Actuator with traction drive of the threaded spindle

Abstract

Actuator (10) with a main housing (20), a cantilever (30) and a threaded spindle (41), wherein the threaded spindle (41) is mounted on the main housing (20) by means of a first pivot bearing (24) relative to a rotational axis (11), wherein the cantilever (30) projects displaceably from the main housing (20) in the direction of the rotational axis (11), wherein it is in screw engagement with the threaded spindle (41), wherein the main housing (20) comprises a housing main body (23) and a first end block (21), wherein the first pivot bearing (24) is accommodated in the first end block (21), wherein the threaded spindle (41) is in rotational drive connection with an electric motor (25) via a traction means (60), wherein the traction means (60) is surrounded by a separate traction means housing (61) which is fastened to the first end block (21), wherein the electric motor (25) is attached to the traction mechanism housing (61),wherein the threaded spindle (41) is rotatably mounted on the traction mechanism housing (61) with respect to the rotational axis (11) by means of a separate second pivot bearing (50), wherein the second pivot bearing (50) is arranged in the direction of the rotational axis (11) between the first end block (21) and the traction mechanism (60), wherein the threaded spindle (41) has a first external thread (42), wherein the threaded spindle (41) is in screw engagement with the boom (30) via the first external thread (42), characterized in that the threaded spindle (41) has a second external thread (43), wherein the first pivot bearing (24) is fastened to the second external thread (43) by means of a first and a separate second clamping nut (81; 82), wherein the first clamping nut (81) comprises a sleeve-like portion (83) on which the first pivot bearing (24) is received.

Description

[0001] The invention relates to an actuator according to the preamble of claim 1.

[0002] DE 10 2013 211 617 A1 discloses an actuator designed as an electric cylinder. The actuator has a main housing from which a cantilever protrudes, movable along a rotational axis. The cantilever is driven by a threaded spindle, which is in screw engagement with the cantilever and is mounted on the main housing by a first pivot bearing for rotation relative to the rotational axis. The threaded spindle is connected to an electric motor via a traction mechanism for rotational drive. The traction mechanism is arranged in a separate traction mechanism housing, which is attached to a first end block of the main housing.

[0003] From JP 2000-266 149 A an actuator is known in which the threaded spindle is rotatably mounted with respect to the axis of rotation by means of a separate second pivot bearing on the traction mechanism housing, wherein the second pivot bearing is arranged in the direction of the axis of rotation between the first end block and the traction mechanism.

[0004] From GB 2 102 910 A an actuator is known whose traction mechanism housing comprises a separate cover.

[0005] A threaded spindle with a cooling bore is known from DE 10 2016 209 654 A1.

[0006] From JP 2012-225 461 A an actuator is known in which an outer ring of a rotary bearing is accommodated in the traction mechanism housing.

[0007] From DE 10 2017 219 848 A1 a threaded spindle is known on which a pivot bearing is fastened by means of a clamping ring.

[0008] Reference is also made to DE 10 2013 211 617 A1.

[0009] One advantage of the present invention is that the traction mechanism drive has a particularly long service life, particularly when a toothed belt is used as the traction mechanism. In particular, pretensioning of the traction mechanism can be absorbed by the actuator without individual components being overloaded. Furthermore, the threaded spindle can be manufactured from a blank which is provided with a first external thread over its entire length, which corresponds to the thread via which the threaded spindle is in screw engagement with the boom. This first external thread is preferably manufactured using the thread rolling process, with very long blanks preferably being produced in this process. This blank only needs to be weakened slightly to produce the bearing seat of the first pivot bearing. It should be noted here that a planetary screw drive is preferably used as the screw drive, in which very considerable forces act in the threaded spindle.

[0010] According to claim 1, it is proposed that the threaded spindle is rotatably mounted on the traction mechanism housing with respect to the axis of rotation by means of a separate second pivot bearing, wherein the second pivot bearing is arranged in the direction of the axis of rotation between the first end block and the traction mechanism. The traction mechanism is preferably a toothed belt. The separate, one-piece housing main body is preferably tubular, wherein it surrounds the threaded spindle and / or the boom in each case at least in sections. The housing main body preferably extends with a constant cross-sectional shape along the axis of rotation. The main housing can comprise a second end block, wherein the first and second end blocks are arranged in the direction of the axis of rotation at opposite ends of the housing main body. The second pivot bearing is preferably supported directly on the traction mechanism housing, in particular on its base body.The boom preferably has a separate nut at one end, which is in screw engagement with the threaded spindle. The screw engagement is preferably designed in the manner of a planetary screw drive.

[0011] Advantageous further developments and improvements of the invention are specified in the dependent claims.

[0012] It can be provided that the traction mechanism housing is composed of a one-piece base body and a separate plate-like cover, wherein the base body has a peripheral wall which surrounds the axis of rotation in a ring-like manner, wherein it has a bottom wall which is integrally connected to the peripheral wall, wherein the first end block is fastened to the bottom wall, wherein the second pivot bearing is accommodated in the bottom wall. The traction mechanism housing is thus designed to be particularly rigid. It can easily absorb the pretensioning force of the traction mechanism. The cover is preferably firmly connected to the peripheral wall, in particular screwed. The electric motor is preferably fastened at least indirectly to the base body, most preferably via a separate support plate which is arranged flush with the bottom wall and is fastened directly to the peripheral wall. The first end block is preferably fastened directly to the bottom wall.The peripheral wall preferably extends with a constant cross-sectional shape in the direction of the axis of rotation.

[0013] It can be provided that the base body comprises a stiffening wall which is integrally connected to the base wall, wherein the stiffening wall is firmly connected to the cover. The stiffening wall preferably extends with a constant cross-sectional shape in the direction of the axis of rotation. The stiffening wall is preferably screwed to the cover. The stiffening wall is preferably arranged within the annular peripheral wall, wherein it has two opposite ends transverse to the axis of rotation, which are arranged at a distance from the peripheral wall. The stiffening wall considerably increases the rigidity of the traction mechanism housing, so that it can absorb the pretensioning force of the traction mechanism without major deformation. As a result, the traction mechanism is subject to minimal wear.

[0014] It is provided that the threaded spindle has a first and a second external thread, wherein the threaded spindle is in screw engagement with the boom via the first external thread, wherein the first pivot bearing is fastened to the second external thread by means of a first and a separate second clamping nut, wherein the first clamping nut comprises a sleeve-like section on which the first pivot bearing is received. With this design of the bearing seat, the weakening of the threaded spindle can be reduced even further compared to the solution known from DE 10 2017 219 848 A1. The threaded spindle should be weakened as little as possible by accommodating the first pivot bearing. The threaded spindle should be able to be produced from a blank which is provided with the first external thread over its entire length. The first external thread can transition seamlessly into the second external thread.However, it is also conceivable that the first and the second external thread are designed differently from one another, wherein an outer diameter or a tip diameter of the second external thread is preferably only slightly smaller than an outer diameter of the first external thread.

[0015] It can be provided that the first clamping nut is in screw engagement with the second external thread via an internal thread, whereby the internal thread of the first clamping nut extends over the entire length of the sleeve-like section and can have at least one interruption. Due to the comparatively long internal thread, an inaccuracy in the internal thread has a comparatively small impact on the concentricity of the first pivot bearing. The optional interruption of the internal thread can prevent distortion during assembly of the first clamping nut.

[0016] It can be provided that the boom is in screw engagement with the first external thread via a planetary screw drive, wherein the second external thread is designed as a pointed thread with a thread pitch between 0.5 mm and 2.0 mm, wherein an outer diameter of the second external thread is between 90% and 100% of a core diameter of the first external thread. The threaded spindle therefore has almost the same strength in the area of ​​the second external thread as in the area of ​​the first external thread. The first external thread is preferably designed as a pointed thread with a thread pitch between 0.5 mm and 5.0 mm. The first external thread of a planetary screw drive typically has a shallow thread depth so that it can be largely completely removed to produce the second external thread without excessively weakening the threaded spindle.

[0017] A sealing ring can be provided which seals an interior of the main housing from the first pivot bearing, wherein the first clamping nut has a sealing surface running around the axis of rotation, against which the sealing ring bears in a sealing manner. Such a seal is particularly desirable when the interior of the main housing is at least partially filled with lubricating oil in order to cool and lubricate the planetary screw drive. With the above design, this seal can be provided in a simple and cost-effective manner. The threaded spindle is not weakened by the sealing surface. The sealing surface is preferably circular-cylindrical with respect to the axis of rotation. It can be provided on a separate sleeve which is firmly connected to the first clamping nut via a press fit. The sealing ring is preferably a radial shaft sealing ring.

[0018] It can be provided that the threaded spindle has a cooling bore extending along the axis of rotation, wherein the threaded spindle passes through the traction mechanism housing, wherein a rotary union is arranged outside the traction mechanism housing, which is firmly connected to the threaded spindle, wherein cooling fluid can be introduced into and / or discharged from the cooling bore via the rotary union. A comparable cooling of a threaded spindle is known, for example, from DE 10 2016 209 654 A1. The proposed arrangement of the corresponding rotary union on the actuator is particularly maintenance-friendly. The cooling fluid is preferably a liquid, which in particular contains water and / or oil.

[0019] The second pivot bearing can be a radial roller bearing whose inner ring is mounted on the threaded spindle so that it can slide in the direction of the rotation axis, while its outer ring is fixedly mounted in the traction mechanism housing. This simplifies the assembly of the traction mechanism housing with the second pivot bearing to the remaining actuator with the threaded spindle. Furthermore, distortion of the second pivot bearing is avoided. The second pivot bearing is preferably designed as a radial deep groove ball bearing.

[0020] It is understood that the features mentioned above and those to be explained below can be used not only in the combination specified in each case, but also in other combinations or on their own, without departing from the scope of the present invention.

[0021] The invention is explained in more detail below with reference to the accompanying drawings. They show: Fig. 1 a perspective view of an actuator according to the invention; Fig. 2 a longitudinal section of the actuator according to Fig. 1; Fig. 3 another perspective view of the actuator according to Fig. 1, with the traction mechanism housing visible without the cover; and Fig. 4 an enlarged section of Fig. 2 in the area of ​​the first end block.

[0022] Fig. 1 shows a perspective view of an actuator 10 according to the invention. The actuator 10 comprises a main housing 20, which is elongated along a rotational axis 11. A boom 30 protrudes from the main housing 20 in the direction of the rotational axis 11 and is movable along the rotational axis 11 by means of the drive motor 25. The drive motor 25 is preferably an electric motor that is rotary-driven to a threaded spindle via a traction mechanism 60, for example, a toothed belt. The traction mechanism 60 is surrounded by a traction mechanism housing 61, which is composed of a base body 70 and a plate-like cover 62, which are firmly connected to one another by means of screw bolts 63. The base body 70 is firmly connected to the first end block 21 of the main housing 20, for example, by means of screws.

[0023] The main housing 20 comprises a housing main body 23, which is made, for example, from aluminum using an extrusion process. The housing main body 23 is tubular, extending with a constant cross-sectional shape along the rotation axis 11. The main housing 20 comprises a first and a second end block 21; 22, which are fastened in the direction of the rotation axis 11 to opposite ends of the housing main body 23, preferably by means of screws. The second end block 22 forms a linear plain bearing for the boom 30, specifically for its tubular section 31, which in this case is designed as a circular cylindrical tube. At the free end of the tubular section 31, an end head 32 is arranged, which in this case is designed as a joint head, although further variants are possible.

[0024] In this case, two fans 90 are provided on the outside of the housing main body 23, which are mounted opposite one another on the housing main body 23. These fans draw in air from the ambient air using an electrically driven fan wheel and force it into the cooling channels in the housing main body 23. Curved deflection channels are provided in the first and / or second end block 21; 22, each connecting two cooling channels in the housing main body 23. Furthermore, air outlets 91 are provided on the housing main body 23, each connected to an associated cooling channel. The air pumped into the cooling channels by the fans 90 can exit the cooling channels again there.

[0025] Fig. 2 shows a longitudinal section of the actuator according to Fig. 1. A threaded spindle 41 is arranged inside the main housing 20 and extends along the axis of rotation 11. At one end, the threaded spindle 41 is rotatably mounted in the first end block 21 with respect to the axis of rotation 11. The corresponding first pivot bearing 24 in this case comprises two angular contact ball bearings, although more individual bearings can be provided depending on the desired axial force. At the first end facing away from the first pivot bearing 24, the threaded spindle 41 projects into the tubular section 31 of the boom 30, passing through a nut 33 that is firmly connected to one end of the boom 30. The nut 33 and the threaded spindle 41 together form a planetary screw drive 40. The threaded spindle 41 has a first and a second external thread 42, 43, which are directly adjacent to one another.The first external thread 42 is in screw engagement with the aforementioned nut 33, wherein the second external thread 43 serves to fasten the first pivot bearing 24 on the threaded spindle 41. As can be seen from . Fig. 4, the outer diameter of the second external thread 43 is only minimally smaller than the outer diameter of the first external thread 42. Accordingly, the strength of the threaded spindle 41 is only minimally reduced by the attachment of the second pivot bearing 24. It should be noted that the one-piece threaded spindle 41 is preferably manufactured from a blank provided with the first external thread over its entire length.

[0026] In Fig. 2 also shows the traction mechanism 60 in the form of a toothed belt, which transmits the rotational movement of the electric motor 25 to the threaded spindle 41. For this purpose, a drive pin of the electric motor 25 is firmly connected to a first toothed belt pulley 64, with the threaded spindle 41 being firmly connected to a second toothed belt pulley 65. The traction mechanism 60 and the first and second toothed belt pulleys 64; 65 are enclosed by the traction mechanism housing 61. The electric motor 25 is fastened to the base body 70 of the traction mechanism housing 61, with the base body 70 in turn being directly fastened to the first end block 21.

[0027] To ensure the toothed belt 60 has a long service life, it is preferably pre-tensioned to such an extent that it is not completely relieved even at the maximum drive torque that can occur. This pre-tension causes considerable transverse forces on the threaded spindle 41. These transverse forces are partially transmitted via the first pivot bearing 24. The design of the first pivot bearing 24 explained below, which is intended to increase the torsional strength of the threaded spindle 41, however, leads to comparatively high stresses if the aforementioned transverse force is absorbed by the first pivot bearing 24 alone. To minimize these stresses, the second pivot bearing 50 according to the invention was introduced and accommodated in the traction mechanism housing 61. The second pivot bearing 50 is thus arranged particularly close to the second toothed belt pulley 65. It thus bears a large portion of the transverse force caused by the pre-tension of the traction mechanism 60.Bending moments resulting from the shear force are particularly small.

[0028] Fig. 3 shows a further perspective view of the actuator 10 according to Fig. 1, whereby the traction mechanism housing 61 without the cover (No. 62 in Fig. 1). The base body 70 of the traction mechanism housing 61 has a ring-like, i.e., in the form of a closed ring, circumferential wall 71 surrounding the rotational axis 11. The circumferential wall 71 encloses the first and second toothed belt pulleys 64; 65 and the traction mechanism 60. It has a constant, rectangular cross-sectional shape over its entire circumference. In the area of ​​the rotational axis 11, the circumferential wall 71 is integral with a bottom wall (No. 72 in Fig. 2 and Fig. 4). The bottom wall is designed in the form of a flat plate of constant thickness, which is integrally connected over almost its entire circumference either to the peripheral wall 71 or to the stiffening wall 73. Only at the two interruption points 76, which serve to guide the traction device 60, is this connection not present. The area of ​​the bottom wall is covered by the cover (No. 62 in Fig. 4), which is attached to the housing base body 70 with a plurality of screw bolts. The cover extends over the entire peripheral wall 71, being screwed to the base body 70 over the entire peripheral wall and the entire stiffening wall 73. The stiffening wall 73 extends diagonally between two sections of the peripheral wall 71, having a constant, rectangular cross-sectional shape over its entire length. At both opposite ends of the stiffening wall 73, a gap is provided from the peripheral wall 71, forming the above-mentioned interruption point 76.

[0029] Aside from the one-piece bottom wall 72, the peripheral wall 71 is screwed to a separate support plate 74. The electric motor 25 is attached to the support plate 74, and exclusively to this, by means of fastening screws 75. The support plate 74 is secured with further fastening screws (No. 75a in Fig. 4) is attached to the peripheral wall 71 in such a way that the distance between a rotational axis of the electric motor 25 and the rotational axis 11 of the threaded spindle is adjustable in order to adjust the pretension of the traction means 60.

[0030] The first and second toothed belt wheels 64; 65 are each fastened to the drive shaft of the electric motor 25 and to the threaded spindle by means of a conical clamping set.

[0031] Fig. 4 shows an enlarged section of Fig. 2 in the area of ​​the first end block 21. The cooling bore 44 in the threaded spindle 41 and the rotary feedthrough 45 have been drawn using dashed lines. This cooling device can be optionally present, and is preferably designed according to DE 10 2016 209 654 A1. The entire content of DE 10 2016 209 654 A1 is incorporated herein by reference and incorporated into the present application. Within the scope of the present invention, it is important that the rotary feedthrough 45 is arranged outside the traction mechanism housing 61, specifically on the side facing away from the main housing 20. Due to the second pivot bearing 50 according to the invention, the weight-related transverse forces caused thereby are uncritical. The cover 62, which is designed in the form of a flat plate with a constant thickness, can be provided with an opening in the area of ​​the rotary union 45, which is closed with a separate auxiliary cover 62a when the rotary union 45 is not mounted.

[0032] In Fig. 4, the area of ​​the threaded spindle 41 is identified by reference numerals 42; 43, over which the first and second external threads 42; 43 extend. The first and second external threads 42; 43 are directly adjacent to each other with a small shoulder. The first external thread 42 is a pointed thread, which is designed for engagement with the nut (No. 33 in Fig. 2) of a planetary screw drive. The second external thread 43 has a slightly smaller outer diameter than the first external thread 42. It is also designed as a tapered thread and is designed for screwing on the first and second clamping nuts 81; 82. The first clamping nut 81 has a sleeve-like section 83 which has an outer circumferential surface that is circularly cylindrical with respect to the axis of rotation 11, on which the first pivot bearing 24 is mounted. The remaining first clamping nut 81 forms a stop for the first pivot bearing 24 in the direction of the axis of rotation 11. There, a sealing surface 86 that is circularly cylindrical with respect to the axis of rotation can be provided directly on the clamping nut or on a pressed-on sealing sleeve. The sealing lip of an optional sealing ring 26, which is firmly connected to the first end block 21, rests there.In the present case, the sealing ring 26 is installed in a separate intermediate plate 27, which is considered to be a component of the first end block 21 in the context of the present application.

[0033] The second clamping nut 82 is also screwed onto the second external thread 43, clamping the first pivot bearing 24, in particular the corresponding inner rings, against the first clamping nut 81 in the direction of the rotation axis 11. The first pivot bearing 24 comprises two angular contact ball bearings.

[0034] The second pivot bearing 50 is mounted directly on the one-piece threaded spindle 41. The corresponding bearing seat for the inner ring 51 is circularly cylindrical with respect to the rotational axis 11, with a diameter minimally smaller than the outer diameter of the second external thread 43. There, too, the threaded spindle 41 is only slightly weakened in terms of torsional strength. The outer ring 52 of the second pivot bearing 50 is mounted directly in the bottom wall 72 of the base body 70 of the traction mechanism housing 61. The corresponding bearing seat is designed as a tight fit or interference fit, so that the second pivot bearing 50 is firmly held on the traction mechanism housing 61. The bearing seat on the inner ring 51, in contrast, is designed as a sliding fit, so that a slight displacement of the inner ring 51 relative to the threaded spindle 41 in the direction of the rotational axis 11 is possible. This eliminates the risk of distortion of the second pivot bearing 50.The second pivot bearing 50 is designed as a radial deep groove ball bearing.

[0035] In Fig. 4 also shows the conical clamping set 66 with which the second toothed belt wheel 65 is mounted on the threaded spindle 41. Reference symbol 10 Actuator 11 axis of rotation 12 Interior 20 main housing 21 first end block 22 second end block 23 Housing main body 24 first pivot bearing 25 electric motor 26 Sealing ring 27 Intermediate plate 30 booms 31 tube-like section 32 End head 33 Mother 40 planetary screw drive 41 threaded spindle 42 first external thread 43 second external thread 44 Cooling hole 45 rotary union 50 second pivot bearing 51 Inner ring of the second pivot bearing 52 Outer ring of the second pivot bearing 60 traction devices 61 traction mechanism housing 62 lids 62a Auxiliary cover 63 screw bolts 64 first toothed belt wheel 65 second toothed belt wheel 66 taper clamping set 70 basic bodies 71 Perimeter wall 72 floor wall 73 stiffening wall 74 Carrier plate 75 fixing screw 75a fixing screw 76 Interruption point 81 first clamping nut 82 second clamping nut 83 sleeve-like section of the first clamping nut 84 Internal thread of the first clamping nut 86 Sealing surface 90 blowers 91 Air outlet

Claims

[1] Actuator (10) with a main housing (20), a boom (30) and a threaded spindle (41), wherein the threaded spindle (41) is mounted on the main housing (20) by means of a first pivot bearing (24) relative to a rotational axis (11), wherein the boom (30) projects displaceably from the main housing (20) in the direction of the rotational axis (11), wherein it is in screw engagement with the threaded spindle (41), wherein the main housing (20) comprises a housing main body (23) and a first end block (21), wherein the first pivot bearing (24) is accommodated in the first end block (21), wherein the threaded spindle (41) is in rotational drive connection with an electric motor (25) via a traction means (60), wherein the traction means (60) is surrounded by a separate traction means housing (61) which is fastened to the first end block (21), wherein the Electric motor (25) is attached to the traction mechanism housing (61),wherein the threaded spindle (41) is rotatably mounted with a separate second pivot bearing (50) on the traction mechanism housing (61) with respect to the rotational axis (11), wherein the second pivot bearing (50) is arranged in the direction of the rotational axis (11) between the first end block (21) and the traction mechanism (60), wherein the threaded spindle (41) has a first external thread (42), wherein the threaded spindle (41) is in screw engagement with the boom (30) via the first external thread (42), , characterized by in that the threaded spindle (41) has a second external thread (43), wherein the first pivot bearing (24) is fastened to the second external thread (43) by means of a first and a separate second clamping nut (81; 82), wherein the first clamping nut (81) comprises a sleeve-like section (83) on which the first pivot bearing (24) is received. [2] Actuator according to claim 1, wherein the traction mechanism housing (61) is composed of a one-piece base body (70) and a separate plate-like cover (62), wherein the base body (70) has a peripheral wall (71) which surrounds the rotation axis (11) in a ring-like manner, wherein it has a bottom wall (72) which is integrally connected to the peripheral wall (71), wherein the first end block (21) is fastened to the bottom wall (72), wherein the second pivot bearing (50) is received in the bottom wall (72). [3] Actuator according to claim 2, wherein the base body (70) comprises a stiffening wall (73) which is integrally connected to the bottom wall (72), wherein the stiffening wall (73) is fixedly connected to the cover (62). [4] Actuator according to one of the preceding claims, wherein the first clamping nut (81) is in screw engagement with the second external thread (43) via an internal thread (84), wherein the internal thread (84) of the first clamping nut (81) extends over the entire length of the sleeve-like portion (83), wherein it may have at least one interruption. [5] Actuator according to one of the preceding claims, wherein the first pivot bearing (24) is received between the first and the second clamping nut (81; 82), wherein the second external thread (43) extends at least from the first to the second clamping nut (81; 82). [6] Actuator according to one of the preceding claims, wherein the boom (30) is in screw engagement with the first external thread (42) via a planetary screw drive (40), wherein the second external thread (43) is designed as a pointed thread with a thread pitch between 0.5 mm and 2.0 mm, wherein an outer diameter of the second external thread (43) is between 90% and 100% of a core diameter of the first external thread (42). [7] Actuator according to one of the preceding claims, wherein a sealing ring (26) is provided which seals an interior space (12) of the main housing (20) with respect to the first pivot bearing (24), wherein the first clamping nut (81) has a sealing surface (86) surrounding the axis of rotation (11), against which the sealing ring (26) bears in a sealing manner. [8] Actuator according to one of the preceding claims, wherein the threaded spindle (41) has a cooling bore (44) extending along the axis of rotation (11), wherein the threaded spindle (41) passes through the traction mechanism housing (61), wherein a rotary feedthrough (45) is arranged outside the traction mechanism housing (61), which is fixedly connected to the threaded spindle (41), wherein cooling fluid can be introduced into and / or discharged from the cooling bore (44) via the rotary feedthrough (45). [9] Actuator according to one of the preceding claims, wherein the second rotary bearing (50) is a radial rolling bearing, the inner ring (51) of which is slidably received on the threaded spindle (41) in the direction of the rotation axis (11), the outer ring (52) of which is fixedly received in the traction mechanism housing (61).

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