Roller screw transmission device

Abstract

The roller screw drive (1) comprises a plurality of roller-shaped rolling bodies (5) which roll between the two screw drive elements (2, 3), namely the threaded spindle (3) and the nut (2). Each rolling body (5) has a thread (6) in the middle portion (7) thereof, which thread meshes with the thread (4) of the threaded spindle (3) and the internal thread (11) of the nut (2), and each rolling body has a toothing system (10) at at least one of the two ends thereof. The toothing system (10) engages in the form of a spur gear in the toothing system of at least one of the screw drive elements (2, 3). A toothing system (10) provided as an element of the spur gear mechanism is formed in a portion (8) of the thread (6) of the rolling body (5) having a uniform diameter.

Description

TECHNICAL FIELD

[0001] The invention relates to a roller screw drive according to the preamble of claim 1, which is suitable, for example, for electromechanical actuators. BACKGROUND

[0002] A generic roller screw drive is known, for example, from DE 92 14 062 U1. The known roller screw drive has a plurality of threaded rollers, i.e. rolling bodies, which are arranged between a screw spindle, i.e. a threaded spindle, and a rolling nut. The rolling nut, i.e. the nut provided with an internal thread, of the known roller screw drive can have a single-part or a multi-part design. In any case, an internally toothed sprocket is inserted into both end portions of the nut. At the end portions of the rolling bodies, there are outer toothing portions which are spaced apart from the thread of the rolling bodies and which engage with the inner toothing of the sprocket.

[0003] A further roller screw drive is disclosed in FR 3 095 487 B1. In this case, in addition to the threaded spindle and the nut of the screw drive, a plurality of roller-shaped rolling bodies also have a thread. The thread-like configured middle portion of each rolling body is adjoined on both sides by relatively thin portions provided with outer toothing. An element in the shape of an annular disc provided for guiding the rolling bodies has C-shaped recesses for receiving the externally toothed end portions of the rolling bodies.

[0004] US 2015 / 0276030 A1 relates to a roller screw drive which also comprises roller-shaped rolling bodies which have a threaded portion as a middle portion and two toothed outer portions. Here, the toothing system of the outer portions can describe a profile in the form of an internal cycloid. Towards the end faces of the rolling bodies, the toothed portions are adjoined by short cylindrical portions which engage in recesses of a ring. SUMMARY

[0005] The invention is based on the object of providing a roller screw drive which is further developed compared to the above-mentioned prior art and which has a particularly compact and production-friendly design.

[0006] According to the application, this object is achieved by a roller screw drive having the features of claim 1. In a manner known per se, the roller screw drive comprises a plurality of roller-shaped rolling bodies which roll between two elements, generally referred to as screw drive elements, namely a threaded spindle and a nut, wherein, during operation of the roller screw drive, one of the screw drive elements can serve as a drive element and the other screw drive element can serve as an output element of the roller screw drive. Each rolling body has a cylindrical, elongated basic shape and has a thread in its middle portion, which engages with both the thread of the threaded spindle and the inner thread of the nut. The thread can generally be configured as a single- or multi-start thread. At at least one of its two end portions, the entire roller-shaped rolling body has a toothing system which engages in the toothing system of at least one of the two screw drive elements mentioned in the manner of a spur gear mechanism.

[0007] According to claim 1, the toothing system provided by the rolling body as an element of a spur gear mechanism is formed in a portion of the thread of the rolling body which has a uniform diameter. In particular, the rolling body, generally also referred to as a planet wheel, is designed in the form of a threaded bolt, optionally with a pin-shaped extension at the end face. In any case, at least one portion in which the toothing system is formed has a dual function, namely on the one hand the function of a thread and on the other hand the function of a spur gear toothing. This means that there is a planet pinion toothing integrated into the thread, which engages with the toothing system of the nut, namely the nut ring and / or the threaded spindle of the roller screw drive.

[0008] The completely or substantially uniform diameter of the rolling body represents a simplification in terms of production engineering compared to the conventional rollers of roller screw drives with a diameter step. This still applies despite the fact that at least one portion of the rolling body used in the roller screw drive according to the application has a significantly more complex shape compared to conventional toothing systems or thread geometries. In the engagement area of the nut ring or the spindle, there is no gap between the teeth of the toothing system of the roller either in the tooth profile area or in the outer diameter, which allows a good space utilization and an advantageous design in terms of production engineering.

[0009] In particular, the thread of the rolling body extends over its entire length, apart from any pin of the rolling body by means of which it is mounted at the end face in the guide element. Due to the long length of the thread portion of the rolling body, there is a particularly good relationship between the force and torque that can be received on the one hand and the measurable length of the roller screw drive in the axial direction on the other hand.

[0010] At one or both ends of the rolling body, a spur gear toothing can be formed which is integrated into the thread of the rolling body in the described manner. In any case, the middle section of the rolling body is free of structures which would enable it to be used in a spur gear mechanism.

[0011] In contrast, the middle section which extends over more than half, in particular more than three quarters, of the length of the rolling body can be formed exclusively as a thread. This thread extends seamlessly into at least one section which additionally has the profile of a toothing system. The additional toothing structure slightly reduces the load capacity of the thread in the respective area. Due to the principles involved, there is no axial distance between the thread of the rolling body and the toothing structure which is also provided by the rolling body. In terms of the installation of the roller screw drive, the elimination of interfering edges represents a simplification compared to the old solutions.

[0012] Particularly advantageous kinematic conditions can be achieved in an embodiment in which the effective diameter of at least one toothing system of the rolling body, i.e. the pinion toothing, which is provided as an element of a spur gear mechanism, coincides with the effective diameter of the thread of the rolling body. Here, the toothing faces of the pinion toothing which are present in the form of notches in the thread of the rolling body, i.e. the roller, can each extend from a first toothing face of a thread tooth of the thread of the roller to the opposite toothing face of the same thread tooth of the thread of the roller.

[0013] The circumferential speeds which necessarily match in the area of the thread of the roller and in the area of the toothing system of the roller are of decisive importance here. Thus, due to the principles involved, the tensions and / or friction losses which arise due to different circumferential speeds on the profile of the same component are excluded.

[0014] The type of interaction between the threaded section and the simultaneously toothed section of the rolling body and the mentioned screw drive elements, i.e. the drive element and the output element of the roller screw drive, is in fact not different from the interaction between a rolling body which has only a threaded middle section and the two screw drive elements on the input side and on the output side.

[0015] Various design options exist for the tooth pairing which is given by the roller of the roller screw drive and the screw drive elements on its input and output side.

[0016] Various designs can be implemented in which exactly one of the two elements, the threaded spindle and the nut, has at least one toothing system which engages in the manner of a spur gear mechanism with the toothing of the roller. In this respect, the toothing system on the spindle or nut side can be formed directly by the respective screw drive element or by a separate component which is firmly connected to the element in question.

[0017] In all embodiments, one advantage of the invention is particularly the fact that the fusion of different profiles, namely the thread profile on the one hand and the tooth profile on the other hand, simplifies assembly and improves the ratio between installation space and mechanical load-bearing capacity.

[0018] In this context, the roller screw drive is part of the actuator in industrial devices, such as industrial robots or machine tools. Mobile applications are also conceivable, such as its use in actuators of motor vehicles. Attached Figure Description

[0019] Two exemplary embodiments of the invention will now be described in more detail with reference to the accompanying drawings. The drawings are shown in a simplified manner in some respects:

[0020] Figure 1 A cross-sectional view showing a first exemplary embodiment of the roller screw drive is shown.

[0021] Figure 2 With Figure 1 A similar illustration shows a second exemplary embodiment of the roller screw drive.

[0022] Figure 3 A perspective view of the rolling elements used in a roller screw drive is shown. Detailed Implementation

[0023] Unless otherwise stated, the following description relates to two exemplary embodiments. In all the figures, parts that correspond to each other or have substantially the same effect are indicated by the same reference numerals.

[0024] The roller screw drive, generally designated by reference numeral 1 in the accompanying drawings, is intended for use as a rotary linear drive in electromechanical actuators (not shown further). For the main function of the roller screw drive 1, refer to the prior art cited at the beginning.

[0025] The roller screw drive 1 includes a threaded spindle 3 and an associated nut 2, wherein the nut 2, also known as a nut ring, can be used as the drive element of the roller screw drive 1, and the threaded spindle 3 can be used as the output element of the roller screw drive capable of preventing rotational displacement. Conversely, the threaded spindle 3 can also be rotatably driven, and the nut 2 can be used as a linearly adjustable output element of the roller screw drive 1. The threaded spindle 3 and the nut 2 are collectively referred to as screw drive elements 2 and 3. The central axis of the two concentric screw drive elements 2 and 3, i.e., the central axis of the entire roller screw drive 1, is marked MG.

[0026] The rollers 5 are arranged as rolling elements between the threaded spindle 3 and the nut 2 of the roller screw drive 1. The thread of the threaded spindle 3 is designated with 4, the thread of the nut 2 is designated with 11. In a manner not shown, the nut 2 can have a multi-part design, wherein in particular the individual nut parts can be tensioned against one another in order to operate the roller screw drive 1 under preloading. The thread 6 of each roller 5 interacts with the thread 4, 11 of the drive element 2 or the output element 3. The center axis of the roller 5, designated MP, lies on the surface of an imaginary cylinder which is concentric with the center axis MG of the entire roller screw drive 1.

[0027] Each roller 5 has a middle portion 7 which is adjoined by two side portions 8. The middle portion 7 together with the seamlessly adjoined side portions 8 of the same diameter forms an effective portion 12 of the roller 5, which is also generally referred to as a planetary wheel. The effective portion 12 extends over a large part of the length of the roller 5. In contrast to the simplified sketch in Figure 1 and Figure 2 The sum of the lengths of the two side portions 8 is less than the length of the middle portion 7 in comparison with the simplified sketch in Figure 3 In addition to the thread 6 which extends over the entire effective portion 12, the side portions 8 have a toothing system 10 in the form of pinion toothing, which is incorporated into the thread 6, as can be seen in particular in Figure 3 The rolling element 5 according to Figure 1 is suitable for installation in a roller screw drive 1 according to Figure 2 is suitable for installation in a roller screw drive 1 according to

[0028] As can also be partially seen in Figure 3 , pins 13 with a relatively small diameter are adjoined to the side portions 8. The pins 13, which are not shown in Figure 1 , are guided in a cage disc of the roller screw drive 1, which is also not shown. Instead of the pins 13 of the roller 5, there can also be pins with the same function on the cage disc, which engage in the end face holes of the roller 5. In this case, the length of the effective portion 12 is identical to the length of the roller 5.

[0029] The toothing system 10 formed in each side portion 8 of the roller 5 is provided in the form of individual notches 14, which interrupt the helical shape of the thread 6. As can be seen from Figure 3As can be seen, the depth of the recess 14 decreases from the end face of the roller 5 towards the intermediate portion 7. Finally, the intermediate portion 7 is free of recesses. The thread teeth of the thread 6 of the roller 5 are designated by 16. The thread teeth 16 have a tooth face 17 which is interrupted at defined points by the more or less deep recesses 14 of the pinion teeth 10. The tooth face of the recess 14, designated by 18, extends from one tooth face 17 of a thread tooth 16 to the opposite tooth face 17 of the same thread tooth 16.

[0030] In the case shown in Figure 1 , the toothing system 10 of the roller 5 in the form of the recesses 14 engages in the toothing system 9 of the nut 2 in the manner of a spur gear mechanism. The effective diameter of the toothing system 10 of the roller 5 coincides with the effective diameter of the thread 6.

[0031] In contrast to the nut 2, the threaded spindle 3 is not provided with a spur gear mechanism in the case shown in Figure 1 . If such spur gear teeth are provided which are incorporated into the thread 4, the threaded spindle 3, the roller 5 and the nut 2 would work together in the manner of a planetary gear in addition to the function as a rotary-linear transmission.

[0032] The exemplary embodiment according to Figure 2 differs from the exemplary embodiment according to Figure 1 in that, instead of the nut 2, the threaded spindle 3 is provided with a toothing system which is designated here by 15. Thus, in the case shown in Figure 2 , there is an interaction of gear elements in the manner of a spur gear mechanism between each roller 5 and the threaded spindle 3.

[0033] In both the exemplary embodiment according to Figure 1 and the exemplary embodiment according to Figure 2 , a defined conversion of rotary into linear movement is given. In each of these cases, exactly one of the two screw drive elements 2, 3, i.e. either the nut 2 or the threaded spindle 3, is provided with a toothing system 9, 15.

[0034] In both cases, the fact that the thread 6 extends over a large part or even the entire length of the roller 5 leads to a high load capacity of the roller screw drive 1 in comparison with its outer dimensions, in particular in the axial direction.

[0035] List of reference signs

[0036] 1 roller screw drive

[0037] 2 nut

[0038] 3 threaded spindle

[0039] 4 thread of the threaded spindle

[0040] 5 roller, rolling body

[0041] 6 thread of the roller

[0042] 7 middle portion of the roller

[0043] 8 side portion of the roller

[0044] 9 toothing system of the nut

[0045] 10 toothing system of the roller, pinion toothing

[0046] 11 thread of the nut

[0047] 12 effective portion

[0048] 13 bore

[0049] 14 recess

[0050] 15 toothing system of the threaded spindle

[0051] 16 thread teeth of the thread of the roller

[0052] 17 flank of the thread teeth of the thread of the roller

[0053] 18 flank of the pinion toothing

[0054] MG center axis of the threaded spindle

[0055] MP center axis of the roller

Claims

1. A roller screw drive device (1) having a plurality of roller-shaped rolling elements (5) rolling between two screw drive elements (2, 3), namely a threaded spindle (3) and a nut (2), wherein, Each rolling element (5) has a thread (6) in its middle portion (7) that meshes with the thread (4) of the thread spindle (3) and the internal thread (11) of the nut (2), and each rolling element has a tooth system (10) at at least one of its two ends that engages in a spur gear mechanism with the tooth system of at least one of the screw drive elements (2, 3), characterized in that the tooth system (10) provided as an element of the spur gear mechanism is constructed as pinion teeth in the portion (8) of the thread (6) of the rolling element (5) having a uniform diameter.

2. The roller screw drive device (1) according to claim 1, characterized in that, The thread (6) of the rolling element (5) extends to the end face pin (13) of the rolling element (5).

3. The roller screw drive device (1) according to claim 2, characterized in that, At the two ends of the effective portion (12) of the roller-shaped rolling element (5) where the thread (6) is provided, a tooth system (10) that can belong to the spur gear mechanism is formed respectively.

4. The roller screw drive device (1) according to any one of claims 1 to 3, characterized in that, The effective diameter of the tooth system (10) provided by the rolling element (5) as an element of the spur gear mechanism is consistent with the effective diameter of the thread (6) of the rolling element (5).

5. The roller screw drive device (1) according to claim 4, characterized in that, The tooth surface (18) of the pinion tooth (10) extends from the first tooth surface (17) of the thread tooth (16) of the thread (6) of the roller (5) to the opposite tooth surface (17) of the same thread tooth (16) of the thread (6) of the roller (5).

6. The roller screw drive device (1) according to any one of claims 1 to 5, characterized in that, Only the threaded spindle (3) has a tooth system (15) that interacts with the pinion teeth (10) of each rolling element (5) in a spur gear mechanism.

7. The roller screw drive device (1) according to any one of claims 1 to 5, characterized in that, Only the nut (2) has a tooth system (9) that interacts with the pinion teeth (10) of each rolling element (5) in a spur gear mechanism.

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