Linearantrieb

Abstract

Linear drive (1), comprising: an actuator unit (3) with at least one actuator (3a, 3b); two guide elements (4a, 4b) and a movement element (5), wherein the movement element (5) is adjustable by a movement generated by the actuator unit (3) due to a static friction effect along both guide elements (4a, 4b), characterized in that the movement element (5) can be brought into engagement with each of the two guide elements (4a, 4b) by means of static friction for adjustment along both guide elements (4a, 4b) due to the static friction effect, wherein the movement element (5) and the guide elements (4a, 4b) are coupled in such a way that contact forces in different directions and symmetrically to a plane are generated between each guide element (4a, 4b) and the movement element (5) during the static friction phase.

Description

[0001] The present invention relates to a linear drive, in particular for precision positioning devices, comprising: an actuator unit with at least one actuator; two guide elements and a movement element, wherein the movement element is adjustable by a movement generated by the actuator unit due to a stick-slip effect along both guide elements.

[0002] The US 5 786 654 A reveals (among other things in Fig. 1 and column 4, line 19 to column 5, line) a linear drive according to the preamble of claim 1, wherein a first of the two guide elements (16) serves to generate the stick-slide effect (see column 4, lines 19 to 31) and a second of the two guide elements (17) provides anti-rotation protection (see column 4, lines 19 to 31) in order to lock the degree of rotational freedom of the moving element about the first guide element (see column 4, lines 46 to 54). As an alternative to the second guide element (17), a linear ball guide (142, Fig. 23) provided so that the moving element (12) does not rotate around the first guide element (16) when it is moved along it. Further related prior art is disclosed in DE 10 2008 003 879 A1, US 9 692 323 B2, US 6 188 161 B1, WO 98 / 19347 A2, US 2017 / 0310247 A1, US 6 940 210 B2 and EP 0 464 764 A1.

[0003] Regardless of the actuation method, electromagnetic or piezoelectric, precision guide elements such as linear bearings are extensively used in precision positioning tables. Despite the advantages of providing high rigidity with concentric or parallel surfaces that fit over a large contact area, these linear guide elements occupy the most space, limiting the miniaturization of a device.

[0004] The present invention is based on the objective of providing a generic linear drive with a compact design and more precise adjustability of the moving element.

[0005] To solve this problem, the present invention provides the linear drive according to claim 1, comprising: an actuator unit with at least one actuator; two guide elements and a motion element, wherein the motion element is adjustable along both guide elements by means of a static friction effect generated by the actuator unit, and wherein the motion element can be brought into engagement with each of the two guide elements by means of static friction for adjustment along both guide elements due to the static friction effect. This allows both guide elements to be used to generate the propulsion of the motion element and reduces the risk of the motion element becoming jammed between the two guide elements, which exists with a one-sided drive. Thus, the clearance required for adjusting the motion element between the motion element and each of the two guide elements can be made comparatively small.Furthermore, the moving element can be precisely positioned on both guide elements by means of static friction. According to the invention, the moving element and the guide elements are coupled such that, during the static phase, contact forces are generated in different directions and symmetrically about a plane between each guide element and the moving element. This plane preferably includes the axes of extension of the guide elements. This makes it particularly easy to center the moving element in its intended central position and plane between the two guide elements.

[0006] Advantageous embodiments of the claimed invention are the subject of the dependent claims.

[0007] The actuator is, for example, an electromagnetic or piezoelectric actuator. Preferably, the movement generated by the actuator unit is an electrically generated oscillation. The actuator unit can comprise one or more actuators, in particular piezoelectric actuators, which serve as electromechanical transducers and convert an alternating electrical voltage into an oscillating movement of the piezoelectric actuator.

[0008] It can be advantageous if the actuator unit is designed to move both guide elements simultaneously and / or synchronously and / or along parallel paths. This allows the two guide elements to drive the motion element for generating the feed with exceptional uniformity and thus position it with extreme precision. It is also possible for the actuator unit to move both guide elements at least partially simultaneously and / or synchronously and / or along parallel paths, and at least partially asynchronously and / or along non-parallel paths.

[0009] However, it can also prove helpful if the moving element, when the actuator unit is in a stress-free state (i.e., in the absence of control voltages or movement generated by the actuator unit), engages with each of the two guide elements via static friction. This effectively prevents relative movement to either guide element when the moving element is stationary. This design is particularly advantageous for the application of linear drives in precision positioning devices.

[0010] It can also prove advantageous if each of the two guide elements and / or the moving element and / or at least one contact section of the moving element is / are made of a non-magnetic or non-magnetizable material, preferably ceramic, preferably oxide ceramic, and particularly preferably aluminum oxide. There are applications where a linear drive, or at least its moving element, must be non-magnetic. However, if the guide elements are made of non-magnetic materials such as structural ceramic or titanium, the linear drive can also be used for special applications requiring a non-magnetic or non-magnetizable linear drive. Furthermore, in this embodiment, a high static friction force can be generated between the guide elements and the moving element.

[0011] It can prove practical if the actuator unit has two actuators, each driving one of the two guide elements. Preferably, each guide element is articulated or rigidly connected to the actuator unit. The two actuators can be identical and connected in parallel to drive the guide elements synchronously and generate a uniform feed of the moving element. Furthermore, different movement patterns of the moving element can be implemented compared to a single actuator. Preferably, the two actuators can be controlled independently of each other. This also allows for particularly precise fine-tuning of the position of the moving element.

[0012] It can be advantageous if each guide element and / or the motion element has / have only one translational degree of freedom, preferably all in parallel directions. Preferably, the other two translational degrees of freedom as well as all rotational degrees of freedom of both guide elements and / or the motion element are locked. This effectively prevents positional errors when adjusting the motion element along its travel path. Furthermore, the motion control of the motion element becomes relatively simple.

[0013] However, it can also be advantageous if each guide element is designed as a cylinder and the path of movement of the guide element preferably extends along the cylinder axis. In this embodiment, the moving element can be positioned with particular stability both during a feed along the travel path and when stationary. Additionally, a linear bearing is normally the most expensive component in a precision stage and can be omitted in this embodiment of the linear drive according to the invention.

[0014] It can also be advantageous if the moving element accommodates each guide element in its own channel-shaped recess, the channel-shaped recess preferably being designed as a V-shaped groove that extends along the respective guide element and opens towards it. This allows the moving element to be statically determinate and stably fixed to each of the guide elements, and enables the transmission of large static friction forces.

[0015] It can be advantageous if the linear drive has a preferably self-contained frame, wherein the frame preferably surrounds the actuator unit, the two guide elements, and the motion element, and wherein the frame particularly preferably has a cuboid outline. In an advantageous embodiment, the frame comprises four parts that approximately form a rectangle, in particular a base part, a counterpart, and two side parts that connect the base part and the counterpart. The base part and the counterpart are, for example, cuboid in shape. The two side parts can be leaf-spring or plate-shaped. It can be advantageous if the actuator unit has two actuators and the first actuator is rigidly coupled to the frame or the base part, while the second actuator is rigidly or movably coupled to the frame or the base part.

[0016] However, it can also be advantageous if each guide element is resiliently mounted relative to the frame of the linear drive, preferably in and / or transverse to its direction of extension, preferably via at least one leaf spring. This allows the contact pressure between the moving element and the guide element to be precisely adjusted. Preferably, each guide element is resiliently mounted against the counterpart of the frame opposite to its direction of movement, so that the deflection of the guide element in its direction of movement leads to an increase in the spring tension.

[0017] In an advantageous embodiment, each guide element is slidably mounted on the frame via a sliding bearing. The sliding bearing can, for example, support the guide element slidably between its end bearing points to prevent bending of the guide element. The sliding bearing is preferably located on a side of the guide element facing away from the moving element.

[0018] However, it can also be advantageous if each guide element is spring-loaded in the direction of the moving element and / or in the direction of the actuator unit. This increases the contact pressure between the guide element and the moving element, or between the guide element and the actuator unit. In this way, the vibration behavior of the guide element or the static friction between the moving element and the guide element can be precisely controlled. Preferably, the spring force is applied to the guide element by a leaf spring and, if necessary, a sliding bearing.

[0019] It can be advantageous if the frame and / or the moving element has / have a mechanical interface that can be coupled to the mechanical interface of an identical linear drive, so that the travel paths of the coupled linear drives run in mutually perpendicular planes. In this way, a multi-axis adjustable arrangement can be modularly constructed from identical linear drives.

[0020] Another aspect of the present invention relates to an arrangement comprising two or three linear actuators according to one of the preceding embodiments, wherein the linear actuators are coupled to one another such that the travel paths of the coupled linear actuators extend in two or three mutually perpendicular planes. The coupling of the linear actuators is preferably accomplished via the mechanical interfaces according to the preceding embodiment.

[0021] Further preferred developments result from combinations of the features disclosed in the claims, drawings and description. Terms and definitions Linear actuator

[0022] The term linear actuator refers to a drive system that produces translational movement. The movement of the linear actuator can occur along a straight path or another predefined path. Adhesive sliding effect

[0023] The stick-slip effect (from the English words "stick" and "slip") describes the jerky sliding motion of solid bodies moving against each other and is known, among other sources, from US 5,786,654 A. According to the invention, the adjustment of the moving element along the guide elements by means of the stick-slip effect comprises a sticking phase in which the moving element engages with both guide elements by means of static friction, and a sliding phase in which the moving element moves relative to at least one guide element. Actuator or piezo actuator

[0024] The term actuator refers to a drive element that converts electrical signals into mechanical motion. An example of an actuator is a piezoelectric actuator. Brief description of the characters

[0025] They show: Fig. 1 a perspective view of an embodiment of the linear drive according to the invention. Fig. 2 a perspective exploded view of the linear drive according to Fig. 1. Fig. 3 in view (a) a top view of the linear drive according to Fig. 1 and in view (b) a section along line IIIb-IIIb from Fig. 3 (a). Fig. 4 a perspective view of the motion element of the linear drive according to Fig. 1. Fig. 5 different views of the linear drive's motion element according to Fig. 1, and in particular in view (a) a schematic side view with a viewing direction in the intended direction of movement of the moving element, in view (b) a side view with a viewing direction perpendicular to the intended direction of movement of the moving element and in view (c) a top view with a viewing direction perpendicular to the intended direction of movement of the moving element. Fig. 6 a perspective view of an arrangement A according to the invention, comprising two linear drives according to Fig. 1, whose motion elements are coupled to each other in such a way that the linear drives generate movements in two planes perpendicular to each other. Fig. 7 a perspective view of an arrangement B according to the invention, comprising the arrangement A according to Fig. 6 and another linear drive according to Fig. 1, whose frame is coupled to the frame of a linear drive of arrangement A in such a way that the three linear drives of arrangement B generate movements in a total of three planes perpendicular to each other. Fig. 8 a perspective view of a second embodiment of the linear drive according to the invention. Fig. 9 in view (a) a top view of the linear drive according to Fig. 8 and in view (b) a section along line IXb-IXb from Fig. 9 (a). Fig. 10 a perspective exploded view of the linear drive according to Fig. 8. Detailed description of the preferred embodiment

[0026] The linear drive 1 according to the preferred embodiment of the invention comprises an actuator unit consisting of a pair of piezoelectric multilayer actuators 3a, 3b, each with a guide element 4a, 4b attached thereto in the form of a cylindrical rod 4a, 4b made of structural ceramic, which are arranged in parallel in a frame 2.

[0027] The frame 2 is constructed from a cuboid base part 2a and an approximately equal-sized, cuboid counterpart 2b. The base part 2a and the counterpart 2b are connected via two plate-shaped side parts 2c and 2d to form an approximately rectangular, circumferential frame 2 with a substantially cuboid outline, as shown, for example, in Fig. 2 can be seen.

[0028] The basic part 2a comprises on a Fig. 3 (a) On the visible upper surface and preferably also on a side surface facing away from the counterpart 2b, there are two engagement sections 2a1 designed as screw openings with a predetermined distance A1. The screw openings 2a1 function as a standardized interface to mechanically couple the linear drive 1 with another identical linear drive 1, so that the two linear drives 1 perform movements in two planes perpendicular to each other (X; Y). The frame 2 and its components are preferably made of plastic and / or metal and / or ceramic.

[0029] From two sides of the frame 2, a compressive force is exerted on the guide elements 4a, 4b and indirectly on the movement element 5 arranged between the two guide elements 4a, 4b via sliding bearing shells 2e, 2f by the side parts 2c, 2d, which are designed as leaf springs. The sliding bearing shells 2e, 2f are channel-shaped and each has a concave inner contour complementary to the cylindrical surface of the respective guide element 4a, 4b. The sliding bearing shells 2e, 2f support the guide elements 4a, 4b perpendicular to their direction of extension and movement and allow sliding movement of the guide elements 4a, 4b in their direction of extension and movement.This reduces or prevents bending of the guide elements 4a, 4b perpendicular to their extension and direction of movement caused by the spreading force of the intermediate movement element 5 and increases the contact pressure between the movement element 5 and each of the guide elements 4a, 4b.

[0030] The counterpart 2b preferably also has engagement sections (2a1) for coupling with an identical linear drive 1 corresponding to the base part 2a. On the side facing the base part 2a, the counterpart 2b includes a substantially cuboid projection in the center, to which a leaf spring 2g extending in one plane is attached. The two ends of the leaf spring 2g, which are opposite each other in the direction of extension, run parallel to the side of the counterpart 2b facing the base part 2a and serve as resilient bearing sections for the axial ends of the two guide elements 4a, 4b.

[0031] The two drive units of the piezoelectric linear actuator 1 are identical in construction and each consists of a piezoelectric actuator 3a, 3b and a guide element 4a, 4b coupled to it. The piezoelectric actuator 3a, 3b is constructed in layers and is approximately cube-shaped. The guide element 4a, 4b has a cylindrical shape with a diameter that essentially corresponds to the edge length of the cube-shaped actuator 3a, 3b. By applying an alternating electrical voltage to the piezoelectric actuator 3a, 3b, it deforms such that the coupled guide element 4a, 4b performs an oscillating movement along its axis of extension. The two guide elements 4a, 4b are aligned exactly parallel to each other and are set in motion synchronously by the associated actuators 3a, 3b.The end surfaces of the guide elements 4a, 4b, which are repelled by the actuators 3a, 3b, are each resiliently mounted on the counterpart 2b of the frame 2 by the leaf spring 2g and are pressed by the leaf spring 2g in the direction of the respective actuator 3a, 3b.

[0032] In the assembled state according to Fig. 1. The end of the actuator 3a that points away from the guide element 4a is fixedly connected to the base part 2a of the frame 2. In contrast, the end of the actuator 3b that points away from the guide element 4b can be movably mounted along the base part 2a of the frame 2. By sliding or pivotally mounting the actuator 3b on the base part 2a of the frame 2, jamming caused by tilting of the movement element 5 between the two guide elements 4a and 4b can be prevented.

[0033] In the present embodiment, the movement element 5 is approximately cuboid in shape. It comprises wedge-shaped recesses 5b on its two smallest side faces in the form of channel-shaped V-grooves extending along the respective guide elements 4a, 4b, as shown in Fig. 3 (b) are illustrated in detail, designed to receive the respective guide element 4a, 4b and to be guided by it in a stick-slip effect. On the two opposing inner surfaces of the wedge-shaped receptacle 5b, there are three annular contact sections 5c in the form of friction couplings 5c made of structural ceramic, which serve as friction elements and alternately slide and stick in a stick-slip effect on the associated contact surface of the respective guide element 4a, 4b. As shown in Fig. As illustrated in Figure 5(c), the cuboid shape of the moving element 5 is interrupted by two projections 5d, which extend along opposite sides of the moving element 5 in the intended direction of movement of the moving element 5. Between the Fig. 5 (c) Through holes or screw openings extend along the visible upper surface and the opposite underside of the moving element 5. These serve as engagement sections 5e, 5f for coupling the linear drive 1 with another identical linear drive 1. The diameters and distances of these engagement sections 5e and 5f are identical, but offset by 90°. Two identical linear drives 1 can be coupled to each other via these engagement sections 5e, 5f such that their travel paths along two axes (X, Y; cf. Fig. 5) run in two planes arranged perpendicular to each other.

[0034] To adjust the movement element 5 along the path between base part 2a and counterpart 2b, an alternating electrical voltage is applied to the actuator unit 3, causing both guide elements 4a, 4b to move synchronously and parallel to each other. The acceleration of the two guide elements 4a, 4b is sufficiently small during the initial engagement phase to maintain the static engagement between the movement element 5 and each of the two guide elements 4a, 4b, allowing the movement element 5 to follow the movement of the guide elements 4a, 4b. Consequently, the movement element 5 is advanced along a path. By changing the control voltage applied to the actuators 3a, 3b, the direction of movement of the guide elements 4a, 4b can be abruptly reversed, causing the movement element 5 to slide along the two guide elements 4a, 4b in a sliding phase.During the sliding phase, the inertial force of the moving element 5 is greater than the static friction force between the moving element 5 and the two guide elements 4a, 4b.

[0035] The engagement structure between the motion element 5 and the two guide elements 4a, 4b replaces a separate guide device, since both the guide elements 4a, 4b and the motion element 5 only have one translational degree of freedom, while the other two translational degrees of freedom and all rotational degrees of freedom of both guide elements 4a, 4b and the motion element 5 are locked.

[0036] The linear actuator 1 operates according to the inertial drive principle. To achieve movements with multiple degrees of freedom (DoF), several linear actuators 1 can be stacked on top of each other, as shown in the Fig. 6 and Fig. 7 is clearly illustrated.

[0037] In order A according to Fig. 6 Two linear drives 1 according to the invention are coupled to each other via respective engagement sections (5e, 5f) of the movement elements 5 such that the positioning paths of the two linear drives 1 (neglecting the thickness of the linear drives 1) run along two axes X, Y in two planes arranged perpendicular to each other.

[0038] In order B according to Fig. 7, which is based on Order A according to Fig. 6 is based on a further linear drive 1 according to the invention, with its base part (2a) coupled to the base part (2a) of a linear drive 1 of the arrangement A, so that the three linear drives 1 in total (neglecting the thickness of the linear drives 1) run along three axes X, Y, Z in three planes arranged perpendicular to each other.

[0039] With the linear drive 1 according to the invention, multi-axis adjustable precision positioning devices can be manufactured particularly easily and cost-effectively.

[0040] In the second embodiment of the linear drive 1 according to the invention, which is described below with reference to the Fig. As described in Figures 8 to 10, the frame parts 2a, 2b, and 2c, unlike in the first embodiment, are made in one piece and form a C-shaped frame element, which is connected to the strip- or plate-shaped side part 2d to form a rectangle or square. The C-shaped frame element 2a, 2b, and 2c is essentially rigid and inflexible, while the preload on the guide elements 4a, 4b, and the movement element 5 arranged between them is applied by the side part 2d, which is screwed to the C-shaped frame part 2a, 2b, and 2c, with the side part 2d acting as a leaf spring.

[0041] Also differing from the first embodiment, the leaf spring 2g for axially preloading the guide elements 4a, 4b in their direction of extension is designed as an H-shaped spring element, the two long legs of which extend in planes offset by 90° from each other, with the short leg located centrally between the long legs being bent by 90°. One long leg of the H-shaped spring element is screwed to the upper side of the frame part 2b via appropriately provided engagement sections or screw openings using bolts, while the part of the leaf spring 2g that preloads the guide elements 4a, 4b extends parallel to the inner side of the frame part 2b facing the actuators 3a, 3b.

[0042] The linear drives 1 according to the second embodiment according to the invention can be coupled in the same way as the linear drives 1 according to the first embodiment according to the invention in order to form multi-axis adjustable arrangements. In contrast to the first embodiment according to the invention, however, the linear drive 1 according to the second embodiment according to the invention has fewer individual parts overall and a more stable basic construction, so that the freedom of movement of the individual components, in particular of the two guide elements 4a, 4b, is further restricted and an even more precise positioning of the movement element 5 between the guide elements 4a, 4b can be achieved overall.

[0043] In the second embodiment according to the invention, similar elements are provided with the same reference numerals as in the first embodiment. To avoid repetition, a separate description of the identically functioning elements is omitted. Reference symbol list 1 Piezoelectric linear actuator 2 frames 2a Base part 2a1 Engagement section(s) or screw openings in the base part 2b counterpart 2c, d side panel(s) or leaf spring(s) 2e, f Coupling section(s) or sliding bearing shell(s) 2g leaf spring 3 actuator units 3a, b Actuator(s) 4a, b Guide element(s) 5 movement element 5a Body 5b Recording(s) 5c Contact section(s) 5d advantage 5e Engagement section(s) or screw openings in the moving element 5f Engagement section(s) or screw openings in the movement element A1 Distance between screw holes in the base part A2 Distance between screw openings in the moving element B Direction of movement of the guide elements

Claims

[1] Linear drive (1) comprising: an actuator unit (3) with at least one actuator (3a, 3b); two guide elements (4a, 4b) and a motion element (5), wherein the motion element (5) is adjustable by a movement generated by the actuator unit (3) due to a stick-slip effect along both guide elements (4a, 4b), characterized by , that the movement element (5) can be brought into engagement with each of the two guide elements (4a, 4b) by means of static friction due to the static sliding effect, wherein the movement element (5) and the guide elements (4a, 4b) are coupled in such a way that contact forces in different directions and symmetrically to a plane are generated between each guide element (4a, 4b) and the movement element (5) during the adhesion phase. [2] Linear drive (1) according to claim 1, characterized by, that the actuator unit (3) is designed to move both guide elements (4a, 4b) simultaneously and / or synchronously and / or along parallel motion paths. [3] Linear drive (1) according to any one of the preceding claims, characterized by , that the movement element (5) is engaged with each of the two guide elements (4a, 4b) by means of static friction in the stress-free state of the actuator unit (3a, 3b). [4] Linear drive (1) according to any one of the preceding claims, characterized by , that the actuator unit (3a, 3b) has two actuators (3a, 3b) which each drive one of the two guide elements (4a, 4b). [5] Linear drive (1) according to any one of the preceding claims, characterized by that each guide element (4a, 4b) and / or the motion element (5) has / have only one translational degree of freedom, preferably in parallel directions. [6] Linear drive (1) according to any one of the preceding claims, characterized by, that each guide element (4a, 4b) is designed as a cylinder and the path of movement of the guide element (4a, 4b) preferably extends along the cylinder axis. [7] Linear drive (1) according to any one of the preceding claims, characterized by , that the movement element (5) receives each guide element (4a, 4b) in its own trough-shaped receptacle, wherein the trough-shaped receptacle is preferably designed as a V-shaped groove which extends along the respective guide element (4a, 4b) and opens towards it. [8] Linear drive (1) according to any one of the preceding claims, characterized by , that the linear drive (1) has a preferably self-contained frame (2), wherein the frame preferably surrounds the actuator unit (3), the two guide elements (4a, 4b) and the movement element (5), wherein the frame particularly preferably has a cuboid outline. [9] Linear drive (1) according to any one of the preceding claims, characterized by , that each guide element (4a, 4b) is resiliently mounted relative to the frame (2) of the linear drive (1), preferably in and / or transverse to its direction of extension, preferably via at least one leaf spring (2c, 2d; 2g). [10] Linear drive (1) according to any one of the preceding claims, characterized by , that each guide element (4a, 4b) is slidably mounted on the frame (2) via a sliding bearing (2e, 2f). [11] Linear drive (1) according to any one of the preceding claims, characterized by , that each guide element (4a, 4b) is spring-loaded in the direction of the movement element (5) and / or in the direction of the actuator unit (3). [12] Linear drive (1) according to any one of the preceding claims, characterized by, that the frame (2) and / or the movement element (5) has / have a mechanical interface which can be coupled to the mechanical interface of an identical linear drive (1), such that the positioning paths (X, Y, Z) of the coupled linear drives run in planes perpendicular to each other. [13] Arrangement comprising two or three linear actuators (1) according to any one of the preceding claims, characterized by , that the linear drives (1) are coupled to each other in such a way that the travel paths (X, Y, Z) of the coupled linear drives run in two or three mutually perpendicular planes.

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