Steering actuator for a steering system of a motor vehicle

Abstract

The invention relates to a steering actuator (4) for a steering system (1) of a motor vehicle, comprising an actuator rod (5) which is axially translationally linearly movable relative to a sliding bushing (7) in its longitudinal direction and which has a measuring portion (52) mounted in a displaceable manner in an opening in the sliding bushing (7), the steering actuator further comprises a drive device (42), in which the measuring part (52) and the sliding bushing (7) have a sensor device designed to detect at least one actuator parameter. In order to achieve a lower level of expenditure in terms of design and production and an improved flexibility in terms of application, the invention proposes that a sliding sleeve (8) extending in the longitudinal direction on the measuring part (52) is fitted on the actuator rod (5).

Description

TECHNICAL FIELD

[0001] The invention relates to a steering actuator for a steering system of a motor vehicle, comprising an actuator rod which is linearly movable in axial translation with respect to a sliding bushing in its longitudinal direction and which has a measuring portion which is mounted in a displaceable manner in an opening in the sliding bushing, and a drive device, wherein the measuring portion and the sliding bushing have a sensor device which is designed to detect at least one actuator parameter. BACKGROUND

[0002] In a motor vehicle steering system, a steering actuator is used to generate a mechanical steering angle of one or more steerable wheels.

[0003] Steering actuators of this general type have an actuator rod which, in its longitudinal direction, i.e. in axial adjustment with respect to its longitudinal axis, is generally transverse to the direction of travel with respect to the vehicle body. The actuator rod can be connected in a hinged manner to the axle members of two steerable wheels of a vehicle axle, or, in the case of a single-wheel steering system, to a single steerable wheel. Axial translational displacement of the actuator rod generates a mechanical steering angle of the one or more steerable wheels.

[0004] In order to generate the steering angle, the actuator rod can be moved in axial translation by means of a drive device. This drive device can have a manual force introduction device, for example as is known from conventional rack steering systems. As an alternative or in addition, a motorized drive or an assisted force drive can be provided. This drive comprises a drive device with an electric motor which can transmit an axial steering or actuator force into the actuator rod, for example via a rack or spindle drive.

[0005] The actuator rod is mounted in the steering actuator in axial displacement in a sliding bushing which is arranged in a housing, actuator housing or transmission housing which is fixed to the vehicle body.

[0006] To monitor functionality and enable motor actuation, a sensor device is known to have at least one electrical sensor designed to detect at least one current actuator parameter and output a corresponding electrical measurement value. The detected actuator parameter can be, for example, the position of an actuator rod, as described in DE 10 202 1205 316A1, where the sensor has a running wheel that interacts with the actuator rod. Alternatively, DE 199 15105A1 proposes mounting the actuator rod in a linearly displaceable sliding manner within a sliding bushing. An axially continuous mark formed in the measuring portion of the actuator rod can be detected by means of a sensor element designed as a detector, located in the region of the sliding bushing for detecting the position of the actuator rod.

[0007] Known sensor devices allow for the measurement of various actuator parameters, such as detecting the position of the actuator rod. However, it is always necessary to machine the actuator rod, for example, by manufacturing a gear system or sensor markings, to form or mount the sensor element. This results in a relatively high level of cost in design and manufacturing, as well as a relatively high level of cost to accommodate different steering actuator designs.

[0008] In view of the above problems, the object of the present invention is to achieve a lower level of cost in design and manufacture as well as improved flexibility in application. Summary of the Invention

[0009] According to the invention, this objective is achieved by a steering actuator having the features of the main aspects. Advantageous improvements can be found in other aspects.

[0010] In a steering actuator for a steering system of a motor vehicle, the steering actuator includes an actuator rod capable of linearly translating axially relative to a sliding bushing in the longitudinal direction of the actuator rod, and the actuator rod has a measuring portion mounted in an opening in the sliding bushing in a displaceable manner. The steering actuator also includes a drive mechanism, wherein the measuring portion and the sliding bushing have sensor devices designed to detect at least one actuator parameter. According to the invention, a sliding sleeve is provided that extends longitudinally on the measuring portion to be fitted onto the actuator rod.

[0011] According to the invention, the sliding sleeve is initially provided separately and then coaxially fitted onto the outer periphery of the actuator rod. Axially, that is, in the longitudinal direction defined by the longitudinal axis of the actuator rod, the sliding sleeve is preferably at least as long as the measuring portion and surrounds the measuring portion.

[0012] The outer cross section of the sliding sleeve is adapted to the inner cross section or opening cross section of the opening in the sliding bushing in order to achieve a linear sliding bearing of the actuator rod in the sliding bushing, the outer cross section of the sliding sleeve having the outer contour of the actuator rod, which is provided by the cross section profile and surrounds the longitudinal axis.

[0013] The actuator rod according to the application has a body, which has a receiving portion, which extends in the longitudinal direction, and on which the sliding sleeve is fixed in an axially fixed and co-rotating manner with respect to rotation about the longitudinal axis. The sliding sleeve is arranged coaxially in the receiving portion on the body. The sliding sleeve thus forms a kind of sheath or cover for the actuator rod in the region of the measuring portion, which is held in a linearly movable manner in the sliding bushing.

[0014] Since the sliding sleeve can be adapted to the receiving portion of the body in a flexible manner and only has a low level of expenditure by virtue of the construction of the receiving opening, the machining expenditure for the actuator rod itself can advantageously be reduced.

[0015] The body of the actuator rod can be produced, for example, from a dimensionally stable raw material, such as, for example, a drawn cylindrical or polygonal steel rod material, which can retain its original shape in the region of the receiving portion for the sliding sleeve according to the application. According to the application, the sliding sleeve can be fitted on the body and preferably does not need to be further machined as in the previous case, so that expensive machining of the raw material is not necessary in this region in order to adapt to the inner cross section of the sliding bushing.

[0016] A further advantage is that the outer cross section of the sliding sleeve can be constructed largely independently of the outer cross section of the body of the actuator rod. Different embodiments of the actuator rod and / or the sliding bushing can thus be adapted to one another in terms of design and manufacture at a relatively low level of expenditure, so that, for example, an actuator rod based on a standardized body can be used in different steering mechanisms with different sliding bushings. In other words, by virtue of the construction of the sliding sleeve at a low level of expenditure, the actuator rod can be adapted to the guide in the sliding sleeve.

[0017] In a further advantageous embodiment, the measuring portion can be designed without sensor devices. Here, the portion forms a region, which is designed only for the sliding bearing of the actuator rod with security against rotation.

[0018] It is preferably provided that the sliding sleeve has a hollow body. The hollow body can preferably be designed in the form of a tubular profile or a tube. The hollow body can have an axial receiving opening which corresponds in shape and size to the receiving portion of the main body and which can preferably be designed as an axially continuous passage opening. The receiving opening is configured in its shape and size and adapts to the outer profile in the receiving portion of the main body of the actuator rod such that an axial fixed and co-rotating connection is allowed.

[0019] The outer cross section of the hollow body corresponds in shape and size to the open cross section (inner cross section) of the sliding sleeve in order to form a sliding bearing.

[0020] The hollow body can be designed to be continuous over its entire length or at least partially, preferably circumferentially closed over its circumference.

[0021] The length of the hollow body measured in the longitudinal direction is equal to or preferably greater than the length of the measuring portion, the hollow body being installed in the sliding bushing in a linearly displaceable sliding manner.

[0022] For the purpose of fitting, the hollow body can be pushed onto the main body of the actuator rod coaxially in the axial direction until the hollow body sits in the region of the measuring portion and can be fixed therein. For the reception of the sliding sleeve, the receiving portion of the main body is designed to be at least as long as the hollow body.

[0023] Advantageously, the hollow body has a receiving opening with a receiving cross section which has a different cross-sectional shape than the outer cross section. The receiving cross section corresponds to an axially open passage cross section of the axially continuous receiving opening in the hollow body which adapts to the cross-sectional shape in the region of the receiving portion of the main body for fixing purposes. As mentioned above, this cross-sectional shape can preferably be provided by the unprocessed original cross section of the raw material and can be circular, for example in the case of a cylindrical raw material.

[0024] The outer cross section of the sliding sleeve, which corresponds to the inner cross section of the sliding bushing, can preferably be a non-circular configuration, preferably having a polygonal, for example triangular, basic cross section, in order to form a sliding bearing which is fixed in terms of rotation. The shape of the outer cross section can be designed differently than the shape of the inner cross section of the sliding sleeve. However, the basic shape can also be the same and only the size is different.

[0025] The corresponding configuration of the sliding sleeve according to the application allows the implementation of manufacturing-related and function- or measurement-related optimizations independently of one another. For example, in order to efficiently manufacture the actuator rod, it is possible to use a readily available circular material on which the sliding sleeve is fixed in a machined cylindrical portion, which has a polygonal outer cross section on the outside and is slidably guided in the sliding bushing in an interlocking rotationally fixed manner.

[0026] It is preferably provided that the sliding sleeve is connected to the actuator rod in a co-rotating and fixed manner in the longitudinal direction. Thus, the sliding sleeve is fixed to the actuator rod in a coaxially fixed manner in the direction of the longitudinal axis and in terms of rotation about the longitudinal axis.

[0027] The fixing operation can be carried out by the sliding sleeve being connected to the actuator rod in a material-to-material bond and / or interlocking and / or force-fit manner. The fixing of the sliding sleeve can be optimized in terms of manufacturing and adapted to the loads during operation. The material-to-material bond connection can be carried out, for example, by adhesive bonding or welding and ensures a secure retention when the sliding sleeve is fixed on the cylindrical portion of the body of the actuator rod. The sliding sleeve and the actuator rod can also have corresponding interlocking elements which produce an axial and / or interlocking connection in terms of rotation about the longitudinal axis. This can be achieved, for example, by a non-circular cross section of the body and a receiving opening in the sliding sleeve. Additionally or as an alternative, a force-fit connection can be achieved, for example, by corresponding frictional engagement elements.

[0028] The sliding sleeve can be held in the sliding bushing in a rotationally fixed manner. This ensures that the actuator rod, on which the sliding sleeve is fitted co-rotating in terms of rotation about the longitudinal axis, can be moved linearly relative to the sliding bushing only in the longitudinal direction.

[0029] The sliding sleeve can preferably have a torsionally rigid design. Since the sliding sleeve itself and the connection to the actuator rod in terms of rotation about the longitudinal axis also have a torsionally rigid design, it can be ensured that the actuator rod or the body of the actuator rod does not rotate relative to the sliding bushing, which is fixed in place on the steering actuator. The following advantages can thus be achieved: a clear and precise orientation of the actuator rod relative to the sliding bushing and a correspondingly high degree of measurement accuracy in terms of position detection and measurement of torsional and / or bending moments which can act on the actuator rod.

[0030] It can be advantageous for the sliding sleeve to have a flexurally soft or flexurally slack design. A flexurally soft or flexurally slack design means that the sliding sleeve essentially does not generate a restoring force counter to the bending moment or a negligible restoring force in terms of measurement when the actuator rod is bent transversely to the longitudinal direction. If the sensor device is intended to measure the bending load acting on the actuator rod, the advantage is that the measurement result is not adversely affected by the sliding sleeve. In practice, a flexurally soft or flexurally slack design can be achieved by using a material that is easily deformed, for example a plastic material, which has a low level of dimensional stiffness.

[0031] As an alternative to the design mentioned above, the sliding sleeve can have a flexurally stiff design. In this case, it is provided that the sliding sleeve itself has a defined flexural stiffness, which sliding sleeve exerts a defined return moment in the event of a bending load acting on the actuator rod and thus increases the flexural stiffness of the arrangement formed by the actuator rod and the sliding sleeve according to the application. The sliding sleeve can thus act as an additional mechanical support element for increasing the stiffness of the actuator rod.

[0032] Preferably, the sliding bushing and the sliding sleeve can have corresponding sensor elements. In this case, a measuring device, which can have a measuring device that is at least partially combined with the sliding bushing, is provided in the region of the sliding bushing. This measuring device comprises at least one active detector or sensor element, which can detect the relative or absolute position of the corresponding sensor elements connected to the actuator rod according to a specified measurement method, for example a marker or scale for position detection in the longitudinal direction. For example, capacitive, inductive, resistive, magnetic, optical or other measurement methods known per se and suitable for detecting actuator parameters can be used for this purpose. According to the application, it is preferably provided that the sliding sleeve has sensor elements connected to the actuator rod. These sensor elements do not therefore have to be inserted into the actuator rod itself, for example into the main body, but can be incorporated into the sliding sleeve according to the application.

[0033] This has several advantages. Firstly, in order to fit the sensor elements, the actuator rod does not need to be additionally machined. These sensor elements can simply be installed when the sliding sleeve is fitted to the actuator rod. Furthermore, by virtue of the corresponding configuration of the sliding sleeve, it is possible to provide different sensor elements adapted to the respective requirements on the standardized main body of the actuator rod at a low level of expense. It is therefore possible to change or adapt the measurement principle or the sensor geometry without changing the shape of the actuator rod. Flexibility can thus be improved and manufacturing costs can be reduced.

[0034] Advantageously, the sensor element is designed to detect the linear movement of the actuator rod relative to the sliding bushing. To this end, a transmitter / receiver device known per se, for example a capacitive, inductive incremental encoder, an optical measuring element, etc., can be provided in order to detect an absolute or relative position measurement in the direction of the longitudinal axis. Thus, the instantaneous position of the actuator rod in the steering actuator, which correlates with the mechanical steering angle of the wheel or wheels steered by the steering actuator, can be detected reliably and accurately.

[0035] The sensor element can be designed to detect a bending moment and / or a torsional moment applied between the actuator rod and the sliding bushing. In addition to or as an alternative to the position detection, a sensor element responsive to a deformation of the actuator rod can be provided. The elastic torsion and / or bending of the actuator rod can be caused by forces acting during operation. Monitoring these actuator parameters enables monitoring of the load during operation and thus reliably identifies potentially harmful overloads or malfunctions.

[0036] Advantageously, the sliding sleeve comprises a plastic. The sliding sleeve can have a plastic hollow body, for example of a tubular or tube-contoured design. This hollow body can advantageously be provided, for example, as a plastic injection-molded part from a thermoplastic polymer. Here it is conceivable and possible to design at least one sensor element to be combined with the plastic part, preferably by a non-releasable connection. For example, a capacitive, inductive or other sensor element can be embedded in the plastic, for example by encapsulation with the plastic during injection molding.

[0037] It is likewise conceivable and possible to manufacture the sliding sleeve from a composite plastic material in order to produce a higher degree of stiffness.

[0038] Forming the sliding sleeve from plastic also enables optimization of the sliding properties of the linear plain bearing of the actuator rod in the stationary sliding bushing. For example, this sliding bushing can likewise comprise a plastic at least in the region of its passage opening, which is selected with the aim of a particularly low-friction friction pairing with the material of the sliding sleeve.

[0039] The actuator rod can have a body formed from steel. The raw material used can be, for example, a drawn round steel material or the like.

[0040] The body can preferably be designed to interact with the drive device. For example, the drive device can have a spindle drive which can be driven by a motor. In this case, the actuator rod has a spindle thread which extends over an axially threaded portion and engages into a spindle nut. The spindle nut is supported in an axially fixed manner and can be driven in rotation by the motor relative to the threaded shaft of the actuator rod. According to the functional principle of spindle drives known per se, in particular of plunger spindle drives, the motor-driven rotation of the spindle nut is converted into a linear axial movement of the actuator rod. The spindle drive can preferably be designed as a ball screw drive (KGT), the spindle nut as a ball nut (recirculating ball nut) and the spindle thread as a corresponding ball screw.

[0041] When using a spindle drive, the actuator rod is preferably fixed in rotation about the threaded axis (spindle axis) in the sliding bushing, which is held in the sliding sleeve in an interlocking manner, preferably due to the non-circular outer cross-section of the sliding sleeve according to the application. Suitable sensor elements can be used to monitor the axial compression and tensile forces introduced between the spindle thread and the sliding bushing, and in addition the torsional forces transmitted by the spindle thread. Thus, the functioning of the spindle drive and the sliding bushing can advantageously be monitored during ongoing operation.

[0042] It is likewise conceivable and possible that the drive unit has a rack drive in which the actuator rod has a tooth system portion into which a pinion which can be driven in rotation by a motor engages.

[0043] The actuator rod can have a one-piece body. The body can be designed as a shaped metal part which has a measuring portion on which the sliding sleeve according to the application is fixed coaxially and a drive portion, for example with a spindle thread or a tooth system portion, is integrally connected to the measuring portion.

[0044] As an alternative, it can be provided that the body consists of two or more separate axial segments. BRIEF DESCRIPTION OF DRAWINGS

[0045] Advantageous embodiments of the application will be explained in more detail below with reference to the drawings, in which:

[0046] Figure 1 a schematic view of a steering system according to the application is shown,

[0047] Figure 2 a cross section B-B through a steering actuator according to Figure 1 the application is shown,

[0048] Figure 3 a cross section B-B through a steering actuator according to Figure 1a longitudinal section along the axis A of the steering actuator,

[0049] Figure 4 independently schematically shows a steering actuator according to Figure 2 and Figure 3 a view of the actuator rod of the steering actuator. DETAILED DESCRIPTION

[0050] In the various figures, identical parts are always denoted by identical reference numerals, and the identical parts will therefore normally also be named or referred to only once in each case.

[0051] Figure 1 A steer-by-wire steering system 1 comprising a steering column 2 is schematically shown. The steering column has a support unit 21 which can be mounted on a not shown vehicle body and by which a steering spindle 22 can be rotatably supported about its longitudinal axis L. A steering wheel 23 is mounted in a co-rotating manner on the steering spindle 22 at its driver side end, which steering wheel 23 is located behind with respect to the driving direction for inputting a manual steering command.

[0052] In the steering column 2 there is accommodated a not specifically shown rotation angle and torque detection sensor system which converts a steering command introduced into the steering spindle 22 by rotation of the steering wheel 23 into an electrical control signal.

[0053] The control signal is conducted via an electrical control line 3 to an electrical steering actuator 4 according to the invention.

[0054] The steering actuator 4 - which is shown in a detailed view in Figures 2 to 4 - has an actuator rod 5 which extends along an axis A, the so-called actuator axis A, transversely to the driving direction of the vehicle. As indicated by the double-headed arrow, the actuator rod is axially displaceably mounted in an actuator housing 41 in its longitudinal direction designated by the axis A. The actuator housing 41 has connection elements not shown here for attaching it to a not shown vehicle body.

[0055] The two outer ends of the actuator rod 5 are each connected via a track rod 6 to a steerable wheel 61, so that an axial displacement of the actuator rod 5 produces a steering angle of the wheel 61 with respect to a road 62.

[0056] For producing the steering angle, the steering actuator 4 has an electrical drive which can be electrically actuated via the control line 3, and has an electrical motor 42 which is fitted to the actuator housing 41. In Figure 2 and Figure 3The axially supported spindle nut 43, which is shown in cross section and is mounted in rotation in the actuator housing 41, can be driven in rotation by the motor 42. A spindle thread 51 formed on the actuator rod 5 engages into this spindle nut. In this way a linear spindle drive is formed in which the actuator rod 5 can be moved axially, i.e. in the longitudinal direction, forwards and backwards relative to the actuator housing 41 by corresponding rotation of the motor 42, as indicated by the double-headed arrow.

[0057] The spindle nut 43 can preferably be designed as a circulating ball nut.

[0058] Figure 2 A cross section B-B perpendicular to the axis A is shown, and Figure 3 A longitudinal section along the axis A is shown. Figure 4 A perspective view of the spindle drive formed by the actuator rod 5 together with the spindle nut 43 is shown schematically independently.

[0059] The actuator rod 5 has a cylindrical body which can for example be formed from a steel rod material. The spindle thread 51 is made in this cylindrical body.

[0060] The actuator rod 5 has a measuring portion 52 at an axial distance from the spindle thread 51. This measuring portion is guided through an axially continuous opening in a sliding bushing 7 which is fitted in the actuator housing 41.

[0061] The measuring portion 52 and the sliding bushing 7 have corresponding sensor elements, which are not shown here in detail, which can have sensor markings etc. which are connected to the actuator rod in a manner known per se and can be detected by means of a sensor or detection element fitted to or incorporated in the sliding sleeve 8, for example, for detecting the position of the actuator rod 5 in the actuator housing 41.

[0062] The actuator rod 5 has a sliding sleeve 8 according to the application in the region of the measuring portion 52. This sliding sleeve can for example be designed as a tubular or tube profiled plastic hollow body or comprise such a hollow body. The hollow body can be designed as a plastic injection molded part. The sliding sleeve 8 can have a continuous receiving opening through which it is fixed axially coaxially on the actuator rod 5 and in the receiving portion of the body in a rotationally joint manner on the cylindrical raw material, as in the example shown.

[0063] The outer cross section of the sliding sleeve 8 is adapted to the opening cross section of the opening in the sliding bushing 7, so that a linear sliding guide is formed. As Figure 4The outer cross-section shown has a polygonal prism profile, such as a square profile. This creates a linear guide with rotational safety in an interlocking manner within the same polygonal opening that conforms to the profile of the sliding sleeve 8.

[0064] The main body of the actuator rod 5 can maintain the original shape of the raw material in the area of ​​the measuring section 52. The sliding bushing 7 can be fixedly connected to the actuator rod 5 by material-to-material bonding, such as by adhesive bonding or welding.

[0065] The sliding sleeve 8 may preferably have a sensor element, which may be fixedly connected to the hollow plastic body, for example, by means of a plastic encapsulation.

[0066] The main body of the actuator rod 5 can be formed into a single piece from the area from the threaded portion 51 to the measuring portion 52.

[0067] List of reference numerals

[0068] 1. Steering System

[0069] 2. Steering column

[0070] 21 Support Unit

[0071] 22 Steering spindle

[0072] 23 Steering wheels

[0073] 3 Control Lines

[0074] 4. Steering actuator

[0075] 41 Actuator housing

[0076] 42 motors

[0077] 43 Spindle Nut

[0078] 5 Actuator rod

[0079] 51 Spindle Thread

[0080] 52 Measurement Section

[0081] 6 track poles

[0082] 61 rounds

[0083] Road 62

[0084] 7. Sliding bushing

[0085] 8. Sliding sleeve

[0086] L longitudinal axis

[0087] A actuator axis

Claims

1. A steering actuator (4) for a steering system (1) of a motor vehicle, the steering actuator (4) comprising an actuator rod (5) linearly movable axially in the longitudinal direction of the actuator rod (5) relative to a sliding bushing (7), and the actuator rod (5) having a measuring portion (52) displaceably mounted in an opening in the sliding bushing (7), the steering actuator (4) further comprising a drive device (42), wherein, The measuring section (52) and the sliding bushing (7) have sensor devices designed to detect at least one actuator parameter. Its features are, A sliding sleeve (8) is mounted on the actuator rod (5), and the sliding sleeve (8) extends along the longitudinal direction on the measuring part (52).

2. The steering actuator according to claim 1, characterized in that, The sliding sleeve (8) has a hollow body.

3. The steering actuator according to claim 2, characterized in that, The hollow body has a receiving opening, the receiving opening has a receiving cross section, and the receiving cross section has a cross section shape different from the outer cross section.

4. The steering actuator according to any one of the preceding claims, characterized in that, The sliding sleeve (8) is connected to the actuator rod (5) in a manner that allows for common rotation and fixation in the longitudinal direction.

5. The steering actuator according to any one of the preceding claims, characterized in that, The sliding sleeve (8) is connected to the actuator rod (5) in a material-to-material bonding and / or interlocking and / or force-fit manner.

6. The steering actuator according to any one of the preceding claims, characterized in that, The sliding sleeve (8) is held in the sliding bushing (7) in a way that is fixed in terms of rotation.

7. The steering actuator according to any one of the preceding claims, characterized in that, The sliding sleeve (8) has a torsional rigidity design.

8. The steering actuator according to any one of the preceding claims, characterized in that, The sliding sleeve (8) has a flexural relaxation design.

9. The steering actuator according to any one of claims 1 to 7, characterized in that, The sliding sleeve (8) has a flexural rigidity design.

10. The steering actuator according to any one of the preceding claims, characterized in that, The sliding bushing (7) and the sliding sleeve (8) have corresponding sensor elements.

11. The steering actuator according to claim 10, characterized in that, The sensor element is designed to detect the linear movement of the actuator rod (5) relative to the sliding bushing (7).

12. The steering actuator according to claim 10 or 11, characterized in that, The sensor element is designed to detect bending and / or torsional torques applied between the actuator rod (5) and the sliding bushing (7).

13. The steering actuator according to any one of the preceding claims, characterized in that, The sliding sleeve (8) is made of plastic.

14. The steering actuator according to any one of the preceding claims, characterized in that, The actuator rod (5) has a body made of steel.

15. The steering actuator according to any one of the preceding claims, characterized in that, The actuator rod (5) has a one-piece body.

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