Linear actuators and manufacturing methods

Abstract

This invention relates to a linear actuator (1) and a method for manufacturing such a linear actuator (1). A roller screw nut (3), a roller screw shaft (4), and a plurality of planetary rollers (5) form an inverted planetary roller screw mechanism. According to the invention, a bearing (2) is provided to support a rotating component (6) of the linear actuator (1). The bearing (2) includes a mounting member (7) and a plurality of bearing rollers (8) engaging with a first bearing portion (9) of the mounting member (7) and a second bearing portion (10) of the rotating component (6). The plurality of slotted bearing rollers (8) are axially fixed relative to the rotating component (6) and the mounting member (7).

Description

Technical Field

[0001] The present invention relates to a linear actuator and a method for manufacturing such a linear actuator. Background Technology

[0002] Linear actuators typically comprise mechanisms that convert rotary motion, such as the rotational motion of a motor shaft, into translational or “linear” motion. Several such mechanisms are known in the art, ranging from simple screw-nut configurations to ball screws and (planetary) roller screws.

[0003] Such linear actuators are used, for example, to translate machine parts. A particular area of ​​application is transportation, such as trains or airplanes. Linear actuators can be used to move, for example, flaps, landing gear, or rudders.

[0004] However, in many such applications, weight and space requirements are challenging. For example, to activate flaps on an aircraft wing, the corresponding actuator must be adapted to the wing. Furthermore, the actuator height must be able to handle high (axial) loads. These requirements can be met using inverted roller screw mechanisms. These mechanisms can be implemented in a very compact manner and allow for very precise and rapid linear motion. Summary of the Invention

[0005] Therefore, the object of the present invention is to provide an improved linear actuator, particularly a lightweight and / or compact linear actuator.

[0006] This objective is achieved by the linear actuator according to the independent claim and the method of manufacturing the linear actuator.

[0007] Preferred embodiments of the present invention are governed by the dependent claims and the following description.

[0008] According to a first aspect of the invention, a linear actuator includes a roller screw nut, a roller screw shaft, and a plurality of planetary rollers forming an inverted roller screw mechanism. According to the invention, a bearing is provided to support a rotating component of the linear actuator. The bearing includes a mounting member and a plurality of bearing rollers engaging with a first bearing portion of the mounting member and a second bearing portion of the rotating component. The plurality of slotted bearing rollers are axially fixed relative to the rotating component and the mounting member.

[0009] An aspect of the invention is based on supporting the rotating component of a linear actuator, such as a roller screw nut, with a bearing comprising a plurality, preferably a plurality, elongated, slotted bearing rollers. For this purpose, the rotating component advantageously includes a second bearing portion, which can be engaged by the plurality of slotted bearing rollers. Furthermore, the bearing advantageously includes a mounting member having a first bearing portion, which can also be engaged by the plurality of slotted bearing rollers. By supporting the rotating component of the linear actuator with a plurality of slotted bearing rollers, high loads can be transmitted. However, the space required to achieve the same load capacity can be significantly reduced compared to conventional bearings, such as thrust bearings or angular contact ball bearings.

[0010] For example, each of a plurality of bearing rollers can provide multiple contact points for the rotating component in the second bearing section and for the mounting component in the first bearing section. To achieve the same number of contact points as an angular contact ball bearing, a corresponding number of balls must be used. However, this large number of balls requires more space and further contributes to high weight.

[0011] To support the rotating component of the actuator, a plurality of bearing rollers are advantageously arranged radially between the rotating component and the mounting member, so that they engage with either a second bearing portion or a first bearing portion, respectively. Preferably, the bearing rollers are distributed radially around the rotating component. In particular, the bearing rollers may be radially distributed around the rotating component at equal intervals. When the rotating component rotates, especially relative to the mounting member, the bearing rollers can roll circumferentially along the surface of the rotating component. Advantageously, the bearing rollers roll in such a way that they do not make any axial movement relative to either the rotating component or the mounting member.

[0012] Preferred embodiments of the present invention and further aspects thereof are described below, wherein each aspect, unless explicitly excluded, may be combined with each other as needed and in conjunction with aspects of the invention described below.

[0013] In a preferred embodiment, each bearing roller includes at least one groove forming a thread. The thread preferably engages with a first thread of the mounting and a second thread of the rotating component. Advantageously, the first bearing portion includes the first thread and / or the second bearing portion includes the second thread. This thread facilitates the rolling of the bearing roller along the surface of the rotating component in the circumferential direction. Simultaneously, the thread can provide a large number of contact points between the rotating component or mounting and each bearing roller, thereby enabling the transmission of high loads axially.

[0014] In another preferred embodiment, the helix angles of the bearing roller threads, the first thread helix angle, and the second thread helix angle are equal. In this way, axial movement of the bearing roller relative to the rotating component or mounting component can be suppressed respectively. In other words, with equal helix angles, the bearing roller can be axially fixed without any additional means. Therefore, equal helix angles are advantageous for compact and lightweight actuators.

[0015] In yet another preferred embodiment, the roller screw nut includes a second bearing portion. In other words, the nut, corresponding to the rotating component, is engaged not only by a plurality of planetary rollers but also by a plurality of bearing rollers. Thus, the nut can be rotatably mounted on a machine component, such as an aircraft wing, via a mounting element, so that the axis translates (linearly) as the nut rotates.

[0016] In yet another preferred embodiment, the second bearing portion axially at least partially overlaps with the third thread of a ball screw nut that engages with a plurality of planetary rollers. For example, the nut includes the third thread on its inner surface. Thus, the nut advantageously includes the second bearing portion located on its outer surface. Preferably, the third thread extends axially substantially the entire length of the nut. Conversely, it is preferred that the second bearing portion extends axially only to about the length of one bearing roller. Thus, the second bearing portion and the third thread can be radially spaced and partially overlap axially. This results in an actuator with a shorter axial length.

[0017] In yet another preferred embodiment, the ball screw shaft includes a second bearing portion. In other words, the shaft, corresponding to the rotating component, is engaged not only by a plurality of planetary rollers but also by a plurality of bearing rollers. Thus, the shaft can be rotatably mounted on a machine component, such as an aircraft wing, via a mounting bracket, so that the ball screw nut translates (linearly) as the ball screw shaft rotates.

[0018] In yet another preferred embodiment, the mounting member is at least partially hollow, and a first bearing portion is arranged on the inner surface of the mounting member, particularly the inner surface of the hollow portion. For example, the mounting member can be configured as a bushing. The at least partially hollow mounting member can be arranged around the circumferential outer surface of a rotating component, such as a nut or shaft. In such an arrangement, the mounting member can be designed to be particularly thin, thereby reducing space requirements and weight.

[0019] In yet another preferred embodiment, the second bearing portion is disposed on the outer circumferential surface of the rotating component. For example, the nut may include an internal thread for engaging with the threads of the planetary rollers and an external thread for engaging with the threads of the bearing rollers. The second bearing portion being located on the outer surface of the rotating component allows the mounting component to be arranged around the outer circumference of the rotating component, saving axial space.

[0020] In yet another preferred embodiment, the second bearing portion is arranged on the inner surface of the roller screw nut. Therefore, the bearing rollers can be arranged inside the nut. This enables an actuator with a particularly small cross-section.

[0021] In yet another preferred embodiment, the second bearing portion is arranged axially adjacent to the threads of the rotating component that engage with a plurality of planetary rollers. In particular, the second portion can be directly connected to the threads. For example, the threads for engaging with the planetary rollers can be directly connected to the second threads for engaging with the bearing rollers. It is even conceivable that the threads for engaging with the planetary rollers can be incorporated into the threads for engaging with the bearing rollers. In other words, a section of the thread for engaging with the planetary rollers can form the second portion. Arranging the second bearing portion and the threads adjacent to each other on the rotating component facilitates efficient manufacturing.

[0022] In yet another preferred embodiment, at least a portion of the mounting member extends axially into the roller screw nut. For example, the mounting member may include a shaft portion extending axially into the nut. Preferably, the bearing rollers are arranged radially between the interior of the shaft portion and the exterior of the nut. In this way, the mounting member can function similarly to a shaft, on which the nut, i.e., the rotating component, is rotatably supported. This allows for a significant reduction in the cross-sectional area of ​​the linear actuator.

[0023] In yet another preferred embodiment, the first bearing portion is arranged on the outer circumferential surface of the mounting member, which is located inside the roller screw nut. Preferably, the mounting member includes a shaft portion on which the first bearing portion is arranged. In this way, a particularly thin actuator with a significantly reduced cross-section can be achieved.

[0024] In yet another preferred embodiment, the rotating component of the actuator includes a collar with a second bearing portion disposed thereon. Preferably, the collar is integrated into the rotating component; that is, the collar and the rotating component are manufactured as a single piece. Alternatively, the collar is mounted onto the rotating component. For example, the collar can be clamped onto the rotating component. Preferably, the second bearing portion is disposed on the outer circumferential surface of the collar. The second bearing portion can extend from the rotating component via the collar. This simplifies the mounting of the linear actuator on, for example, machine parts, particularly for mounting actuators inside aircraft wings.

[0025] In yet another preferred embodiment, the grooves of each bearing roller form their own closed loops separated by a plurality of ridges. These ridges engage with a plurality of complementary grooves of the mounting element and a plurality of complementary grooves of the rotating component. Advantageously, the first bearing portion includes, and is particularly defined by, the separate closed grooves of the mounting element, and / or the second bearing portion includes, and is particularly defined by, the separate closed grooves of the rotating component. Preferably, each ridge and / or groove has an annular shape. In other words, each ridge and / or groove extends perpendicular to the axial direction. The ridges of the bearing rollers can facilitate the rolling of the bearing rollers circumferentially along the surface of the rotating component. In particular, the ridges engaging with the corresponding grooves can prevent axial movement of the bearing rollers as they rotate along the surface of the rotating component.

[0026] The method according to the second aspect of the invention is used to manufacture linear actuators, particularly linear actuators according to the first aspect of the invention. The threads of the rotating component engaging with a plurality of planetary rollers and the second portion of the rotating component for engagement with a plurality of slotted bearing rollers are formed in a single machining step. For example, the threads of the rotating component for engaging with the plurality of planetary rollers and the second thread of the rotating component can be cut into the rotating component in a single machining step. In particular, the threads can be cut into the rotating component sequentially or at least partially simultaneously. In this way, the actuator can be manufactured in a particularly efficient and time-saving manner.

[0027] Preferred applications of the linear actuator according to the first aspect of the invention relate to aircraft, particularly airplanes or spacecraft. The actuator of the invention is particularly suitable for flight control due to its high compactness, low weight, and long service life. However, such actuators can also be used in other fields, such as valve control in oil and gas applications, or tool positioning in spot welding or other robotic applications.

[0028] The nature, features, and advantages of the invention described above, as well as the ways in which they are implemented, will be explained in more detail in the following exemplary description in conjunction with the accompanying drawings. Where appropriate, the same reference numerals are used in the drawings for the same or corresponding elements of the invention. The examples are intended to explain the invention and do not limit the invention to the combinations of features shown therein, even in terms of functional features. Furthermore, any feature disclosed in the above description and in the examples below can be considered individually and appropriately combined with features of any of the above embodiments and their further aspects. In particular, each feature described above and below can be combined individually or in combination with other described features, in conjunction with the linear actuator according to the first aspect of the invention and the method according to the second aspect of the invention. Attached Figure Description

[0029] At least in part, in a schematic diagram,

[0030] exist Figure 1 An example of a linear actuator is shown, including an outer bearing for rotating a support roller screw nut;

[0031] exist Figure 2 An example of a linear actuator is shown, including an inner bearing for rotating a support roller screw nut;

[0032] exist Figure 3 An example of a linear actuator is shown, including an outer bearing for rotating a support roller screw shaft. Detailed Implementation

[0033] Figure 1 An example of a linear actuator 1 is shown, including an outer bearing 2 for rotating a support roller screw nut 3. The actuator 1 further includes a roller screw shaft 4 and a plurality of planetary rollers 5 arranged radially between the nut 3 and the shaft 4. The nut 3, shaft 4, and the plurality of planetary rollers 5 form an inverted planetary roller screw mechanism.

[0034] exist Figure 1 In the example shown, nut 3 corresponds to the rotating component 6 of actuator 1. This means that during operation, nut 3 rotates not only relative to shaft 4 but also relative to the mounting member 7 of bearing 2. Preferably, actuator 1 is mounted to an external machine component via mounting member 7. For example, actuator 1 can be mounted inside an aircraft wing via mounting member 7. Advantageously, mounting member 7 can therefore be rotatably fixed relative to the environment surrounding actuator 1, thereby allowing bearing 2 to rotatably support rotating component 6. Thus, rotating component 6 can rotate relative to the environment surrounding actuator 1 in its mounted state.

[0035] When the nut 3 rotates, the planetary roller 5 moves axially along the inner circumferential surface 3a of the nut 3. For this purpose, the nut 3 includes a third thread 3b arranged on the inner surface 3a, which meshes with the external thread 5a of the planetary roller 5. The thread 5a of the planetary roller 5 also meshes with a fourth thread 4b of the shaft 4, which is arranged on the outer circumferential surface 4a of the shaft 4.

[0036] The threads 5a of the planetary roller 5, the third thread 3b of the nut 3, and the fourth thread 4b of the shaft 4 are configured to fix the planetary roller 5 axially relative to the shaft 4. This means that during rotation, the planetary roller 5 will not move along the outer surface 4a of the shaft 4, i.e., it will not move axially. This is preferably achieved by providing equal helix angles for the fourth thread 4b and the thread 5a of the planetary roller 5. Conversely, the helix angle of the third thread 3b is different from that of the thread 5a of the planetary roller 5, which facilitates axial movement of the nut 3 when it rotates relative to the shaft 4.

[0037] To rotatably support the rotating component 6, i.e., the nut 3, the bearing 2 includes a plurality of slotted bearing rollers 8. The bearing rollers 8 are arranged and / or configured to engage with the first bearing portion 9 of the mounting member 7 and the second bearing portion 10 of the rotating component 6.

[0038] Preferably, the slotted bearing rollers 8 are arranged parallel to the rotation axis of the rotating component 6 and / or the symmetry axis of the mounting component 7.

[0039] When the rotating component 6, i.e., the nut 3, rotates, the bearing rollers 8 move circumferentially along the outer surface 6c of the rotating component 6, thereby facilitating low friction. In other words, the bearing rollers 8 are configured to rotate around the rotating component 6 in a planetary manner.

[0040] The bearing roller 8 is fixed axially relative to the mounting member 7 and the rotating member 6. This means that during the operation of the actuator 1, i.e., when the rotating member 6 rotates, the bearing roller 8 will not move axially.

[0041] Therefore, in this example, each bearing roller 8 includes an external thread that engages with a first thread 11 of the mounting member 7 and a second thread 12 of the rotating member 6. Advantageously, the thread of each bearing roller 8 is formed by a helical groove. Preferably, a first bearing portion 9 is defined by the first thread 11, and / or a second bearing portion 10 is defined by the second thread 12. By providing equal helix angles for the threads of the bearing roller 8, the first thread 11, and the second thread 12, axial movement of the bearing roller 8 relative to the rotating member 6 and the mounting member 7 can be suppressed.

[0042] In this example, the mounting member 7 is hollow. Therefore, the first thread 11 is preferably arranged on the inner surface of the mounting member 7. Therefore, the second thread 12 is preferably arranged on the outer surface of the rotating component 6. The advantage of this configuration is that the actuator 1 can be designed very compactly. In particular, less space is required in the radial direction compared to actuators that include conventional thrust bearings.

[0043] In other words, by using bearing 2, which includes bearing rollers 8 for supporting the rotating component 6, particularly the nut 3, the cross-section of actuator 1 can be reduced. This is because the second bearing portion 10, particularly the second thread 12, is arranged on the outer surface 6c of the rotating component 6, i.e., the nut 3, while the third thread 3b of the nut 3 is arranged on the inner surface 3a, and the second bearing portion 10 can at least partially overlap with the third thread 3b in the axial direction. In this way, the axial length of actuator 1 can be minimized.

[0044] Figure 2 An example of a linear actuator 1 is shown, including an inner bearing 2 for rotating a support roller screw nut 3. Figure 1Similarly, in the example shown, nut 3, together with multiple planetary rollers 5 and roller screw shaft 4, forms an inverted roller screw mechanism, wherein nut 3 corresponds to the rotating part 6 of actuator 1. Bearing 2 includes mounting member 7 and multiple slotted bearing rollers 8 arranged radially between mounting member 7 and rotating part 6 so as to engage with a first bearing portion 9 of mounting member 7 and a second bearing portion 10 of rotating part 6.

[0045] Figure 2 The example shown is the same as Figure 1 The difference in this example is that the second bearing portion 10 is arranged on the inner surface 3a of the nut 3. Therefore, a plurality of bearing rollers 8 are arranged inside the nut 3.

[0046] For this purpose, the mounting member 7 is preferably designed as a shaft. In particular, the mounting member 7 may include a shaft portion. Advantageously, the mounting member 7, especially the shaft portion, extends partially into the nut 3. More preferably, a first bearing portion 9 is arranged on the outer circumferential surface of the mounting member 7, particularly on the outer circumferential surface of the portion of the mounting member 7 arranged inside the nut 3.

[0047] The advantage of this configuration of actuator 1 is that the cross-section can be further reduced. In particular, the outer diameter of nut 3, i.e., the outer circumferential surface 6c of rotating component 6, can limit the maximum cross-section of actuator 1. Therefore, actuator 1 can be easily installed in confined spaces, such as the interior of an aircraft wing.

[0048] Preferably, the second bearing portion 10 is axially adjacent to the third thread 3b of the nut 3, which is provided for engagement with the thread 5a of the planetary roller 5. Although not shown in this example, it is conceivable that the planetary roller 5 and the bearing roller 8 share the same thread. In other words, the third thread 3b can be consistent with the second thread 12. This can significantly reduce manufacturing work. In particular, the second and third threads 12, 3b can be formed in a single machining step.

[0049] Figure 3 An example of a linear actuator 1 is shown, including an outer bearing 2 for rotating a support roller screw shaft 4. Figure 1 Similarly, in the example shown, shaft 4 is part of an inverted ball screw mechanism, in which multiple planetary rollers 5 engage with the fourth thread 4b of shaft 4 and the third thread 3b of ball screw nut 3.

[0050] Figure 3 The example shown is the same as Figure 1The difference in this example is that shaft 4 corresponds to the rotating component 6 of actuator 1, rather than nut 3. In other words, shaft 4 is advantageously rotatably supported relative to the surrounding environment of actuator 1. For this purpose, bearing 2 includes mounting 7 and a plurality of bearing rollers 8 that engage with mounting 7 in a first bearing portion 9. The bearing rollers 8 further engage with the rotating component 6, i.e., shaft 4, in a second bearing portion 10.

[0051] The bearing rollers 8 are axially fixed relative to the rotating component 6, i.e., the shaft 4, and relative to the mounting component 7.

[0052] Therefore, in this example, when shaft 4 rotates, nut 3 translates axially relative to mounting piece 7.

[0053] Preferably, shaft 4, i.e., rotating component 6, includes collar 13, wherein a second bearing portion 10 is arranged on the outer circumferential surface of collar 13. This allows mounting member 7 to have a larger diameter. In particular, in this way, mounting member 7 can protrude radially from nut 3. In other words, mounting member 7 can define the maximum cross-section of actuator 1. Therefore, actuator 1 can be mounted via mounting member 7 without being interfered with by nut 3.

[0054] In another variant of actuator 1, the collar 13 is sized so that the mounting 7 does not protrude radially from the nut 3. In particular, the collar 13, including the mounting 7, can be integrated into the actuator end interface (not shown).

[0055] The collar 13 can be integrated with the shaft 4. That is, the shaft 4 and the collar 13 can be manufactured as a single piece. Alternatively, the collar can also be attached to the shaft 4, for example, by clamping. In this way, the actuator 1 can be easily adapted to different environments. In yet another case, the shaft 4 can be replaced by a corresponding female interface.

[0056] List of reference numerals

[0057] 1. Linear actuator

[0058] 2 bearings

[0059] 3. Roller screw nut

[0060] 3a Inner surface

[0061] 3b Third thread

[0062] 4. Roller screw shaft

[0063] 4a Outer surface

[0064] 4b Fourth thread

[0065] 5 planetary rollers

[0066] 5a Planetary Roller Thread

[0067] 6 Rotating components

[0068] 6c outer surface

[0069] 7 Installation components

[0070] 8 Bearing Rollers

[0071] 9 Part 1

[0072] 10 Part Two

[0073] 11 First Thread

[0074] 12 Second Thread

[0075] 13 collars

Claims

1. A linear actuator (1) comprising a roller screw nut (3), a roller screw shaft (4), and a plurality of planetary rollers (5) forming an inverted roller screw mechanism, wherein, The plurality of planetary rollers (5) are axially fixed relative to the ball screw shaft (4), and the rotating component (6) is further characterized in that a bearing (2) supporting the rotating component (6) includes a mounting member (7) and a plurality of slotted bearing rollers (8), the plurality of slotted bearing rollers (8) engaging with a first bearing portion (9) of the mounting member (7) and a second bearing portion (10) of the rotating component (6), the plurality of slotted bearing rollers (8) being axially fixed relative to the rotating component (6) and the mounting member (7).

2. The linear actuator (1) according to claim 1, wherein, Each bearing roller (8) includes at least one groove forming a thread that engages with the first thread (11) of the mounting member (7) and the second thread (12) of the rotating component (6).

3. The linear actuator (1) according to claim 2, wherein, The helix angles of the threads of the bearing roller (8), the first thread (11), and the second thread (12) are equal.

4. The linear actuator (1) according to any one of the preceding claims, wherein, The roller screw nut (3) includes a second bearing portion (10).

5. The linear actuator (1) according to claim 1, wherein, The second bearing portion (10) at least partially overlaps axially with the third thread (3b) of the roller screw nut (3), which meshes with the plurality of planetary rollers (5).

6. The linear actuator (1) according to any one of claims 1 to 3, wherein, The ball screw shaft (4) includes the second bearing portion (10).

7. The linear actuator (1) according to claim 1, wherein, The mounting member (7) is at least partially hollow, and the first bearing portion (9) is arranged on the inner surface of the mounting member (7).

8. The linear actuator (1) according to claim 1, wherein, The second bearing portion (10) is arranged on the outer circumferential surface (6c) of the rotating component (6).

9. The linear actuator (1) according to claim 1, wherein, The second bearing portion (10) is arranged on the inner surface (3a) of the roller screw nut (3).

10. The linear actuator (1) according to claim 1, wherein, The second bearing portion (10) is arranged axially adjacent to the threads (3b; 4b) of the rotating component (6), which mesh with the plurality of planetary rollers (5).

11. The linear actuator (1) according to claim 1, wherein, At least a portion of the mounting component (7) extends axially into the ball screw (3).

12. The linear actuator (1) according to claim 1, wherein, The first bearing portion (9) is arranged on the outer circumferential surface of the mounting member (7), which is arranged inside the roller screw nut (3).

13. The linear actuator (1) according to claim 1, wherein, The rotating component (6) includes a collar (13) on which the second bearing portion (10) is arranged.

14. The linear actuator (1) according to claim 1, wherein, The grooves of each bearing roller (8) form their own closed loops separated by a plurality of ridges, which engage with a plurality of complementary grooves of the mounting (7) and a plurality of complementary grooves of the rotating component (6).

15. A method for manufacturing a linear actuator (1) according to any one of the preceding claims, characterized in that, The threads of the rotating component (6) that mesh with the plurality of planetary rollers (5) and the second bearing portion (10) of the rotating component (6) for engagement with the plurality of slotted bearing rollers (8) are formed in a single machining step.

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