Steering actuator

Abstract

The invention relates to an adjusting actuator (1) for a steering device, in particular a steer-by-wire steering device, comprising: a drive unit (2) configured to generate a drive torque, an adjusting unit (3) configured to convert the drive torque of the drive unit (2) into an adjusting movement, and a brake unit (4) arranged between the drive unit (2) and the adjusting unit (3), and configured to selectively couple the drive unit (2) and the adjusting unit (3) in a torque-transmitting manner, wherein the brake unit (4) comprises a brake device (6), a preload unit (7), and an actuating unit (8), wherein the brake device (6) is configured to block the adjusting movement of the adjusting unit (3) in a closed state, and wherein the preload unit (7) is configured toto close the brake device (6) in a drive-free state of the adjusting actuator (1), wherein the actuating unit (8) is configured to open the brake device (6) in a driven state of the adjusting actuator (1), wherein the actuating unit (8) has a ramp pinion (23) with a first ramp geometry (28) and a ramp sleeve (24) with a second ramp geometry (31), wherein the ramp pinion (23) is torque-transmittingly coupled to the drive unit (2) and the ramp sleeve (24) is rotationally fixed and axially displaceable to the adjusting unit (3), wherein the first ramp geometry (28) and the second ramp geometry (31) each have ramp-like guide surfaces (29, 32) which interact directly or indirectly such that a rotation of the ramp pinion (23) causes an axial displacement of the ramp sleeve (24) against a preload force of the preload unit (7).

Description

[0001] The present invention relates to an adjustment actuator for a steering device, in particular a steer-by-wire steering device. State of the art

[0002] Adjustment actuators for steering systems are used to adjust the position of a steering wheel in the longitudinal and / or vertical direction and are well known in the art. Adjustment actuators that are currently commonly used are mechanically self-locking to prevent unintentional adjustment of the position, e.g., due to a steering movement while driving. Furthermore, it is also known in the art to use non-self-locking drives to adjust the position of the steering wheel. For example, DE 10 2017 114 517 A1 discloses the use of a magnetorheological fluid in bearings, which can be switched accordingly to either enable or prevent adjustment of the steering wheel position. DE 10 2020 204 297 A1 discloses an adjustment drive in which a worm gear with a loop around the worm shaft is used.

[0003] It has now been found that there is a further need to improve a known adjustment actuator for a steering device, in particular for a steer-by-wire steering device, and in particular to provide an adjustment actuator with improved efficiency which at the same time ensures that the set position is maintained in a drive-free state of the adjustment actuator. Disclosure of the invention

[0004] These and other objects, which will be mentioned upon reading the following description or which may be recognized by a person skilled in the art, are achieved by the subject matter of the independent claim. Advantageous embodiments and further developments can be found in the dependent claims and the following description.

[0005] The adjustment actuator according to the invention for a steering device, in particular a steer-by-wire steering device, has a drive unit, an adjustment unit, and a brake unit. The drive unit, e.g. a motor, in particular an electric motor, is designed to generate a drive torque. The adjustment unit, e.g. a transmission unit, is designed to convert the drive torque of the drive unit into an adjustment movement. For example, the adjustment unit can translate the drive torque of the drive unit into an actuating torque and / or an actuating movement of the adjustment actuator. The brake unit is arranged between the drive unit and the adjustment unit and is designed to selectively couple the drive unit and the adjustment unit in a torque-transmitting manner. The brake unit has a braking device, a pretensioning unit, and an actuating unit.The braking device is configured to block the adjustment movement of the adjustment unit in a closed state. The preload unit is configured to close the braking device when the adjustment actuator is not driven, and the actuating unit is configured to open or release the braking device when the adjustment actuator is driven. The actuating unit has a ramp pinion with a first ramp geometry and a ramp sleeve with a second ramp geometry. The ramp pinion is coupled to the drive unit in a torque-transmitting manner, and the ramp sleeve is coupled to the adjustment unit in a rotationally fixed and axially displaceable manner.The first ramp geometry and the second ramp geometry each have ramp-like guide surfaces which interact directly or indirectly in such a way that rotation of the ramp pinion causes an axial displacement of the ramp sleeve against a preload force of the preload unit.

[0006] It can therefore be said that the actuating unit has a drivable or driven ramp pinion and a substantially complementary ramp sleeve assigned to the adjustment side. The ramp pinion is rotationally driven by the drive unit, whereby they rotate the ramp pinion and the ramp sleeve relative to one another, which leads to an axial displacement of the ramp sleeve. This axial displacement, caused in particular by driving the ramp pinion, serves to open or release the braking device. Furthermore, the preload unit is designed and / or arranged in such a way that it creates a preload force that closes the braking device. It can therefore be said that the preload force of the preload unit counteracts the axial displacement of the ramp sleeve to release the braking device.

[0007] Furthermore, the axial displacement of the ramp sleeve, in particular in the direction of the preload force of the preload unit, can also cause the ramp pinion to rotate. When the first ramp geometry and the second ramp geometry interact directly, the respective ramp-like guide surfaces are in contact with one another, in particular in sliding and / or frictional contact. Alternatively, when the respective ramp-like guide surfaces of the first ramp geometry and the second ramp geometry interact indirectly, the respective ramp-like guide surfaces are in operative contact via at least one further element arranged between them. In particular, the ramp pinion can further be configured to be axially fixedly coupled to the drive unit of the actuator.

[0008] Furthermore, the ramp sleeve can be coupled directly or indirectly to the adjustment unit. If the ramp sleeve is directly coupled to the adjustment unit, the ramp sleeve is at least partially in direct contact with the adjustment unit. For example, the ramp sleeve can be arranged on a shaft, such as a threaded spindle, of the adjustment unit in a rotationally fixed but axially displaceable manner, in particular, for example, via a spline. If the ramp sleeve is indirectly coupled to the adjustment unit, the ramp sleeve is coupled to the adjustment unit in a rotationally fixed but axially displaceable manner, for example, via the braking device.

[0009] The advantage of the solution according to the invention lies in particular in the fact that the efficiency of the adjustment actuator, in particular of the adjustment unit, can be increased or improved. In particular, an efficiency of up to more than 85% can be achieved. Thus, compared to known adjustment systems, in particular adjustment systems based on self-locking, the required drive power can be approximately halved, or the adjustment speed can be approximately doubled with approximately the same drive power. This makes it possible to use smaller and / or more cost-effective drive units. Due to the elimination of self-locking, smaller and / or more cost-effective adjustment units can also be used. Furthermore, the energy consumption of the adjustment actuator for adjusting the steering device is significantly reduced, in particular due to the higher efficiency.This makes it possible to realize the required, comparatively large adjustment paths, in particular from approximately 60 mm to approximately 24 mm, and / or the required comparatively fast adjustment speeds, in particular from approximately 12 mm / s to approximately 60 mm / s, which are increasingly required, in particular for steer-by-wire steering systems, in a cost-effective and space-saving manner.

[0010] In other words, one can say that the controllable brake unit makes it possible to hold the adjustment unit in the set position even when the drive unit is deactivated, i.e. when the adjustment actuator is in a drive-free state. This eliminates the need for a self-locking design of the adjustment unit, and instead of a self-locking adjustment unit with a comparatively low efficiency of less than 45%, a non-self-locking adjustment unit with a higher efficiency, in particular an adjustment unit with an efficiency of at least 60% or more, can be used. In order to release the brake unit, in particular the braking device, the drive unit overcomes a so-called dead travel, in which the torque generated by the drive unit is not yet transferred to the adjustment unit, but serves to move the actuating unit in order to release the braking device.It can therefore be said that in the dead travel, the torque generated by the drive unit is used as the actuating force to release the braking device.

[0011] Furthermore, the brake unit or braking device can be opened solely by the drive unit of the adjustment actuator, and can be released independently of the drive rotation direction, i.e., in both rotation directions of the ramp pinion. Actuating the brake device by the drive unit eliminates the need for a separate control unit for the brake device. This reduces the number of components and the required installation space of the brake unit, resulting in a particularly compact brake unit. Furthermore, the brake device can also be closed independently of a so-called reverse load rotation direction of the adjustment unit, i.e., in both rotation directions of the ramp pinion.

[0012] The adjustment actuator can be operated, for example, as follows: When the adjustment actuator is not driven, i.e., in a state in which the drive unit is not generating any torque, the braking device which maintains the preload force of the preload unit is kept in the closed state. This means that the adjustment unit is coupled to the housing of the steering actuator in a fixed manner, in particular in a rotationally and displacement-proof manner, furthermore in particular via a positive connection or a frictional connection. When the adjustment actuator is driven, i.e., in a state in which the drive unit is generating a torque, the ramp pinion is rotated relative to the ramp sleeve by the torque generated by the drive unit, with the ramp-like guide surfaces sliding against one another. A resulting axial force increases with increasing axial displacement of the ramp sleeve and counteracts the preload force of the preload unit.This opens or releases the braking device, and thus the braking unit. With the braking device or braking unit released, the full torque of the drive unit, particularly at synchronous speed, is transferred to the adjusting unit, thus moving the adjusting actuator to a desired setting position. Once the actuator has reached the setting position, the torque generation in the drive unit is stopped. As a result, no force counteracts the preload force of the preload unit, and the preload unit returns the braking device, and thus the braking unit, to the closed state. In the process, the ramp sleeve and ramp pinion rotate relative to each other again until they return to their original or neutral position.In particular, the preload force must be selected in such a way that it is sufficiently large in the axial direction to ensure the return of the actuating unit, as well as the return of the ramp groove and the ramp sleeve, to the neutral position.

[0013] According to one embodiment, the braking device is configured to couple the adjustment unit to a housing of the actuator in a torque- and / or axially fixed manner when closed. It can therefore also be said that a torque acting on the adjustment unit is supported on the housing of the adjustment actuator via the closed braking unit. This prevents adjustment, in particular rotation and / or displacement, of the adjustment unit when the braking device, and thus when the braking unit, is closed.

[0014] According to one embodiment, the adjustment unit is designed as an adjustment gear, for example, as a screw drive, in particular without self-locking (i.e., with high efficiency). In particular, all self-locking screw drives can be used, e.g., a trapezoidal screw drive, a ball screw drive, a planetary roller screw drive, etc.

[0015] According to one embodiment, the braking device is designed as a clutch unit, for example as a frictionally engaged clutch unit or as a positively engaged clutch unit, or as a wrap spring. Frictionally engaged clutch units have a lower hysteresis between the release and engagement of the braking device than positively engaged clutch units. Positively engaged clutch units are either released (no positive engagement) or engaged (positive engagement). Frictionally engaged clutch units have a transition region, i.e., when the clutch is released, there is a region in which the frictional force decreases substantially continuously, and when the clutch is engaged, there is a region in which the frictional force increases substantially continuously.This makes the braking device particularly robust against impacts and / or potential excess torques, so-called torque peaks, and can absorb these, particularly by compensating for slipping of the clutch unit, thus protecting other components of the variable-speed actuator. The frictional clutch unit can be designed, for example, as a multi-disk clutch or a conical friction clutch (cone brake). The positive clutch unit can be designed, for example, as a claw clutch.

[0016] According to one embodiment, the braking device is designed as a split nut which is arranged on a threaded spindle of the adjusting gear, wherein a first nut half and a second nut half are prestressed against each other via the prestressing unit in the drive-free state of the adjusting actuator.

[0017] According to one embodiment, the braking device is designed as a nut which is arranged on a threaded spindle of the adjusting gear, wherein the nut is pretensioned via a pretensioning unit in the drive-free state of the adjusting actuator such that the nut is arranged in a tilted or a translationally displaced position relative to the threaded spindle.

[0018] According to one embodiment, the pretensioning unit is designed as a spring unit, in particular as a disc spring. The disc spring is arranged such that the spring force acts in the closing direction of the braking device. The disc spring has a small width, in particular in the axial direction, whereby the braking unit can be designed to be compact, in particular in the axial direction. In particular, the spring unit has a spring force that is designed to return the actuating unit to its initial position, a so-called neutral position, in a drive-free state of the adjustment actuator. For this purpose, the spring force is preferably selected such that it can move the actuating unit into the initial position, i.e. the neutral position, via the ramp gradient against a drag torque acting on the drive side.Alternatively, it is conceivable to support the return of the actuating unit to the neutral position, and thus the engagement of the braking device, on the drive side by applying a corresponding return torque to the ramp pinion, which, in combination with the spring force of the spring unit, returns the actuating unit to the neutral position. This ensures that the braking unit closes even with slight gradients of the ramp-like guide surfaces.

[0019] According to one embodiment, the adjustment actuator further comprises a crash element configured to reduce a crash impact force, in particular by ensuring a defined force-displacement curve upon compression or compression of the steering column in the event of a crash. In other words, the crash element is configured to enable a steering column of the steering device to retract under a defined counterforce in the event of a crash, i.e., an accident, and thus to ensure a defined force-displacement curve. Effectively, by compressing the steering column, the impulse is distributed over a longer period than without compression, thereby reducing force peaks.

[0020] According to one embodiment, the adjustment movement of the adjustment unit is configured to adjust a height position and / or a longitudinal position of the steering device, in particular a steering wheel of the steering device. In other words, the adjustment actuator can be used as a height adjustment actuator and / or as a length adjustment actuator in the steering device.

[0021] According to one embodiment, the ramp pinion and / or the ramp sleeve have at least one end stop configured to limit relative rotation between the ramp pinion and the ramp sleeve. The end stop ensures that the ramp pinion and the ramp sleeve are always in operative contact and thus the actuating unit is always functional. The at least one end stop can be designed as a rotational limitation of the relative rotation between the ramp pinion and the ramp sleeve or as an axial limitation of the axial displacement of the ramp sleeve. The rotational limitation can in particular be designed as at least one, in particular several, end stop fingers. The end stop finger(s) can preferably be formed integrally in one piece with the respective ramp geometry.The axial limitation can be designed in particular as a stop extending in the radial direction, in particular substantially completely circumferential, which is positioned such that it limits the axial displacement of the ramp sleeve in the axial direction.

[0022] According to one embodiment, the ramp sleeve and the braking device are formed integrally in one piece. This allows the installation space of the braking unit and thus of the adjustment actuator to be further reduced. For example, an outer circumference of the second ramp geometry of the ramp sleeve can be conical, with the conical outer surface being configured to form a frictionally engaged braking device with a complementary conical surface, e.g., on the housing.

[0023] According to one embodiment, the ramp-like guide surfaces extend from an inner diameter to an outer diameter of the respective ramp geometry. In particular, the ramp-like guide surfaces are arranged in a circumferential direction of the ramp geometry, more particularly substantially evenly distributed, wherein the ramp-like guide surfaces of the first and second ramp geometries, arranged parallel to one another, are configured to be in direct or indirect operative contact in the axial direction. In the case of direct operative contact, the ramp-like guide surfaces of the first ramp geometry and the ramp-like guide surfaces of the second ramp geometry are in direct contact with one another, in particular in sliding contact.In the case of indirect operative contact, at least one rolling element is arranged between the ramp-like guide surface of the first ramp geometry and the ramp-like guide surfaces of the second ramp geometry, wherein the ramp-like guide surface of the first ramp geometry is at least partially in rolling contact with the at least one rolling element, and the ramp-like guide surfaces of the second ramp geometry are also at least partially in rolling contact with the at least one rolling element. Furthermore, the ramp pinion and / or the ramp sleeve can each have a connecting geometry configured to couple the ramp pinion to the drive unit or the ramp sleeve to the adjustment unit, at least in a torque-transmitting manner.

[0024] According to one embodiment, the ramp-like guide surfaces are essentially screw-thread shaped. As a result, the ramp-like guide surfaces have a pitch that can be specified in an axial travel per revolution, e.g., in mm / rev. Thus, the ramp angle becomes flatter with increasing friction diameter, i.e., from the inner diameter to the outer diameter. In other words, one can say that the pitch and the resulting ramp angle of the essentially screw-thread shaped ramp-like guide surfaces are greater at the inner diameter than at the outer diameter. Therefore, the pitch of the ramp-like guide surfaces is determined, in particular, as an average value. This averaged pitch can be determined, in particular, based on an average friction diameter, which is calculated as follows: average friction diameter = 23 × (outer diameter 3 − inner diameter 3) (outer diameter 2 − inner diameter 2)

[0025] According to one embodiment, the actuating unit further comprises rolling elements arranged between the first ramp geometry and the second ramp geometry. This allows sliding friction, which occurs during direct contact between the ramp-like guide surfaces of the respective ramp geometries, to be reduced to rolling friction. This further improves the efficiency of the braking unit and thus of the adjustment actuator. In particular, the rolling elements can be arranged in a so-called rolling cage.

[0026] According to one embodiment, the ramp pinion is made of a metal or a metal alloy, and the ramp sleeve is made of a plastic or a plastic mixture. The metal-plastic combination makes it possible to reduce friction in the direct operative contact of the ramp-like guide surfaces. Furthermore, particularly in the case of a dry, i.e., ungreased, actuating unit, other material pairings or combinations for the ramp pinion and the ramp sleeve are also conceivable, such as a bronze-steel pairing or a steel-steel pairing, with at least the ramp-like guide surfaces of the ramp pinion or the ramp sleeve having a coating.

[0027] If the actuating unit is greased, the coating can be omitted for the steel-to-steel pairing. Detailed description based on drawing

[0028] Further measures improving the invention are described in more detail below, together with the description of a preferred embodiment of the invention, with reference to the figures. It shows: Fig. 1 a schematic sectional view of an adjustment actuator according to an embodiment of the invention, Fig. 2A to 2C are schematic sectional views of an adjustment actuator according to an embodiment of the invention, wherein a brake unit is in a closed state ( Fig. 2A), in an intermediate state ( Fig. 2B) and in an open state ( Fig. 2C), and Fig. 3A to 3C are schematic perspective views of an actuating unit according to an embodiment of the invention in a neutral position ( Fig. 3A), an intermediate layer ( Fig. 3B) and an end position ( Fig. 3C).

[0029] The figures are merely schematic and serve only to clarify the invention. The same elements are designated by the same reference numerals.

[0030] Fig. 1 shows schematically and by way of example an adjustment actuator 1 for a steering device, in particular for a steer-by-wire steering device, according to an embodiment of the invention in a sectional view. Fig. 2A to 2C show schematic and exemplary sectional views of an adjustment actuator 1 for a steering device, in particular a steer-by-wire steering device, according to another embodiment of the invention. The adjustment actuator 1 is embodied, for example, as an electromechanical actuator and can be used for vertical and / or longitudinal adjustment of the steering device.

[0031] The adjustment actuator 1 in Fig. 1 and Fig. 2A to 2C comprises a drive unit 2, an adjustment unit 3, a brake unit 4, and a housing 5. The drive unit 2 is designed, for example, as an electric motor and is configured to generate a drive torque. The adjustment unit 3 is configured to convert the drive torque of the drive unit 2 into an adjustment movement. In particular, the adjustment unit 3 is designed as a self-locking screw drive, such as a trapezoidal screw drive, a ball screw drive, a planetary roller screw drive, etc. The brake unit 4 is arranged between the drive unit 2 and the adjustment unit 3 and is configured to selectively couple the drive unit 2 and the adjustment unit 3 in a torque-transmitting manner.In other words, it can be said that the brake unit 4 can assume at least two states, namely at least one closed state and one open state, wherein in the open state it enables a torque transmission between the drive unit 2 and the adjustment unit 3 and in the closed state it prevents such a torque transmission.

[0032] The brake unit 4 has a braking device 6, a pre-tensioning unit 7 and an actuating unit 8. The braking device 6 is designed to block the adjustment movement of the adjustment unit 3 in a closed state. In the Fig. In the embodiment shown in Figure 1, the braking device 6 is designed, for example, as a cone brake 9, which has a main body 10 with a conical outer contour, which, in a closed state of the cone brake 9, is in frictional contact with a correspondingly designed conical counter-contour 11, which is received or arranged in the housing 5 in a rotationally and axially fixed manner, thereby preventing rotation of the main body 10 and the counter-contour 11 relative to one another. The main body 10 is, on the one hand, coupled in a rotationally and axially fixed manner to a drive shaft 12 of the drive unit 2, and, on the other hand, the main body 10 is coupled in a rotationally fixed but axially displaceable manner to the adjustment unit 3.

[0033] In the Fig. In the embodiment shown in Figures 2A to 2C, the braking device 6 is designed, by way of example, as a multi-plate clutch 13 having a plate pack 14 with three inner plate disks 15 and three outer plate disks 16, which are arranged alternately in the axial direction A. The three inner plate disks 15 are arranged in a plate carrier 17 in a rotationally fixed but axially displaceable manner, and the three outer plate disks 16 are arranged in a plate cage 18 in a rotationally fixed but axially displaceable manner. The plate cage 18 is arranged in a rotationally and axially fixed manner in the housing 5 of the adjustment actuator 1, and the plate carrier 17 is coupled to an output shaft 19 of the adjustment unit 3 in a rotationally fixed but axially displaceable manner.

[0034] The pre-tensioning unit 7 is designed to close the braking device 6 in a drive-free state of the adjustment actuator 1 and thus to prevent the torque transmission between the drive unit 2 and the adjustment unit 3. For this purpose, the pre-tensioning unit 7 is designed according to the Fig. 1, which is embodied here by way of example as a disc spring 20, is arranged such that a preload force of the preload unit 7, here via a pressure pot 21, presses the main body 10 of the cone brake 9 toward the counter contour 11, so that the cone brake 9 is closed in a load-free state, i.e., in a state in which no external forces act on the brake unit 2. Therefore, the cone brake 9 can also be referred to as a "normally closed" braking device.

[0035] According to the Fig. 2A to 2C, the multi-plate clutch 13 likewise has the pressure pot 21 and an axially fixed counterpressure plate 22, wherein the pressure pot 21 is arranged in the axial direction A on a side of the plate pack 15 facing the adjustment unit 3 and the axially fixed counterpressure plate 22 is arranged in the axial direction A on a side of the plate pack 14 facing the drive unit 2. The pressure pot 21 is pressed towards the plate pack 14 by the pretensioning unit 7, which here is also designed as a plate spring 20, such that the multi-plate clutch 13 is closed in a load-free state, i.e., in a state in which no external forces act on the multi-plate clutch 13. Therefore, the multi-plate clutch 13 can also be referred to as a “normally closed” braking device.

[0036] The operating unit 8 (see also Fig. 3A to 3C) is designed to open or release the braking device 6 in a driven state of the adjustment actuator 1 and thus enable the torque transmission between the drive unit 2 and the adjustment unit 3. The actuating unit 8 is described below with reference to Fig. 3A to 3C are described in more detail.

[0037] The actuating unit 8 has a ramp pinion 23 and a ramp sleeve 24. The ramp sleeve 24 can be connected, for example, via a spline 25, in a rotationally fixed but axially displaceable manner to an element 26 of the braking device 6 which is acted upon by the preload force of the preload unit 7, wherein the element 26 in the Fig. 1 corresponds to the main body 10 of the cone brake 9 and in the embodiment shown in Fig. 2A to 2C corresponds to the plate carrier 17. Alternatively, it is also conceivable that the ramp sleeve 24 is coupled directly to the output shaft 19 of the adjustment unit 3 in a rotationally fixed but axially displaceable manner.

[0038] The ramp pinion 23 has, for example, a spline 27 on an inner diameter, via which it is rotationally and axially fixedly coupled to the drive shaft 12 of the drive unit 2. The ramp pinion 23 and the ramp sleeve 24 interact in such a way that a rotation of the ramp pinion 23 causes an axial displacement of the ramp sleeve 24 counter to the preload force of the preload unit 7, i.e., a displacement toward the adjustment unit 3, which will be described in more detail later.

[0039] For this purpose, the ramp pinion 23 has a first ramp geometry 28 with ramp-like guide surfaces 29 on an outer diameter, which is arranged circumferentially and extends in the axial direction A in a crenellated manner. The "crenellations" of the first ramp geometry 28 are so-called end stop fingers 30. The ramp sleeve 24 has a second ramp geometry 31, which interacts with the first ramp geometry 28 of the ramp pinion 23. The second ramp geometry 31 of the ramp sleeve 24 is essentially complementary to the first ramp geometry 28 and has ramp-like guide surfaces 32 (here essentially concealed by the first ramp geometry 28), which interact with the ramp-like guide surfaces 29 of the first ramp geometry 28 as follows:

[0040] In a so-called neutral position ( Fig. 3A), the ramp pinion 23 and the ramp sleeve 24 engage with each other in such a way that the end stop fingers 30 of the first ramp geometry 28 engage in corresponding recesses or depressions 33 of the second ramp geometry 31, wherein the end stop fingers 30 are arranged substantially centrally in the depressions 33 in the neutral position. The ramp-like guide surfaces 29 of the first ramp geometry 28 and the ramp-like guide surfaces 32 of the second ramp geometry 31 are each designed like a screw thread, i.e., they have a pitch that is specified by an axial travel per revolution. Thus, the guide surfaces 29, 32 of the ramp geometries 28, 31 have a pitch angle that varies from an inner diameter to an outer diameter, i.e., a pitch angle that varies from radially inside to radially outside.

[0041] By turning the ramp pinion 23 in the direction of arrow P1 (see Fig. 3B), the ramp-like guide surfaces 29, 32 of the two ramp geometries 28, 31 slide against each other, whereby the ramp sleeve 24 moves in the axial direction A in the direction of the arrow P2 (see Fig. 3B) is moved in such a way that the ramp pinion 23 is axially fixed and the ramp sleeve 24 is arranged in a rotationally fixed but axially displaceable manner. In Fig. 3C, the ramp pinion 23 and the ramp sleeve 24 are in an end position in which the end stop fingers 30 of the first ramp geometry 28 are in the direction of rotation indicated by the arrow P1 with end stop fingers (in Fig. 3A to 3C not visible) of the second ramp geometry 31, thus preventing further relative rotation between the ramp pinion 23 and the ramp sleeve 24, and thus limiting the displacement of the ramp sleeve 24 in the axial direction A.

[0042] A setting process or an adjustment process of the adjustment actuator 1 is carried out with reference to the Fig. 2A to 2C will now be described in more detail, wherein the braking device 6 is designed, for example, as the multi-disk clutch 13. In Fig. 2A, the drive unit 2 is not in operation. In the case of a drive unit 2 configured as an electric motor 34, this means that the electric motor 34 is not energized. Thus, the preload unit 7 compresses the disk pack 14 via the pressure pot 21. This creates a frictional connection between the output shaft 19 of the adjustment unit 3 and the housing 5. Thus, the braking device 6 is closed, and rotation of the output shaft 19 of the adjustment unit 3 is prevented.

[0043] If the electric motor 34 is energized, it builds up a torque that is transmitted via the drive shaft 12 to the ramp pinion 23 (see Fig. 2B). This means that the ramp pinion 23 rotates relative to the ramp sleeve 24, whereby the respective ramp-like guide surfaces 29, 32, as described above with reference to Fig. 3A to 3C. The resulting axial force, which causes the axial displacement of the ramp sleeve 24 against the preload force of the preload unit 7, increases. As a result, the contact pressure acting on the disk pack 14 is increasingly reduced and causes a decreasing braking torque and thus a release or opening of the braking device 6. In the further course of the process, the pressure pot 21 is lifted off the disk pack 14 by the axial displacement of the ramp sleeve 24, whereby the ramp pinion 23 and the ramp sleeve 24 reach their end position, in which further relative rotation between the ramp pinion 23 and the ramp sleeve 24 is prevented by the end stop fingers 30 (see Fig. 2C). During this relative movement between the ramp pinion 23 and the ramp sleeve 24, essentially no torque is transferred from the drive unit 2 to the adjustment unit 3. Therefore, this movement can also be referred to as "dead travel" with reference to the drive unit 2. During the dead travel, the drive unit 2 already generates a drive torque, which, however, does not yet cause any adjustment movement of the adjustment unit 3.

[0044] With the braking device 6 released, the engagement of the first ramp geometry 28 and the second ramp geometry 31 serves to transmit the full torque of the electric motor 34 serving as the drive unit 2 at a synchronous speed to the output shaft 19 of the adjustment unit 3, thus achieving the desired adjustment movement. After the adjustment actuator 1 has reached the desired setting position, the current supply to the electric motor 34 is deactivated, thus no longer transmitting torque to the ramp pinion 23.

[0045] The preload force of the preload unit 7 is thus counteracted by only a comparatively small axial force, which essentially results from the friction between the ramp geometries 28, 31. Thus, the preload unit 7 now presses the disk pack 14 together again via the pressure pot 21 and thus closes the braking device 6 again. In the process, the actuating unit 8 is moved back to the neutral position (see Fig. 2A and Fig. 3A).

[0046] In particular, the preload force of the preload unit 7 is sufficiently large to rotate the electric motor 34 back against a motor drag torque via the gradient of the ramp geometries 28, 31 until the neutral position of the actuating unit 8 is reached and thus the full braking torque is achieved. When the electric motor 34 is rotated back, the restoring torque is generated, so to speak, from the "downhill force" resulting from the gradient and / or the ramp shape. For this purpose, a small ramp gradient, i.e., a flat gradient angle, in combination with high friction values ​​of the ramp-like guide surfaces 29, 32 is counterproductive. Therefore, material pairings with low friction values, such as a steel-plastic pairing, are particularly suitable for the actuating unit 8. Alternatively, it is also conceivable to move the actuating unit 8 back to the neutral position by a so-called restoring torque of the drive unit 2.The restoring torque corresponds to a torque in the opposite direction to the drive torque for a very short time. For this purpose, for example, the electric motor 34 can be briefly energized so that it generates a torque opposite to the drive torque, after which the energization is deactivated.

[0047] It can therefore be said that the actuating unit 8 ensures that any movement of the adjustment unit 3 is blocked when the drive unit 2 is deactivated. Thus, as already described above, the adjustment unit 3 can be designed, in particular, as a screw drive without self-locking, thereby increasing the efficiency of the adjustment actuator 1. The higher efficiency, in turn, makes it possible to use smaller motors as the drive unit 2 and / or smaller gears as the adjustment unit 3, while simultaneously achieving the same or even improved travel distances and / or travel speeds. List of reference symbols 1 adjustment actuator 2 drive unit 3 adjustment unit 4 brake unit 5 housings 6 Braking device 7 Pre-tensioning unit 8 Actuating unit 9 Cone brake 10 main bodies 11 Counter contour 12 Drive shaft 13 multi-plate clutch 14 slat pack 15 inner lamella disc 16 outer lamella disc 17 slat carriers 18 slatted basket 19 Output shaft 20 disc springs 21 Pressure cooker 22 Counterpressure plate 23 ramp pinions 24 Ramp sleeve 25 spline 26 elements 27 spline 28 first ramp geometry 29 ramp-like guide surfaces 30 end stop fingers 31 second ramp geometry 32 ramp-like guide surfaces 33 Deepening 34 electric motor A axial direction P1, P2 arrow

Claims

[1] Adjustment actuator (1) for a steering device, comprising: a drive unit (2) which is designed to generate a drive torque, an adjusting unit (3) which is designed to convert the drive torque of the drive unit (2) into an adjusting movement, and a brake unit (4) which is arranged between the drive unit (2) and the adjustment unit (3) and is designed to selectively couple the drive unit (2) and the adjustment unit (3) in a torque-transmitting manner, wherein the brake unit (4) has a braking device (6), a pretensioning unit (7), and an actuating unit (8), wherein the braking device (6) is designed to block the adjustment movement of the adjustment unit (3) in a closed state, wherein the pretensioning unit (7) is designed to close the braking device (6) in a drive-free state of the adjustment actuator (1), wherein the actuating unit (8) is designed to open the braking device (6) in a driven state of the adjusting actuator (1), wherein the actuating unit (8) has a ramp pinion (23) with a first ramp geometry (28) and a ramp sleeve (24) with a second ramp geometry (31), wherein the ramp pinion (23) is coupled to the drive unit (2) in a torque-transmitting manner and the ramp sleeve (24) is coupled to the adjusting unit (3) in a rotationally fixed and axially displaceable manner, wherein the first ramp geometry (28) and the second ramp geometry (31) each have ramp-like guide surfaces (29, 32) which interact directly or indirectly in such a way that rotation of the ramp pinion (23) causes an axial displacement of the ramp sleeve (24) counter to a prestressing force of the prestressing unit (7). [2] Adjustment actuator (1) according to claim 1, wherein the braking device (6) is designed to couple the adjustment unit (3) to a housing (5) of the adjustment actuator (1) in a closed state in a torque-resistant manner. [3] Adjustment actuator (1) according to claim 1 or 2, wherein the adjustment unit (3) is designed as an adjustment gear. [4] Adjustment actuator (1) according to one of claims 1 to 3, wherein the braking device (6) is designed as a clutch unit (13) or as a wrap spring or as a cone brake (9). [5] Adjustment actuator (1) according to claim 3, wherein the braking device (6) is designed as a split nut which is arranged on a threaded spindle of the adjustment gear, wherein a first nut half and a second nut half are prestressed against each other via the prestressing unit (7) in the drive-free state of the adjustment actuator (1). [6] Adjustment actuator (1) according to claim 3, wherein the braking device (6) is designed as a nut which is arranged on a threaded spindle of the adjustment gear, wherein the nut is pretensioned via the pretensioning unit (7) in the drive-free state of the adjustment actuator (1) such that the nut is arranged in a tilted position relative to the threaded spindle. [7] Adjustment actuator (1) according to one of claims 1 to 6, wherein the pretensioning unit (7) is designed as a spring element (20). [8] Adjustment actuator (1) according to one of claims 1 to 7, further comprising a crash element configured to reduce a crash impact force. [9] Adjustment actuator (1) according to one of claims 1 to 8, wherein the adjustment movement of the adjustment unit (3) is designed to adjust a height position and / or a longitudinal position of the steering device. [10] Adjustment actuator (1) according to one of claims 1 to 9, wherein the ramp pinion (23) and / or the ramp sleeve (34) have at least one end stop (30) which is designed to limit a relative rotation between the ramp pinion (23) and the ramp sleeve (24).

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