Actuator for a steering system of a motor vehicle

Abstract

An actuator for a steering system of a motor vehicle, the actuator comprising a connecting rod (3) which is movable longitudinally in a housing (1) along an actuation path between axial stops (19, 24), passes through the housing (1) and is connectable at one end to a toe link for articulating a wheel, the stops (19, 24) of the actuator being arranged axially one behind the other and facing each other. The stops (19, 24) and a stop member (18) interacting with the two stops (19, 24) are located inside the housing (1).

Description

Technical Field

[0001] The invention relates to an actuator for a steering system of a motor vehicle, in particular a rear axle steering system. Background Art

[0002] DE102018129103 A1 discloses a rear axle steering system with an actuator, which is provided with a connecting rod that can be longitudinally displaced in a housing. The connecting rod passes through the housing and can be displaced along an actuation path between axial stop portions. The connecting rod is provided with a fork-shaped head at one end, which can be connected to a toe-shaped link for articulating the wheel. The connecting rod passes through a spacer ring fixed to the housing. The axial actuation path in one direction of travel is stopped by one fork-shaped head hitting one spacer ring in an interlocking manner. The axial actuation path in the other direction of travel is stopped by the other fork-shaped head hitting the other spacer ring in an interlocking manner. The spacer ring on the housing forms a stop portion, and the end face of the fork-shaped head facing the housing forms a stop member.

[0003] The interlocking stop according to DE 10 2018 129 103 A1 requires additional measures to ensure a complete actuation path, including a bellows enclosing the end face of the fork-shaped head and the spacer ring. The volume of air enclosed by the bellows varies depending on the position of the connecting rod, so ventilation may be required to ensure reliable protection against the ingress of foreign matter. Summary of the Invention

[0004] The object of the present invention is to specify an alternative actuator which reliably enables mechanical actuation path definition of a connecting rod in a simple manner.

[0005] According to the invention, this object is achieved by the following actuator.

[0006] An actuator for a steering system, preferably a rear-axle steering system, of a motor vehicle comprises a connecting rod, which is arranged in a housing and can be displaced longitudinally along an actuation path. The housing can be split laterally—i.e., transversely relative to the connecting rod axis—or longitudinally. A motor can be mounted on the housing, preferably driving a rotation-translation gear via a rotation-rotation gear, the translation output member of which can be part of the connecting rod. According to an advantageous embodiment, the electric motor rotationally drives a spindle drive via a belt drive, the threaded spindle of which is actuated in a translational manner, i.e., the spindle is displaced along its spindle axis.

[0007] For example, the ends of the connecting rod can be provided with screw-in eyes or fork-shaped heads or other connecting elements that can be screwed onto the two ends of the connecting rod. These connecting elements can be connected in an articulated manner to a so-called toe link, which articulates the wheel and changes the track of the wheel. The connecting rod itself can be designed in several parts and include a plurality of components rigidly connected to each other. The connecting rod preferably includes a threaded spindle as part of the screw drive. The longitudinally displaceable connecting rod can be mounted in the housing in a manner fixed to prevent rotation. To this end, the connecting rod can include a connecting rod part with a lateral surface, which is designed, for example, as a dihedral or polygonal profile and is mounted on a sliding surface on the housing.

[0008] The connecting rod can pass through the housing with its two ends so as to be connected to the toe links of the two wheels of the axle. Such an actuator can also be called a central actuator.

[0009] Starting from the neutral position, in which both wheels are set to travel straight ahead, the axial actuation path of the connecting rod is delimited in both axial directions by interlocking stops. The entire actuation path extends from one end position of the connecting rod to the other. The connecting rod is arranged to be longitudinally displaceable between these axial stops.

[0010] The stops are arranged axially one after another and axially facing each other. For example, a groove parallel to the longitudinal axis of the connecting rod may be provided in the housing or the connecting rod, the axial end groove walls of the groove forming the stops.

[0011] In addition, a stop is provided that interacts with the two stops. For example, the stop can be designed in the form of a pin and arranged transversely with respect to the connecting rod axis and engaged between the two stops. The stops facing each other can advantageously be impacted by a common stop and reduce the number of components for defining the actuation path. When the connecting rod moves axially in one direction, the stop hits one of the stop parts at the end of the actuation path. In the case of axial movement of the connecting rod in the other direction, the stop hits the other stop part at the end of the actuation path. Alternatively, the stop can be formed by two spatially separated stop parts, one of the two stop parts being associated with one stop part and the other of the two stop parts being associated with the other stop part.

[0012] Both the stopper and the stop member are arranged within the housing and are therefore protected from foreign objects outside the housing. These actuators are located on the underside of the vehicle with their housings and are therefore exposed to environmental influences. The arrangement within the housing reliably prevents foreign objects from entering between the stopper and the stop member, and reliably ensures that the connecting rod can reliably move along its intended actuation path.

[0013] The connecting rod can have a threaded spindle on a screw drive, preferably a planetary roller screw drive, and a connecting rod portion that is non-rotatably connected to the threaded spindle and is provided with a stop that can engage between two stops on the housing. As an alternative to this, the connecting rod portion can be provided with stops, between which the stop on the housing engages.

[0014] The use of a planetary roller screw drive is particularly advantageous because such a screw drive does not jam when the connecting rod moves against one of the stops in an interlocking manner. The connecting rod portion can also be configured as an anti-rotation device for the connecting rod in the housing, as already described above.

[0015] The housing can have a housing opening covered by a cover. Axially opposite sides of the housing opening can be provided with stops for the stop. The wall of the housing opening itself can serve as the stop. However, it may be advantageous to insert a separate stop in the housing opening. Depending on the type of vehicle, the desired actuation path can change. The stop portion provides the following advantage: the stop portion can be adapted to the desired actuation path without changing the housing opening. Alternatively, the cover can be provided with a stop that engages in the housing opening. For example, the cover can have an edge that engages in the housing opening and forms a stop in both directions of travel.

[0016] The actuator can be provided with a linear displacement sensor for detecting the axial position of the connecting rod, the signal transmitter of the linear displacement sensor being arranged on the connecting rod portion of the connecting rod, and the signal receiver of the linear displacement sensor covering the actuation path being associated with the housing. A contactless linear displacement sensor can advantageously be provided with a conductive signal transmitter forming a stop. Capacitive linear displacement sensors are particularly advantageous. For example, the signal transmitter can be formed from coated or uncoated steel or aluminum, as can be provided in a capacitive linear displacement sensor. In this case, the component can have a dual function, on the one hand as a signal transmitter for the linear displacement sensor, and on the other hand as a stop for a mechanical stop defining the actuation path. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The invention will be described in more detail below with reference to two exemplary embodiments shown in a total of five figures. In the figures:

[0018] Figure 1 The actuator is shown in one view;

[0019] Figure 2 The longitudinal section shows the Figure 1 Details of the actuator;

[0020] Figure 3 Shown from Figure 2 A magnified view of the details;

[0021] Figure 4 With Figure 3 The same enlarged detail shows a variation of the actuator;

[0022] Figure 5 Shown from Figure 2 Cross-sectional view of a detail of the actuator. DETAILED DESCRIPTION

[0023] Figure 1 and Figure 2 An actuator for a rear-axle steering system of a motor vehicle is shown. The actuator comprises a multi-part connecting rod 3, which is arranged in a housing 1 so as to be longitudinally displaceable along an actuation path. The multi-part connecting rod passes through the housing 1 and is provided at its end with a fork-shaped head 4 screwed to the end of the connecting rod 3. The fork-shaped head 4 is connected to a toe link (not shown), which in turn articulates the wheels (not shown) of the rear axle. Such an actuator can also be referred to as a central actuator.

[0024] Housing 1 is divided into two housing parts 5 and 6 transversely relative to the connecting rod axis. An electric motor 7 is screwed to housing 1 and drives a planetary roller screw drive 8 (rotation-translation gear) via a toothed belt drive (rotation-rotation gear), not shown. The planetary rollers 9 of this planetary roller screw drive mesh with the threads 10 of a threaded spindle 11, which is part of the connecting rod 3. Driven by the rotation of a planetary roller carrier 12, the planetary rollers 9 rotate about their axes and the non-rotatable threaded spindle 11. Each complete rotation of the planetary roller carrier 12 forces the connecting rod 3 to advance axially by the pitch of the threads 10 of the threaded spindle 11.

[0025] The connecting rod 3 comprises a plurality of parts rigidly connected to one another. The connecting rod comprises a threaded spindle 11 and a further connecting rod part, of which a first connecting rod part 13 screwed together with the threaded spindle 11 is designed as an anti-rotation device 14 for the connecting rod 3. The anti-rotation device 14 comprises a dihedron 15 ( Figure 5 ).

[0026] from Figure 1 Starting from the neutral position shown in , in which both wheels are set to travel straight ahead, the axial actuation path of the connecting rod 3 is interlockingly delimited in both axial directions by the actuation path limiter 17 .

[0027] Figure 3A detail of the actuation path definer 17 is shown, which includes a pin-shaped stop 18 screwed to the anti-rotation device 14. The stop 18 engages between two stops 19 on the housing, which are arranged axially one behind the other and face each other. When the connecting rod 3 moves axially in one direction, the stop 18 strikes one of the stops 19 at the end of the actuation path. When the connecting rod moves axially in the other direction, the stop 18 strikes the other stop 19 at the end of the actuation path.

[0028] The housing 1 has a housing opening 20 which is covered by a cover 21 . In this exemplary embodiment, housing walls 22 of the housing opening 20 which are situated axially opposite one another form the stop 19 .

[0029] Figure 4 A variant is shown with an insert 23 which is inserted into the housing opening 20 and forms stops 24 between which the stop 18 can move. The axial extension of the insert 23 is matched to the desired actuation path.

[0030] The actuator is provided with a contactless linear displacement sensor 25, in particular a capacitive linear displacement sensor 25, for detecting the axial position of the connecting rod 3. An electrically conductive signal transmitter 26, also referred to as a target, is screwed onto the anti-rotation device 14 of the connecting rod 3. The cover 21 includes a signal receiver 27, which is provided with a plurality of coils (not shown in any further detail) and which extends over the length of the actuation path of the connecting rod 3.

[0031] In the exemplary embodiment, stop 18 is formed by a pin-shaped signal transmitter 26. This component thus performs a dual function, serving as a signal transmitter for the linear displacement sensor and, on the other hand, as a stop for the actuation path limiter. For calibration purposes, signal receiver 27, which is tightened with screw 28, is provided with an elongated hole 29. This allows signal receiver 27 to be axially displaced on anti-rotation device 14 for calibration purposes when screw 28 is loosened.

[0032] Reference Signs List

[0033] 1 Housing

[0034] 2-3 Connecting rod

[0035] 4 Fork-shaped head

[0036] 5. Shell

[0037] 6 Shell part

[0038] 7 Electric Motor

[0039] 8 Planetary Roller Screw Drives

[0040] 9 Planetary Rollers

[0041] 10 threads

[0042] 11 threaded spindle

[0043] 12 Planetary roller bearings

[0044] 13 First connecting rod part

[0045] 14 Anti-rotation device

[0046] 15 Dihedron

[0047] 16 Opposing surfaces

[0048] 17 Actuation Path Definer

[0049] 18 Stopper

[0050] 19 stopper

[0051] 20 Shell opening

[0052] 21 Cover

[0053] 22 Shell wall

[0054] 23 Inserts

[0055] 24 stopper

[0056] 25 Linear Displacement Sensor

[0057] 26 Signal Transmitter

[0058] 27 Signal Receiver

[0059] 28 screws

[0060] 29 oblong hole.

Claims

1. An actuator for a steering system of a motor vehicle, comprising a connecting rod (3) which is movable longitudinally in a housing (1) along an actuation path between axial stops (19, 24), passes through the housing (1) and is connectable at one end to a toe link for articulating a wheel, characterized in that Stoppers (19, 24) arranged axially one after another and facing each other in the axial direction and a stopper (18) interacting with the two stoppers (19, 24) are located inside the housing (1), and a cover (21) of the actuator covers an opening (20) of the housing, and the cover (21) is provided with the stoppers engaged in the housing opening (20).

2. An actuator according to claim 1, wherein the connecting rod (3) of the actuator has a threaded spindle (11) of a screw drive and a first connecting rod part (13), the first connecting rod part being non-rotatably connected to the threaded spindle (11) and provided with the stop (18) engaging between the two stops (19, 24) on the housing.

3. The actuator according to claim 1, wherein the connecting rod (3) of the actuator has a threaded spindle (11) of a screw drive and a first connecting rod part (13), the first connecting rod part is connected to the threaded spindle (11) in a non-rotatable manner, and the first connecting rod part is provided with the two stop parts, and the stop member on the housing is engaged between the two stop parts.

4. The actuator according to claim 2 or 3, wherein the first connecting rod part (13) of the actuator is mounted in the housing (1) as an anti-rotation device (14) for the connecting rod (3).

5. The actuator according to any one of claims 1 to 3, wherein the stopper portion of the actuator is formed on at least one insert (23) inserted into the housing opening (20).

6. An actuator according to any one of claims 1 to 3, provided with a linear displacement sensor (25) for detecting the axial position of the connecting rod, a signal transmitter (26) of the linear displacement sensor being arranged on one of the connecting rod parts of the connecting rod (3), and a signal receiver (27) of the linear displacement sensor covering the actuation path being associated with the housing (1).

7. The actuator according to claim 6, wherein the non-contact linear displacement sensor (25) of the actuator has a conductive signal transmitter (26) forming the stop (18).

8. The actuator according to claim 2 or 3, wherein the motor of the actuator drives the screw drive, the threaded spindle (11) of the screw drive being arranged in the housing (1) in a non-rotatable and axially movable manner.

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