WO2024179646A1

WO2024179646A1 - Linear actuator and method for operating a linear actuator, in particular for an electromechanically operable wheel brake

Info

Publication number: WO2024179646A1
Application number: PCT/DE2024/200000
Authority: WO
Inventors: Hans-Jörg Feigel; Kristijan Tarandek
Original assignee: Continental Automotive Technologies GmbH
Priority date: 2023-02-28
Filing date: 2024-02-13
Publication date: 2024-09-06
Also published as: DE102023201822A1

Abstract

The present invention relates generally to a linear actuator, in particular for moving a brake piston of an electromechanically operable wheel brake of a motor vehicle, and to a method for operating a linear actuator of this type. The present invention proposes a linear actuator (1), in particular for moving a brake piston of an electromechanically operable wheel brake of a motor vehicle, comprising a ramp mechanism (10), a support bearing (21), and a wear mechanism having a nut thread (20) with an internal screw thread and having a support element (22) with an external screw thread.

Description

Linear actuator and method for operating a linear actuator, in particular for an electromechanically operated wheel brake

The present invention relates generally to a linear actuator, in particular for moving a brake piston of an electromechanically operable wheel brake of a motor vehicle, and a method for operating such a linear actuator.

Electromechanical wheel brakes (EMBs) are increasingly being used in modern motor vehicles, for example as service brakes. These wheel brakes offer a number of advantages over conventional, hydraulically operated wheel brakes. A complex hydraulic system is no longer required, and an electromechanical wheel brake is also much more space-saving.

Such electromechanical wheel brakes typically have an electric or electronic drive unit that interacts with a mechanism or a gear. A brake unit can then be arranged on the output side, which can include a brake piston with a friction lining that can be pressed onto a brake disc or drum by means of a translatory movement. This can cause deceleration during operation.

The electronic drive unit typically includes at least one electric motor, which has a correspondingly high power density. The mechanical connection to the friction brake can then be established using at least the gearbox. In addition to factors such as efficiency and rigidity, the mechanical structure, the installation space required and the gear ratio characteristic determine the suitability of the gearbox.

There are known mechanisms for converting the rotational movement of the electric motor into the required translational or linear movement. One known mechanism is, for example, a rotation-to-translation converter comprising a so-called ramp mechanism or ramp unit.

Such a mechanism is known, for example, from the applicant's document DE 199 22 333 A1.

Even though such mechanisms in conjunction with electromechanical wheel brakes can offer various advantages, such as the application of large axial forces, there are also disadvantages. One disadvantage is wear on components that are subject to high levels of stress, such as the ramp discs or balls.

Therefore, appropriate wear compensation must be provided, which may, however, lead to a larger installation space or a longer installation length and/or additional components. The rigidity of the arrangement may also be reduced by the additional wear compensation.

For example, it may be planned to arrange adjusting threaded screws inside the ramp mechanism, which may mean that the ramp discs require a larger diameter. On the one hand, this can lead to a significantly larger installation space, which is considered disadvantageous in many cases.

In the case of ramp discs with grooves and balls running in them, the grooves are then offset further outwards. This increases the pitch circle diameter of the grooved tracks. This can lead to poorer efficiency of the ball ramp, which can reduce the self-release behavior of the ball ramp mechanism and thus of the wheel brake.

What is therefore desirable is a rotation-to-translation converter, in particular comprising a ramp mechanism, preferably for a linear actuator of a wheel brake, which at least mitigates the above-mentioned disadvantages or ideally does not have them. The linear actuator should be both compact in design and have a long product life.

The inventors have taken on this task.

This object is achieved surprisingly simply by a linear actuator, in particular for moving a brake piston of an electromechanically operable wheel brake of a motor vehicle, an actuating device and an electromechanical wheel brake and a method for operating an electromechanical wheel brake of a motor vehicle according to one of the independent claims.

Preferred embodiments and further developments of the invention can be found in the respective subclaims.

The invention therefore comprises, in a first aspect, a linear actuator, in particular for moving a brake piston of an electromechanically operable wheel brake of a motor vehicle.

The linear actuator according to the invention can not only be used for or in connection with a wheel brake of a motor vehicle. Rather, the linear actuator according to the invention can also be used in connection with braking devices for other means of transport, such as wheels of rail vehicles or aircraft. Furthermore, the linear actuator according to the invention can also be used with other devices or apparatuses in which an axial force application or axial force generation is desired.

The linear actuator according to the invention can comprise: a ramp mechanism with at least one drive-side ramp disk, a driven ramp disk and a plurality of rolling elements,

- a support bearing, - and a wear mechanism comprising

- a nut thread with an internal thread, in particular an internal screw thread,

- a support element with an external thread, in particular an external screw thread, wherein the screw thread of the nut thread engages with the screw thread of the support element, the support bearing is arranged between the drive-side ramp disk and the support element, the nut thread encloses at least the support element and/or at least one ramp disk, preferably both ramp disks at least in regions, and wherein the support element can be moved in operation by rotation about the central axis in the axial direction.

A ramp mechanism is assumed to be generally known to the person skilled in the art and will therefore only be outlined briefly here. In a ramp mechanism, one or two ramp disks can be provided, between which rolling elements can be arranged. The ramp disks can have grooves as ramp tracks on the side surfaces facing each other or the rolling elements, which can run in the circumferential direction. The depth of the grooves can vary over the length of the grooves.

In other words, the grooves can be arranged at an angle relative to the clamping direction. They can also include a stop for the rolling elements at both ends. This makes the ramp mechanism in the

Able to transmit a torque or to convert it into a translational movement. Preferably, several grooves are provided, each of which can be occupied by at least one rolling element. For even power transmission, the grooves can be evenly distributed on the ramp disk. A particularly simple design is achieved when cylindrical, conical or preferably spherical rolling elements are arranged in the essentially groove-shaped grooves. In the case of spherical rolling elements, this is also referred to as a ball ramp mechanism. In a ball ramp mechanism with two ramp disks, as provided in a preferred embodiment of the invention, the grooves can be arranged in pairs corresponding to one another. The depth of the grooves can then change in opposite directions on the two side surfaces, with a gradual change, i.e. a slight gradient, preferably being present.

The linear actuator according to the invention can comprise a wear mechanism, which can have a female thread and a support element. The support element and the female thread can be operatively connected to one another via a thread, in particular via a screw thread. In particular, it can be provided that the female thread comprises an internal screw thread, into which an external screw thread of the support element can engage.

The support element can therefore be designed in such a way that it can be arranged at least in sections, in particular with regard to the section with the internal thread, within the nut thread. For this purpose, it can be designed to be rotationally symmetrical, for example disk-shaped or generally cylindrical. The support element can be moved in the axial direction during operation by rotating around a central axis of the linear actuator.

Furthermore, a support bearing can be provided, which can be arranged between the drive-side ramp disk and the support element. The support bearing can be designed as an axial bearing and comprise a corresponding roller bearing. In this way, a transmission of axial forces from the support element to the drive-side ramp disk can be made possible. The nut thread and the support element as well as the ramp disks can be rotationally symmetrical. According to the invention, the nut thread, support element and ramp disks can be arranged coaxially.

In order to save on overall length, the nut thread can be arranged according to the invention in such a way that it encloses at least the support element and/or at least one ramp disk, at least in part. It can also extend over the length of the ramp mechanism and enclose both ramp disks. In other words, in accordance with the invention, the ramp mechanism can be arranged at least in part in the interior of the nut thread or protrude into it.

In this way, the drive-side ramp disk can be adjusted in the direction of the driven ramp disk by rotating the support element relative to the nut thread. The wear mechanism thus enables the axial distance between the two ramp disks to be changed in the sense of readjustment or calibration.

The invention therefore provides wear compensation that does not require a larger installation space or a larger installation length of the linear actuator. The rigidity of the arrangement is also not reduced or not significantly reduced by the additional wear compensation.

The linear actuator according to the invention can be used to move a brake piston of an electromechanically operable wheel brake of a motor vehicle. The electromechanically operable wheel brake can be designed as an electromechanical disc brake with an electromechanically operated brake caliper or as an electromechanical drum brake.

The nut thread can be connected to the saddle housing in a rotationally fixed manner. According to one embodiment of the invention, the nut thread can be designed as part of the saddle housing. In other words, the saddle housing and Nut threads can be manufactured monolithically or in one piece from the same material.

According to a further embodiment of the invention, the nut thread can also be manufactured as a separate component and connected to the saddle housing in a rotationally fixed manner. This makes it possible to provide at least one sensor between the nut thread and the saddle housing. For this purpose, at least one corresponding recess can be provided on the saddle housing and/or nut thread. The sensor can, for example, be designed as a force sensor and in this way detect a force component acting in the axial direction between the nut thread and the saddle housing.

The linear actuator according to the invention can further comprise an adjustment mechanism. This can be arranged, for example, next to or adjacent to the support element, preferably in the direction of the drive side.

The adjustment mechanism can be designed to cause the support element to rotate around the central axis during operation. For this purpose, a drive sleeve can also be provided which can cause the rotation. The drive sleeve can also be rotationally symmetrical and arranged coaxially to the nut thread or the support element.

According to a particular embodiment of the invention, the drive sleeve can be hollow, so that a drive shaft can be guided through the drive sleeve at least in sections in a particularly simple manner.

The adjustment mechanism can be set up to carry out an incremental left or right rotation. For this purpose, locking elements can be provided on the outer surface, for example, which can engage in corresponding recesses or grooves. The drive shaft and the support element can be operatively connected in such a way that an incremental adjustment in the form of an incremental rotation is only possible in one direction of rotation. The adjustment mechanism can be designed in a similar way to a switching mechanism or locking mechanism of a ballpoint pen.

Such an incremental rotation in the intended direction of rotation can be combined with a lifting movement, so that an incremental rotation can cause a corresponding incremental lifting movement such that the distance between the two ramp disks can be changed, in particular reduced. To support this, an idle rotation angle can be provided between the drive shaft and the drive sleeve, within which no rotation of the support element takes place.

According to one embodiment of the invention, at least one section of the drive shaft can be guided centrally through the ramp mechanism, at least in sections. For this purpose, the drive shaft can also comprise at least a first section of larger diameter and at least a second section of smaller diameter, wherein the section of smaller diameter can then be guided through the ramp mechanism. The guiding of the drive shaft through the ramp mechanism requires the presence of through-openings or bores in the ramp disks. Accordingly, these are arranged centrally so that the drive shaft can be guided through the ramp disks along the central axis.

According to a preferred embodiment of the invention, the drive shaft is only connected to the drive-side ramp disk. This makes it possible for the drive shaft not to pass through the ramp mechanism, in particular not through the drive-side and/or driven ramp disk, so that the ramp disks can be designed to cover the entire surface, i.e. without through-openings, in particular in the area of the center axis. This can increase the stability of the ramp disks, or the ramp disks can be made correspondingly thinner, which has a positive effect on the overall length. The omission of such through openings leads to another, highly advantageous effect of the linear actuator according to the invention, which is seen in the fact that the grooves can be arranged closer to the center. This allows the rolling elements to run on a very small pitch circle diameter, which leads to a significantly better efficiency of the ramp mechanism.

A particularly good efficiency can be achieved if the grooves run in the circumferential direction with a pitch circle diameter D, where the ratio of the pitch circle diameter D to the diameter of the rolling elements d is: 1.05 * d < D < 20 * d, preferably 1.1 * d < D < 10 * d, particularly preferably 1.1 * d < D < 5 * d, 1.2 * d < D < 3 * d. If the rolling elements are spherical, d refers to the diameter of these balls. If the rolling elements are cylindrical or conical, d refers to the largest diameter of the rolling element in a cross-section perpendicular to the center axis.

According to a further embodiment of the invention, it can be provided that the grooves in the ramp discs are formed non-linearly.

Furthermore, according to yet another embodiment of the invention, it can be provided that the grooves in the ramp discs comprise a plateau for a parking brake function.

In a further aspect, the present invention relates to an actuating device, in particular for an electromechanical wheel brake, comprising a linear actuator as described above. The actuating device can further comprise an electromotive drive unit, for example an electric motor. The electromotive drive unit can be designed to apply a drive torque to the drive shaft. The drive torque can be transmitted to the ramp mechanism. In other words, the drive torque can be transmitted to the drive-side ramp disk, whereby the rolling elements can be moved along the grooves via the rotation. The distance between the ramp disks in The axial direction relative to one another can then be changed due to the slope of the ramp tracks or the grooves in which the rolling elements run. In this way, the rotation of the drive shaft can be converted into a corresponding translational movement. The electric motor drive unit can drive the drive shaft directly or via another gear.

The driven ramp disc can in turn be operatively connected to a brake piston of an electromechanically operated wheel brake, so that the corresponding translational movement of the driven ramp disc can cause a linear movement of the brake piston. In a further aspect, the invention therefore relates to such an electromechanically operated wheel brake with an actuating device as described above.

The electromechanical wheel brake can be designed as a service brake and/or as a parking brake of a motor vehicle.

In yet another aspect, the present invention also relates to a method for operating an electromechanical wheel brake, in particular of a motor vehicle, comprising at least one electromechanical wheel brake according to the preceding claim, wherein during operation a braking force can be generated by means of the linear actuator of the actuating device of the electromechanical wheel brake, which can cause braking or deceleration of a wheel.

The brake piston can, for example, be part of a disc brake and can be arranged so that it can be moved linearly relative to the caliper housing. In a known manner, the brake piston can be connected to a friction element that is designed to rest on a brake disc. The brake piston can then be moved out of the caliper housing in the brake application direction using the adjusting device.

Further details of the invention emerge from the description of the illustrated embodiments and the appended claims. The drawings show:

Fig. 1 shows a longitudinal section through an exemplary linear actuator with essential components, and

Fig. 2 is a plan view of a section through the linear actuator according to the invention from Fig. 1.

In the following detailed description of preferred embodiments, for the sake of clarity, like reference numerals designate substantially like parts in or on those embodiments. However, to better illustrate the invention, the preferred embodiments shown in the figures are not always drawn to scale.

Fig. 1 shows a longitudinal section through an exemplary linear actuator 1. For reasons of clarity, only the elements relevant to the design of the linear actuator 1 according to the invention are shown.

The linear actuator 1 according to the invention is designed to move a brake piston 50 of an electromechanically operable wheel brake of a motor vehicle.

The linear actuator 1 according to the invention comprises

- a ramp mechanism 10 with at least one drive-side ramp disk 13, a driven ramp disk 12 and a plurality of rolling elements 11,

- a support bearing 21 ,

- and a wear mechanism comprising

- a nut thread 20 with an internal screw thread 26,

- a support element 22 with an external screw thread 27, wherein the screw thread 26 of the nut thread 20 engages with the screw thread 27 of the support element 22, the support bearing 21 is arranged between the drive-side ramp disk 13 and the support element 22, the nut thread 20 encloses at least the support element 22 and/or at least one ramp disk 12, 13, preferably both ramp disks 12, 13 at least in regions, and wherein the support element 22 can be moved in the axial direction during operation by rotating about the central axis 15.

The ramp mechanism 10 shown has two ramp disks 12, 13 between which the rolling elements 11 are arranged. The ramp disks 12, 13 have grooves 16, 17 as ramp tracks on the side surfaces facing each other or the rolling elements 11, which run in the circumferential direction. The depth of the grooves 16, 17 varies over the length of the grooves 16, 17. In particular, the grooves 16, 17 are arranged at an angle with respect to the clamping direction. They also have a stop for the rolling elements 11 at both ends.

The ramp mechanism 10 shown has several grooves 16, 17, each of which is equipped with at least one rolling element 11. For uniform force transmission, the grooves 16, 17 are evenly distributed on the ramp disks 12, 13.

In the present example, spherical rolling elements 11, in particular balls, are provided, so that a ball ramp mechanism is present. The grooves 16, 17 are arranged in pairs corresponding to one another, with the depth of the grooves 16, 17 changing in opposite directions on the two side surfaces. The change in depth takes place continuously and gradually, so that there is a slight gradient.

The linear actuator 1 according to the invention comprises a wear mechanism which has a nut thread 20 and a support element 22. The Support element 22 and nut thread 20 are operatively connected to one another via a thread, which in this case is designed as a screw thread. Nut thread 20 comprises an internal screw thread 26, into which an external screw thread 27 of support element 22 can engage.

As can be seen from Fig. 1, the support element 22 is arranged completely within the nut thread 20. For this purpose, it is correspondingly rotationally symmetrical and of cylindrical shape. The support element 22 can be moved in the axial direction during operation by rotating about a central axis 15 of the linear actuator 1.

Furthermore, a support bearing 21 is provided, which is arranged between the drive-side ramp disk 13 and the support element 22. The support bearing 21 is designed as a roller bearing and in the example comprises a needle bearing. In this way, a transmission of axial forces from the support element 22 to the drive-side ramp disk 13 can be made possible.

The nut thread 20 and the support element 22 as well as the ramp discs 12, 13 are rotationally symmetrical and arranged coaxially to one another.

In the exemplary embodiment, the nut thread 20 is designed such that it completely encloses the support element 22 and both ramp disks 12, 13. In this way, the overall length of the linear actuator 1 can be reduced. However, it is not absolutely necessary for the invention that both ramp disks 12, 13 are completely enclosed. Rather, it may also be sufficient if the nut thread 20 only encloses the support element 22 so that the threads can engage with one another.

A readjustment or calibration of the ramp mechanism 10 can be achieved by a corresponding rotation of the support element 22 relative to the nut thread 20, whereby the distance between the two ramp disks 12, 13 can be changed or adjusted. The linear actuator 1 according to the invention can be used to move a brake piston 50 of an electromechanically operable wheel brake of a motor vehicle. The electromechanically operable wheel brake can be designed as an electromechanical disk brake with an electromechanically actuated brake caliper or as an electromechanical drum brake.

The nut thread 20 is connected to the saddle housing 51 in a rotationally fixed manner. According to the embodiment of the invention shown, the nut thread 20 is designed as part of the saddle housing 51, which enables simple production since no assembly effort is required.

In the embodiment shown in Fig. 1, the nut thread 20 is sleeve-shaped, with the side wall, which carries the internal screw thread 26, projecting from a bottom area of the caliper housing 51 in the direction of the brake disk. The resulting interior space can, as explained above, accommodate the support element 22 and/or the two ramp disks 12, 13. The two ramp disks 12, 13 are located in the interior space, in particular in the retracted position.

In the exemplary embodiment, an annular recess is formed opposite the outer wall of the caliper housing 51. This makes it possible in a particularly advantageous manner to accommodate a section of the brake piston 51, in particular in the retracted position. In the exemplary embodiment, the brake piston 51 has a precisely matching, annular section for this purpose. In the exemplary embodiment shown in Fig. 1, this section of the brake piston 50 is completely retracted into the annular recess. This allows for greater stability, in particular guidance of the brake piston 51. On the other hand, this structure is very compact in the axial direction. According to a further embodiment of the invention, the nut thread 20 can also be manufactured as a separate component and connected to the saddle housing 51 in a rotationally fixed manner, for example inserted via guide rails and screwed. This makes it possible to arrange at least one sensor between the nut thread 20 and the saddle housing 51. For this purpose, at least one corresponding recess can be provided, for example on the front sides of the saddle housing 51 and/or nut thread 20. The sensor can be designed as a force sensor, for example. In this way, a force component acting in the axial direction between the nut thread 20 and the saddle housing 51 can be detected.

The linear actuator 1 shown is also designed with an adjustment mechanism 24. This is indicated schematically in Fig. 1 and is arranged adjacent to the support element 22. The adjustment mechanism 24 is designed to cause the support element 22 to rotate about the center axis 15 during operation. A drive sleeve 25 is provided to support this and can cause the rotation. The drive sleeve 25 is rotationally symmetrical and is arranged coaxially to the nut thread 20 or the support element 22.

The drive sleeve 25 is designed as a hollow body. This allows the drive shaft 23 to be guided through the drive sleeve 25 in a space-saving manner. The adjustment mechanism 24 enables incremental left or right rotation. For this purpose, locking elements 28 can be provided on the outer surface of the drive sleeve 25, for example, which can engage in corresponding recesses or grooves. The drive shaft 23 and the support element 22 can be operatively connected in such a way that incremental adjustment in the form of an incremental rotation can only be made in one direction of rotation.

Such an incremental rotation in the intended direction of rotation can be combined with a lifting movement, so that an incremental rotation can cause a corresponding incremental lifting movement in such a way that that the distance between the two ramp disks 12, 13 can be changed, in particular reduced. To assist, an idle rotation angle can be provided between the drive shaft 23 and the drive sleeve 25, within which no rotation of the support element 22 takes place. In Fig. 1, the reference symbol P1 indicates a position of the drive shaft 23 without an idle rotation angle and the reference symbol P2 indicates a position of the drive shaft 23 with an idle rotation angle.

According to an embodiment of the invention, at least a portion of the drive shaft 23 can be guided at least partially centrally through the ramp mechanism 10

According to a preferred embodiment of the invention, as shown in Fig. 1, the drive shaft 23 is only connected to the drive-side ramp disk 13 or only abuts against this ramp disk 13. This makes it possible for the drive shaft 23 not to pass through the ramp mechanism 10, in particular not through the ramp disks 12, 13, so that the ramp disks 12, 13 are formed over the entire surface, i.e. without through-openings, in particular in the area of the center axis. This can increase the stability of the ramp disks 12, 13, or the ramp disks 12, 13 can be made correspondingly thinner, which has a positive effect on the overall length of the linear actuator 1.

The omission of such through openings leads to a further, highly advantageous effect of the linear actuator according to the invention, which is seen in the fact that the grooves 16, 17 of the ball tracks can be arranged closer to the center of the ramp disks 12, 13. This allows the rolling elements 11 to run on a very small pitch circle diameter, which leads to a significantly better efficiency of the ramp mechanism 10.

A particularly good efficiency can be achieved if the grooves 16, 17 run in the circumferential direction with a pitch circle diameter D, where the ratio of the pitch circle diameter D to the diameter of the rolling elements d is: 1.05 * d < D < 20 * d, preferably 1.1 * d < D < 10 * d, particularly preferably 1.1 * d < D < 5 * d, 1.2 * d < D < 3 * d. If the rolling elements 11 are spherical, as shown in Fig. 1, d refers to the diameter of these balls. If the rolling elements are cylindrical or conical, d refers to the largest diameter of the rolling element 11 in a cross section perpendicular to the center axis.

The pitch circle diameter D can be, for example, less than 20 cm, preferably less than 10 cm, less than 8 cm, 6 cm, 5 cm, 4 cm, 3 cm or even less than 2 cm.

According to a further embodiment of the invention, it can be provided that the grooves 16, 17 in the ramp disks 12, 13 are formed non-linearly.

Furthermore, according to yet another embodiment of the invention, it can be provided that the grooves 16, 17 in the ramp discs 12, 13 comprise a plateau for a parking brake function.

In a further aspect, the present invention relates to an actuating device, in particular for an electromechanical wheel brake, comprising a linear actuator 1 as described above. The actuating device can further comprise an electromotive drive unit (not shown), for example an electric motor. The electromotive drive unit can be designed to apply a drive torque to the drive shaft 23. The drive torque can be transmitted to the ramp mechanism. In other words, the drive torque can be transmitted to the drive-side ramp disk 13, wherein the rolling elements 11 can be moved along the grooves 16, 17 via the rotation.

The distance between the ramp discs 12, 13 in the axial direction can then be changed due to the slope of the ramp tracks or the grooves 16, 17 in which the rolling elements 11 run. In this way, the rotation of the drive shaft 23 into a corresponding translational movement.

In this way, the driven ramp disk 12 can be set in a corresponding translational movement. The electric motor drive unit can drive the drive shaft directly or via another gear.

In the embodiment of Fig. 1, the driven ramp disk 12 is connected to a brake piston 50 of an electromechanically operable wheel brake and is thus operatively connected thereto. The translatory movement of the driven ramp disk 12 is therefore converted into a linear movement of the brake piston. The invention therefore relates in a further aspect to such an electromechanically operable wheel brake with an actuating device as described above.

The electromechanical wheel brake is designed as a service brake and/or as a parking brake of a motor vehicle.

In yet another aspect, the present invention also relates to a method for operating an electromechanical wheel brake, in particular of a motor vehicle, comprising at least one electromechanical wheel brake according to the preceding claim, wherein during operation a braking force can be generated by means of the linear actuator 1 of the actuating device of the electromechanical wheel brake, which can cause braking or deceleration of a wheel.

In the exemplary embodiment, the brake piston 50 is part of a disk brake. For this purpose, it is arranged so that it can be moved linearly relative to the caliper housing. In a known manner, the brake piston can be connected to a friction element that is intended to rest on a brake disk. The brake piston can then be moved out of the caliper housing in the brake application direction using the adjusting device. Fig. 2 shows a plan view of a section through the linear actuator 1 according to the invention approximately along the section line AA. The drive shaft 23 and the drive sleeve 25 can be seen in the section, with locking elements 28 also being indicated.

List of reference symbols:

I Linear actuator

10 Ramp mechanism

I I Rolling elements

12 driven ramp disc

13 drive-side ramp disc

15 Center axis

16 groove

17 groove

20 nut thread

21 Support bearings

22 Support element

23 Drive shaft

24 Adjustment mechanism

25 Drive sleeve

26 screw threads

27 screw threads

28 Locking element

50 brake pistons

51 Saddle housing

Claims

Patent claims

1. Linear actuator (1), in particular for moving a brake piston (50) of an electromechanically operable wheel brake of a motor vehicle, comprising:

- a ramp mechanism (10) with at least one drive-side ramp disc (13), a driven ramp disc (12) and a plurality of rolling elements (11),

- a support bearing (21 ),

- and a wear mechanism comprising

- a nut thread (20) with an internal screw thread (26),

- a support element (22) with an external screw thread (27), wherein the screw thread (26) of the nut thread (20) engages with the screw thread (27) of the support element (22), the support bearing (21) is arranged between the drive-side ramp disk (13) and the support element (22), the nut thread (20) encloses at least the support element (22) and/or at least one ramp disk (12, 13), preferably both ramp disks (12, 13) at least in regions, and wherein the support element (22) can be moved in the axial direction during operation by rotating about the central axis (15).

2. Linear actuator (1) according to the preceding claim, characterized in that the electromechanically operable wheel brake is designed as an electromechanical disc brake with electromechanically operated brake caliper or as an electromechanical drum brake.

3. Linear actuator (1) according to one of the preceding claims, characterized in that the nut thread (20) is designed as part of the saddle housing (51).

4. Linear actuator (1) according to one of the preceding claims, characterized in that the nut thread (20) and the saddle housing (51) are designed as different components, wherein the nut thread is connected to the saddle housing (51) in a rotationally fixed manner, and wherein at least one sensor is arranged between the nut thread (20) and the saddle housing (51), preferably a force sensor for receiving a force component acting in the axial direction between the nut thread (20) and the saddle housing (51).

5. Linear actuator (1) according to one of the preceding claims, characterized in that an adjustment mechanism (24) is provided, which is arranged next to the support element (22), preferably in the direction of the drive side.

6. Linear actuator (1) according to one of the preceding claims, characterized in that, during operation, the adjustment mechanism (24) can cause a rotation of the support element (22) about the central axis (15) by means of a drive sleeve (25), wherein the rotation can preferably be an incremental left or right rotation.

7. Linear actuator (1) according to one of the preceding claims, characterized in that the rotation is made possible by an idle rotation angle between the drive shaft (23) and the drive sleeve (25), within which no rotation of the ramp disk takes place.

8. Linear actuator (1) according to one of the preceding claims, characterized in that at least a portion of the drive shaft (23) is at least partially guided through the ramp mechanism (10).

9. Linear actuator (1) according to one of the preceding claims, characterized in that at least one, preferably both ramp discs (12, 13) are formed over the entire surface, in particular without a continuous opening.

10. Linear actuator (1) according to one of the preceding claims, characterized in that the ramp discs (12, 13) have pairwise corresponding grooves (26, 27) on the side surfaces facing each other, and wherein preferably the depth of the grooves (26, 27) changes correspondingly in opposite directions.

11. Linear actuator (1) according to one of the preceding claims, characterized in that the grooves (26, 27) run in the circumferential direction with a pitch circle diameter D, wherein the ratio of the pitch circle diameter D to the diameter of the rolling elements (11) d is: 1.05 * d < D < 20 * d, preferably 1.1 * d < D < 10 * d, particularly preferably 1.1 * d < D < 5 * d, 1.2 * d < D < 3 * d.

12. Linear actuator (1) according to one of the preceding claims, characterized in that the grooves (26, 27) in the ramp discs (12, 13) are non-linear.

13. Linear actuator (1) according to one of the preceding claims, characterized in that the grooves (26, 27) in the ramp disc (12, 13) comprise a plateau for a parking brake function.

14. Actuating device, in particular for an electromechanical wheel brake, comprising a linear actuator (1) according to one of the preceding claims and an electromotor drive unit which is operatively connected to the linear actuator (1).

15. Electromechanical wheel brake, in particular for a motor vehicle, comprising an actuating device according to the preceding claim, wherein the electromechanical wheel brake is designed as a service brake and/or as a parking brake.

16. Method for operating an electromechanical wheel brake, in particular of a motor vehicle, comprising at least one electromechanical wheel brake according to the preceding claim, wherein during operation a braking force can be generated by means of the linear actuator (1) of the actuating device of the electromechanical wheel brake, which can cause braking or deceleration of a wheel.