belt wheel

[0105] 53 second toothed belt wheel

[0106] 54 timing belts

[0107] 55 Ball screw

[0108] 56 ball screw nut

[0109] 56a ball

[0110] 57 adjustable bearings

[0111] 58 inner ring

[0112] 59 Outer ring

[0113] 60 bearing clamping device

[0114] 61 threaded bolts

[0115] 70 guide bushing

[0116] A axis of rotation of the electric motor 3

[0117] B Longitudinal axis of the push rod 4 L1 first bearing point

[0118] L2 second bearing point

Claims

Patent claims 1. An electromechanical vehicle steering system (1), comprising a housing (2), an electric motor (3) with a rotational axis (A), a push rod (4) with a longitudinal axis (B), wherein the push rod (4) is arranged in the housing (2) so as to be axially movable in the direction of the longitudinal axis (B), and the longitudinal axis (B) runs parallel to the rotational axis (A) of the electric motor (3), a gear (5) via which the electric motor (3) is drivingly coupled to the push rod (4) in order to translate a rotational movement of the electric motor (3) into a linear movement of the push rod (4), wherein the gear (5) comprises a toothed belt drive (51) and a ball screw drive (55), wherein a ball screw nut (56) of the ball screw drive (55) engages with the push rod (4) and supports the push rod (4) in the housing (2), wherein the ball screw nut (56) is connected to the housing (2) via an adjustable bearing (57). is stored,and wherein a toothed belt (54) of the toothed belt drive (51) can be tensioned via the adjustable bearing (57), characterized in that the push rod (4) is further mounted in the housing (2) via a guide bush (70) and the guide bush (70) is adjustable in its position radially to the push rod (4) in the housing (2).

2. Electromechanical vehicle steering system (1) according to claim 1, characterized in that the guide bush (70) has a sliding bearing in which the push rod (4) is axially guided with a section (42) and secured against rotation about its longitudinal axis (B).

3. Electromechanical vehicle steering system (1) according to claim 1 or 2, characterized in that a section (22) with a motor receiving space (21) for the electric motor (3) is fastened to the housing (2) or formed integrally thereon, the electric motor (3) has an output shaft (32) on which a first toothed belt wheel (52) of the toothed belt drive (51) is arranged in a rotationally fixed manner, and the electric motor (3) is inserted axially into the motor receiving space (21) from a side opposite the first toothed belt wheel (52).

4. Electromechanical vehicle steering system (1) according to claim 3, characterized in that the output shaft (32) of the electric motor (3) is rotatably mounted in the housing (2) via a rolling bearing (33), an outer ring (34) of the rolling bearing (33) being supported on an inner wall shoulder (23) of the housing (2).

5. Electromechanical vehicle steering system (1) according to one of claims 1 to 4, characterized in that the adjustable bearing (57) comprises a rolling bearing and a bearing clamping device (60), an outer ring (59) of the rolling bearing is displaceable radially to the longitudinal axis (B) of the push rod (4) in the housing (2) and can be fixed to the housing (2) by means of the bearing clamping device (60), wherein the bearing clamping device (60) is clamped to the housing (2) preferably radially outside a second toothed belt wheel (53) of the toothed belt drive (51) arranged on the ball screw nut (56) in a rotationally fixed manner.

6. Electromechanical vehicle steering system (1) according to one of claims 1 to 5, characterized in that the housing (2) integrally forms a section (24) with a gear receiving space (25), the outer wall of which extends radially around the toothed belt drive (51) and the gear receiving space (25) is closed at the end by a gear cover (26) which has a through opening for the push rod (4).

7. A method for producing an electromechanical vehicle steering system (1) of the type with an axially parallel arrangement of a push rod (4) and an electric motor (3), characterized by: - Attaching the electric motor (3) to a housing (2) of the push rod (4), - Inserting a ball screw nut (56) with a rolling bearing into a gear receiving space (25) of the housing (2), wherein the ball screw nut (56) is designed to support the push rod (4), - Pre-fixing the rolling bearing to the housing (2), - arranging toothed belt wheels (52, 53) of a toothed belt drive (51) on an output shaft (32) of the electric motor (3) and on the ball screw nut (56), - loosely placing a toothed belt (54) of the toothed belt drive (51) on the mounted toothed belt wheels (52, 53), - Tensioning the toothed belt (54) by radially displacing the rolling bearing of the ball screw nut (56) and fixing the rolling bearing with the toothed belt (54) tensioned, - Providing a guide bush (70) for guiding the push rod (4) and radially positioning the guide bush (70) in the housing (2) according to the position of the rolling bearing of the ball screw nut (56) and fixing the guide bush (70) to the housing (2).

8. Method according to claim 7, characterized in that the push rod (4) with the ball screw nut (56) and the guide bush (70) in the housing (2) can be displaced radially parallel to the longitudinal axis (B) of the push rod (4).

9. Method according to claim 7 or 8, characterized in that the electric motor (3) and the ball screw nut (56) are inserted into the housing (2) from opposite sides and in opposite directions.

10. Method according to one of claims 7 to 9, characterized in that the electric motor (3) with a first toothed belt pulley (52) pre-mounted on an output shaft (32) is pushed into the motor receiving space (21), wherein the first toothed belt pulley (52) is guided through a bearing point on the housing (2) for the output shaft (32).

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