Linear actuator having a radial centering function for a stroke component thereof, braking device having the linear actuator, and method for operating the linear actuator

Abstract

The invention relates to a linear actuator (10), which has a screw drive (14) with a rotationally driven part (12) and with a part (16) that can be linearly moved relative thereto. Furthermore, the linear drive (10) has a component (18) that can be displaced by means of the linearly movable part (16) of the screw drive (14). Furthermore, a separate adjusting element (20) is provided, by means of which the linearly movable part (16) of the screw drive (14) and the aforementioned component (18) are provided about a common axis (22).

Description

[0001] LINEAR ACTUATOR WITH RADIAL CENTERING OF A LIFTING COMPONENT THEREOF. A BRAKING DEVICE USING THE LINEAR ACTUATOR, AND A METHOD FOR OPERATING THE LINEAR ACTUATOR.

[0002] The invention relates to a linear actuator, a braking device with the linear actuator and a method for operating the linear actuator.

[0003] Linear actuators, in which a rotational movement is converted into a linear movement for the purpose of actuating an object, are, by design, primarily suitable for absorbing forces in an axial direction relative to a rotational axis of the rotational movement. If, on the other hand, radial forces occur, demands on shape and position tolerances as well as on the stability of the linear actuator components increase. Therefore, with increased exposure to radial forces on the linear actuator, both the manufacturing effort and the weight of the actuator increase. In order to be able to use compact and weight-saving linear actuators, attempts are made to keep radially acting forces as small as possible. One known option for this is to arrange linearly moving parts of the linear actuator around a common axis. This allows acting forces to be advantageously introduced into the linear actuator in the axial direction.Such arrangements around a common axis have so far been realized using geometric shapes that are complementary to one another, such as a cone or a partial sphere, or with the help of fits. Although this can reduce weight and improve service life, these known adjustment options still require a high level of design and manufacturing effort. Furthermore, the adjustment options known to date have the disadvantage that adjustment is only realized in connection with a forward stroke. In the case of a return stroke, for example, the complementary geometries separate or a relative movement occurs due to a fit tolerance. As a result, an arrangement around the common axis is often lost. Tilting then leads to increased radial loads.This, in turn, can lead to increased wear and thus to a reduced service life and reduced reliability of the linear actuator. A common application for a linear actuator of the type described above involves moving a brake pad attached to a brake piston in an electromechanical braking device. Typically, the brake piston is operatively connected to a linearly movable part of the linear actuator. The forward stroke presses the brake pad onto a brake disc. The brake piston is aligned relative to a linearly movable part of the linear actuator, for example, in the manner described above. To end a braking operation, the linearly movable part of the linear actuator is moved away from the brake disc using a return stroke. The linearly movable part of the linear actuator lifts off the brake piston.As a result, the alignment of the brake piston can easily change. Furthermore, the brake pad often remains in contact with the brake disc because there is no tensile connection between the linearly moving part and the brake piston. While it is known to implement such a tensile connection for the purpose of retracting the brake pad using a positive connection, this makes maintenance and repair more difficult. Without a tensile connection, however, a brake pad cannot be reliably spaced from a brake disc. Therefore, correct adjustment of the air gap cannot be achieved. As a result, the braking effect of an associated braking device can be impaired, thus reducing its operational reliability.

[0004] An object of the present invention is to provide an improved braking device with a linear actuator that can be manufactured at low cost.

[0005] This object is achieved by a linear actuator having the features of claim 1. Furthermore, this object is achieved by a braking device having the features of the independent claim.

[0006] Furthermore, the present invention is based on the object of providing an improved method for operating the linear actuator.

[0007] This problem is solved by a method having the features of the subordinate method claim. Advantageous further developments are the subject of dependent subclaims.

[0008] The linear actuator according to the invention comprises a screw drive with a rotationally driven part and a part that is linearly movable relative thereto. Linearly movable in this context should be understood in the sense of linear technology, specifically such that the part in question is movable along a straight line. The linearly movable part of the screw drive is expediently movable substantially parallel to a longitudinal axis of the screw drive, in particular a rotational axis of the rotationally driven part. The screw drive can be designed as a ball screw drive, roller screw drive, planetary roller screw drive, planetary roller screw drive, trapezoidal screw drive, high-pitch screw drive, a ball ramp, a hydrostatic screw drive, or another type of screw drive known to those skilled in the art. Furthermore, the linear actuator comprises a component that is displaceable by means of the linearly movable part of the screw drive.

[0009] The linearly movable part of the screw drive can optionally comprise either a threaded spindle or a threaded nut of the screw drive. If the linearly movable part comprises the threaded nut of the screw drive, the threaded spindle of the screw drive is rotationally driven and axially fixed. In this context, by means of a rotational movement of the threaded spindle, the threaded nut operatively connected to this threaded spindle is linearly movable. In an alternative embodiment, the linearly movable part comprises the threaded spindle of the screw drive. The threaded nut of the screw drive is rotationally driven and preferably axially fixed. In this alternative embodiment, by means of a rotational movement of the threaded nut, the threaded spindle operatively connected to the threaded nut is linearly movable.

[0010] The screw drive is expediently designed to effect a forward stroke and a return stroke of the linearly movable part. A stroke should be understood as a straight path covered by the linearly movable part as a result of a rotation of either the threaded spindle or the threaded nut. The orientation of the stroke in three-dimensional space is not restricted to a predetermined direction. Instead, the orientation of the stroke in three-dimensional space can be provided as desired. In addition, the linear actuator has a separate adjusting element by means of which the linearly movable part of the screw drive and the aforementioned displaceable component are arranged around a common axis. In the context of the present invention, an axis is understood to be a non-physical axis in the mathematical sense that extends infinitely.In particular, the extension of the axis is not limited by the physical extension of a reference object. Preferably, a central axis of the linearly movable part of the screw drive and a central axis of said displaceable component are arranged substantially parallel to the common axis.

[0011] By means of the separate adjusting element, the arrangement of the linearly movable part of the screw drive and the aforementioned component can be maintained around the common axis during operation of the linear actuator. Axis offset, such as tilting of the linearly movable part relative to the aforementioned component, can be avoided. Furthermore, the separate adjusting element allows forces acting on the screw drive to be absorbed predominantly in the axial direction. Radially acting forces, on the other hand, can be kept small. This can increase the service life of the linear actuator. In principle, the separate adjusting element can be used in addition to or as an alternative to previously known adjustment methods.In individual applications, a complementary geometry or fit intended for aligning the linearly movable part of the screw drive relative to the movable component can be omitted, or it can be supplemented using the separate adjustment element. Furthermore, the separate adjustment element enables the creation of a lightweight linear actuator with low manufacturing costs.

[0012] Preferably, the linearly movable part of the screw drive and the said component are arranged coaxially around the common axis by means of the separate adjusting element. For this purpose, a central axis of the linearly movable part of the screw drive and a central axis of the said component are expediently arranged coaxially by means of the separate adjusting element. In this way, the central axes of the linearly movable part of the screw drive and the said component form the common axis. The coaxial arrangement enables a space-saving and compact arrangement of the linearly movable part and the said component. Furthermore, a symmetrical arrangement can be realized. In a preferred embodiment, a rotation axis of the rotationally driven part of the screw drive is provided as the common axis.In the case of a rotary-driven threaded spindle, the common axis is, in particular, a rotational axis of the threaded spindle. This enables central force absorption.

[0013] In an advantageous embodiment, the separate adjusting element allows the linearly movable part of the screw drive and the aforementioned movable component to be arranged coaxially relative to one another, in particular radially centered, regardless of their axial arrangement. This allows for relative movement between the linearly movable part of the screw drive and the aforementioned component. For example, the linearly movable part can, under certain circumstances, lift off from the aforementioned component, such as during a return stroke, without losing centering. In this way, radially acting forces can be kept small, and any forces that occur can be absorbed primarily axially.

[0014] An advantageous development provides that the separate adjustment element is arranged in a direction substantially perpendicular to the aforementioned common axis between the linearly movable part of the screw drive and the displaceable component. Alignment of the linearly movable part of the screw drive and the aforementioned component relative to one another in a radial direction can thus be realized with minimal effort. Furthermore, components with only low requirements for shape tolerances can be used to manufacture the linear actuator. Furthermore, the design effort required to manufacture the linear actuator can be kept to a minimum.

[0015] A further advantageous development provides that the separate adjusting element is connected on one side either to the linearly movable part of the screw drive or to the movable component in a force-locking manner. This allows the said component, optionally together with the adjusting element, to be separated from the linearly movable part with a predetermined amount of force. Consequently, the linear actuator can be easily serviced and / or maintained.

[0016] In a first embodiment, a force-locking connection can be designed, for example, such that a clearance fit is realized between the linearly movable part of the screw drive and the displaceable component by means of the separate adjusting element. In this way, a relative movement between the linearly movable part of the screw drive and the aforementioned component can be enabled. Nevertheless, in this first embodiment, a reliable arrangement of the linearly movable part of the screw drive and the component displaceable by this part around the common axis can be enabled by means of the separate adjusting element.

[0017] In a second embodiment, it can be provided that the linearly movable part of the screw drive and the component that can be moved with it are non-positively connected to one another by means of the separate adjusting element in such a way that relative movement between them is prevented as long as an actuating force is kept below a predetermined threshold. This makes it possible, for example, to realize a return stroke movement of the movable component using the separate adjusting element. In the second embodiment, the separate adjusting element can therefore be used to both center the movable component and apply tensile forces to it. If the aforementioned threshold is exceeded, the linearly movable part of the screw drive and the movable component can still be separated from one another, for example for the purpose of maintenance or repair.

[0018] Furthermore, an advantageous development provides that the separate adjusting element is positively connected on one side either to the linearly movable part of the screw drive or to the displaceable component. This enables a one-sided, stationary arrangement of the separate adjusting element on either the linearly movable part of the screw drive or the displaceable component. In the preferred application, the separate adjusting element can thus be securely attached to either the linearly movable part of the screw drive or the displaceable component. This enables reliable operation of the linear actuator as well as easy maintenance and servicing.

[0019] In an advantageous embodiment, the separate adjusting element is accommodated either in a recess of the linearly movable part of the screw drive or in a recess of the component that can be moved with it. This allows for a simple, form-fitting connection with minimal manufacturing effort.

[0020] The separate adjusting element is preferably designed to be elastic. This allows for the compensation of shape and / or positional differences between the linearly movable part of the screw drive and the movable component. When assembling the linear actuator, quickly and inexpensively manufactured and readily available components can therefore be used. For example, the separate adjusting element can be designed as a tolerance ring, a spring, a bushing, or an O-ring. Particularly preferably, the separate adjusting element is made of an elastic plastic and / or rubber. Furthermore, the material can be metal.

[0021] The braking device according to the invention comprises the linear actuator according to the invention.

[0022] In the braking device according to the invention, the displaceable component of the linear actuator according to the invention is designed as a piston provided with a brake pad of the braking device. This allows the braking device to be equipped with a lightweight and inexpensively manufactured linear actuator. High braking forces can be reliably introduced axially into the linear actuator, thereby ensuring reliable operation of the braking device. Furthermore, this enables a long service life of the braking device. When the braking device is used in a vehicle, shorter braking distances can be achieved by optimizing the air gap.

[0023] Advantageously, the braking device is designed as an electromechanical braking device. This allows for an electromechanical braking device that can reliably absorb high braking forces. Furthermore, it enables finely controlled wear adjustment of a brake pad. Furthermore, a predetermined clearance length can be achieved with minimal effort. Furthermore, a braking device with high rigidity can be provided.

[0024] Furthermore, the invention provides a method for operating the linear actuator according to the invention.

[0025] In the method according to the invention, a return stroke movement of the displaceable component of the linear actuator is realized by means of the separate adjusting element of the linear actuator. This allows for reliable return of said component without the use of additional components. Advantageously, a forward stroke of the displaceable component is realized by means of direct contact between the linearly movable part of the screw drive and said component. In this way, even large axial forces can be reliably absorbed. The method therefore enables safe operation of the linear actuator.

[0026] Furthermore, the invention provides that the linear actuator is used in the braking device, and a brake pad is spaced apart from a brake disc using the separate adjusting element. A return stroke movement of the linearly movable part of the screw drive is expediently transmitted to the displaceable component of the linear actuator, designed as a piston, on which the brake pad is arranged, using the separate adjusting element. As a result, the brake pad is spaced apart from the brake disc by means of the separate adjusting element. This enables simple, active distancing between the brake disc and the brake pad based on a force flow mediated by the separate adjusting element between the linearly movable part of the screw drive and the displaceable component. Furthermore, tensile forces can be provided as needed for the purpose of separating the brake pad and the brake disc.In this way, a clearance between a brake pad and a brake disc can be reliably achieved in a predetermined manner. Consequently, a reduction in wear of a brake pad and / or a brake disc can be achieved. The invention is explained in more detail below with reference to figures. Where appropriate, elements with the same effect are provided with the same reference numerals. The invention is not limited to the exemplary embodiments shown in the figures or variations thereof - not even with regard to functional features. The previous description as well as the following description of the figures contain numerous features, some of which are summarized in the dependent claims. However, a person skilled in the art will also consider these features, as well as all other features disclosed above and in the following description of the figures, individually and combine them into further meaningful combinations.In particular, all of the aforementioned features can be combined individually and in any suitable combination with the method, use, and device according to the invention. The figures are schematic drawings, not to scale.

[0027] They show:

[0028] Fig. 1 shows an embodiment of a braking device according to the invention with an embodiment of a linear actuator according to the invention; and

[0029] Fig. 2 is an illustration of an example of a method for operating the linear actuator according to the invention using a schematic flow diagram.

[0030] Fig. 1 shows a schematic representation of an embodiment of a braking device 26. This braking device 26 is embodied, for example, as an electromechanical braking device 26. Furthermore, Fig. 1 shows a schematic representation of an embodiment of a linear actuator 10, which is provided for moving a brake pad 28 arranged on a piston 18.

[0031] For this purpose, the linear actuator 10 has a screw drive 14 with a rotationally driven and axially fixed threaded spindle 12. The screw drive 14 also has a linearly movable part 16. This linearly movable part 16 is designed, for example, as a threaded nut 16 engaging with the threaded spindle 12. This threaded nut 16 has, for example, an internal thread (not shown in detail), which is complementary to an external thread (not shown in detail) of the threaded spindle 12. Furthermore, the linear actuator 10 has a component 18 that can be displaced by means of the threaded nut 16. In the exemplary embodiment of the braking device 26 described here, the displaceable component 18 is designed as a piston 18, on which the brake pad 28 is attached.

[0032] Furthermore, the linear actuator 10 has a separate adjusting element 20, by means of which the threaded nut 16 and the piston 18 are arranged around a common axis 22. In the present case, the common axis 22 is, for example, the rotational axis 22 of the rotationally driven threaded spindle 12. In the present embodiment, both a central axis of the threaded nut 16 and a central axis of the piston 18 are arranged coaxially with the rotational axis 22 of the threaded spindle. Thus, the piston 18 and the screw drive 14 are radially centered with respect to the common axis 22. Such a coaxial or concentric arrangement has proven particularly useful in braking devices in order to reliably absorb actuating forces axially.

[0033] The separate adjusting element 20 is preferably designed to be elastic. Such elasticity can be provided, for example, by a suitable selection of a material. For example, a plastic with high elasticity or a rubber material can be selected as the material for the adjusting element 20. Alternatively or additionally, the elasticity can be provided by a predetermined geometry of the adjusting element 20. For example, the separate adjusting element 20 can be designed as a metallic tolerance ring, as a spring element, or as a clamping ring. In the present exemplary embodiment, the separate adjusting element 20 is designed, for example, as an elastic rubber ring. This makes it possible to compensate for larger shape tolerances and / or a deviating geometry between the threaded nut 16 and the piston 18.The threaded nut 16 and the piston 18 can be arranged around a common axis 22 in a simple manner with little assembly effort.

[0034] In the presently described embodiment, the separate adjusting element 20 is arranged in a direction substantially perpendicular to the rotational axis 22 between the threaded nut 16 and the piston 18. Furthermore, the separate adjusting element 20 is positively connected to the piston 18 on one side. For this purpose, the piston 18 has a circumferential recess 24 on an inner side for the purpose of receiving the adjusting element 20, which is designed, for example, as a rubber ring. The adjusting element 20 is received in this recess 24 in a fixed position relative to the piston 18. In contrast, the aforementioned separate adjusting element 20 is non-positively connected to the threaded nut 16 on one side. This non-positive connection can be designed such that tensile forces can be transmitted by means of the adjusting element 20 and yet a relative movement between the piston 18 and the threaded nut 16 is possible when a predetermined axial force threshold is reached or exceeded.In an alternative embodiment not shown in detail, the aforementioned recess 24 can be provided on an outer side of the threaded nut 16 for the purpose of receiving the separate adjusting element 20, instead of on the inner side of the piston 18. In this way, in the alternative embodiment, the separate adjusting element 20 can be connected to the threaded nut 16 in a form-fitting manner and to the piston 18 on one side in a force-fitting manner.

[0035] In principle, the piston can also be connected directly to the threaded spindle 12 in a force-locking or form-locking manner by means of the adjusting element 20. In this case, not shown, the threaded nut 16 is advantageously rotationally driven and preferably axially fixed, with the threaded spindle 12 being linearly movable.

[0036] By means of the separate adjusting element 20, forces acting on the brake pad 28 during a braking operation can be reliably transmitted axially into the linear actuator 10 in a direction along the rotational axis 22 of the threaded spindle 12. Radially acting forces can thus be kept small. In this way, a long service life of the linear actuator 10 and thus of the braking device 26 can be achieved.

[0037] Fig. 2 illustrates an example of a method 100 in which a linear actuator 10 is used 102 in a braking device 26. The linear actuator 10 and the braking device 26 are, in the present case, by way of example, the exemplary embodiment of the linear actuator 10 described in connection with Fig. 1 and the described exemplary embodiment of the braking device 26. In order to achieve a braking force between the brake pad 28 and the brake disc 30, a rotation of the threaded spindle 12 is converted 104 into a linear stroke movement of the piston 18 by means of the linear actuator 10. For this purpose, in the present case by way of example, a pre-stroke movement 106 is transmitted to the piston 18 by means of an end face of the threaded nut 16. The piston 18 then approaches the brake disc 30. During this process, the piston 18 is held 108 centrally around the rotation axis 22 of the threaded spindle 12 by means of the separate adjusting element 20.This allows forces occurring along the rotational axis 22 of the threaded spindle 12 to be introduced axially into the linear actuator 10. Radially acting forces, however, can be kept small.

[0038] To cancel a braking effect, the threaded nut 16 is set into a return stroke movement 110 by means of the threaded spindle 12. In this way, the threaded nut 16 moves away from the brake disc 30 along the rotation axis 22 of the threaded spindle 12. In a first embodiment, a force-locking connection is provided between the separate adjusting element 20 and the threaded nut 16 such that a relative movement between the piston 18 and the threaded nut 16 is enabled. As a result, a return stroke movement 110 of the threaded nut can be realized independently of a movement of the brake pad 28 connected to the piston 18. Nevertheless, in individual applications, a return stroke movement 110 of the piston 18 and the brake pad 28 can occur, depending on the design of the force-locking connection.In a second embodiment, however, a force-locking connection is provided between the separate adjusting element 20 and the threaded nut 16 such that relative movement between the piston 18 and the threaded nut 16 is prevented up to a predetermined force. In this way, a return stroke movement 110 of the piston 18 and the associated brake pad 28 follows a return stroke movement 110 of the threaded nut 16, as long as the predetermined force is not reached or exceeded. As a result, the brake pad 28 is spaced 112 from the brake disc 30 by means of the separate adjusting element 20. A clearance can be created easily and reliably in this way.Although the invention has been illustrated and described in detail by the preferred embodiments and variations thereof, the invention is not limited to the disclosed examples and other variations may be derived therefrom by those skilled in the art without departing from the scope of the invention.

[0039] List of reference symbols

[0040] Linear actuator

[0041] threaded spindle

[0042] screw drive

[0043] Part of the screw drive / threaded nut

[0044] Component / Piston

[0045] Adjusting element

[0046] Axis / rotation axis

[0047] recess

[0048] braking device

[0049] brake pad

[0050] brake disc

[0051] Proceedings

[0052] Use

[0053] Convert

[0054] Pre-stroke movement

[0055] Hold

[0056] Return stroke movement

[0057] Spacing

Claims

AMENDED CLAIMS received by the International Bureau on 21 May 2025 (21.05.2025) 1. Linear actuator (10) comprising - a screw drive (14) with a rotationally driven part (12) and a part (16) which is linearly movable relative thereto; - a component (18) which is displaceable by means of the linearly movable part (16) of the screw drive (14); - a separate adjusting element (20) by means of which the linearly movable part (16) of the screw drive (14) and said component (18) are arranged about a common axis (22), and wherein the separate adjusting element (20) is arranged in a direction substantially perpendicular to said common axis (22) between the linearly movable part (16) of the screw drive (14) and said component (18).

2. Linear actuator (10) according to claim 1, characterized in that a central axis of the linearly movable part (16) of the screw drive (14) and a central axis of said component (18) are arranged coaxially by means of the separate adjusting element (20) and in this way form the common axis (22).

3. Linear actuator (10) according to one of the preceding claims, characterized in that the separate adjusting element (20) is non-positively connected on one side either to the linearly movable part (16) of the screw drive (14) or to the said component (18).

4. Linear actuator (10) according to one of the preceding claims, characterized in that the separate adjusting element (20) is positively connected on one side either to the linearly movable part (16) of the screw drive (14) or to the said component (18). AMENDED SHEET (ARTICLE 19) 5. Linear actuator (10) according to claim 4, characterized in that the separate adjusting element (20) is received either in a recess (24) of the linearly movable part (16) of the screw drive (14) or in a recess (24) of the said component (18).

6. Braking device (26) comprising a linear actuator (10) according to one of the preceding claims, in which said component (18) is designed as a piston (18) provided with a brake pad (28).

7. Braking device (26) according to claim 7, characterized in that the braking device (26) is designed as an electromechanical braking device.

8. Method (100) for operating the linear actuator (10) according to one of claims 1 to 5, in which a return stroke movement (110) of the displaceable component (18) of the linear actuator (10) is realized by means of the separate adjusting element (20) of the linear actuator (10).

9. Method (100) according to claim 8, wherein the linear actuator (10) is used in the braking device (26) according to one of claims 7 or 8 (102) and a brake pad (28) is spaced apart from a brake disc (30) by means of the separate adjusting element (20) (112). AMENDED SHEET (ARTICLE 19)

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