DE102024111871A1 - Electromechanical spindle drive - Google Patents

Abstract

The invention relates to an electromechanical spindle drive (1) with a threaded spindle (2) having an external thread and a spindle axis (SA), and with at least two drive units (3) spaced apart from each other with respect to the spindle axis (SA), wherein each of the drive units (3) has an elastically deformable frame body (4) comprising two receiving spaces (40) in each of which an electromechanical actuator (6) is inserted, and with a connecting device (7) for mechanically connecting the drive units (3), wherein each of the frame bodies (4) has a receiving section (42) for the threaded spindle (2), which has two drive sections (44) integrally formed with the frame body (4), which contact opposite circumferential sections of the external thread of the threaded spindle (2) and which are moved by applying suitable electrical signals to the electromechanical actuators (6) via a deformation of the frame body (4) thereby caused. A characteristic feature of the invention is the provision of a solid lubricant element (8) which is arranged between adjacent drive units (3) such that it at least partially surrounds the threaded spindle (2) and is in contact with it. Furthermore, the invention relates to a method for operating such a spindle drive and to a positioning device with such a spindle drive.

Description

Background of the invention

The invention relates to an electromechanical spindle drive and a method for operating such a spindle drive.

The DE 10 2021 113 751 A1 The applicant discloses a generic spindle drive in which a threaded spindle received in a spindle chamber of a frame device is set into a rotary motion by means of two actuator devices, which, according to one embodiment shown therein, move an actuating device that partially surrounds the spindle and is in threaded contact with it, and simultaneously provide for a deformation supporting the drive movement of a section of a frame device that partially surrounds the threaded spindle on the opposite side and is also in threaded contact with it there, which is converted into a linear movement of the threaded spindle due to the thread engagement. In other embodiments shown therein, DE 10 2021 113 751 A1 In disclosed embodiments, the two actuator devices each act directly on a drive element that is section by section engaged with the threaded spindle on opposite sides, and which is part or section of a frame device surrounding the threaded spindle or is connected to it, wherein the actuator devices are controlled in such a way that their resulting deformations are opposite in direction and thus cause a rotational movement of the threaded spindle.

A certain disadvantage here is that the respective spindle drive has a complex or relatively difficult-to-handle design in terms of assembly, and is also not suitable for use at low temperatures.

From the DE 10 2022 113 382 B3 The applicant is aware of a generic spindle drive in which contact elements engaged in the threads of a driven threaded spindle, and which are both rigidly connected to a base element and mechanically connected to each other, are moved in opposite directions by means of piezoelectric actuators in contact with them in order to generate a rotary movement of the threaded spindle. This spindle drive is also comparatively complex in design and only conditionally suitable for low to very low temperatures.

Object of the invention

It is an object of the invention to provide an electromechanical spindle drive which, with a simple and easy-to-assemble structure, allows use down to the lowest temperatures, i.e. under cryogenic conditions.

Inventive solution

The above problem can be solved, for example, with an electromechanical spindle drive comprising a threaded spindle, two drive units mechanically connected to or in contact with the threaded spindle and spaced apart from each other via a connecting device, each drive unit comprising at least two electromechanical actuators, and a solid lubricant element arranged between the drive units. It is conceivable that the electromechanical spindle drive according to the invention comprises more than two drive units, with each pair of drive units arranged adjacent to each other forming a drive unit pair, wherein at least one of the drive unit pairs has a solid lubricant element arranged between its two drive units and at least one of the drive unit pairs has a connecting device connecting its two drive units to each other.

By providing a solid lubricant element positioned between adjacent drive units in such a way that it at least partially surrounds and is in contact with the threaded spindle, sufficient lubrication of the thread engagement between the threaded spindle and the drive units, which are at least partially in contact with it, is achieved even under cryogenic conditions. As the threaded spindle, through its rotational movement, picks up solid lubricant from the solid lubricant element, which at least partially surrounds it and is in contact with it within the surrounding area, and transports it into the thread engagement area between the threaded spindle and the drive units, effective lubrication is achieved there, which is maintained even under cryogenic conditions.

According to one embodiment, the solid lubricant element has a hollow cylindrical geometry and is in contact with the external thread of the threaded spindle via a complementary internal thread.

According to another embodiment, the solid lubricant element comprises carbon or boron nitride and preferably consists of it.

According to another embodiment, the frame body forms receiving spaces for the The electromechanical actuators or a receiving section of the frame body for the threaded spindle each form a closed structure, such that the receiving spaces for the electromechanical actuators completely surround them, or the receiving section for the threaded spindle completely surrounds them. It can be particularly advantageous if a surface of a corresponding receiving space intended for contact with an electromechanical actuator is formed by a surface of a clamping device for clamping or securing the respective electromechanical actuator in the associated receiving space. It can be particularly advantageous if the clamping device is formed by a plurality of wedge-shaped elements or by a screw. By using an arrangement of wedge-shaped elements in contact with each other or by providing a screw that can be screwed into the frame body at a corresponding location, tolerances in the geometry of the electromechanical actuators can be easily accommodated, and the electromechanical actuator can be clamped or secured in the receiving space with a defined force.

According to a further embodiment, the two receiving spaces for the electromechanical actuators are connected or coupled to each other via a coupling web section, which simultaneously couples the two drive sections. It can be particularly advantageous here that the two drive sections are additionally coupled to each other via a connecting web section of the frame body, the connecting web section being arranged opposite the coupling web section with respect to the threaded spindle, and the coupling web section, the connecting web section, and the two drive sections together forming a closed receiving section for the threaded spindle.

According to another embodiment, the electromechanical actuators are designed as piezoelectric or electrostrictive or magnetostrictive actuators, whereby in the case of magnetostrictive actuators it can be particularly advantageous for the frame bodies to have a material with magnetostrictive properties.

According to a further embodiment, the electromechanical spindle drive has a device for acquiring and processing measurement or operating data relevant to the state of the electromechanical spindle drive, which is designed to continuously acquire and process the measurement or operating data during the running time of the electromechanical spindle drive and optionally link them together, so that a picture of the state of the electromechanical spindle drive can be derived from it.

The invention further relates to a method for operating an electromechanical spindle drive as described above, in which the two electromechanical actuators of a drive unit are supplied with sawtooth-shaped electrical signals, in particular voltages, that are opposite in time and preferably in phase. "Opposite in time" here means that in a time interval with a rising edge of one of the sawtooth signals, a falling edge is present in the other sawtooth signal, and vice versa. In particular, with regard to the temporal progression of two opposite and in-phase sawtooth-shaped electrical signals, these are arranged as mirror images of each other with respect to the corresponding time axis. "In phase" here means that the periods of the two electrical signals are identical relative to each other and their zero crossings or zero values occur at the same or substantially the same times.

The invention further relates to a positioning device with an electromechanical spindle drive as described above.

The term “essentially” in relation to a feature or value is understood in particular to mean that the feature contains a deviation of up to 20% and specifically up to 10% from the feature or its geometric property or value.

The term "one-piece" in relation to a part or component means that the part or component is manufactured as a single piece. The part or component may be made up of several pieces or parts that are connected, coupled, or joined together. The term "manufactured from a single piece" in this context means that the part or component is manufactured from a single, original workpiece.

The term "electromechanical" here refers to the property of an element or the material of that element, whereby it undergoes a mechanical deformation, such as a change in length, when subjected to an electrical voltage or current. In particular, an electromechanical material is understood to be a piezoelectric, electrostrictive, or magnetostrictive material.

Unless otherwise stated, the logical connective “or” in relation to two alternatives A and B is to be understood as a non-exclusive disjunction, i.e. A or B or both.

When the terms "at least" or "at least" are used herein with reference to the number of a feature, element, or part of the electromechanical spindle drive (hereinafter referred to as the initial feature), then—unless explicitly stated otherwise—the further features directly or indirectly related thereto (hereinafter referred to as reference features) shall be understood as follows: if the minimum number of the respective initial feature is present, the reference features apply to this minimum number; and if the number of the initial feature exceeds the minimum number, the reference features apply either only to the minimum number of the initial feature, or only to a portion of the number of the initial feature exceeding the minimum number, or to the entire number of the initial feature exceeding the minimum number, and thus to the entire number of the initial feature. For example, if a minimum number of two is mentioned with regard to a characteristic A (initial characteristic), then the further characteristics (reference characteristics) relating directly or indirectly to characteristic A either apply exactly to the minimum number of two, or - in the case of the existence of a number exceeding the minimum number of two with regard to characteristic A, for example four - the reference characteristics apply either only to the minimum number of two, or to a part or to the entirety of the number of characteristics A exceeding the minimum number of two.

The features described above and other features of the embodiments according to the invention are explained in the description of the figures and the claims. The individual features can be implemented either separately or in combination as embodiments of the invention. Furthermore, they can describe advantageous embodiments that are independently patentable and whose protection may be claimed only during or after the filing of the application.

Brief description of the characters

• 1a), b): unterschiedliche Ansichten eines erfindungsgemäßen elektromechanischen Spindelantriebs mit magnetostriktiven Aktoren
• 2a, b): unterschiedliche Ansichten eines erfindungsgemäßen elektromechanischen Spindelantriebs mit piezoelektrischen Aktoren
• 3a, b): unterschiedliche Ansichten eines erfindungsgemäßen elektromechanischen Spindelantriebs mit piezoelektrischen Aktoren, die mittels keilförmiger Elemente in dem Aufnahmeraum eingespannt sind
• 4: Positioniervorrichtung in Form eines XY-Tischs mit erfindungsgemäßen elektromechanischen Spindelantrieben

The foregoing, as well as further advantageous features of the invention, are illustrated in the following detailed description of exemplary embodiments of the invention with reference to the accompanying schematic drawings. It shows/show

• 1a) , b): different views of an electromechanical spindle drive according to the invention with magnetostrictive actuators
• 2a , b): different views of an electromechanical spindle drive according to the invention with piezoelectric actuators
• 3a , b): different views of an electromechanical spindle drive according to the invention with piezoelectric actuators which are clamped in the receiving space by means of wedge-shaped elements
• 4 : Positioning device in the form of an XY table with electromechanical spindle drives according to the invention

Detailed description of embodiments according to the invention

In the exemplary embodiments or variants described below, functionally or structurally similar elements are, as far as possible, provided with the same or similar reference numerals. Therefore, to understand the features of the individual elements of a particular exemplary embodiment, reference should be made to the description of other exemplary embodiments or to the general description of the invention.

1 Figures a) and b) show a first possible embodiment of a spindle drive 1 according to the invention. This comprises a threaded spindle 2 with an external thread and a spindle axis SA extending along the longitudinal dimension of the threaded spindle 2. Two identically designed drive units 3 are arranged spaced apart from each other along the spindle axis SA and are mechanically connected to each other via a connecting device 7 in the form of a rigid connecting element. A solid lubricant element 8 in the form of a hollow cylinder is arranged between the two spaced-apart drive units 3. This element has an internal thread complementary to the external thread of the threaded spindle 2 and is thus in thread engagement with the threaded spindle 2. The solid lubricant element 8 is held by the two drive units 3 or clamped between them by means of the connecting element. It is conceivable to use an elastically deformable connecting element, such as a spring element, for the connecting device 7.

Each of the drive units 3 comprises an elastically deformable frame body 4, which has two receiving spaces 40 into which an electromechanical actuator 6 is inserted or clamped. Each of the two receiving spaces 40 has a closed structure, so that the The electromechanical actuator 6 housed therein is completely surrounded or enclosed by the corresponding receiving space 40. The receiving spaces 40 are identical and arranged symmetrically with respect to a separating web section 47, which separates the two receiving spaces 40 and is formed integrally with the frame body 4 and runs essentially along the center of the frame body 4. It is conceivable that one or both of the receiving spaces 40 have a different structure, in particular a structure that is not closed and thus does not completely surround the electromechanical actuator housed therein, whereby an identical structure or a symmetrical arrangement of the corresponding receiving spaces is also advantageous in this case.

The receiving section 42 of the frame body 4 also has a closed structure and completely surrounds or encloses the threaded spindle 2 it contains. The closed structure of the receiving section 42 of the frame body 4 results from the common arrangement of the two drive sections 44, which are positioned laterally to the threaded spindle 2 and engage with it in threaded engagement, the coupling web section 45, which connects the two drive sections 44 in the area of the receiving spaces 40 and thus at the proximal position, and the connecting web section 46, which connects the two drive sections 44 at the distal position. The coupling web section 45 and the connecting web section 46 are essentially the same length.

All previously listed sections of the frame body 4 are formed integrally with it, although it is conceivable to form individual or all sections with a separate part.

The two electromechanical actuators 6 inserted into the frame body 4 or into its receiving chambers 40 are magnetostrictive actuators, each comprising a magnetostrictive and column-shaped element 66, an electrical coil 64 surrounding or enclosing the magnetostrictive element 66, and two permanent magnets 62 adjacent to the respective end sections of the magnetostrictive element 66. The two permanent magnets 62, arranged at the ends of the magnetostrictive element 66, each bear against a wall surface of the receiving chamber 40 with one of their surfaces.

Electrical activation or actuation of the respective electromechanical actuator via an electric current or voltage causes a change in length of the column-shaped magnetostrictive element, resulting in movement of the associated drive section 44. The transmission of the movement or deformation of the electromechanical actuator 6 to the associated and subsequent drive section 44 is made possible by the elastic deformability of the frame body 4 and its specific design or structure. Specifically, a change in length of one of the electromechanical actuators 6 results in an essentially analogous and linear or translational drive movement of the drive section 44 adjoining the corresponding electromechanical actuator 6 with respect to its longitudinal extent, and due to the thread engagement of the section of the drive section 4 in contact with the threaded spindle 2, the linear or translational movement of the drive section 44 leads to a driving movement of the threaded spindle 2, which is converted into a rotational movement of the threaded spindle 2 due to the structural or mechanical boundary conditions.

Preferably, the other electromechanical actuator 6 is electrically controlled by an opposing voltage signal such that it performs an identical but opposite movement or deformation, resulting in an opposing linear or translational drive movement of the other drive section 44, which supports the rotary drive of the threaded spindle 2 caused by the first drive section 44. It is particularly advantageous if the opposing voltage signals applied to the two electromechanical actuators 6 of a drive unit 3 have the same phase or are in phase. The use of sawtooth-shaped or sawtooth-like voltage signals is particularly advantageous here, as the shallower edge of the signal results in a correspondingly slower deformation of the electromechanical actuator 6 and thus a slow drive movement of the drive sections 44. This slow movement, due to static friction between the drive sections 44 and the threaded spindle 2, leads to the spindle 2 being driven or driven. Conversely, the steeper edge of the sawtooth-shaped voltage signals results in a significantly faster movement of the drive sections 44, opposite to the drive movement. This leads to the onset of sliding friction between the drive sections 44 and the threaded spindle 2, resulting in either no drive or only a negligible drive movement of the threaded spindle 2.

The drive sections 44 can therefore be subjected in particular to movement or deformation. The electromechanical actuators 6 follow the movement of the frame body 4 because its structural design gives it elastic deformation capability. The frame body 4 has several thin, web-like sections that function, at least in some areas, like a type of solid-state hinge. In addition to the coupling web section 45, the connecting web section 46, and the separating web section 47 – which have already been described – a side web section 48 for each receiving space 40, which is arranged opposite the separating web section 47 with respect to the intervening electromechanical element 6, also contributes to the elastic deformation capability of the frame body 4. Due to the symmetrical structure of the frame body with respect to a central axis that runs through the center of the separating web section 47 and through the threaded spindle axis, the two side web sections 48 are essentially the same length.

The aforementioned sections, which function at least partially as solid-body joints, also enable a guided and thus defined movement of the drive sections, whereby the corresponding linear or translational drive movement direction is tangential to the threaded spindle and parallel to each other, and the drive sections remain in defined contact or thread engagement with the threaded spindle.

Due to the use of two drive units 3 spaced apart from each other, an additional and in particular passive bearing of the threaded spindle 2 is unnecessary, since its bearing is achieved solely through its arrangement in the two receiving sections 42 and the mechanically fixed connection of the two drive units 3 via the connecting device 7.

2 Figures a) and b) show another possible embodiment of a spindle drive 1 according to the invention. The essential difference to the one shown in 1 The difference in the illustrated embodiment lies in the use of electromechanical actuators 6 in the form of piezoelectric elements. Furthermore, the two receiving chambers 40 and the receiving section 42 have a different geometric shape. It is particularly noticeable that both the coupling web section 45 and the essentially equally long connecting web section 46 are significantly longer than in the embodiment according to [reference to figure]. 1 . At the same time, the side web sections 48 are significantly shorter in this embodiment than in the one described in 1 embodiment shown.

Another difference from the one in 1 The difference in the illustrated embodiment lies in the design of the connecting device 7, which is designed here in such a way that it covers the solid lubricant element laterally.

Each of the frame bodies 4 or each of the two drive units 3 of the in 2a) The electromagnetic spindle drive 1 shown has a corresponding threaded bore 49 for each receiving space 40, which extends through to the corresponding receiving space 40 and into which a clamping device 9 in the form of a screw can be screwed, so that the electromechanical actuator 6 in the form of a piezoelectric element inserted in the respective receiving space 40 can be contacted and clamped or pre-tensioned via its end surface.

3 Figures a) and b) show another possible embodiment of an electromechanical spindle drive 1 according to the invention, which differs essentially in that it is described in 2 The embodiment shown differs in that the clamping device 9, with which the piezoelectric actuator inserted in the respective receiving space 40 can be clamped or pre-tensioned, consists of an arrangement of three wedge-shaped elements 92, wherein adjacent wedge-shaped elements 92 are arranged opposite to each other.

4 Figure 1 shows a positioning device 100 in the form of an XY table, in which the positioning element 104 is movable along two orthogonal directions or axes, each axis being driven by an electromechanical spindle drive 1 according to the invention. The translational displacement and guidance of the positioning element 104 relative to a stationary base plate 106 along the axes of movement is achieved by means of band-shaped solid joints 102 made of nitinol, which together hold the positioning element 104 located in the center of the positioning device 100. For this purpose, the respective end sections of the solid joints 102 facing the positioning element 104 are connected to it, and the opposing end sections of these solid joints 102 are connected to a crossbeam-shaped movement element 110. Each of the movement elements 110 is connected or coupled to two of the four base elements 108 mechanically fixed at the four corners of the base plate 106 by means of two aligned solid joints 102, so that a total of four solid joints 102 are arranged on each movement element 110.

Only two of the motion elements 110 are actively driven linearly by a respective electromechanical spindle drive according to the invention, while the two remaining motion elements 110 passively follow the movement of the two driven motion elements 110 caused by the spindle drives. It is conceivable that all four motion elements 110 are actively driven by an electromechanical spindle drive according to the invention.

The positioning element 104 has essentially a square frame shape, and on all four sides of this frame the corresponding ends of the two associated solid body joints 102 are arranged at the two respective and opposite end sections, wherein these two solid body joints 102 are arranged parallel to each other.

The two solid body joints 102, which are arranged in alignment at the two opposite end sections of each of the movement elements and which connect the respective movement element 110 with the two corresponding base elements 108, are arranged essentially perpendicular to the solid body joints, which are also arranged at the two opposite end sections and which connect this movement element 110 with the positioning element 104.

The foregoing description of exemplary embodiments is to be understood as illustrative. The disclosure thereby enables the person skilled in the art, on the one hand, to understand the present invention and its associated advantages, and, on the other hand, also includes, in the understanding of the person skilled in the art, obvious modifications and alterations of the described structures and methods. Therefore, all such modifications and alterations, insofar as they fall within the scope of the invention as defined in the appended claims, as well as equivalents, are to be covered by the protection of the claims.

Reference symbol list:

1

Electromagnetic spindle drive

2

threaded spindle

3

drive unit

4

frame body

6

electromechanical actuator

7

Connection device

8

Solid lubricant element

9

clamping device

40

Recording space (of frame body 4)

42

Recording section (of frame body 4)

44

Drive section (of the frame body 4)

45

Coupling web section (of frame body 4)

46

Connecting web section (of frame body 4)

47

Separating web section (of frame body 4)

48

Side web section (of the frame body 4)

49

threaded hole

62

Permanent magnet

64

Sink

66

magnetostrictive element

90

Surface (of the clamping device 9)

92

wedge-shaped element (of the clamping device 9)

100

Positioning device

102

Solid body joint

104

Positioning element

106

Base plate

108

Basic element

110

Movement element

QUOTES CONTAINED IN THE DESCRIPTION

This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• DE 10 2021 113 751 A1 [0002]
• DE 10 2022 113 382 B3 [0004]

Claims (15)

Electromechanical spindle drive (1) comprising: a threaded spindle (2) with an external thread and a spindle axis (SA); two drive units (3) spaced apart from each other with respect to the spindle axis (SA), each of the drive units (3) having an elastically deformable frame body (4) comprising two receiving spaces (40) in each of which an electromechanical actuator (6) is inserted; and a connecting device (7) for mechanically connecting the drive units (3), wherein each of the frame bodies (4) has a receiving section (42) for the threaded spindle (2), which has two drive sections (44) integrally formed with the frame body (4), which contact opposite circumferential sections of the external thread of the threaded spindle (2) and which are moved by applying suitable electrical signals to the electromechanical actuators (6) via a deformation of the frame body (4) thereby caused, characterized in that a solid lubricant element (8) is arranged between the drive units (3) such that it at least partially surrounds the threaded spindle (2) and is in contact with it. Electromechanical spindle drive (1) according to Claim 1 , characterized in that the solid lubricant element (8) has a hollow cylindrical geometry and is in contact with the external thread of the threaded spindle (2) via an internal thread shaped complementarily to it. Electromechanical spindle drive (1) according to Claim 1 or 2 , characterized in that the solid lubricant element (8) comprises carbon or boron nitride. Electromechanical spindle drive (1) according to one of the preceding claims, characterized in that the receiving spaces (40) or the receiving sections (42) of the frame body (4) each form a closed structure and completely surround the electromechanical actuators (6) inserted therein or the threaded spindle (2) received therein. Electromechanical spindle drive (1) according to Claim 4 , characterized in that a surface of a receiving space (40) intended for contact with the electromechanical actuator (6) is formed by a surface (90) of a clamping device (9). Electromechanical spindle drive (1) according to Claim 5 , characterized in that the clamping device (9) is formed by a plurality of wedge-shaped elements (92) or by a screw. Electromechanical spindle drive (1) according to one of the preceding Claims 4 until 6 , characterized in that the two receiving spaces (40) for the electromechanical actuators (6) are coupled to each other via a coupling web section (45) of the frame body (4), and the coupling web section (45) simultaneously couples the two drive sections (44) to each other. Electromechanical spindle drive (1) according to Claim 7 , characterized in that the two drive sections (44) are additionally coupled to each other via a connecting web section (46) of the frame body (4), wherein the connecting web section (46) is arranged opposite the coupling web section (45) with respect to the threaded spindle (2), and the coupling web section (45) and the connecting web section (46) and the two drive sections (44) together form the closed receiving section (42) for the threaded spindle (2). Electromechanical spindle drive (1) according to one of the preceding claims, characterized in that the electromechanical actuators (6) are designed as piezoelectric or electrostrictive or magnetostrictive actuators. Electromechanical spindle drive according to Claim 9 , characterized in that the electromechanical actuators (6) are designed as magnetostrictive actuators and the frame bodies (4) have a material with magnetostrictive properties. Electromechanical spindle drive according to one of the preceding claims, characterized in that it has more than two drive units (3), wherein two drive units (3) adjacent with respect to the spindle axis (SA) form a drive unit pair, and one of the drive unit pairs or a part of the drive unit pairs has a solid lubricant element (8) or all drive unit pairs have a solid lubricant element (8). Electromechanical spindle drive according to Claim 11 , characterized in that one of the drive unit pairs or part of the drive unit pairs has a connecting element (7) or all drive unit pairs have a connecting element (7). Electromechanical spindle drive according to one of the preceding claims, wherein this a device for recording and processing measurement or operating data relevant to the condition of the electromechanical spindle drive, which is designed to continuously record and process the measurement or operating data during the running time of the electromechanical spindle drive and optionally link them together, so that a picture of the condition of the electromechanical spindle drive can be derived from it. Method for operating an electromechanical spindle drive (1) according to one of the preceding claims, characterized in that the two electromechanical actuators (6) of a drive unit (3) are supplied with opposing and sawtooth-shaped electrical signals. Positioning device (100) with an electromechanical spindle drive (1) according to one of the preceding Claims 1 until 13 .