Threaded drive and method for assembling such a threaded drive

Abstract

The invention relates to a threaded drive comprising a rotatable spindle nut with an internal toothed section and an internal toothed ring, a threaded spindle axially displaceable therefrom in a rotationally fixed manner and having an external thread wound helically around its spindle axis, two planet carriers arranged axially spaced apart from one another, a first planet, a first planet set with at least two second planets, and a second planet set with at least two third planets, wherein the first planet has a first external toothed section which engages with both the internal toothed section of the spindle nut and the external thread of the threaded spindle, wherein the first planet further accommodates a pinion which engages with the internal toothed ring, and wherein the second planets each have a second external toothed section with several third teeth arranged at least partially circumferentially.the third planets are in tooth engagement with the internal toothed section of the spindle nut, wherein the third planets each have a third external toothed section, the third external toothed section being in tooth engagement with the external thread of the threaded spindle. Furthermore, the invention relates to a method for assembling a threaded drive.

Description

The invention relates to a threaded drive having a rotationally drivable spindle nut and a threaded spindle which is arranged in a rotationally fixed manner thereto and is axially displaceable with an external thread which is wound helically about its spindle axis.DE 10 2011 084 401 A1 discloses a planetary rolling screw drive with a spindle nut arranged on a threaded spindle and with planets arranged distributed over the circumference of the threaded spindle, which are arranged between the spindle nut and the threaded spindle. The threaded spindle is provided with a spindle-side groove profile wound helically around the spindle axis, wherein the spindle nut is provided with a nut-side groove profile. The planets are provided with a planet-side groove profile, wherein the planet-side groove profile is in engagement with the nut-side groove profile and with the spindle-side groove profile. The spindle nut is divided transversely to the spindle axis into nut parts. The nut parts delimit a swept volume provided with filler in a liquid-tight manner and adjustable in the axial directions.The object of the present invention is to provide an efficiency-optimized screw drive which is simple to install. According to the invention, this object is achieved by the screw drive according to claim 1 and a method for assembling such a screw drive according to claim 9. Practical further developments can be taken from the dependent claims.According to a first aspect of the invention, a threaded drive comprises a rotationally drivable spindle nut having an internal toothing portion and an internal toothed ring, a threaded spindle which is arranged rotationally fixedly thereto and is axially displaceable and has an external thread wound helically about its spindle axis, two planet carriers arranged axially spaced apart from one another, a first planet, a first planet set consisting of at least two second planets, and a second planet set consisting of at least two third planets are arranged, wherein the first planet has a first external toothing portion having a plurality of first teeth arranged at least in part encircling fashion and which are in tooth engagement both with a plurality of second teeth arranged at least in part encircling fashion of the internal toothing portion of the spindle nut and with the external thread of the threaded spindle, wherein the first planet furthermore receives a pinion which is in tooth engagement with the internal toothed ring of the spindle nut in a rotationally fixed fashion, wherein the second planets of the first planetary set each have a second external toothing section with a plurality of third teeth arranged at least partially in a circumferential manner, which third teeth are in tooth engagement with the internal toothing section of the spindle nut, wherein the third planets of the second planetary set each have a third external toothing section with a plurality of fourth teeth arranged at least partially in a circumferential manner, wherein the third external toothing section is in tooth engagement with the external thread of the threaded spindle.The screw drive is to be understood as a planetary rolling screw drive. The rotationally fixed threaded spindle is guided axially through a respective central opening on the planet carriers and arranged so as to be axially displaceable. The planet carriers delimit the screw drive spatially in the axial direction. The rotationally drivable spindle nut, in contrast, is arranged axially between the two planet carriers and spatially delimits the screw drive in the radial direction. The spindle nut is preferably arranged axially fixed, i.e. axially substantially non-displaceable.The planets, i.e. the first planet and the second and third planets of the two planetary sets, are arranged axially between the planet carriers and radially between the threaded spindle and the spindle nut. The planets are of simple construction and each have an external toothing section with a plurality of teeth in the axial direction, which teeth are preferably of substantially identical design, that is to say have substantially the same tooth geometry. The planetary set is understood to mean at least two planets which are substantially identical in design, i.e. have substantially the same external dimensions and are formed from the same material and fulfil the same function. The second planets of the first planetary set are substantially identical. The third planets of the second planetary set are also substantially identical.A plurality of axially equally spaced teeth each extend at least partially around the respective planet. Preferably, the teeth are formed in a fully encircling manner around the respective planet, as a result of which the production of the respective planet is simplified.The first teeth of the first external toothing section on the first planet are arranged at substantially uniform distances in the axial direction, lying one behind the other. The second teeth of the internal toothing section of the spindle nut are arranged at substantially uniform spacing in the axial direction, lying one behind the other. The third teeth of the second external toothing section on the respective second planet are arranged at substantially uniform distances in the axial direction, lying one behind the other. The fourth teeth of the third external toothing section on the respective third planet are arranged at substantially uniform distances in the axial direction, lying one behind the other.The teeth of the respective toothing section and the toothing of the external thread of the threaded spindle are substantially of complementary design, since the first teeth of the first external toothing section are in tooth engagement with the second teeth of the internal toothing section of the spindle nut and the toothing of the external thread of the threaded spindle, the third teeth of the second external toothing section are in tooth engagement with the second teeth of the internal toothing section of the spindle nut and the fourth teeth of the third external toothing section are in tooth engagement with the external thread of the threaded spindle.The load capacity of the screw drive can be adjusted as desired by increasing or decreasing the number of teeth of the first planetary gear that bear the axial force.Each of the planets has end portions at both ends, at which no gear portion or the like is provided. The end portions are adapted to be inserted into complementary recesses on one of the two planet carriers and to be loosely received in the axial direction, wherein the planets can rotate relative to the planet carriers. The end sections are preferably cylindrical. The planets are accommodated with axial play on the planet carriers, whereby a free self-centering of the external toothing sections of the planets with respect to toothing sections or threads in meshing engagement therewith is made possible. The end sections are arranged concentrically to the toothed sections of the associated planet.The spindle nut is designed to be rotationally driven by a drive unit, in particular an electric machine. For this purpose, drive means can be provided on the outer periphery of the spindle nut, by means of which drive means the spindle nut can be rotationally driven. This can be, for example, a toothing geometry for effectively receiving a chain, a belt or the like. Alternatively, a rotor can be directly attached to the outer diameter of the spindle nut in order to be able to drive the spindle nut in rotation by a motor.A rotation of the spindle nut sets the pinion engaged with the internal toothed ring of the spindle nut into a rotational movement, so that the first planet, which is connected to the pinion in a rotationally fixed manner, is set into a corresponding rotational movement. At the same time, the rotating spindle nut causes the second planets of the second planetary set to rotate due to the friction. The pinion and the inner toothed ring are to be understood as toothed wheels with outer and inner teeth, respectively. The first planet is supported during its rotation with at least one axial force component on the internal toothing section of the spindle nut in order to transmit a force to the threaded spindle. Since the threaded spindle has a helical external thread, a rotation of the first planet, with the accompanying support of the first planet on the spindle nut, causes a translatory or axial movement of the threaded spindle in its longitudinal direction.The pinion is connected to the first planetary gear in a rotationally fixed manner by positive, frictional and / or materially bonded connection. A multi-part embodiment is conceivable, wherein during or before the assembly of the threaded drive the pinion and the first planet are joined or connected to one another in a rotationally fixed manner. The first planet is therefore firmly connected to the first planet by press-fitting, welding, adhesive bonding or other types of connection. The pinion serves to minimize friction and slip between the first planet and the spindle nut by performing forced rotation. The rotation of the first planet then generates an axial force on the threaded spindle, whereby the axial displacement of the threaded spindle is effected. In this sense, the first planet is configured to provide a force transmission between the spindle nut and the threaded spindle, wherein a rotational movement of the spindle nut is converted into a longitudinal movement of the threaded spindle. The first planet bears the axial force over its entire length or at least over the length of the first external toothing section.The planets of the first and second planetary sets are in turn configured to axially and radially secure the system, i.e. to hold it in place, wherein the planets of the first and second planetary sets can move freely according to the predetermined rotations. Thus, a free-wheeling operation is made possible. As a result, in particular during assembly, no so-called pairing of planets takes place.The second planets of the first planetary set are configured in particular to axially secure the spindle nut. Preferably, the first planetary set comprises exactly two second planetary gears.The third planets of the second planetary set are configured in particular to radially secure the threaded spindle, in particular with respect to the first planet. The threaded spindle is therefore fixed by the third planets of the second planetary set. Preferably, the second planetary set comprises exactly two third planetary gears.Furthermore, the threaded spindle is preferably arranged spatially between the first planet and the two third planets of the second planetary set. This prevents a radial deflection of the threaded spindle when the first planetary gear is rotated. The third planets of the second planetary set are also preferably arranged spatially between the two second planets.The longitudinal axes of the threaded spindle, the spindle nut and all planets are arranged axially parallel and spaced apart from one another or next to one another.The advantages of the invention consist in the fact that the distribution of the loads in the screw drive is homogenized. Furthermore, simpler assembly without pairing of the planets is made possible, as a result of which a more cost-effective solution can be achieved. Moreover, axially abutting bearings are completely eliminated, since the planet carriers do not have any axial load and only hold the various parts of the screw drive together. For this purpose, the system provides that an axial play exists between all planets and the planet carriers. The planet carriers merely ensure the position retention of the planets and their free rotation.In order to keep the planet carriers in their position spaced apart from one another, it is preferably provided that the planet carriers are connected to one another via at least two connecting struts and are positioned axially with respect to one another. The connecting struts are arranged axially parallel and spaced apart from one another and axially parallel and spaced apart from the threaded spindle, the spindle nut and all planets. Preferably, three connecting struts are provided in order to make the system compact and stable. The connecting struts are fixedly connected, in particular welded or pressed, at their ends to one of the two planet carriers in each case during the mounting of the threaded drive. The connecting struts are therefore connected axially and radially fixedly to the planet carriers and thus form a coherent component together with the planet carriers in the assembled state. The connecting struts arrange the planet carriers so far from one another that the planets are arranged with axial play between the planet carriers so that they center themselves to one another on the own.The inner toothed ring and the inner toothed section of the spindle nut are preferably arranged concentrically with respect to one another and with respect to an outer diameter of the spindle nut. The internal toothed ring and the internal toothed section are preferably arranged directly axially adjacent. The spindle nut is the drive part of the threaded drive. The spindle nut is also to be understood as a ring gear of the planetary gearing of the threaded drive, since it is in toothed engagement with the first planetary gear via the pinion and directly with the second planetary gear.Further preferably, the first external toothing section of the first planet and the pinion are arranged concentrically with respect to one another. Preferably, the first external toothing section of the first planet and the pinion arranged thereon in a rotationally fixed manner are arranged directly axially adjacent to one another. The pinion is preferably pressed axially onto one of the two end sections of the first planetary gear, in particular an end section facing the internal toothed ring of the spindle nut, and connected thereto in a rotationally fixed manner. The pinion can additionally be axially secured on the respective end section by axial securing means, for example in the form of a securing ring or the like.The invention includes the technical teaching that the planet carriers are each formed from plastic or steel. The planet carriers are machined in particular. The planet carriers are thus of cost-effective and simple design. A hybrid design of the planet carriers, for example primarily made of plastic with metal inserts, in particular steel inserts, is of course likewise conceivable.According to a second aspect of the invention, a method for assembling a screw drive comprises the steps of:providing a spindle nut having an internal toothed section and an internal toothed ring, a threaded spindle having an external thread wound helically about its spindle axis, two planet carriers arranged axially spaced apart from one another, a first planet, a first planet set consisting of at least two second planets, a second planet set consisting of at least two third planets, and at least two connecting struts,mounting a first sub-assembly, wherein the at least two connecting struts are joined to the first planet carrier at the ends facing a first planet carrier, and wherein the third planets of the second planet set are loosely inserted with a respective end section into complementary recesses on the first planet carrier,mounting a second sub-assembly, wherein the first planet and the second planets of the first planet set are loosely positioned on the internal toothing portion of the spindle nut,joining the first and second sub-assemblies to form an intermediate assembly, wherein end portions of the first planet and of the second planet facing the first planet carrier are loosely inserted into complementary recesses on the first planet carrier,positioning the second planet carrier on the intermediate assembly, wherein the end sections of the planets facing the second planet carrier are loosely inserted into complementary recesses on the second planet carrier, and wherein simultaneously or subsequently the at least two connecting struts are joined to the second planet carrier at the ends facing the second planet carrier, androtationally driving the spindle nut, wherein at the same time the threaded spindle is inserted into the screw drive through a first central opening on the first or second planet carrier until it comes into toothed engagement with the first external toothing section of the first planet and the third external toothing sections of the third planets.The assembly of the first subassembly is to be understood as a first stage of the assembly of the threaded drive. In this case, the connecting struts are joined to the first planetary carrier, i.e. arranged axially and radially fixed, and the third planets of the second planetary set are inserted loosely, i.e. axially displaceable and supported only in the radial direction, into matching recesses on the first planetary carrier. The third planets are arranged coaxially to a longitudinal axis of the first planet carrier.The assembly of the second subassembly is to be understood as a second stage of the assembly of the threaded drive. In this case, the first planet and the second planets of the first planetary set are positioned spatially within the spindle nut. The second planets and the first planet are each arranged coaxially to a longitudinal axis of the spindle nut. Preferably, the first planet and the second planets of the first planetary set are held loose in their position on the internal toothing section of the spindle nut by a tool during the assembly of the second subassembly and until the first and second subassemblies are combined in a further step after the second stage.The joining of the subassemblies is to be understood as a third stage of the assembly of the threaded drive. In this case, the first subassembly is threaded or introduced axially into the second subassembly until the end sections of the first planet and of the second planet facing the first planet carrier have been loosely inserted into matching recesses on the first planet carrier.The positioning of the second planetary carrier on the intermediate assembly is to be understood as a fourth stage of the assembly of the threaded drive. In this case, the second planet carrier is pushed onto the end sections of the planets facing the second planet carrier. During or subsequently, the connecting struts are arranged axially and radially fixedly on the second planetary carrier.The insertion of the threaded spindle either from one or the other axial end of the threaded drive, i.e. either through the first or second planet carrier, is to be understood as a fifth stage of the assembly of the threaded drive. The spindle nut is rotationally driven, as a result of which at least the first planet also rotates about its longitudinal axis. If the threaded spindle is axially brought up to the first external toothing section, when the direction of rotation of the spindle nut is appropriate, the external thread of the threaded spindle comes into tooth engagement with the first external toothing section of the first planet and the fourth external toothing section of the third planet. Upon further rotational drive of the spindle nut, the threaded spindle is thus guided into the threaded drive, as it were, pulled axially in until the threaded spindle reaches the desired axial position relative to the spindle nut and lies spatially between the first planet and the third planet.Further measures which improve the invention are illustrated in more detail below together with the description of a preferred exemplary embodiment of the invention on the basis of the figures, identical or similar elements being provided with the same reference symbols. They show FIG. 1 shows a first schematic perspective view of a threaded drive according to the invention according to a preferred embodiment, FIG. 2 is a second schematic perspective view of the inventive threaded drive according to FIG. 1, with the exception of a second planetary carrier, FIG. 3 shows a third schematic perspective view of the threaded drive according to the invention according to FIG. 1, with the exception of a spindle nut, FIG. 4 shows a first schematic longitudinal sectional illustration of the threaded drive according to the invention according to FIGS. 1 to 3 in the assembled state, FIG. 5 shows a second schematic longitudinal sectional illustration of the threaded drive according to the invention according to FIGS. 1 to 4 in the assembled state, FIG. 6 shows a third schematic longitudinal sectional illustration of the threaded drive according to the invention according to FIGS. 1 to 5 in the assembled state, FIG. 7 shows a first schematic cross-sectional illustration of the threaded drive according to the invention according to FIGS. 1 to 6 at a first axial position, FIG. 8 shows a second schematic cross-sectional illustration of the threaded drive according to the invention according to FIGS. 1 to 7 at a second axial position, FIG. 9a shows a first schematic perspective illustration of a first subassembly of the threaded drive for illustrating the sequence of a method according to the invention for mounting the threaded drive according to FIGS. 1 to 8 in a first stage, FIG. 9 bshows a second schematic perspective illustration of a second subassembly of the screw drive for illustrating the sequence of the mounting method according to the invention of the screw drive according to FIG. 9 ain a second stage, FIG. 9 cshows a third schematic perspective illustration of an intermediate assembly of the screw drive for illustrating the sequence of the assembly method according to the invention of the screw drive according to FIGS. 9 aand 9 bin a third stage, and FIG. 9 dis a fourth schematic perspective illustration of the intermediate subassembly of the threaded drive according to FIGS. 9 ato 9 cin a fourth stage, wherein the second planet carrier is positioned on the intermediate subassembly.FIGS. 1 to 8 show a screw drive G in different views in the assembled state. According to FIGS. 1 to 8, the screw drive G comprises two planet carriers 3 a, 3 bformed of plastic or steel, which are arranged axially spaced apart from one another via three connecting struts 10 distributed uniformly over the circumference and spatially delimit the screw drive G in the axial direction. The connecting struts 10 are connected axially and radially fixedly to the planet carriers 3 a, 3 b, here pressed axially into associated recesses 14 and 16 of the respective planet carrier 3 a, 3 b.Axially between the planet carriers 3 a, 3 bis arranged a rotationally drivable, sleeve-shaped spindle nut 2 in an axially fixed manner, which spatially delimits the threaded drive G in the radial direction. The spindle nut 2 has on an inner circumferential surface an internal toothing section 11 with a plurality of second teeth Z 2 arranged at least partially encircling and directly axially adjacent thereto an internal toothed ring 9. The inner toothed ring 9 and the inner toothed section 11 of the spindle nut 2 are arranged concentrically with respect to one another and with respect to an outer diameter 12 of the spindle nut 2. The connecting struts 10 and the further components mentioned below are arranged spatially within the spindle nut 2.The screw drive G further comprises a threaded spindle 1 arranged in a rotationally fixed manner and axially displaceable relative to the spindle nut 2 and having an external thread 8 wound helically about its spindle axis. In addition, a first planet 4, a first planetary set with exactly second planets 5 a, 5 band a second planetary set with exactly two third planets 6 a, 6 bare provided.The first planet 4 has a first external toothing section A 1 arranged between two end sections 13, 15 and having a plurality of first teeth Z 1 arranged at least partially in a circumferential manner. The first external toothing section A 1 with the first teeth Z 1 meshes both with the internal toothing section 11 of the spindle nut 2 and with the external thread 8 of the threaded spindle 1. A pinion 7 is pressed onto the end section 15 of the first planetary gear 4 facing the second planetary carrier 3 b, i.e. it is held in a rotationally fixed and axially fixed manner, which pinion is in toothed engagement with the internal toothed ring 9 of the spindle nut 2. The first external toothing section A 1 and the end sections 13, 15 of the first planet 4 are arranged concentrically with respect to the pinion 7.The two second planets 5 a, 5 bof the first planetary set each have a second external toothing section A 2 arranged between two end sections 13, 15 and having a plurality of third teeth Z 3 arranged at least partially in a circumferential manner, wherein the respective second external toothing section A 2 is in tooth engagement with the third teeth Z 3 with the internal toothing section 11 of the spindle nut 2. The second external toothing section A 2 of the respective second planet 5 a, 5 band the two end sections 13, 15 axially delimiting the respective second external toothing section A 2 are arranged concentrically with respect to one another. By means of the two second planet gears 5 a, 5 b, the spindle nut 2 is held in its axial position between the planet carriers 3 a, 3 bwhen in operation.The third planets 6 a, 6 bof the second planetary set each have a third external toothing section A 3 arranged between two end sections 13, 15 and having a plurality of fourth teeth Z 4 arranged at least partially in a circumferential manner. The respective third external toothing section A 3 with the fourth teeth Z 4 is in toothed engagement with the external thread 8 of the threaded spindle 1. the threaded spindle 1 is arranged spatially between the first external toothing section A 1 of the first planetary gear 4 and the two third external toothing sections A 3 of the third planetary gears 6 a, 6 bof the second planetary gear set, wherein the threaded spindle 1 is positioned and secured radially by the third planetary gears 6 a, 6 band the first planetary gear 4. The third external toothing section A 3 of the respective third planet 6 a, 6 band the two end sections 13, 15 axially delimiting the respective third external toothing section A 3 are arranged concentrically with respect to one another.The end sections 13, 15 and the external toothing sections A 1, A 2, A 3 of the planets 4, 5 a, 5 b, 6 a, 6 care designed in such a way that the planets 4, 5 a, 5 b, 6 a, 6 care arranged with axial play between the planet carriers 3 a, 3 bto realize self-centering of the components operatively connected to one another.The spindle nut 2 can be driven in rotation by a drive unit-not shown here-for example in the form of an electric machine. For this purpose, the spindle nut 2 can preferably be set on its outer circumference 18 in a rotation about its axis of rotation. Via the internal toothed ring 9, the pinion 7 is set into a rotation about its own axis of rotation during rotation of the spindle nut 2. In addition, as a result of friction, the second planets 5 a, 5 bare set into a rotational movement about their respective own rotational axis. As a result of the rotation of the pinion 7, the first planet 4 connected thereto in a rotationally fixed manner rotates with it and is supported on the internal toothing section 11 of the spindle nut 2 in order to transmit a force to the threaded spindle 1, which force sets the threaded spindle 1 in a longitudinal movement.Only the first planet 4 absorbs axial forces or supports them on the spindle nut 2. The further planets 5 a, 5 b, 6 a, 6 band the planet carriers 3 a, 3 bdo not absorb any axial forces.With reference to FIGS. 9a to 9d, an assembly process of the screw drive G is illustrated. FIG. 9 ashows a first stage of the assembly in which a first sub-assembly U 1 is assembled. FIG. 9 ashows the assembled first sub-assembly U 1. In the first stage, three connecting struts 19 with first end sections 13 facing the first planetary carrier 3 aare pressed into corresponding recesses 14 on the first planetary carrier 3 ain an axially parallel manner and at a distance from one another, so that a press fit is present between the connecting struts 19 and the first planetary carrier 3 a. Likewise, the third planets 6 a, 6 bof the second planetary set are inserted with a respective first end section 13 axially loose into recesses 14 on the first planet carrier 3 athat are complementary thereto in the first mounting stage, so that the two third planets 6 a, 6 bremain axially displaceable and are supported only radially on the first planet carrier 3 a.FIG. 9 bshows a second stage of assembly in which a second subassembly U 2 is assembled. FIG. 9 bshows the assembled second subassembly U 2. In the second stage, the first planet 4 and the two second planets 5 a, 5 bof the first planet set are loosely positioned on the internal toothing section 11 of the spindle nut 2. Loosely positioned here means that the first planet and the second planets of the first planetary set are held in their position on the internal toothing section 11 of the spindle nut 2 by a tool-not shown here-during assembly of the second subassembly.FIG. 9 cshows a third stage of the assembly in which an intermediate assembly ZB is assembled. FIG. 9 cshows the assembled intermediate assembly ZB. In the third stage, the two subassemblies U 1, U 2 are combined to form an intermediate assembly ZB, wherein the end sections 13 of the first planet 4 facing the first planet carrier 3 aand end sections 13 of the second planets 5 a, 5 b facing the first planet carrier 3 aare inserted in axially loose fashion into complementary recesses 14 on the first planet carrier, so that the first and the two second planets 5 a, 5 bremain axially displaceable and are supported only radially on the first planet carrier 3 a.FIG. 9 d shows a fourth stage of the assembly in which the interior of the threaded drive G is closed. Accordingly, the second planetary carrier 3 bis positioned on the intermediate assembly ZB, wherein the end sections 15 of the planets 4, 5 a, 5 b, 6 a, 6 bfacing the second planetary carrier 3 bare inserted axially loosely into complementary recesses 16 on the second planetary carrier 3 b, so that planets 4, 5 a, 5 b, 6 a, 6 bremain axially displaceable in each case and are supported only radially on the second planetary carrier 3 b.Here, the connecting struts 19 with corresponding end sections 15 are pressed simultaneously with second end sections 15 facing the second planetary carrier 3 a, parallel to the axis and spaced apart from one another, into corresponding recesses 16 on the second planetary carrier 3 b,so that there is also a press fit between the connecting struts 19 and the second planetary carrier 3 b.Following the fourth stage, in a fifth stage of the assembly, the threaded spindle 1 is guided either through a central opening 17 of the first or of the second planetary carrier 3 a, 3 buntil the external thread 8 of the threaded spindle 1 comes into engagement with the first external toothing section A 1 of the first planetary gear 4 and the third external toothing sections A 3 of the third planetary gears 6 a, 6 b. If the spindle nut 2 is then simultaneously driven in rotation, the threaded spindle 1 is axially displaced in the manner described above and, as it were, drawn into the threaded drive G. The spindle nut 2 can be driven in rotation in the fifth mounting stage until the threaded spindle 1 on the opposite side of the threaded drive G emerges again from the central opening 17 of the respective other planetary carrier 3 a, 3 b. This state then corresponds to the illustration in FIG. 1.List of reference characters1 Threaded spindle 2 Spindle nut 3 a, 3 b Planetenträger carrier 4 First planet 5 a, 5 bSecond planet of a first planetary set 6 a, 6 bThird planet of a second planetary set 7 Pinion 8 External thread 9 Internal toothed ring 10 Connecting strut 11 Internal toothing section 12 External diameter 13 End section 14 facing the first planetary carrier Recess on the first planetary carrier 15 End section 16 facing the second planetary carrier 17 Opening 18 External circumference 19 Connecting strut A 1 First external toothing section A 2 Second external toothing section A 3 Third external toothing section G Screw drive U 1 First subassembly U 2 Second subassembly ZB Intermediate subassembly Z 1 First teeth Z 2 Second teeth Z 3 Third teeth

Claims

A threaded drive (G) comprising a rotationally drivable spindle nut (2) having an internal toothing portion (11) and an internal toothed ring (9), a threaded spindle (1) which is arranged in a rotationally fixed manner thereto and is axially displaceable and has an external thread (8) wound helically about its spindle axis, two planet carriers (3a, 3b) arranged axially spaced apart from one another, a first planet (4), a first planet set consisting of at least two second planets (5a, 5b), and a second planet set consisting of at least two third planets (6a, 6b), wherein the first planet (4) has a first external toothing portion (A1) having a plurality of first teeth (Z1) arranged at least in a part-encircling manner, which are in toothed engagement both with a plurality of second teeth (Z2) of the internal toothing section (11) of the spindle nut (2) arranged at least in part-circumferential fashion and with the external thread (8) of the threaded spindle (1), wherein the first planet (4) furthermore non-rotatably accommodates a pinion (7) which is in toothed engagement with the internal toothed ring (9) of the spindle nut (2), wherein the second planets (5a, 5b) of the first planet set each have a second external toothing section (A2) with a plurality of third teeth (Z3) arranged at least in part-circumferential fashion and are in toothed engagement with the internal toothing section (11) of the spindle nut (2), wherein the third planets (6a, 6b) of the second planet set each have a third external toothing section (A3) with a plurality of fourth teeth (Z4) arranged at least in part-circumferential fashion, wherein the third external toothing portion (A3) is in toothed engagement with the external thread (8) of the threaded spindle (1).The screw drive (G) according to claim 1, characterized in that the planet carriers (3a, 3b) are connected to each other via at least two connecting struts (10, 19) and are positioned axially with respect to each other.The screw drive (G) according to claim 1 or claim 2, characterized in that the internal toothed ring (9) and the internal toothing section (11) of the spindle nut (2) are arranged concentrically to one another and to an outer diameter (12) of the spindle nut (2).The screw drive (G) according to any one of the preceding claims, characterized in that the first external toothing section (A1) of the first planet (4) and the pinion (7) are arranged concentrically with respect to one another.The screw drive (G) according to any one of the preceding claims, characterized in that the first planetary set comprises exactly two second planetary gears (5a, 5b).The screw drive (G) according to one of the preceding claims, characterized in that the second planetary set has exactly two third planetary gears (6a, 6b).The screw drive (G) according to claim 6, characterized in that the threaded spindle (1) is arranged spatially between the first planet (4) and the two third planets (6a, 6b) of the second planetary set.The screw drive (G) according to any one of the preceding claims, characterized in that the planet carriers (3a, 3b) are each formed from plastic or steel.Method for mounting a threaded drive (G), comprising the steps of: - providing a spindle nut (2) having an internal toothing section (11) and an internal toothed ring (9), a threaded spindle (1) having an external thread (8) wound helically about its spindle axis, two planet carriers (3a, 3b) arranged axially spaced apart from one another, a first planet (4), a first planet set consisting of at least two second planets (5a, 5b), a second planet set consisting of at least two third planets (6a, 6b) and at least two connecting struts (10, 19), - mounting a first subassembly (U1), wherein the at least two connecting struts (10, 19) are joined to the first planet carrier (3a) at the ends facing a first planet carrier (3a), and wherein the third planets (6a, 6b) of the second planetary set with a respective end section (13) are loosely inserted into complementary recesses (14) on the first planetary carrier (3a), - mounting a second sub-assembly (U2), wherein the first planetary (4) and the second planetary (5a, 5b) of the first planetary set are loosely positioned on the internal toothing section (11) of the spindle nut (2), - joining the first and second sub-assemblies (U1, U2) to form an intermediate assembly (ZB), wherein end sections (13) of the first planetary (4) and the second planetary (5a, 5b) facing the first planetary carrier (3a) are loosely inserted into complementary recesses (14) on the first planetary carrier, - positioning the second planetary carrier (3b) on the intermediate assembly (ZB), wherein the end sections (15) of the planets (4, 5a, 5b, 6a, 6b) facing the second planet carrier (3b) are loosely inserted into complementary recesses (16) on the second planet carrier (3b), and wherein at the same time or subsequently the at least two connecting struts (10, 19) are joined to the second planet carrier (3b) at the ends facing the second planet carrier (3b), and - the spindle nut (2) is driven in rotation, wherein at the same time the threaded spindle (1) is pushed through a first central opening (17) on the first or second planet carrier (3a, 3b) until it reaches in toothed engagement with the first external toothing section (A1) of the first planet (4) and the third external toothing sections (A3) of the third planets (6a, 6b).Method according to claim 9, characterised in that the first planet (4) and the second planets (5a, 5b) of the first planetary set are held loose in their position on the internal toothing section (11) of the spindle nut (2) by a tool during the assembly of the second sub-assembly (U2) and until the first and second sub-assemblies (U2) are combined.

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