Lead screw drive and method for manufacturing such a lead screw drive

Abstract

The invention relates to a lead screw drive (10) for adjusting a movable component in a motor vehicle, having a lead screw (20) with a lead screw thread (22), and a worm wheel (30) arranged in a rotationally fixed manner on the lead screw (20), wherein the lead screw (20) can be rotated by means of a motor-driven worm (32) via the worm wheel (30), wherein the worm wheel (30) is arranged at a first axial end (21) of the lead screw (20) and a separately produced thrust element (40) is arranged at an axial end side (31) of the worm wheel (30), which surrounds the lead screw (20) over the entire circumference and is supported in an axially elastic manner at an axial stop (50) with a thrust face (42).

Description

Technical Field

[0001] The present invention relates to a lead screw drive device according to the preamble of the independent claim, and a method for manufacturing such a lead screw drive device. Background Technology

[0002] A lead screw drive device is known from DE 10 2018 204 196 A1, which is used as a component of a comfort drive system for seat adjustment in a motor vehicle. The lead screw drive device includes a drive motor that rotates the lead screw about its longitudinal axis. A lead screw nut is arranged on the lead screw thread, which is at least indirectly connected to the element to be adjusted, particularly the seat. As the lead screw rotates about its axis of rotation, the lead screw nut moves along the axis of rotation of the lead screw, thus causing the seat to move.

[0003] DE 202 00 928 U1 discloses a lead screw drive device in which the lead screw is axially supported at an axial stop in the transmission mechanism housing. Here, a metal ball is arranged between the metal lead screw and the axial stop, by means of which the lead screw is supported axially at the axial stop in an approximately point-like manner. This axial thrust has very low friction and therefore very high efficiency along with low braking torque. If this axial force is applied to the lead screw towards the axial stop, there is a risk of impact movement of the components to be adjusted. Summary of the Invention

[0004] The purpose of this invention is to overcome the aforementioned disadvantages and provide a stop element for a lead screw drive mechanism that can be used universally.

[0005] The lead screw drive device according to the invention, having the features of the independent claims, and the method for manufacturing such a lead screw drive device, have the following advantages compared to others: by arranging a separately manufactured thrust element at the axial end of the worm gear, a lead screw drive device with higher self-locking efficiency can be achieved without any other structural changes, using a point-like axial thrust drive device with optimized efficiency. Thus, the lead screw drive device can be used, on the one hand, in applications where maximum adjusting torque should be generated with relatively small drive power. On the other hand, the same lead screw drive device, together with a single additional thrust element, can be used in applications where, when applying torque on the load side, the adjusting motion should be specifically braked, as desired, for example, by the weight of a passenger adjusting a seat.

[0006] Advantageous improvements and refinements to the features specified in the dependent claims are obtained through the measures enumerated in the dependent claims. If the separately manufactured thrust element has an annular thrust surface, the direct axial point thrust of the lead screw is increased. Here, the axial thrust friction can be specifically set by selecting the diameter of the annular thrust surface, and thus its self-locking is set. Preferably, the annular surface has a closed structure, such that the separately manufactured thrust element is pushed axially onto the lead screw, and thus surrounds the lead screw over its entire circumference.

[0007] In a preferred embodiment, the lead screw is axially supported at an axial stop by a metal thrust surface. This metal thrust surface is approximately point-like, achieved through an arched surface, particularly through metal balls secured within a worm gear. Thus, even in embodiments where a targeted braking torque serves as the axial stop, an ideal point-like axial thrust is maintained to achieve the most efficient drive mechanism. The annular thrust surface surrounding the point-like axial thrust generates additional braking torque for the lead screw drive mechanism.

[0008] Of particular advantage is that the annular thrust surface is constructed of plastic, which provides thrust at the opposing axial stop made of metal. This plastic-metal pairing provides a higher braking effect compared to metal-metal friction pairing. By selecting a plastic material or, alternatively, a metal softer than steel, the braking force for the leadscrew can be pre-defined using a separately manufactured thrust element.

[0009] If the thrust element is manufactured separately and has a retaining ring that can be directly and form-fitted onto the worm gear, no additional connection means are required for its assembly. Thus, the integrally manufactured thrust element can be directly engaged with the worm gear in the axial direction by a single assembly step. Here, the retaining ring is connected to the annular thrust surface by means of a spring element, such that the thrust surface elastically presses against the axial stop along the axial direction.

[0010] Here, the separately manufactured thrust element can be particularly advantageously produced as a plastic injection molded part, in which the retaining ring is integrally connected to the annular thrust surface via a spring tab. The spring tab can be constructed, for example, in an arcuate and / or helical and / or spiral shape, and provides axial spring travel between the retaining ring and the annular thrust surface. Preferably, the outer diameter of the annular thrust surface is constructed to be smaller than the outer diameter of the retaining ring, which abuts axially against the worm gear.

[0011] The shape-locking between the retaining ring and the worm gear can be easily achieved by means of a radially extending groove into which radially extending ribs are correspondingly inserted to construct an anti-rotation mechanism in the circumferential direction. For example, the radially extending ribs are injection molded directly at the axial end side of the worm gear, so that the retaining ring of the separately manufactured thrust element can be directly pushed axially onto the radial ribs by its radially extending groove.

[0012] In another embodiment, the retaining ring can also be connected to the worm gear by means of a locking element or a snap-fit ​​element, wherein the connecting element is preferably integrally formed at the retaining ring and / or at the worm gear. It is also possible to make the retaining ring forcefully locked to the worm gear, especially by means of an interference fit, in which the retaining ring is pressed axially within the peripheral edge of the worm gear.

[0013] The worm gear has radial worm teeth, wherein journals for radial support of the worm gear are formed axially on both sides of the worm teeth. Preferably, the journals are integrally constructed as plastic parts with the worm teeth. For example, the worm gear is directly injected into a threaded screw made of metal. The journal at the axial end of the screw is preferably constructed as a hollow cylinder, which is supported radially inward toward the screw by radial ribs. Here, the radial support ribs can simultaneously form a form-locking mechanism for a separately manufactured thrust element.

[0014] The worm teeth of the worm gear have an outer diameter larger than the two journals. Therefore, an annular surface can be constructed as a second axial stop on the side of the worm teeth facing away from the lead screw, allowing the worm gear to be axially supported in the opposite direction by the second axial stop. Here, the second axial thrust surface abuts, for example, against a U-shaped thrust plate, which can be radially connected to the transmission housing via the journals, and particularly can be pressed axially against the second axial thrust surface by means of an axial spring element.

[0015] The integrally constructed worm gear can be injected directly into the threaded teeth of the lead screw, thereby ensuring a good form lock between the worm gear and the lead screw in the axial direction.

[0016] The lead screw drive device according to the invention is particularly advantageously configured as a steering column adjustment device or a seat adjustment device, wherein the component to be adjusted is connected to the lead screw nut or to the transmission housing of the drive motor. Accordingly, the transmission housing or lead screw nut is connected to the vehicle body via a corresponding interface. If the lead screw is made of steel, for example, and the separate thrust element is made of polyoxymethylene (POM), then the lead screw drive mechanism achieves frictional characteristics that can be set very well, even over a long lifespan and large temperature fluctuations. This ensures that the lead screw drive device, and especially the separately manufactured thrust element, meets the requirements for comfort drive systems in the vehicle interior throughout its entire lifespan without causing intrusive noise.

[0017] By means of manufacturing according to the present invention, the separately manufactured thrust element can be assembled at the worm gear at a very low cost without the need for additional connecting means to secure it. By optionally constructing a point-like axial stop or an annular axial stop, a very small or specifically larger braking torque can be optionally set at the lead screw drive. Thus, the lead screw drive can be used for very different applications with different required braking torques by means of a single additionally assembled component (thrust element).

[0018] Here, by selecting the area and material of the annular stop surface, and further by determining the size of the spring contact plate, the braking torque can be set very specifically in order to set the axial clamping force of the annular thrust surface. Attached Figure Description

[0019] Further advantages, features, and specific details of the invention will become apparent from the following description of preferred embodiments and from the accompanying drawings. Wherein: Figure 1 A first embodiment of the lead screw drive device according to the present invention is shown. Figure 2 It shows according to Figure 1 Detailed diagram of the thrust element according to the present invention. Figure 3 It shows according to Figure 1 The lead screw according to the invention, which is installed in the housing of the transmission mechanism, and Figure 4 A cross-sectional view of another thrust element according to the invention is shown. Detailed Implementation

[0020] exist Figure 1A lead screw drive device 10 is shown, which is used, for example, as a component of a comfort drive system in a motor vehicle for adjusting a seat or steering column. The lead screw drive device 10 includes a lead screw 20 having a lead screw thread 22 constructed on it. A worm gear 30 is arranged anti-rotationally at a first axial end 21 of the lead screw 20, the worm gear being injected directly onto the lead screw 20, for example, as a plastic injection molded part. The worm gear 30 has worm teeth 34 that mesh with a worm (not shown), which is preferably driven by an electric motor. The worm teeth 34 are constructed as inclined cylindrical gear teeth, corresponding to the pitch of the worm. Columnar journals 36 are formed axially on both sides of the worm teeth 34 at the worm gear 30, by means of which the worm gear 30 is supported in a transmission housing 52. Figure 1 The left side shows a lead screw 20 with a worm gear 30 but without a separate thrust element 40. When the lead screw 20 is installed in the transmission housing 52, it directly abuts against the axial stop 50 of the transmission housing 52 at its first axial end 21 with a point-like thrust 24. Here, the first axial end 21 of the lead screw 20 is arched, forming a spherical thrust 24. In this embodiment, the worm gear 30 preferably does not abut against the axial stop 50 of the transmission housing 52 axially, thereby minimizing friction and thus self-locking, and correspondingly optimizing efficiency. As seen on the left, at the axial end side 31 of the worm gear 30, the journal 36 is supported radially inward relative to the lead screw 20 by means of radial ribs 38. Here, the lead screw 20 is radially surrounded within the journal 36, for example by a hub member 37, wherein the hub member 37 is integrally connected to the external columnar journal 36 via radial ribs 38. The outer diameter 34a of the worm gear tooth 34 is larger than the outer diameter 36a of the journal 36, thereby constructing annular shoulders 33 on each of the two axial sides of the worm gear tooth 34. Figure 1 The right side shows an identical lead screw 20 with the same worm gear 30, wherein a separately manufactured thrust element 40 is placed at the axial end side 31 of the worm gear 30. The separately manufactured thrust element 40 is axially engaged to the axial end side 31 of the journal 30, for example by means of a press connection, a snap-fit ​​or locking element, or a form-locking mechanism. The separate thrust element 40 has an annular thrust surface 42 that surrounds the lead screw 20 and abuts axially against the axial stop 50 of the transmission housing 52 in the installed state.

[0021] Figure 1 The thrust element 40, which is manufactured separately according to the method described on the right, is in... Figure 2The image is enlarged in size. The annular thrust surface 42 is integrally connected to the retaining ring 44 via elastic spring tabs 46. In this embodiment, the retaining ring 44 has a larger diameter than the annular thrust surface 42, wherein the spring tabs 46 are constructed in an approximately helical or arcuate shape. The annular thrust surface 42 is axially spaced relative to the retaining ring 44 in the unloaded state, wherein the spring tabs 46 are deformable in the axial direction 8 when an axial force is applied to the thrust surface 42. For example, exactly three or exactly four spring tabs 46 are constructed between the thrust surface 42 and the retaining ring 44. In the assembled state, the separately manufactured thrust element 40 abuts axially against the first axial end side 31 of the journal 36, and together with the journal, forms an anti-rotation mechanism 49. Thus, the thrust element 40 rotates synchronously with the worm gear 30 in the transmission housing 52.

[0022] Another embodiment of the separately manufactured thrust element 40 is in Figure 3 The image is shown in cross-section. In the unloaded state, the annular thrust surface 52 is arranged at a distance 68 relative to the retaining ring 44. The spring tab 46 is elastically deformable in the axial direction 8 and, if necessary, allows compensating movement in the radial direction 7. The radial extension 43 and diameter of the annular thrust surface 42 can be predetermined at the separately manufactured thrust element 40 such that the friction between the thrust element 40 and the axial stop 50, and therefore the self-locking, can be predetermined in a defined manner corresponding to the intended use. Similarly, the axial clamping force of the thrust surface 42 against the axial stop 50 can be predetermined by selecting the material thickness and geometry of the spring tab 46. A groove 48 is formed in the axial direction 8 at the retaining ring 44, which, when inserted into the axial end side 31 of the worm gear 30, receives, for example, the radial rib 38 of the journal 36. An anti-rotation mechanism 49 is constructed by axially inserting radial ribs 38 into grooves 48. This anti-rotation mechanism ensures that the individually manufactured thrust element 40 remains reliably anti-rotatingly connected to the worm gear 30 throughout its lifespan.

[0023] Figure 4 Now shown is from Figure 1 The right-side lead screw 20 is supported in the transmission housing 52 as described above. The two journals 36 of the worm gear 30 form radial supports and correspondingly abut against the radial bearing receiver 60 in the transmission housing 52. An axial stop 50 is formed here by a thrust plate 54, which is inserted into the transmission housing 52 in the radial direction 7. The thrust plate 54 is preferably made of metal, for example, as a steel plate. The worm gear 30 is supported on the thrust plate 54 by a separate thrust element 40. Here, the friction radius of the annular thrust surface 42 is significantly larger than that of the ideally positioned thrust 24 of the lead screw 20. Therefore, relative to... Figure 1In the embodiment on the left side where the thrust element 40 is not manufactured separately, friction at the axial stop 50 is significantly increased, thereby enabling the self-locking of the lead screw drive 10. In the opposite axial direction 8, the worm gear 30 is supported by a thrust washer 62, which is here constructed, for example, in a U-shape and engages in the radial direction 7 via a journal 36. To eliminate axial backlash in the lead screw 20, the thrust washer 62 is preferably pressed against an annular shoulder 33 by means of a spring element 64, which is laterally constructed at the worm teeth 34. The worm gear 30 is fully received in the transmission housing 52 with its two journals 36, wherein... Figure 4 In the diagram, the cover supporting the worm gear in particular, of the transmission mechanism housing 52, is not shown. The lead screw 20 extends axially from the worm wheel 30 and from the transmission mechanism housing 52, wherein a lead screw nut (not shown) is rotatably arranged on the lead screw thread 22. The transmission mechanism housing 52 has a bracket 70 behind the axial stop 50, by means of which the transmission mechanism housing 52 can be fastened to the vehicle body or the component to be adjusted. Accordingly, the lead screw nut (not shown), arranged on the lead screw 20, is fastened to the component to be adjusted or to the vehicle body. The thrust element 40 according to the invention ensures uniform and smooth adjustment of the movable component, especially when an external force is applied in the adjustment direction towards the movable component.

[0024] It should be noted that, in the embodiments shown in the figures and description, a wide variety of combinations of the various features are possible. The described lead screw drive 10 can be modified or altered in a variety of ways and manners without departing from the inventive concept. The worm gear 30 and the thrust element 40 can be made of, for example, plastic, such as PA or POM. Alternatively, the materials used for the worm gear 30, the individual thrust element 40, and the axial stop 50 can be changed according to the requirements of the lead screw drive 10. Similarly, the specific geometry of the separately manufactured thrust element 40 with the thrust surface 42 can be changed according to requirements. The electric lead screw drive 10 according to the invention is particularly suitable for adjusting movable components in motor vehicles, especially for adjusting steering column or seat assemblies.

Claims

1. A lead screw drive device (10) for adjusting a movable component in a motor vehicle, the lead screw drive device having a lead screw (20) having a lead screw thread (22) and a worm gear (30) arranged anti-rotatingly on the lead screw (20), wherein, The lead screw (20) can be rotated by means of a worm (32) driven by a motor via a worm wheel (30), wherein the worm wheel (30) is arranged at the first axial end (21) of the lead screw (20), and a separately made thrust element (40) is arranged at the axial end side (31) of the worm wheel (30), the thrust element surrounding the lead screw (20) over the entire periphery and elastically supported axially at an axial stop (50) with a thrust surface (42).

2. The lead screw drive device (10) according to claim 1, characterized in that, The thrust element (40) has an annular thrust surface (42) that surrounds the lead screw (20) in the peripheral direction (9).

3. The lead screw drive device (10) according to claim 1 or 2, characterized in that, The lead screw (20) is supported at the axial stop (50) by an approximately point-like thrust (24), especially a spherical stop.

4. The lead screw drive device (10) according to any one of the preceding claims, characterized in that, The thrust surface (42) is made of plastic or brass, and in particular the axial stop (50) is made of metal, and preferably the friction pair of the thrust element (40) and the axial stop (50) has a higher coefficient of friction than the friction pair of the spherical thrust (24) and the axial stop (50).

5. The lead screw drive device (10) according to any one of the preceding claims, characterized in that, The annular thrust surface (42) is elastically connected to the fastening ring (44) along the axial direction, and the fastening ring is inserted into the axial end side (31) of the worm gear (30) in a locking shape.

6. The lead screw drive device (10) according to any one of the preceding claims, characterized in that, The annular thrust surface (42) is integrally connected to the fastening ring (44) by means of an arc-shaped or spiral spring tab (46), wherein, in particular, the annular thrust surface (42) is concentrically arranged within the fastening ring (44).

7. The lead screw drive device (10) according to any one of the preceding claims, characterized in that, The fastening ring (44) is connected to the thrust surface (42) of the annulus by means of a radially extending groove (48), which works together with a radially extending rib (38), wherein the radially extending groove (48) and the radially extending rib (48) together form a shape-locking anti-rotation mechanism (49).

8. The lead screw drive device (10) according to any one of the preceding claims, characterized in that, The fastening ring (44) is connected to the worm gear (30) by means of locking or snap-fit ​​connection or force-transmitting locking.

9. The lead screw drive device (10) according to any one of the preceding claims, characterized in that, The worm gear (30) has journals (36) on both sides of the worm teeth (34) for support in the transmission housing (52) along the axial direction, wherein the journals (36) of the end side (31) are radially supported at the lead screw (20) by means of radially extending ribs (38).

10. The lead screw drive device (10) according to any one of the preceding claims, characterized in that, At the side of the off-end side (31) of the worm gear tooth (32), an annular shoulder (33) is constructed there as a second thrust surface (35), which is axially supported at the thrust plate (54), which elastically presses against the second thrust surface (35).

11. The lead screw drive device (10) according to any one of the preceding claims, characterized in that, The worm gear (30) and the two journals (36) are integrally injected into the lead screw (20) as a plastic injection molded part.

12. A method for manufacturing a lead screw drive device (10), particularly according to any one of the preceding claims, for adjusting a movable component (11) in a motor vehicle, wherein, A worm gear (30) is arranged anti-rotationally on the lead screw (20), and a separately made thrust element (40) can be fastened at the axial end side (31) of the worm gear. In order to form a small braking torque with a small self-locking, the lead screw drive (10) is assembled without the separate thrust element (40), and in order to form a larger braking torque with a larger self-locking, the separate thrust element (40) is engaged to the end side (31) of the worm gear (30).

13. The method according to claim 12, characterized in that, In order to set the braking torque, when machining the individual thrust element (40), the axial spring force and / or the size of the annular thrust surface (42) are given in advance according to the desired braking torque.

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