ELECTROMECHANICAL SPINDLE DRIVE

Description

[0001] The invention relates to an electromechanical spindle drive comprising a housing, a rotation unit with a spindle nut which can be rotated about a rotation axis by means of a motor; and a spindle which has a threaded section cooperating with the rotation unit and which can be axially adjusted by means of the rotation unit by means of the rotation unit, so that the spindle can be adjusted vice versa from a spindle exit end of the rotation unit, wherein several rolling elements for bearing the spindle are arranged between an adjusting thread of the rotation unit and the threaded section and the adjusting thread in an effective section of the rotation unit has a limiting outer diameter radial to the rotation axis for guiding the rolling elements.

[0002] From EP2334450B1, an electromechanical actuator for press brakes is disclosed, comprising an outer housing body and a leadscrew positioned in the housing body, the leadscrew having an internal threaded surface. Furthermore, the actuator has a shaft capable of being connected to a press brake tool and having a thread that is internally operationally connected to the leadscrew; and motor means positioned in the outer body to rotate the leadscrew about its own longitudinal axis, the rotation of the leadscrew causing the axial displacement of the shaft.Furthermore, at least one connecting rod is provided to dampen the axial loads acting on the shaft, as well as means for transferring the axial loads from the shaft to the connecting rod, the connecting rod being positioned at a connection section of the housing body to be connected to a holding flange of a press brake in order to transfer the loads directly to the connection section and the flange. US 6,453,761 B1 discloses a linear actuator with a ball screw and a nut driven by an electric motor. The actuator comprises an enclosing motor housing with a front and a rear wall having axially oriented openings for the free passage of the ball screw, and an externally rotating electric motor integrated into the housing, comprising a radially inner, hollow stator assembly and a radially outer rotor assembly.

[0003] A disadvantage of such electromechanical drives from the prior art is that, despite the ball guides and recirculating elements, they still do not exhibit optimal adjustment movements with regard to starting behavior without load and positioning behavior under load with respect to the spindle relative to its rotating parts.

[0004] The object of the present invention was to overcome the disadvantages of the prior art and to provide an electromechanical spindle drive that ensures improved starting behavior and yet enables precise positioning of an actuator.

[0005] This problem is solved by an electromechanical spindle drive according to claim 1. The dependent claims describe advantageous embodiments of the invention.

[0006] The electromechanical spindle drive according to the invention is characterized in that, like the rotating unit, it has a receiving section arranged away from the spindle exit end, which is designed to partially receive the threaded section of the spindle with the roller elements. The diameter of the receiving section is dimensioned larger than the outer diameter to limit the roller elements radially to the axis of rotation, so that the roller elements have radial mechanical play between the threaded section and the receiving section of the rotating unit. In this way, the receiving section can be used as a "parking position" for the roller elements, with the roller elements being largely unloaded in the area of ​​the receiving section between the spindle and the rotating unit. Thus, it can be provided that the roller elements are essentially (at least radially) unloaded over the entire receiving section.

[0007] The design according to the invention has the advantage that the spindle can be moved particularly smoothly when starting from or returning to its starting position and exhibits significantly better stick-slip behavior, or requires less breakaway force to set the spindle in motion. Likewise, this results in significantly less resistance from the roller elements when returning to the starting position, making the adjustment by the electric motor more energy-efficient.

[0008] The production of the rotary unit or the spindle nut is also significantly simpler and cheaper, since the adjusting thread only needs to be manufactured up to the receiving section, and the receiving section itself can be manufactured with larger tolerances or with simpler and more economical methods.

[0009] Furthermore, the system stroke can be shifted towards the spindle exit end using the inventive measure, since the spindle of the spindle drive is generally not operated under load in the area of ​​the receiving section, thus enabling greater stroke distances of the system. The realization of an adjusting thread requires precise manufacturing processes, which are axially limited with respect to the thread lengths during the cutting and grinding operations for producing the adjusting thread. Due to the axial extension provided by the receiving section, the overall length of the system can therefore be increased. For example, a stroke system with a stroke length of 230 to 250 mm can be increased to 430 to 450 mm.

[0010] Depending on the exact embodiment, the receiving section can preferably be formed by turning and does not require any further special process steps for its manufacture.

[0011] At this point, it should be mentioned that it is known from the prior art that such mounted rolling elements generally exhibit a certain amount of play with respect to rotation relative to their bearings and also due to their tolerances. However, the mechanical play according to the invention refers to an additional, extended play between the spindle and the rotating unit by means of the rolling elements, which is designed such that the rolling elements in the receiving section can be relieved of at least radial loads relative to the working section. Preferably, only those rolling elements located in the working section can be subjected to radial loads relative to the spindle bearings, while the rolling elements in the receiving section exhibit the play according to the invention.

[0012] One possible embodiment provides that the receiving section is hollow cylindrical, with the diameter being formed by an inner surface of the hollow cylindrical receiving section. This design allows the rolling elements in the receiving section to be guided only by the threaded section of the spindle and to be freely movable relative to the rotating unit, thus enabling a particularly smooth-running bearing design and weight reduction. Furthermore, the hollow cylindrical section offers the additional advantage of improved lubricant application and distribution within the receiving section, as the lubricant can flow freely between the rolling elements.

[0013] Another possible embodiment provides that the receiving section has an internal thread, the diameter of which is defined by the thread diameter of the internal thread. An advantage of this embodiment is that the rolling elements can be guided uniformly with respect to their movement within the receiving section or transferred into the adjusting thread, while still exhibiting radial play due to the larger thread diameter. Thus, the internal thread of the receiving section can essentially mimic the adjusting thread with respect to its thread pitch, differing only in its radial diameter.

[0014] Furthermore, it may also be provided that a thread is formed in the receiving section, which is dimensioned axially with respect to its thread pitch such that two rolling elements can be received one above the other axially within its thread pitch, or two thread pitches of the thread section of the spindle can be received in one thread pitch of the receiving section.

[0015] An advantageous further development provides that the difference between the diameter and the outer diameter, or the mechanical clearance, is 0.025 to 0.35 mm, preferably 0.05 mm to 0.2 mm, and particularly 0.1 mm to 0.15 mm. This ensures largely precise bearing and guidance of the rolling elements while simultaneously relieving stress on them in the receiving section. The outer diameter of the thread can preferably be in the range of approximately 100 mm to 140 mm, and the ball diameter of the rolling elements approximately 10 to 16 mm.

[0016] In a further development, it can be provided that the height of the receiving section along the axis of rotation is selected such that the threaded section can be received within the receiving section and simultaneously supported in the working section of the adjusting thread by means of the rolling elements radially to the axis of rotation at an angle of at least 270°. This design offers the advantage that the receiving section can be made as large as possible while still allowing the spindle to be supported by the rolling elements in the working section via at least four contact points offset by 90°, thus ensuring the spindle's alignment with the axis of rotation.

[0017] One possible embodiment provides that, along the axis of rotation, the height of the receiving section corresponds to the length of the threaded section minus at least one pitch of the threaded section. In this way, the spindle can be supported or received by means of at least one circumferential arrangement of the rolling elements relative to the effective section of the adjusting thread.

[0018] Furthermore, it may be provided that a coating is provided in the receiving section facing the rolling elements, wherein the coating has at least one of the following properties; a higher thermal conductivity than the material of the adjusting thread; a lower coefficient of friction than the material of the adjusting thread.

[0019] The advantages of this measure include improved cooling of the rolling elements due to the higher thermal conductivity, as well as even better stick-slip behavior, or smoother operation of the rolling elements and the spindle relative to the rotating unit due to the lower coefficient of friction. Furthermore, the layer can also have a lower hardness.

[0020] An advantageous embodiment provides that a plastic housing for receiving the roller elements is arranged in the receiving section. Preferably, the diameter is formed by means of the plastic housing. The plastic housing can, in turn, have an internal thread or a hollow cylindrical shape. A significant advantage of the plastic housing is noise reduction as well as weight and cost savings. Particularly preferably, the plastic housing can extend over the entire length or height of the receiving section. A further advantage is the design freedom of the plastic housing, as it can, for example, be freely formed and then inserted into the rotating unit, or it can be molded onto it, for example by extrusion.

[0021] One embodiment provides that at least one lubricant channel is included in the receiving section. The lubricant channel preferably opens into the receiving section leading to the rolling elements. A first opening of the lubricant channel for introducing the lubricant can be located at an upper end of the rotating unit, facing away from the spindle exit end. The lubricant channel can particularly preferably be formed within a previously mentioned plastic housing.

[0022] A preferred embodiment provides that, with respect to the axis of rotation, a second end of the rotating unit is formed axially by means of the receiving section with respect to the adjustment of the spindle. Thus, the effective section of the adjusting thread is arranged only between the receiving section and the spindle exit end, and the receiving section can therefore form an end position with respect to the adjustment of the spindle.

[0023] An alternative embodiment provides that, along the axis of rotation, opposite the spindle exit end, a further portion of the working section of the adjusting thread is arranged after the receiving section, so that the receiving section is positioned between subsections of the adjusting thread with respect to the axis of rotation. For example, it can be provided that, upon reaching an end position opposite the spindle exit end, the rolling elements re-enter a portion of the working section of the adjusting thread, thus enabling the threaded section of the spindle to be guided at two end regions of the receiving section.

[0024] Furthermore, the aforementioned problem is solved by a forming machine, in particular a bending machine, for forming a workpiece, preferably plate-shaped; at least one electromechanical drive, at least one forming tool whose working movement is effected by the electromechanical drive, wherein the electromechanical drive comprises a spindle drive according to the invention.

[0025] A forming machine with a spindle drive according to the invention also has the advantages mentioned at the outset, which ensures improved start-up behavior of the forming machine as well as energy-efficient operation.

[0026] In forming machines, usually only the lower range of the spindle drive, i.e., the maximum stroke, is used for the forming processes, as in a bending machine, with the remaining stroke being used to open the working area for handling the components. In these areas, a larger spindle stroke range is usually required, but there is no application under load (in the form of forming). This makes the spindle drive design according to the invention advantageous, as the spindle drive is better suited for such working movements and still exhibits precise pressing behavior in the stroke range for the forming process.

[0027] To better understand the invention, it is explained in more detail with reference to the following figures.

[0028] They each show, in a highly simplified, schematic representation: Fig. 1 an electromechanical spindle drive; Fig. 2 an embodiment of the rotary unit with an internal thread; Fig. 3 an embodiment with a hollow cylindrical receiving section; Fig. 4 an oblique view of a rotary unit with a spindle; Fig. 5 the rotary unit according to Fig. 4 in sectional view; Fig. 6 a further embodiment of a rotary unit; Fig. 7 a forming machine with a spindle drive according to the invention.

[0029] It should be noted at the outset that in the differently described embodiments, identical parts are provided with the same reference numerals or component designations, and the disclosures contained in the entire description can be applied analogously to identical parts with the same reference numerals or component designations. Furthermore, the positional designations chosen in the description, such as top, bottom, side, etc., refer to the figure directly described and illustrated, and these positional designations must be applied analogously to the new position if the position changes.

[0030] Fig. 1Figure 1 shows an electromechanical spindle drive 1 comprising a housing 2, a motor 3, and a rotation unit 4, which can be rotated about a rotation axis R by the motor 3. The rotation unit 4 is designed in the form of a spindle nut or at least includes a spindle nut. A spindle 5 interacts with the rotation unit 4. The threaded section 6, or an external thread, of the spindle 5 is received within the rotation unit 4 and interacts with the adjusting thread 8 of the spindle nut of the rotation unit 4 via rolling elements 9. The spindle 5 exits the rotation unit 4 at a spindle exit end 7.

[0031] The motor 3 has a stator 25, which is mounted, for example, on the inside of the housing 2 (e.g., in the form of windings), and a rotor 26, which is connected to the rotating unit 4 and / or arranged directly on the rotating unit 4 (e.g., in the form of permanent magnets). It is preferred that the stator 25 of the motor 3 surrounds the rotating unit 4. The rotor 26 of the motor 3 can include pole elements, preferably in the form of permanent magnets, which are preferably removable and attached to the outside of the rotating unit 4. The motor 3 is preferably a synchronous motor.

[0032] According to the invention, the rotation unit 4 has a receiving section 12 arranged facing away from the spindle exit end 7, wherein the receiving section 12 is provided along the axis of rotation R for the partial receiving of the threaded section 6 of the spindle 5 with the rolling elements 9, and a diameter 13 of the receiving section 12 for limiting the rolling elements 9 radially to the axis of rotation R is dimensioned larger than the outer diameter 11, so that the rolling elements 9 have a mechanical clearance 14 radially between the threaded section 6 and the receiving section 12 of the rotation unit 4.

[0033] The spindle drive 1 can also have bearings 27, 28 and 29, by means of which the rotary unit 4 is rotatably mounted relative to the housing 2. As shown in Fig. 1As can be seen, at least one – preferably at least two – of the bearings 27 can be arranged in the region of the spindle exit end 7 of the rotating unit 4 and / or be designed in the form of a radial bearing. This is preferably a rolling bearing, in particular a ball bearing.

[0034] In a preferred embodiment of the Fig. 1 At least one bearing 27 is arranged within the rotating unit 4 – as shown, on an inner surface of the rotating unit 4 – in the region of the spindle exit end 7 of the rotating unit 4. It is located between the inner surface of the rotating unit 4 and a bearing receptacle 30 projecting into the interior of the rotating unit 4, which is formed on a housing part, preferably an end cover, of the housing 2.

[0035] Out of Fig. 1It can also be seen that at least one bearing 27, located in the region of the spindle exit end 7 of the rotating unit 4, can be arranged axially overlapping with the stator 25 and / or the rotor 26 of the motor 3. In other words, the bearings 27 are arranged within a region enclosed by the stator 25 and / or rotor 26 of the motor 3.

[0036] In the area of ​​the end of the rotation unit 4 opposite the spindle exit end 7, a radial bearing 29 can be arranged, by which the rotating part is supported relative to the housing part 2.

[0037] An axial bearing 28 may also be provided, preferably in the area between the motor 3 and a possible braking device 31.

[0038] The electromechanical spindle drive 1 preferably comprises a braking device 31 that can be actuated between a brake position and a released position and is arranged in the region of the end of the rotation unit 4 opposite the spindle exit end 7. Furthermore, the braking device 31 can have a brake disc 32 that rotates with the rotation unit 4 and an axially adjustable brake element 33 that acts on the brake disc 32 in the brake position.

[0039] As from the Fig. 1 As can be seen, the inner area of ​​the brake disc 32 can be axially fixed to the rotating unit 4. In the illustrated embodiments, the inner area of ​​the brake disc 32 is rigidly connected to the rotating unit. This is achieved by means of screws that protrude through the holes and press the brake disc against the rotating unit 4.

[0040] The brake element 33 can be pre-tensioned in the direction of the braking position, e.g. by a plurality of springs arranged in a ring shape and preferably overlapping.

[0041] The braking device 31 can comprise an actuator 34, preferably in the form of an electromagnet, by which the braking element 33 can be moved into the released position and / or into the braking position. The actuator 34 can be installed in a removable housing part of the electromechanical spindle drive.

[0042] Out of Fig. 1It is evident that the spindle drive is a roller spindle drive in which rolling elements 9, in particular in the form of balls, are guided in a circulating path. A first section of the circulating path is located between the rotating unit 4 and the threaded section 6 of the spindle 5, and a second section is formed by a return channel 35. The return channel 35 can be formed inside the spindle 5, as in the illustrated embodiment.

[0043] As shown, an attachment part 36 can be connected to the rotating unit 4 at the end opposite the spindle exit end 7. Preferably, the attachment part 36 has a section located within the rotating unit 4 and / or forms a stop for the spindle 5. A section of the attachment part 36 located outside the rotating unit 4 can be in the form of a pin, the longitudinal axis of which coincides with the axis of rotation R of the rotating unit 4. The maximum diameter of the section of the attachment part 36 located inside the rotating unit 4 is preferably at least three times, and preferably at least four times, the diameter of the pin-shaped section.The section of the attachment part 36 located outside the rotation unit 4 can preferably be within the detection range of a sensor device 37, which is preferably a rotary encoder that detects the rotation of the attachment part 36 or the rotation unit.

[0044] The attachment part 36 may have an opening 38 for supplying lubricant to the interior of the rotating unit 4. The course of a first section of the channel – preferably in a section of the attachment part 36 located outside the rotating unit 4 – may be aligned with the axis of rotation R of the rotating unit 4.

[0045] The path of a second section of the opening 38 has a radial component with respect to the axis of rotation R and / or is oblique to the axis of rotation R. The second section of the opening 38 runs in a section of the attachment part 36 located within the rotating unit 4 or ends at an exit point which is arranged in a peripheral region of the attachment part 36 with respect to the axis of rotation R.

[0046] In the illustrated embodiment, the attachment part 36 is surrounded by the braking device 31 of the spindle drive 1. The attachment part 36 can lie within a central recess of the brake disc 32 and even form a preferably positive-locking receptacle for the brake disc 32, thus performing a centering function for the brake disc.

[0047] Cooling fins (e.g. removable) may be arranged on the outside of the housing 2 - at least in the area of ​​the motor 3.

[0048] The spindle drive 1 can be modularly designed, allowing a spindle drive component set to be provided for the manufacture and / or adaptation of spindle drives. Such a component set comprises components for several electromechanical spindle drives. It includes components of various types, and these components have connection interfaces for linking them together. Components of the same type have different sizes, but the connection interfaces of differently sized components of the same type are dimensioned identically.

[0049] In one example, the component set includes First housing parts of different length and / or width and second housing parts of different length and / or width on, wherein the connection interfaces of the first housing parts for connection with the second housing parts are dimensioned the same for all first housing parts and for all second housing parts.

[0050] In one example, the component set includes Rotary units of different lengths and / or widths, housing parts of different lengths and / or widths, and / or motors of different lengths and / or widths on, wherein the connection interfaces of the rotary units for connection with the housing parts and / or motors are dimensioned the same for all rotary units and / or wherein the connection interfaces of the housing parts and / or motors for connection with the rotary unit are dimensioned the same for all housing parts and / or motors.

[0051] In Fig. 2 and 3 Possible embodiments of the receiving section 12 are shown.

[0052] The receiving section 12 can have an internal thread 16 which has the larger diameter 13 for limiting the rolling elements 9, or which is formed by its thread diameter, as in Fig. 2depicted.

[0053] The internal thread 16 can have a trapezoidal cross-section, as shown in the right-hand figure in Fig. 2 , particularly as shown in the accompanying detailed view. Alternatively, this cross-section can also be rectangular or triangular, with the diameter 13 corresponding at least to the radial distance with respect to which the rolling elements 9 are radially limited.

[0054] As mentioned at the beginning, this can bring particular manufacturing and economic advantages, or also optimal axial guidance of the rolling elements with a mechanical clearance 14, which is primarily radial.

[0055] In the left-hand illustration in Fig. 2The thread form is round (as also shown in detail) and can be produced, for example, with a correspondingly shaped turning tool, whereby the internal thread is preferably manufactured with a larger diameter than the adjusting thread. An axial clearance is preferably less than 0.05 mm, in particular 0.01 mm to 0.03 mm.

[0056] As also shown, along the axis of rotation R, a height 17 of the receiving section 12 can correspond to a length 18 of the threaded section 6 minus at least one pitch 20 (also known as thread height) of the threaded section 6.

[0057] This results in the spindle 5 being received in the receiving section 12 at least one thread of the thread section 6, i.e. a radial arrangement of the rolling elements 9 by at least 360° to the axis of rotation R, being located in the effective section 10 of the adjusting thread 8 and the spindle 5 being centered and guided by the rolling elements 9 in at least one revolution with respect to the thread with this area.

[0058] Depending on the type and arrangement of the guide for the roller elements 9, as in Fig. 1While depicted with a return channel within the spindle, the rolling elements can also have multiple return or circulation systems and be subdivided into these systems. For example, if two circuits of the rolling elements 9 are provided and a recess is provided between the circuits, then a larger contact area in the working section can be provided for the correct bearing of the spindle, e.g., corresponding to twice the thread pitch. Furthermore, a pre-tensioned arrangement of individual groups of the circulating rolling elements can also be provided, as is known from the prior art, for which the receiving section would have to be adapted accordingly.

[0059] Furthermore, regardless of the embodiment of the receiving section 12, a plastic housing 22 for receiving the roller elements 9 can be provided, as shown in dashed lines in Fig. 2 and 3 as indicated.

[0060] Furthermore, the receiving section 12, regardless of its embodiment, can at least partially have a coating 21. The coating 21 preferably has at least one material property that differs from that of the adjusting thread 8, comprising: a higher thermal conductivity than the material of the adjusting thread 8 and / or a lower coefficient of friction or higher sliding properties.

[0061] At this point, it should be mentioned that if such a coating 21 or a previously mentioned plastic housing 22 is provided, the diameter 13 of the receiving section 12 can be defined by these elements, and thus the rolling elements are radially limited by these elements. Furthermore, the plastic housing can also have the coating.

[0062] For example, the receiving section 12 can first be formed in a wooden cylindrical shape, with the plastic housing 22 being inserted into the cylindrical shape and the plastic housing having, for example, the internal thread for the receiving section 12, as well as the diameter for limiting the rolling elements.

[0063] Furthermore, a lubricant channel 23 for introducing lubricant can be provided in the rotating unit 4 or in the receiving section 12, wherein the lubricant channel 23 preferably opens into the receiving section 12 in its receiving area for the rolling elements. As in Fig. 2 As indicated, the lubricant channel 23 can be used to convey the lubricant introduced via the opening 38 to Fig. 1 be formed which can preferably be displaced radially outwards into the channel due to rotation.

[0064] As in Fig. 3As further indicated, the lubricant channel 23 can also be formed in the plastic housing 22, which allows for a simplified introduction of such a channel when inserting the plastic housing, as well as enabling a significantly more complex design of the channel.

[0065] Recording section 12 after Fig. 3 The device is designed in the form of a hollow cylinder, with the diameter 13 being formed by an inner surface 15 of the hollow cylinder. In this embodiment, the rolling elements 9 can be axially free to move relative to the spindle nut from the point of entry into the receiving section 12 and are limited in this respect only by the threaded section 6 of the spindle 5 in the axial direction (i.e., along the axis of rotation R). The hollow cylindrical receiving section 12 can in turn have a coating as described above.

[0066] Furthermore, in Fig. 3A guide aid 39 is indicated, which can be provided to facilitate the insertion of the roller elements 9 into the working section 10 of the adjusting thread 8. The guide aid 39 is preferably formed on the inner side of the receiving section 12 facing the roller elements and can have the form of a ramp, a step, a radial projection or the like.

[0067] As from the Figs. 4 and 5 It can be seen that along the axis of rotation R the height 17 of the receiving section 12 is selected such that the threaded section 6 can be received in the receiving section 12 with respect to its length 18 and is simultaneously mounted in the working section 10 of the adjusting thread 8 radially to the axis of rotation R by means of the rolling elements 9 at an angle 19 of at least 270° (or a 3 / 4 turn).

[0068] In this embodiment, the spindle 5 is centrally mounted in one end of the working section by means of at least one radial 4-point contact support of the roller elements 9, so that they are arranged offset by 90° to each other in the area of ​​the angle.

[0069] In Fig. 4 Part of the rotation unit 4 is removed, as well as a majority of the roller elements, so that the 4-point support of the roller elements 9 is visible, as is also shown in Fig. 5 as indicated.

[0070] In Fig. 6Figure 1 schematically illustrates an embodiment of the rotation unit 4, in which a further part 10b of the working section 10 of the adjusting thread 8 is arranged along the axis of rotation R opposite the spindle exit end 7 after the receiving section 12, such that the receiving section 12 is arranged between partial regions of the working section 10a, 10b of the adjusting thread 8 with respect to the axis of rotation R. Thus, the adjusting thread 8 forms the second end 24 of the rotation unit 4 with respect to the axial adjustment of the spindle with respect to the axis of rotation R.

[0071] The height 17 of the receiving section 12 can be chosen such that the difference corresponds to at least one thread pitch of the adjusting thread, relative to the length 18 of the threaded section 6. Furthermore, it can be provided that the spindle 5 is supported at least in the aforementioned 4-point support, over an angle of 270°, relative to the effective section 10a, 10b of the adjusting thread 8.

[0072] In the Figures 2 to 6 Further and potentially independent embodiments of the rotating unit 4 are shown, whereby the same reference numerals or component designations are used for identical parts as in the preceding figures. To avoid unnecessary repetition, reference is made to the detailed description in the preceding figures.

[0073] Furthermore, the one in the Figures 1 to 6The spindle is shown in its upper end position or starting position, and the roller elements are shown in their respective positions in the sectional views. It should be noted that when the spindle is adjusted along the axis of rotation, the roller elements are positioned along with the spindle in the respective position of the threaded section relative to the current adjustment position and are axially limited or carried along by the spindle.

[0074] Fig. 7Finally, Figure 1 shows a forming machine 40 in the form of a press brake for forming a preferably plate-shaped workpiece 41, with at least one drive for the working movement (of a forming tool), in particular a press drive. The drive(s) are designed as electromechanical drive(s) 1 according to the invention. Such a forming machine can comprise a first (e.g., upper) tool carrier 42 (for holding at least one first forming tool 43) and a second (e.g., lower) tool carrier 44 (for holding at least one second forming tool 45), the relative movement of which is the working movement. As shown in Figure 1, the tool carrier can be configured as follows: Fig. 7 As shown, the second tool carrier 44 is stationary, while the first tool carrier 42 is movable by the drive(s) 1.

[0075] The forming machine usually only loads the spindle of the spindle drive when the stroke lengths are (almost) fully extended, which makes load-free bearing in the receiving section and smooth operation of the spindle in this area particularly advantageous.

[0076] The exemplary embodiments show possible embodiment variants, whereby it should be noted at this point that the invention is not limited to the specifically illustrated embodiment variants, but rather various combinations of the individual embodiment variants are also possible and this possibility of variation lies within the skill of the person skilled in this technical field due to the teaching on technical action by the present invention.

[0077] All references to value ranges in this description are to be understood as encompassing any and all sub-ranges thereof, e.g., the reference 1 to 10 is to be understood as including all sub-ranges, starting from the lower limit 1 and the upper limit 10, i.e., all sub-ranges begin with a lower limit of 1 or greater and end with an upper limit of 10 or less, e.g., 1 to 1.7, or 3.2 to 8.1, or 5.5 to 10.

[0078] Finally, for the sake of clarity, it should be noted that, for a better understanding of the structure, some elements have been shown not to scale and / or enlarged and / or reduced in size. Reference numeral list

[0079] 1 Electromechanical spindle drive 30 Storage 31 Braking system 2 Housing 32 brake disc 3 Motor 33 Brake element 4 Rotary unit 34 actuator 5 spindle 35 Return channel 6 Threaded section 36 attachment part 7 Spindle exit end 37 Sensor device 8 Adjusting thread 38 breakthrough 9 Rolling elements 39 Guidance aid 10 Effective section 40 forming machine 11 Outer diameter 41 workpiece 12 Recording section 42 first tool carrier 13 diameter 43 first forming tool 14 mechanical game 44 second tool carrier 15 Inner surface of the mantle 45 second forming tool 16 internal thread 17 Height 18 length 19 angle 20 gradient 21 coating 22 plastic housing 23 Lubricant channel 24 second ending 25 stator 26 rotor 27 Storage 28 Storage 29 Storage

Claims

1. An electromechanical spindle drive (1), comprising - a housing (2); - a motor (3); - a rotation unit (4) with a spindle nut, wherein the rotation unit (4) can be set in rotation about an axis of rotation (R) by means of the motor (3); - a spindle (5), wherein the spindle (5) has a threaded section (6) which interacts with the rotation unit (4) and is axially adjustable relative to the axis of rotation (R) by means of the rotation unit (4), such that the spindle (5) can be adjusted back and forth from a spindle exit end (7) of the rotation unit (4); wherein multiple rolling elements (9) for supporting the spindle (5) are arranged between an adjustment thread (8) of the rotation unit (4) and the threaded section (6); and the adjustment thread (8), radially to the axis of rotation (R) in an effective section (10) of the rotation unit (4), has an outer diameter (11) for guiding the rolling elements (9), and wherein the rotation unit (4) comprises a receiving section (12) arranged facing away from the spindle exit end (7), wherein the receiving section (12) is provided along the axis of rotation (R) to partially receive the threaded section (6) of the spindle (5) together with the rolling elements (9), characterized in that a diameter (13) of the receiving section (12) for confining the rolling elements (9) is dimensioned to be larger, radially with respect to the axis of rotation (R), than the outer diameter (11), such that the rolling elements (9) have a mechanical clearance (14) radially between the threaded section (6) and the receiving section (12) of the rotation unit (4).

2. The electromechanical spindle drive (1) according to claim 1, characterized in that the receiving section (12) is formed hollow-cylindrically, wherein the diameter (13) is defined by an inner lateral surface (15) of the hollow cylindrical receiving section (12).

3. The electromechanical spindle drive (1) according to claim 1, characterized in that the receiving section (12) has an internal thread (16), wherein the diameter (13) is formed by a thread diameter of the internal thread (16).

4. The electromechanical spindle drive (1) according to one of claims 1 to 3, characterized in that the difference between the diameter (13) and the outer diameter (11) is 0.05 mm to 0.2 mm, in particular 0.1 mm to 0.15 mm.

5. The electromechanical spindle drive (1) according to one of claims 1 to 4, characterized in that, along the axis of rotation (R), a height (17) of the receiving section (12) is selected such that the threaded section (6) can be received within the receiving section (12) and, at the same time, is supported within the effective section (10) of the adjustment thread (8) by means of the rolling elements (9) radially to the axis of rotation (R) at an angle (19) of at least 270°.

6. The electromechanical spindle drive (1) according to one of claims 1 to 5, characterized in that, along the axis of rotation (R), a height (17) of the receiving section (12) corresponds to a length (18) of the threaded section (6) minus at least one pitch (20) of the threaded section (6).

7. The electromechanical spindle drive (1) according to one of claims 1 to 6, characterized in that a coating (21) is provided in the receiving section (12) facing the rolling elements (9), wherein the coating (21) has at least one of the following properties: - a higher thermal conductivity than a material of the adjustment thread (8), - a lower friction coefficient than the material of the adjustment thread (8).

8. The electromechanical spindle drive (1) according to one of claims 1 to 7, characterized in that a plastic housing (22) for receiving the rolling elements (9) is arranged in the receiving section (12).

9. The electromechanical spindle drive (1) according to one of claims 1 to 8, characterized in that at least one lubricant channel (23) is provided in the receiving section (12).

10. The electromechanical spindle drive (1) according to one of claims 1 to 9, characterized in that, with respect to the axis of rotation (R), a second end (24) of the rotation unit (4) is formed axially by means of the receiving section (12) in relation to the adjustment of the spindle (5).

11. The electromechanical spindle drive (1) according to one of claims 1 to 9, characterized in that, along the axis of rotation (R), a further part of the effective section (10) of the adjustment thread (8) is arranged opposite the spindle exit end (7) and following the receiving section (12), such that the receiving section (12) is arranged between sub-sections of the adjustment thread (8) relative to the axis of rotation (R).

12. A forming machine, in particular a bending machine, for forming a workpiece, preferably in the form of a plate, comprising: - at least one electromechanical drive, - at least one forming tool, the working movement of which is effected by the electromechanical drive, characterized in that the electromechanical drive is a spindle drive (1) according to one of claims 1 to 11.