Roller screw drive and method for assembling roller screw drive

Abstract

The invention relates to a roller spindle drive (1), in particular a planetary roller spindle, roller spindle or reverse roller spindle drive, comprising a spindle (2) with an external thread (5), a plurality of planetary rollers (4) and a spindle nut (3) with an inner contour (6). Each planetary roller (4) has a contoured central section (7) which engages with the external thread (5) of the spindle (2), and two likewise contoured side sections (9) which are thinner than the central section (7) and which each engage with a section of the inner contour (6) of the spindle nut (3). An end section (11) on each planetary roller (4), which is connected to the side section (9), is held in a recess (14) of a separate guide disk (12, 13). Each groove (14) for fixing the planetary roller (4) is provided with an assembly retaining contour (15) and a separate working retaining contour (16).

Description

Technical Field

[0001] This invention relates to a roller screw drive device constructed according to the preamble of claim 1, which is applicable, for example, to electromechanical actuators, and particularly in the form of a planetary roller screw, a roller screw, or a reverse roller screw. Furthermore, this invention also relates to a method for assembling the roller screw drive device. Background Technology

[0002] DE102011075950B4 illustrates a conventional ball screw drive, namely a planetary ball screw (also commonly referred to as a planetary ball screw drive). The illustrated planetary ball screw drive has multiple elongated planetary rollers with annular groove profiles, the ends of which are held in guide rings. Two separate guide rings may be present, and these two guide rings need not be mirror images of each other. Furthermore, DE102011075950B4 also illustrates an embodiment in which the guide rings are interconnected by bridging members.

[0003] WO2011 / 113724A1 discloses a planetary roller screw drive with planetary rollers supported within a centering disc. Each centering disc has drilled holes or slots distributed along its circumference corresponding to the number of planetary rollers, into which the journals of the planetary rollers are embedded. A preload device ensures that the planetary rollers remain engaged even when the planetary roller screw drive is unloaded, thereby converting the relative rotation between the nut and the screw into axial displacement between the aforementioned transmission elements (i.e., the screw and the screw nut), with minimal slippage.

[0004] The roller screw drive shown in DE102021202539A1, like the devices in DE102011075950B4 and WO2011 / 113724A1, comprises multiple rollers (i.e., planetary rollers) with a pitchless profile (i.e., non-helical grooves). In the DE102021202539B4 design, the cage is designed to radially compress the screw of the roller screw drive to its radial center position within the nut. Summary of the Invention

[0005] The purpose of this invention is to further improve the roller screw transmission device (e.g., planetary roller screw type) that converts rotary motion into linear motion, in view of the prior art, especially from the perspective of manufacturing technology.

[0006] The aforementioned objective is achieved by a roller screw drive device designed according to the features described in claim 1 of the present invention. In particular, this roller screw drive device is especially suitable for planetary roller screw drives. Similarly, this objective can also be achieved by the roller screw drive device assembly method described in claim 8. When planetary roller screw drives are mentioned in this document, the corresponding technical solutions can be applied to roller screw drive devices of other structural forms, provided there are no technical inconsistencies. Similarly, the construction and advantages of the present invention explained in the assembly method section also apply to the device involved in this application (i.e., the roller screw drive device), and vice versa.

[0007] Planetary roller screw drives or other roller screw drives generally include, in their basic construction, the following components known in the art: a screw with external threads, a plurality of planetary rollers, and a screw nut with an inner profile. The diameter of each planetary roller, typically referred to as the roller diameter (Ro), has a profiled central section that engages with the external threads of the screw. Specifically, the profile of the central section is an annular groove, i.e., a pitchless or leadless design. In addition to the central section with diameter Ro, the planetary roller also includes two equally profiled side sections (particularly designed as annular grooves, i.e., pitchless or leadless), which are smaller in diameter than the central section. Each side section engages with the inner profile section of the screw nut. The end sections to which the two side sections of each planetary roller connect are respectively held in grooves in a guide plate.

[0008] According to claim 1, each guide plate has a groove for selectively holding the planetary rollers in different positions, each groove having an assembly holding profile and a working holding profile separate from the assembly holding profile.

[0009] After assembly of a ball screw drive (especially a planetary ball screw drive), the assembly retaining profile ceases to function. It is only reused when disassembly is possible. Practice has shown that adding a separate assembly retaining profile alongside the working retaining profile (where the planetary roller end sections are located during normal operation of the planetary ball screw drive) significantly simplifies the assembly process and improves reliability (and disassembly when necessary), without significantly increasing space requirements. The individual planetary rollers, commonly referred to as "rollers," can move, in particular, radially from the assembly position (i.e., the position defined by the assembly retaining profile) to the working position (i.e., the position defined by the working retaining profile). Switching between the assembly and working positions does not require removing the planetary rollers from the guide plate.

[0010] The assembly method of the planetary roller screw drive or other roller screw drive involved in this application includes the following steps:

[0011] -Prepare

[0012] There are two types of lead screw transmission elements: the screw and the lead screw nut. One of them acts as the driving element of the transmission device, and the other acts as the driven element.

[0013] Multiple elongated, contoured planetary rollers are used for direct engagement with two transmission elements, and

[0014] Two guide discs: each guides one end of each planetary roller, and the guide discs are provided with grooves to selectively hold the end of the planetary roller in an assembled position within the groove or in a working position spaced apart from it.

[0015] - Assemble all planetary rollers and the two guide discs into a single assembly, at which point each planetary roller is in its assembled position.

[0016] - Combine the above component assembly with one of the two types of lead screw drive elements.

[0017] - Move each planetary roller from its assembly position to its working position.

[0018] - The assembly of the roller screw drive device is completed by installing a second screw drive element.

[0019] Therefore, there are two different ways to form a component assembly including planetary rollers and a guide plate, and then combine this component assembly with one of two types of lead screw drive elements:

[0020] According to the first scheme, the assembly retaining profile is located radially outside the working retaining profile. The planetary rollers are first inserted into the grooves of the guide plate in such a way that the end sections of all planetary rollers are held within the assembly retaining profile, i.e., at the radially outermost position. The resulting assembly allows the screw to be inserted without any interference and without the need for screwing. To distinguish it from the assembly that did not include any screw drive element, this combination, which includes one of two screw drive elements (in this case, the screw) in addition to the planetary rollers and guide plate, is called a "part assembly". In short, by adding any screw drive element, the above assembly can be transformed into a so-called part assembly.

[0021] Once the component assembly is complete, the planetary rollers are pressed inward to bring them into the working position. Then, the entire assembly, now in its working state, is screwed into the second screw drive element (in this case, the screw nut). At this point, the planetary roller screw drive is assembled, except for any necessary seals, connecting elements, or auxiliary components (such as elastic retaining rings for fixing the axial position of individual components). Similarly, the planetary roller screw drive can also be assembled by screwing the screw nut onto the assembled component assembly.

[0022] In this planetary roller screw drive design, the assembly retaining profile is located radially outside the working retaining profile (i.e., the planetary rollers need to be pressed inward during assembly). The centers of the planetary rollers positioned by the assembly retaining profile form an outer assembly circle with an outer diameter of DP_1a, while the centers of the planetary rollers positioned by the working retaining profile form an inner final position circle with a diameter of DP_2i. Simultaneously, the outer cylinder of the screw forms an interference boundary circle with a diameter of DP_S. In this case, the screw needs to take into account the profile structure connected to the screw that needs to be avoided when assembling with the component assembly (composed of planetary rollers and guide discs). The following relationship needs to be satisfied:

[0023] DP_S<(DP_1a-Ro)

[0024] DP_S>(DP_2i-Ro)

[0025] For planetary roller screw drives assembled according to the first scheme described above, if disassembly is required, the entire assembly (in this case, the screw-roller ring unit) must first be unscrewed from the screw nut (also known as the nut ring). Then, the planetary rollers can be pushed outwards to the assembly position with minimal force. Finally, the screw is removed from the assembly including the guide plate and planetary rollers. Alternatively, the screw can be unscrewed from the assembly while the planetary rollers are still in the working position.

[0026] According to the second scheme, the assembly retaining profile is located radially inside the working retaining profile relative to the central axis of the planetary roller screw drive. In this case, the pre-assembled component group is first assembled in the most compact manner possible, meaning that the circumference formed by the centers of all planetary rollers (located in a plane perpendicular to the central axis of the entire component group and the subsequent planetary roller screw drive) has the smallest possible diameter. This compact component group can also be inserted into the screw nut without interference, without rotating any part of the component group or the screw nut. Once the component group reaches the preset axial position relative to the screw nut, the planetary rollers are pushed outward to their working positions. Subsequently, the screw can be screwed into the component group to complete the assembly of the planetary roller screw drive. In this scheme, the planetary roller screw drive can also be disassembled in the reverse order.

[0027] In the second scheme of the planetary roller screw drive, the planetary roller centers positioned by the assembly retaining contour form an inner assembly circle with a diameter of DP_1i, while the planetary roller centers positioned by the working retaining contour form an outer terminal circle with a diameter of DP_2a. Furthermore, in the second scheme, the inscribed cylinder of the screw nut forms an interference boundary circle with a diameter of DP_M. Similar to the logic of defining the interference boundary circle by the circumscribed cylinder of the screw, this interference boundary circle must also consider the contour structures that may cause interference when connected to the relevant screw drive elements (here, the screw nut); that is, no interference contours can exist within the range of the interference boundary circle. At this point, the following relationship is satisfied:

[0028] (DP_1i+Ro) <DP_M

[0029] DP_M<(DP_2a+Ro)

[0030] In both of the above schemes, the difference between the assembly circle diameter and the final position circle diameter of the planetary roller screw drive in the working state can be equivalent to, for example, 15% to 40% of the planetary roller diameter. Similarly, in both schemes, the assembly retaining profile and the working retaining profile can form two locking positions that can switch between each other while overcoming at least a small elastic restoring force.

[0031] In an improved embodiment, the device described in this application can be a roller screw drive, in which each component, such as the screw, rollers, and nut, has threads. Alternatively, the roller screw drive can be designed as a reverse-type roller screw drive. In this case, the rollers of the drive maintain a constant axial position relative to the screw. Attached Figure Description

[0032] Two embodiments of the present invention will now be further described with reference to the accompanying drawings. In these drawings:

[0033] Figure 1 The components to be assembled for a ball screw drive (in this example, a planetary ball screw drive) consist of two guide discs and a planetary roller as exemplarily shown.

[0034] Figure 2 for Figure 1 A partial end view of the device shown, in which the planetary rollers are held in the assembled position;

[0035] Figure 3 With similar Figure 2 The diagram shows one of the two guide disks, and the planetary roller that has been moved to the working position (i.e., moved radially inward);

[0036] Figure 4 and Figure 5This is a side view of a planetary roller screw drive, where the planetary rollers are located as follows: Figure 2 and Figure 3 The assembly and working positions are shown.

[0037] Figure 6 and Figure 7 for Figure 1 The geometric features of a planetary roller screw drive in the assembly process are shown, wherein the planetary rollers are exemplarily shown in the assembly position and the working position, respectively.

[0038] Figure 8 For another type of roller screw drive (in this example, a planetary roller screw drive), namely two guide discs and a planetary roller shown exemplarily;

[0039] Figure 9 for Figure 8 A partial view of a guide plate of the planetary roller screw drive shown.

[0040] Figure 10 and Figure 11 for Figure 8 The planetary roller screw drive shown is similar to Figure 4 and Figure 5 The views, exemplarily shown, depict planetary rollers in the assembly position and the working position, respectively;

[0041] Figures 12 to 14 For those in the assembly process, such as Figure 8 The geometric features of the planetary roller screw drive shown are illustrated, with the planetary rollers in pre-assembled, assembled, and working positions, respectively. Detailed Implementation

[0042] Unless otherwise stated, the following explanation applies to both embodiments. In all the drawings, corresponding or substantially identical components are indicated by the same reference numerals.

[0043] In both embodiments, the roller screw drive, generally indicated by reference numeral 1, is designed as a planetary roller screw drive. The planetary roller screw drive 1 is suitable, for example, for use in electromechanical actuators not further shown. The basic structure and function of the planetary roller screw drive 1 can be referenced to the prior art described above.

[0044] The planetary roller screw drive 1 includes a screw 2 and a screw nut 3, also known as a nut sleeve or simply a nut. The nut 3 can serve as the driving element of the roller screw drive 1, while the screw 2 can be used as a non-rotating, movable driven element. Conversely, the screw 2 can also be rotated to drive the screw 2, and the nut 3 can be used as a linearly moving driven element of the roller screw drive 1.

[0045] Planetary rollers 4, commonly referred to as rollers, are provided between the screw 2 and the nut 3. The screw 2 and the screw-nut 3 are collectively referred to as threaded drive elements 2 and 3. The thread (i.e., external thread) of the screw 2 is indicated by 5. The screw-nut 3 has segmented annular groove-shaped inner contours 6, and can be configured into multiple segments. Notably, the individual nut components can be pre-tightened to allow the roller screw drive device 1 to operate in a pre-tightened state.

[0046] Each planetary roller 4 is an elongated strip with a stepped diameter. The diameter of the planetary roller 4 is largest in the middle section 7, which is called the roller diameter Ro, or the diameter of the planetary roller 4. The middle section 7 has an annular groove profile 8, which meshes with the external thread 5 of the screw 2 during normal operation of the planetary roller screw drive.

[0047] Relatively thinner side sections 9 are connected to both sides of the central section 7. Each side section 9 has a consistent annular groove profile 10, which meshes with the inner profile 6 of the nut 3 when the roller screw drive 1 is running. In each embodiment shown in the figures, the roller screw drive 1 includes six planetary rollers 4. In other embodiments, other numbers of planetary rollers 4 may be included, preferably three to twelve.

[0048] During the adaptation process to the geometry of the external thread 5, the profile 8 of at least one planetary roller 4 is misaligned with each other in the axial direction of the screw 2, and thus in the axial direction of the entire planetary roller screw drive 1. There may be three different planetary rollers 4, with a first group of three planetary rollers 4 installed in a first direction, and a second group of three planetary rollers 4 (with the same composition as the first group) installed in the planetary roller screw drive 1 in the opposite direction.

[0049] Each planetary roller 4 has a side section 9 connected to an end section 11. Unlike the middle section 7 and the side section 9, the end section 11 is a smooth cylinder. Each end section 11 is housed in an independent guide plate 12, 13. Figures 1 to 7 In the illustrated embodiment, a pair of identical guide disks 12 are used; Figures 8 to 13 In the embodiment shown, a pair of identical guide disks 13 are also used.

[0050] Each guide disc 12, 13 has multiple grooves 14 according to the number of planetary rollers 4. The contour design of the grooves 14 allows the planetary rollers 4 to be held in either the assembly retaining contour 15 or the working retaining contour 16, wherein the working retaining contour 16 is spaced apart from the assembly retaining contour 15 in the radial direction of the guide discs 12, 13 (i.e., in the radial direction of the entire planetary roller screw drive 1 to be assembled). In all cases, that is, whether the planetary rollers 4 are in the assembly position (their end sections 11 are embedded in the assembly retaining contour 15) or in the operation-ready position (their end sections 11 are guided by the working retaining contour 16, i.e., in the working position), the centerlines of all planetary rollers 4 are aligned parallel to the centerlines of the pair of guide discs 12, 13. Switching between the assembly position and the working position can be achieved by overcoming a small elastic restoring force. In these cases, the assembly retaining contour 15 and the working retaining contour 16 form a locking contour.

[0051] exist Figures 1 to 7 In the illustrated embodiment, the assembly retaining profile 15 is located radially outside the working retaining profile 16. This means that, as in Figure 1 , Figure 2 , Figure 4 and Figure 6 As shown, for assembly, the planetary rollers 4 are first engaged in the outermost position of the groove 14 of the guide plate 12, at which point the roller screw drive 1 cannot yet operate. The outer assembly circle MKa formed by the center points of all the planetary rollers 4 (as shown) Figure 6 The diameter of the part shown is DP_1a. The assembly consisting of all the planetary rollers 4 and two guide disks 12 is called component group 17. Figure 1 , Figure 2 , Figure 4 and Figure 6 As shown in the partial diagram, after the assembly of component group 17 is completed, the screw 2 can be easily installed into component group 17. At this point, the interference boundary circle SKS of the screw 2 needs to be considered. This interference boundary circle includes the screw 2 (especially its external thread 5) and other contours connected to the screw 2 that may need to be overcome during the assembly process. Its diameter is represented by DP_S.

[0052] Component group 17 and screw 2 are combined and referred to as part group 18. From Figure 4 Starting with the shape of the part assembly 18 shown (with the planetary roller 4 temporarily fixed in the assembly retaining profile 15), the planetary roller 4 is pressed radially inward to form... Figure 3 , Figure 5 and Figure 7 The part group 18 shown is in this state (at which point the planetary roller 4 is finally guided by the working retaining profile 16). In this ready-to-work state, the center point of the planetary roller 4 forms a final positioning circle EK, the diameter of which is denoted by DP_2i.

[0053] exist Figures 1 to 7 In the embodiment shown, the planetary roller 4 needs to be pressed from the outside to the inside when switching from the assembly position to the working position. At this time, the following relationship exists:

[0054] DP_S<(DP_1a-Ro)

[0055] DP_S>(DP_2i-Ro)

[0056] Figures 8 to 14 The illustrated embodiments and Figures 1 to 7 The difference in the illustrated embodiment is that, during assembly, the planetary roller 4 needs to be pressed from the inside out. Accordingly, the assembly retaining profile 15 is located radially inside the working retaining profile 16.

[0057] The component assembly 17, consisting of planetary rollers 4 and guide discs 13, first follows... Figure 12 The assembly configuration shown is called the pre-assembly configuration. At this point, the planetary roller 4 is tangent to the contour of the guide plate 13 from the inside. The diameter of the circle (denoted as TK) formed by the center point of the planetary roller 4 is D_k. Starting from the pre-assembly position of the planetary roller 4, after overcoming a moderate elastic restoring force, it is moved to the assembly position (e.g., ...). Figure 8 , 10 (As shown in Figure 13). At this point, the planetary roller 4 is engaged in the assembly retaining profile 15. Alternatively, each planetary roller 4 can be moved sequentially from its pre-assembly position to the assembly position.

[0058] After that, as Figure 10 As shown, component group 17, consisting of planetary rollers 4 and two guide discs 13, is assembled with lead screw nut 3 to form part group 18. At this time, planetary rollers 4 are initially held in the assembled position. Figure 13 (Taking a single planetary roller 4 as an example). The inner assembly circle MKi formed by the center points of all planetary rollers 4 (e.g.) Figure 13 The diameter of (as shown) is DP_1i.

[0059] also, Figure 13 An interference boundary circle SKM is drawn, which is formed by the contour of the lead screw nut 3 and the contours of other components that may be connected to it (these contours can only be tangent to each other at most during assembly), and its diameter is DP_M. Figure 13 As shown, the planetary roller 4 is located within the interference boundary circle SKM, so the component assembly 17 can be installed into the lead screw nut 3 through pure linear motion.

[0060] After the component assembly 17 is positioned relative to the lead screw nut 3 in a predetermined manner, the planetary roller 4 moves from the inside to the outside to its working position while overcoming a moderate restoring force, thereby forming Figure 11 and Figure 14 The structure shown.

[0061] exist Figures 8 to 14 In the illustrated embodiment, the following relationship exists:

[0062] (DP_1i+Ro) <DP_M

[0063] DP_M<(DP_2a+Ro)

[0064] In this case, Ro also represents the diameter of planetary roller 4. Figures 8 to 14 In the embodiment shown, the planetary roller 4 moves outward during the assembly process, and the diameter of the final circle EK is represented by DP_2a.

[0065] List of reference numerals

[0066] 1. Roller screw drive device, planetary roller screw drive device

[0067] 2 screws

[0068] 3. Lead screw nut

[0069] 4 planetary rollers

[0070] 5 External threads

[0071] 6. Nut inner contour

[0072] 7. Central Section

[0073] 8. Meshing profile of the middle section

[0074] 9 Side Sections

[0075] 10 Side Section Meshing Profile

[0076] 11 End Section

[0077] 12 The boot disk of the first embodiment ( Figure 1-7 Example

[0078] 13 The boot disk of the second embodiment ( Figure 8-13 Example

[0079] 14 Grooves

[0080] 15. Assembly maintains contour

[0081] 16. Maintain the outline of the work.

[0082] 17. Component assembly consisting of planetary rollers 4 and guide disks 12 and 13

[0083] 18 parts group

[0084] Diameter of the D_k TK circle (the circle tangent to the planetary rollers on the guide plate)

[0085] DP_1a Outer assembly circle diameter

[0086] DP_1i Inner Assembly Circle Diameter

[0087] DP_2i is the diameter of the final circle of the planetary roller as it pushes inward.

[0088] DP_2a: The diameter of the final circle of the planetary roller as it pushes outward.

[0089] DP_M Diameter of the nut interference boundary circle

[0090] DP_S is the diameter of the screw interference boundary circle.

[0091] EK End Circle

[0092] MKa outer assembly circle

[0093] MKi internal assembly circle

[0094] Roller diameter (Ro)

[0095] SKM lead screw nut interference boundary circle

[0096] SKS screw interference boundary circle

[0097] The circle tangent to TK and the planetary rollers on the guide plate.

Claims

1. A roller screw drive device (1), comprising a screw (2) having external threads (5), a plurality of planetary rollers (4), and a screw nut (3) having an inner profile (6), wherein, Each of the planetary rollers (4) includes a contoured central section (7) defining the roller diameter (Ro) of the planetary roller (4) and two equally contoured side sections (9) thinner than the central section (7), wherein the central section (7) engages with the external thread (5) of the screw (2), and the side sections (9) engage with sections of the inner contour (6) of the lead screw nut (3), wherein the end section (11) of each of the planetary rollers (4) connected to the side section (9) is held in a groove (14) of separate guide discs (12, 13), characterized in that each groove (14) for fixing the planetary roller (4) is provided with an assembly retaining contour (15) and a working retaining contour (16) separate from the assembly retaining contour (15).

2. The roller screw transmission device (1) according to claim 1, characterized in that, The assembly retaining profile (15) is located radially outside the working retaining profile (16).

3. The roller screw transmission device (1) according to claim 2, characterized in that, The center of the planetary roller (4) positioned by the assembly retaining profile (15) forms an outer assembly circle (MKa) with an outer diameter of DP_1a, and the center of the planetary roller (4) positioned by the working retaining profile (16) forms an inner end circle (EK) with a diameter of DP_2i. The externally tangent cylinder of the screw (2) forms an interference boundary circle (SKS) with a diameter of DP_S, wherein the diameter satisfies the following relationship: DP_S<(DP_1a-Ro) DP_S>(DP_2i-Ro).

4. The roller screw transmission device (1) according to claim 1, characterized in that, The assembly retaining profile (15) is located radially inside the working retaining profile (16).

5. The roller screw transmission device (1) according to claim 4, characterized in that, The center of the planetary roller (4) positioned by the assembly retaining profile (15) forms an inner assembly circle (MKi) with a diameter of DP_1i, the center of the planetary roller (4) positioned by the working retaining profile (16) forms an outer end circle (EK) with a diameter of DP_2a, and the inscribed cylinder of the lead screw nut (3) forms an interference boundary circle (SKM) with a diameter of DP_M, wherein the diameters satisfy the following relationship: (DP_1i+Ro) <DP_M DP_M<(DP_2a+Ro).

6. The roller screw transmission device (1) according to any one of claims 1 to 5, characterized in that, The difference between the diameter (DP_1a, DP_1i) of the assembly circle (MKa, MKi) and the diameter (DP_2a, DP_2i) of the end circle (EK) is 15% to 40% of the roller diameter (Ro).

7. The roller screw transmission device (1) according to any one of claims 1 to 6, characterized in that, The two locking positions formed by the assembly retaining profile (15) and the working retaining profile (16) can switch back and forth while overcoming at least a small elastic restoring force.

8. A method for assembling a roller screw drive (1), comprising the following steps: - Prepare two types of lead screw drive elements (2, 3), namely a screw (2) and a lead screw nut (3), and prepare a plurality of slender, contoured planetary rollers (4) that can directly interact with the lead screw drive elements (2, 3), and two guide disks (12, 13) for guiding the ends of each planetary roller (4) respectively, wherein the guide disks (12, 13) have grooves (14), and the ends of the planetary rollers (4) can be selectively held in the mounting position or working position of the grooves (14). - Assemble all the planetary rollers (4) and the two guide discs (12, 13) into a component group (17), wherein each of the planetary rollers (4) is in the assembled position. - Assemble the component group (17) together with one of the two types of lead screw drive elements (2, 3). - Move each of the planetary rollers (4) from the assembly position to the working position. - The assembly of the roller screw drive device (1) is completed by installing the second screw drive element (3, 2).

9. The method according to claim 8, characterized in that, The component assembly (17), consisting of the planetary roller (4) and the two guide discs (12), is first assembled with the screw (2).

10. The method according to claim 8, characterized in that, The component assembly (17), consisting of the planetary roller (4) and the two guide discs (13), is first assembled with the lead screw nut (3).

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