Spindle drive and method for manufacturing such a

Abstract

The invention relates to a spindle drive (10) for adjusting a movable part in a motor vehicle, and to a method for manufacturing such a spindle drive (10), comprising a spindle (20) having a spindle thread (21), and a spindle nut (30) arranged on the spindle (20) which has a nut thread (31) that meshes with the spindle thread (21), wherein the spindle (20) or the spindle nut (30) is rotatable by means of a drive motor (12) in order to adjust the spindle nut (30) relative to the spindle (20) along a spindle axis (19), wherein a rotationally fixed axial stop element (40) with an axial stop surface (41) is formed on the spindle (20) which limits the axial adjustment travel of the spindle nut (30) on the spindle (20), wherein the stop element (40) is assembled from at least two ring segments (42) which, in the assembled state, extend over the entire circumference of the spindle. (20) extend.

Description

State of the art

[0001] The invention relates to a spindle drive and a method for manufacturing such a drive according to the preamble of the independent claims.

[0002] German patent application DE 10 2018 204 196 A1 discloses a spindle drive that serves as a component of a comfort drive for seat adjustment in a motor vehicle. This drive comprises a motor that rotates a spindle about its longitudinal axis. A spindle nut is arranged on the spindle thread, which in turn is at least indirectly connected to the element to be adjusted, in particular the seat. When the spindle rotates about its axis of rotation, the spindle nut moves along the axis of rotation of the spindle and thus moves the seat. A tubular stop component is arranged on the spindle, which is axially supported against a gearbox housing of the spindle drive. This design of the stop component has the disadvantage that a new stop component must be manufactured for each specific customer requirement and then slid onto the spindle in the axial direction.

[0003] The object of the invention is to overcome the aforementioned disadvantages and to provide a universally applicable stop element for a spindle drive. Disclosure of the invention

[0004] The spindle drive according to the invention, as well as the method for manufacturing one with the features of the independent claims, has the advantage that, by designing the stop element as several angled segments that can be mounted radially onto the spindle, it can be attached to the spindle at any desired position in the axial direction. This eliminates the need for the stop element to be axially supported on the gearbox housing. Therefore, instead of many different customer-specific tubular stop sleeves, a standard component can be used as the stop element, which is attached to the spindle at a defined axial position according to customer requirements. This reduction in part variance significantly decreases the risk of confusion during assembly.

[0005] The measures listed in the dependent claims result in advantageous further developments and improvements of the features specified in the dependent claims. The annular angle segments can be very economically formed as injection-molded plastic parts that directly incorporate an axial stop surface for the spindle nut. Preferably, exactly two ring segments are formed, which are placed radially onto the spindle and connected to each other circumferentially. For this purpose, a positive locking and / or a clip connection is advantageously formed on the ring segments, which are joined together tangentially. Alternatively, the ring segments can also be held together to form a closed stop ring by means of a separate connecting element – ​​such as a clamping ring.

[0006] To absorb the axial forces during block start-up, at least two plastic ring segments are attached to the metal spindle by means of ring-segment-shaped metal components. These metal components engage radially outwards into the plastic of the ring segments and radially inwards into recesses in the spindle, creating a positive fit with respect to the axial direction. This allows the axial forces to be transferred from the spindle nut directly to the spindle via the metal components.

[0007] For the axial positive locking of the metal component with the spindle, a groove is cut into the spindle thread along its entire circumference to provide a receptacle. To avoid weakening the mechanical stability of the spindle, the circumferential groove does not extend radially deeper into the spindle than the root diameter of the spindle thread.

[0008] In a preferred embodiment, the circumferential angle of the metal component is 160° to 270°. In particular, the circumferential angle is greater than 180° so that the ring-segment-shaped metal component expands elastically when radially slid onto the circumferential groove of the spindle and subsequently encompasses the spindle sufficiently to ensure that the metal component remains securely positioned on the spindle until the ring segments are mounted on it. It is also possible to form the separate metal component within a single circumferential groove in multiple parts, particularly in two parts.

[0009] To distribute the axial forces acting on the spindle evenly during block start-up, at least two axially adjacent circumferential grooves are formed on the spindle for at least two adjacent metal components. If the two axial flanks of the metal rings, which bear axially against the spindle, are arranged axially spaced on the spindle thread by half a pitch of the spindle thread – or a multiple thereof – a first metal component can bear axial support on a first radial side and a second metal component on an opposite second radial side of the spindle. This prevents the stop element from tilting on the spindle relative to the spindle axis during block start-up.

[0010] If the metal components and the ring segments are mounted onto the spindle as separate parts, exactly one metal ring can be inserted into each circumferential groove in such a way that it clamps onto the spindle. Two ring segments, for example, can then be radially attached to this metal ring as half-shells.

[0011] In an alternative embodiment, the metal components are each overmolded with the plastic of the respective ring segment as an insert, so that the inserts, together with the ring segments, are placed radially onto the spindle. Since at least two ring segments with a maximum circumferential angle of 180° are pushed onto the circumferential groove, the circumferential angle of the overmolded metal components must not exceed 180°. With two adjacent circumferential grooves, two axially adjacent radial extensions protrude radially inwards from the ring segment as inserts.

[0012] In a preferred embodiment, the overmolded inserts are U-shaped in cross-section along the spindle axis, with two axially adjacent legs. These two legs then form the radial extensions that engage in the circumferential grooves. The parallel legs, extending in the radial plane, are advantageously joined integrally via a connecting area that extends cylindrically in the axial direction. Radial openings are advantageously formed in this connecting area, into which the plastic material of the ring segment engages. This allows the two axially adjacent radial extensions to be realized in each ring segment using a single insert.

[0013] It is particularly advantageous to design a conical stop surface on the stop element that tapers towards the spindle nut. A corresponding cone is formed on the spindle nut, into which the pointed cone of the stop element engages during the block engagement. This causes the two or more ring segments to be radially compressed by the cone in the spindle nut during the block engagement, thereby reinforcing the connecting elements between the ring segments in the tangential direction and allowing them to be designed with a correspondingly weaker profile. This ensures that the multi-part stop element remains securely held on the spindle even under high impact forces. For easier assembly of the stop element, it is advisable to design the ring segments axially symmetrically. This means that the conical stop geometry of the first axial side is also present on the second axial side.However, an asymmetrical solution is also conceivable, in which the stop geometry is only conical towards the spindle nut. The axial side opposite the spindle nut can then be freely designed.

[0014] In both versions where the metal components are designed as inserts and as separately mountable metal components, the plastic ring segments can each be designed as identical components, which significantly simplifies assembly on the spindle. The ring segments are preferably designed as half-shells with a circumferential angle of 180°, whereby connecting elements – such as clips or positive locking mechanisms – can also be formed in one piece and be identical on both components.

[0015] As a connecting element between the ring segments, a pin extending tangentially can preferably be formed on a first tangential side. On the opposite second tangential side, a corresponding hole is formed tangentially into which the pin of the adjacent ring segment can engage. The pin-hole connection can be designed as a pure positive fit and / or as an interference fit, so that when the two ring segments are joined tangentially, they are held together as a closed stop ring on the spindle.

[0016] The spindle drive according to the invention is particularly advantageously designed as a steering column adjustment device or as a seat adjustment device, wherein the parts to be adjusted are connected to the spindle nut or to the gearbox housing of the drive motor. Accordingly, the gearbox housing or the spindle nut is then connected to the vehicle body via a suitable interface. If, for example, the spindle is made of steel and the spindle nut of a polyoxymethylene (POM), which is particularly glass-filled, the spindle drive exhibits very good sliding and friction properties, even over a long service life and across large temperature fluctuations. This ensures that the spindle drive – and in particular the stop element – ​​meets the requirements for a comfortable drive in the vehicle interior throughout its entire service life, does not cause any disturbing noise, and exhibits very good smooth running characteristics.

[0017] The manufacturing process according to the invention allows the stop element to be mounted on the spindle very cost-effectively without having to slide it axially over the entire spindle. By eliminating the tubular stop sleeves that are supported by the gearbox housing, the stop can be easily attached at any desired position on the spindle via radial mounting, which significantly reduces the cycle time of production. Furthermore, it eliminates the need to free the spindle thread on the gearbox housing, while forming the circumferential grooves does not incur significant additional effort. Description of the drawings

[0018] Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings. The drawings show: Fig. 1. A state-of-the-art design of a spindle drive with a known axial stop, Fig. 2 a first embodiment according to the invention in longitudinal section, Fig. 3 a second embodiment according to the invention in longitudinal section, and Fig. 4 schematically a cross-section through the stop element according to the design in Fig. 3.

[0019] In the Fig. Figure 1 shows a spindle drive 10, which serves as part of a comfort drive in a motor vehicle for adjusting a seat 11 (shown only symbolically) or a steering column (not shown). The spindle drive 10 comprises a reversible electric or drive motor 12, the output shaft of which (not shown) projects into a gearbox housing 14. The gearbox housing 14 is connected to the drive motor 12 in the area of ​​a connecting flange 16 of the gearbox housing 14. The gearbox housing 14 is connected to the body 13, for example, via a bearing element 17. The gearbox housing 14 is penetrated by a spindle 20 made of metal – in particular steel – in a manner known per se, such that the drive motor 12 can rotate the spindle 20 about its longitudinal axis 19 in the direction of the double arrow 23 in both circumferential directions 9. A spindle nut 30 is arranged on the spindle 20 at a distance from the gearbox housing 14.The spindle nut 30 is arranged to be rotationally fixed with respect to the axis of rotation 19, so that when the spindle 20 rotates about the axis of rotation 19 in the axial direction 8, it moves linearly along the double arrow 28. The spindle nut 30 is as shown in the illustration. Fig. 1 is connected, at least indirectly, to the part to be adjusted, for example, the seat 11, in a manner not shown. To realize the linear movement of the spindle nut 30 along the axis of rotation 19, the spindle 20 has a spindle thread 21. The spindle nut 30, made of a hard plastic such as PA or POM, has a continuous recess 32 along the longitudinal axis 19 with a nut thread 31, which interacts with the spindle thread 21 of the spindle 20. A tubular stop component 18 with a stop surface 41 is arranged on the spindle 20 and is axially supported against the gearbox housing 14. This design of the stop component 18 has the disadvantage that a new stop component 18 must be manufactured for each specific customer requirement, which is pushed onto the spindle 20 in the axial direction 8 to be axially supported against the gearbox housing 14.

[0020] In the Fig. Figure 2 schematically shows a longitudinal section view of an embodiment of the invention, comprising a spindle 20, a stop element 40, and a spindle nut 30. The spindle thread 21 is formed on the spindle 20 and has a pitch 22 between two axially adjacent tooth profiles 60. Two adjacent circumferential grooves 24 are cut into the spindle thread 21 as radial recesses, extending continuously around the entire circumference of the spindle 20. The circumferential grooves 24 extend with a radial depth 25 approximately in the radial direction 7 to a base circle 26 of the spindle drive 21. Ring-shaped metal components 44 are inserted into the circumferential grooves 24, their axial flanks 48 bearing against a supporting side wall 49 of the circumferential groove 24 in the axial direction 8.The two supporting side walls 49 of the adjacent circumferential grooves 24 have an axial distance 46 that also corresponds to the axial distance 46 between the two axial flanks 48 of the metal components 44. This axial distance 46 preferably corresponds to half the pitch 22 plus a multiple of the pitch 22, i.e., (n + 1 / 2) * pitch 22, where n = 0, 1, 2, 3, ... Preferably, n = 1 or 2. This ensures that each of the two metal components 44 is axially supported at radially opposite circumferential points of the spindle 20 against a full tooth profile 60 of the spindle thread 21. In this embodiment, the two metal components 44 are manufactured as separate parts that extend over a circumferential angle 45, which is preferably greater than 180°. This allows the metal components 44 to be inserted in the radial direction 7 onto the circumferential grooves 24 and spring-loaded to be clamped in place.Two ring segments 42 are slid radially 7 onto the two ring-shaped metal components 44, so that together they form an annular axial stop surface 41 for the spindle nut 30. The two ring segments 42 are preferably made of plastic and have radially internal counter grooves 88 extending circumferentially 9, into which the metal components 44 engage radially to form a positive fit in the axial direction 8. The two ring segments 42 are connected to each other circumferentially 9, for example by a positive fit, or by an interference fit, or by an external clamping ring 70 (in . . Fig. (2 shown schematically in dashed lines). The axial stop surface 41 is designed here as a tapered cone 74 towards the spindle nut 30. Accordingly, a conical recess 34 is formed on the spindle nut 30 towards the axial stop surface 41, into which the pointed cone 74 then plunges during the block approach in order to press the two ring segments 42 together in the circumferential direction 9. Fig. 1. When the spindle 20 is rotated about its longitudinal axis 19, the spindle nut 30 is moved axially 8 against the stop element 40 by means of the nut thread 31 until the spindle nut 30 abuts the axial stop surface 41 in the block start position. Fig. Figure 2 shows the spindle 20 and the metal components 44 in side view, while the spindle nut 30 and the ring segments 42 are shown in longitudinal section. The radial depth of the circumferential grooves 24, which corresponds approximately to the diameter 26 of the root circle of the spindle thread 21, is shown schematically with dashed lines.

[0021] In Fig. Figure 3 shows a further embodiment of a stop element 40 according to the invention in longitudinal section, in which the two circumferential grooves 24 are cut into the spindle 20 in the same way as in Figure 3. Fig. 2. The threaded nut 31 of the spindle nut 30 meshes with the threaded spindle 21 of the spindle 20 – the spindle being shown schematically in a side view. In this embodiment, however, the metal components 44 are overmolded as inserts 43 by the plastic of the ring segments 42. The ring segments 42 are preferably designed as identical parts 82 – for example, as half-shells – which, when assembled, extend together over the entire circumference of the spindle 20. In particular, each ring segment 42 contains exactly one insert 43, which, viewed in longitudinal section, has a first leg 51 that engages in a first circumferential groove 24 in the radial direction 7. The insert 43 further has a second leg 52 that engages radially in a further circumferential groove 24.The first and second legs 51, 52 are radially connected to each other within the ring segment 42 at a connection area 54, so that the insert 43 forms a U-profile in longitudinal section. Radial recesses 55 are formed in the connection area 54, into which the plastic material of the ring segment 42 engages radially, thereby creating an anti-rotation feature in the circumferential direction 9 between the insert 43 and the plastic of the ring segment 42. The two axial flanks 48 of the first and second legs 51, 52 have an axial distance 46 from each other, which is again (n + ½) times the pitch 22. The ring segments 42, with the metal components 44 injected into them, are pushed back onto the circumferential grooves 24 in the radial direction 7 and are thereby connected to each other in the circumferential direction 9.The two circumferential grooves 24 preferably extend exactly transversely to the spindle axis 19 and are again cut out in the spindle thread 21, in particular with a radial depth 25 which approximately corresponds to the depth of the spindle thread 21.

[0022] In Fig. Figure 4 is schematically a cross-section through the spindle 20 of the Fig. Figure 3 shows the connection as indicated by arrow IV. It can be seen that two identical ring segments 42 are preferably formed here, extending in particular over a circumferential angle 85 of exactly 180°. The metal components 44, designed as inserts 43, preferably extend over a circumferential angle 45, which is less than 180°. The two ring segments 42 are connected to each other by means of a positive fit. A pin 64 is formed on a first tangential side surface 61 of the ring segment 42, which engages in a corresponding hole 66 in a second tangential side surface 62 of the adjacent ring segment 42. The positive fit can simultaneously be designed as an interference fit, so that when the two ring segments 42 are joined, their tangential side surfaces 61, 62 are pressed into each other in the tangential direction 9 on the circumferential grooves 24.The circumferential grooves 24 - and thus also the inserts 43 - extend here over a radial depth 25 inwards, which is less than the radial depth of the base circle diameter 26 of the spindle thread 21.

[0023] According to a further embodiment with lower stress during block operation, the stop element 40 can be simplified to such an extent that the separate metal components 44 can be omitted. In this design, the radial ring-shaped areas that engage positively with the spindle 20 are not made of metal, but are formed monolithically with the ring segments 42, also from plastic. This means that during the injection molding of the ring segments 42, the metal inserts 43 are replaced directly by integrally molded plastic components. These radial plastic extensions are produced in the same way as the metal inserts 43. Fig.3 radially slid onto the corresponding circumferential grooves 24. This makes the assembly of the stop element 40 significantly easier in production and is sufficient for applications with lower axial block starting force.

[0024] It should be noted that with regard to the embodiments shown in the figures and the description, numerous combinations of the individual features are possible. The spindle drive 10 described so far can be modified or adapted in a variety of ways without deviating from the inventive concept. For example, the materials used for the stop element 40 and for the spindle nut 30 can be varied according to the requirements of the spindle drive 10.

[0025] Likewise, the geometry of the spindle thread 21, the circumferential grooves 24, and the corresponding metal components 44, as well as the shape of the axial stop surface 41, can be varied. The spindle thread can be designed with straight tooth flanks, particularly as a trapezoidal thread, or the tooth tips and valleys can be curved, for example, by means of a rolling process. The fastening principle of the stop element 40 according to the invention can also be applied to a through-hole spindle in which the worm gear is designed as a spindle nut and has an internal thread that meshes with the spindle thread. The inventive electric spindle drive 10 is particularly suitable for adjusting movable components in motor vehicles, especially for adjusting the steering column or seat components 11. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 10 2018 204 196 A1

[0002]

Claims

[1] Spindle drive (10) for adjusting a movable part in a motor vehicle, comprising a spindle (20) having a spindle thread (21), and a spindle nut (30) arranged on the spindle (20) which has a nut thread (31) which meshes with the spindle thread (21), wherein the spindle (20) or the spindle nut (30) is rotatable by means of a drive motor (12) in order to adjust the spindle nut (30) relative to the spindle (20) along a spindle axis (19), wherein a rotationally fixed axial stop element (40) with an axial stop surface (41) is formed on the spindle (20) which limits the axial adjustment travel of the spindle nut (30) on the spindle (20), wherein the stop element (40) is assembled from at least two ring segments (42) which extend over the entire circumference of the spindle (20) in the assembled state. [2] Spindle drive (10) according to claim 1, characterized by, that the ring segments (42) are made of plastic, and that the axial stop surface (41) is formed as a plastic surface, and that the ring segments (42) are connected to each other in the circumferential direction (9) by means of a clip connection and / or by means of a press fit or by means of a retaining ring (70). [3] Spindle drive (10) according to claim 1 or 2, characterized by , that the ring segments (42) are positively connected to the spindle (20) with respect to the axial direction (8) by means of at least one ring-shaped metal component (44). [4] Spindle drive (10) according to one of the preceding claims, characterized by , that the at least one ring-shaped metal component (44) is inserted into a corresponding circumferential groove (24) in the spindle (20), wherein in particular the radial depth (25) of the circumferential groove (24) is not deeper than a root circle diameter (26) of the spindle thread (21). [5] Spindle drive (10) according to any one of the preceding claims, characterized by , that the at least one ring-shaped metal component (44) extends over a circumferential angle (45) of 160° to 270°, and is inserted in the radial direction (7) into the circumferential groove (24) of the spindle (20). [6] Spindle drive (10) according to any one of the preceding claims, characterized by , that with respect to the axial direction (8) two annular metal components (44) are arranged axially adjacent in two adjacent circumferential grooves (24) on the spindle (20), wherein an axial distance (46) between the two axially supporting flanks (48) of the two metal components (44) is (n + ½) times the pitch (22) of the spindle thread (21), where n is a natural number. [7] Spindle drive (10) according to any one of the preceding claims, characterized bythat the two metal components (44) are designed as separately mountable components which are clamped in the circumferential grooves (24) before the ring segments (42) made of plastic are pushed radially onto the metal components (44), wherein preferably the circumferential angles (45) of the metal components (44) are greater than 180°. [8] Spindle drive (10) according to any one of the preceding claims, characterized by , that the metal components (44) are designed as inserts (43) which are overmolded by the ring segments (42) - wherein in particular only exactly one insert (43) is inserted in each ring segment (42) which engages in two axially adjacent circumferential grooves (24) - wherein preferably the circumferential angles (45) of the metal components (44) are not greater than 180°. [9] Spindle drive (10) according to any one of the preceding claims, characterized by, that the insert parts (43) are designed as bent-stamped parts which are U-shaped in longitudinal section and engage radially with each leg (51, 52) in each circumferential groove (24), and in particular radial recesses (55) are formed in a connection area (54) between the two legs (51, 52) in order to form a positive fit with the plastic of the ring segments (42) with respect to the circumferential direction (9). [10] Spindle drive (10) according to one of the preceding claims, characterized by , that the ring segments (42) are connected to the spindle by means of at least one annular radial extension which is monolithically formed on the ring segments (42) in plastic and engages the circumferential grooves (24) in the spindle thread (21) in a form-fitting manner with respect to the axial direction (8). [11] Spindle drive (10) according to any one of the preceding claims, characterized by, that the stop surface (41) of the stop element (40) tapers conically towards the spindle nut (30), and the spindle nut (30) has a corresponding conical recess (34) towards the stop element (40), and when the spindle nut (30) is brought into contact with the stop element (40), the conical recess (34) presses the ring segments (42) of the stop element (40) radially inwards towards each other. [12] Spindle drive (10) according to one of the preceding claims, characterized by , that the stop element (40) is composed of exactly two ring segments (42) which extend over a circumferential angle (85) of exactly 180° each, wherein preferably the two ring segments (42) are designed as identical parts (82) - in particular as half shells. [13] Spindle drive (10) according to one of the preceding claims, characterized by, that a pin (64) is formed on a first tangential side surface (61) of the ring segment (42) in the tangential direction (9), which engages tangentially in a corresponding hole (66) in an opposite second tangential side surface (62) of the adjacent ring segment (42) in order to form a positive fit and / or an interference fit. [14] Spindle drive (10) according to one of the preceding claims, wherein the part to be adjusted is a steering column or a seat component (11) in the motor vehicle, and the spindle nut (30) is connected to the steering column or to the seat component (11), and the drive motor (12) is arranged fixed to the body via a further interface (15), or the drive motor (12) is connected to the steering column or to the seat component (11), and the spindle nut (30) is fixed to the body via a further interface. [15] Method for manufacturing a spindle drive (10) for adjusting a movable part (11) in a motor vehicle - in particular according to one of the preceding claims - wherein at least two circumferential grooves (24) are cut out as indentations in a spindle thread (21), and then ring-shaped metal components (44) are inserted in the radial direction (7) into the circumferential grooves (24) to secure an axial stop element (40) for a spindle nut (30) on the spindle (20), wherein the metal components (44) are connected to ring segments (42) made of plastic which form an axial stop surface (41).

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