Spindle drive for an adjustment element of a motor vehicle

Abstract

Spindle drive for an adjusting element (1) of a motor vehicle, wherein a drive unit (2) and a spindle-spindle nut drive (3) connected downstream of the drive unit (2) are provided for generating linear drive movements, wherein the spindle-spindle nut drive (3) has a spindle (8) and a spindle nut (9) meshing with the spindle, wherein the spindle drive has two drive sections (10, 11) which telescopically slide into one another during motorized adjustment, wherein the spindle (8) is assigned to one drive section (10) and the spindle nut (9) to the other drive section (11), wherein the two drive sections (10, 11) are torque-transmittingly coupled in the sense of an anti-rotation device, wherein during motorized adjustment the spindle nut (9) runs along the spindle axis (7) within a guide tube (15) of the spindle-side drive section (10) and is anti-rotationally secured against the guide tube (15).wherein, viewed in cross-section, at least one projection (16) within the guide tube (15) engages or can be engaged with an associated counter-projection (17) in the area of ​​the spindle nut (9) for torque transmission, and the two associated projections (16, 17) interact wedge-like for this torque transmission, forming a radial force component, characterized in that, viewed in cross-section, the guide tube-side projection (16) and / or the spindle nut-side counter-projection (17) is / are at least partially curved, and that two connections (12, 13) are provided for discharging the linear drive movements, one connection (12) being connected to the spindle-side drive section (10) and the other connection (13) being connected to the spindle nut-side drive section (11).

Description

The present invention relates to a spindle drive for an adjusting element of a motor vehicle according to the preamble of claim 1.The term "adjusting element" is to be understood broadly in the present case. It comprises, for example, a tailgate, a rear cover, a bonnet, a side door, a cargo space flap, a lifting roof or the like of a motor vehicle. The field of application of the motorized adjustment of a tailgate of a motor vehicle is in the following in the foreground. This is not to be understood as limiting.In the context of the motor-driven actuation of tailgates, spindle drives have proven themselves in recent years. In the present case, a high degree of compactness and a low weight are of primary importance.The known spindle drive (DE 20 2005 000 559 U1), on which the invention starts, has in the usual manner two drive sections, of which one drive section is assigned to a spindle and the other drive section is assigned to a spindle nut which meshes with the spindle.The two drive sections are each assigned a connection for diverting the linear drive movements. In order not to load the connections for rotation about the geometric spindle axis, the two drive sections are secured against one another in a rotationally fixed manner.In the known spindle drive, the spindle nut is connected to the spindle nut-side connection via a spindle nut tube. An outer housing tube extends from the spindle nut-side connection in the direction of the spindle-side connection. Starting from the spindle-side connection, a housing tube again extends in the direction of the spindle nut-side connection such that the spindle-side housing tube runs in the spindle nut-side housing tube.The anti-rotation device is integrated in the known spindle drive into the housing consisting of the two housing tubes. In detail, the two housing tubes are coupled to one another in a torque-transmitting manner for the purpose of preventing rotation. This is effected, for example, by a tongue and groove coupling.A disadvantage of the known spindle drive is the fact that a weight-reducing design of the housing is only possible within narrow limits due to the loads connected with the anti-rotation device.Further spindle drives are known from DE 10 2007 043 391 A1, DE 10 2006 027 523 A1, DE 10 2010 053 226 A1, DE 38 24 867 C1 and U.S. Pat. No. 3738 613 A.The invention is based on the problem of configuring and developing the known spindle drive in such a way that the design limitations relating to the housing are reduced without the scope of operation of the spindle drive being impaired.The above problem is solved in a spindle drive according to the preamble of claim 1 by the features of the characterising part of claim 1.It is firstly structurally essential that a guide tube assigned to the spindle-side drive section is provided, in which guide tube the spindle nut is guided together with the spindle nut tube.It is also important that the engagement between the spindle nut or the spindle nut tube and the guide tube is used in order to ensure the above-mentioned rotation prevention between the two drive sections. For this purpose, at least one formation in the inner region of the guide tube, as seen in cross section, with an associated counter formation in the outer region of the spindle nut and / or of the spindle nut tube is provided.Due to the proposed inward displacement of the anti-rotation device, the anti-rotation device must apply comparatively high forces. In the case of a tongue-and-groove connection, this would lead to correspondingly high shear forces transversely with respect to the extent of the groove. A third aspect of the proposed solution starts here. Specifically, it is the case that the two mutually associated formations for the torque transmission which prevents rotation cooperate in a wedge-like manner with the formation of a radial force component. This means that the anti-rotation device is due to a support of torques via wedge surfaces. Shear forces which in the extreme case could lead to a destruction of a tongue-and-groove connection do not occur at all, or occur only slightly, with the solution proposed. The forces required for the support are "redirected" at least to an appreciable extent via the wedge surfaces into radial forces.The term "wedge-like cooperation" is to be understood broadly in the present case. This means that the bracing of the torques takes place via a surface of some kind which converts at least part of the bracing on the basis of a radial force component. This surface is in the broadest sense a wedge surface, insofar as a corresponding force diversion is carried out in the manner of a wedge in the above sense.It should be noted that the terms "radial" and "tangential" are always related to the geometric spindle axis. The term "cross section" in the present case always means the cross section transverse to the spindle axis.In the particularly preferred embodiment according to claim 3, positive engagement of the two formations has been achieved by the mutually complementary configuration of the formation on the guide tube side and the associated counter formation on the spindle nut side, which leads to a particularly uniform distribution of forces during the support of torques.According to the proposal, the protrusions in question are designed to be at least partially curved. This allows undesired notch effects to be reduced with little effort.In a preferred variant, it has been recognized that straight radial force components can be absorbed by simple structural means, so that the arrangement can be designed easily for flat wedge angles (claim 4).In the particularly preferred embodiment according to claim 7, an extraordinarily stable structural construction can be realized in that the formations form closed contours when viewed in cross section. Due to the flat wedge angles discussed above, the space requirement for the anti-rotation device in the radial direction is small, so that radial apertures, in particular in the guide tube, can be dispensed with.According to claim 10, the spindle nut is designed as a plastic injection-molded part, wherein the spindle nut together with the spindle nut-side shaping for the anti-rotation device is injection-molded into or onto the spindle nut tube in the plastic injection-molding process. The wedge-like interaction between the protrusions in question is not necessarily important here.What is of interest in the further teaching is, rather, that the spindle nut can be produced in a particularly simple manner together with the shaped portion on the spindle nut side. In this context, the fact is to be emphasized in particular that an assembly step for the spindle nut or the shaped portion on the spindle nut side is completely omitted.The invention is explained in more detail below with reference to a drawing which merely represents an exemplary embodiment.The drawing shows FIG. 1 shows a schematic side view of the rear of a motor vehicle with a proposed spindle drive, FIG. 2 shows the proposed spindle drive according to FIG. 1 a) in the assembled state and b) in the partially disassembled state, and FIG. 3 shows the spindle drive according to FIG. 2 a) in a sectional view along the section line III-III.The spindle drive shown in the drawing serves for the motor-driven adjustment of an adjusting element 1 of a motor vehicle, which adjusting element is designed as a tailgate. Other application areas of the proposed spindle drive are conceivable, as explained in detail further below.The spindle drive is equipped in the usual manner with a drive unit 2 and a spindle-spindle nut gear 3 which is connected downstream of the drive unit 2 in terms of drive technology for generating linear drive movements. The drive unit 2 has a drive unit housing here, which is preferably tubular and in particular integral, and a drive motor 5 therein, as well as an intermediate transmission 6 connected downstream of the drive motor 5 in terms of drive technology. Depending on the configuration of the drive motor, an intermediate transmission 6 can also be dispensed with.A particularly slender configuration results from the fact that the drive unit 2 and the spindle-spindle nut transmission 3 are arranged one behind the other on the geometric spindle axis 7.It should be pointed out again at this point that the terms "radial" and "tangential" are always related to the geometric spindle axis 7 of the spindle-spindle nut transmission 3. For the purposes of a clear illustration, corresponding explicit indications are omitted in the following.The spindle-spindle nut transmission 3 is equipped in the usual manner with a spindle 8 and a spindle nut 9, wherein the spindle nut 9 is in meshing engagement with the spindle 8.The spindle drive has two drive sections 10, 11 which, in the case of a motorized adjustment, run telescopically one inside the other and are secured against rotation with respect to one another, wherein the spindle 8 is assigned to the drive section 10 and the spindle nut 9 is assigned to the drive section 11.Two connections 12, 13 are provided for deriving the linear drive movements, one connection 12 being connected to the spindle-side drive section 10 and the other connection 13 being connected to the spindle nut-side drive section 11. FIG. 2 b) shows that the spindle nut 9 is connected to the spindle nut-side connection 13 via a spindle nut tube 14.It is first of all essential that the spindle nut 9 together with the spindle nut tube 14 is guided along the geometric spindle axis 7 in a guide tube 15 of the spindle-side drive section 10, wherein a rotation prevention is realized between the spindle nut 9 or spindle nut tube 14 and guide tube 15. In detail, as seen in cross section transversely to the geometric spindle axis 7, at least one formation 16 in the inner region of the guide tube 15 is in torque-transmitting engagement with an associated counter-formation 17 in the outer region of the spindle nut 9 and here and preferably also of the spindle nut tube 14 for the purpose of preventing rotation. Finally, the formation 16 and the counter-formation 17 form a positive fit, on which the anti-rotation means derives. Here and preferably, a plurality of formations 16 and counter formations 17 are provided, as will be explained further below.The fact is of particular importance first of all that, viewed in cross section, two mutually associated formations 16, 17 cooperate in a wedge-like manner for the above torque transmission and forming a radial force component. It has already been pointed out that "wedge-like" means that a radial force component is involved in supporting possible torques. For this purpose, the formations 16, 17 are designed such that a wedge surface and, as a result, a wedge-like interaction results. This can best be seen from the sectional representation according to FIG. 3.The proposed wedge-like interaction of the respectively associated formations 16, 17 leads, as explained further above, to a particularly compact and at the same time to low-wear stress due to the only low shear stresses acting on the formations 16, 17 in the tangential direction.FIG. 3 shows the respective wedge surfaces 18, 19 for the formations 16, 17. Rather, the present invention is directed to the fact that the geometry of the arrangement results in a wedge-like interaction according to the proposal between the formations 16, 17. Furthermore, it becomes clear here that, owing to the symmetry of the formations 16, 17, the anti-rotation means acts in both rotational directions.For a rotation of the spindle-side drive section 10 relative to the spindle nut-side drive section 11 on the left in FIG. 3, a part 16 aof the formation 16 engages with a part 17 aof the counter-formation 17. The illustration according to FIG. 3 is also interesting insofar as the guide-tube-side formation 16 and the associated spindle-nut-side counter formation 17 are configured to be complementary to one another, such that the two formations 16, 17 engage in one another in a substantially positive-locking manner. In the exemplary embodiment illustrated in FIG. 3 and thus preferred, the contours formed by the associated formations 16, 17 are shaped very similarly, at least in sections, as seen in cross section.In detail, it is here and preferably the case that the guide tube-side formation 16 is configured convexly and that the spindle nut-side counter-formation 17 is configured concavely accordingly. This arrangement is advantageous in particular with regard to the limited wall thickness of the guide tube 15. In principle, however, it can also be provided that the guide tube-side formation 16 is designed concave and that the spindle nut-side counter-formation 17 is designed convex accordingly. The terms "convex" and "concave" are to be understood broadly and are accordingly not restricted to curved progression.In the exemplary embodiment shown in FIG. 3, the fact is also particularly advantageous that, viewed in cross section, the formation 16 on the guide tube side and the counter-formation 17 on the spindle nut side are each designed to be partially curved. Notch effects can thus be largely reduced, as mentioned above. In principle, it is also conceivable that only one of the two formations 16, 17 is designed to be correspondingly curved.According to the proposal, the two mutually associated formations 16, 17 cooperate in a wedge-like manner, that is to say via the wedge slopes 18, 19 which form a wedge angle α. Preferably, when viewed in cross section, the resulting wedge angle α is below 50° and preferably below 45°. Specifically, the wedge angle α is preferably in a range between 30° and 35°. These small wedge angles can be realized in that the guide tube-side formation 16 and the spindle nut-side counter-formation 17 are each configured flat. In principle, however, it is also sufficient for the realization of such a wedge angle α that only one of the two formations 16, 17 is configured to be flat.In the present case, almost all reference is made to only one guide-tube-side formation 16 and only one spindle-nut-side counter formation 17. FIG. 3, however, shows that a plurality of guide tube-side formations 16 and a plurality of spindle nut-side counter formations 17 are provided. All the explanations relating to a single guide-tube-side formation 16 and a single spindle-nut-side counter formation 17 apply correspondingly to the plurality of formations 16, 17.In order to achieve a uniform distribution of forces, it is in a preferred embodiment such that the guide tube-side formations 16 and the spindle nut-side counter formations 17 are arranged uniformly distributed about the geometric spindle axis 7. Accordingly, both the guide-tube-side formations and the spindle-nut-side counter formations 17 are spaced apart from one another by an angle of 120°.Due to the wedge-like cooperation of the formations 16, 17, apertures in the guide tube 15 can be dispensed with without any problem. Correspondingly, the formations 16, 17 form a closed contour when viewed in cross section. In a particularly preferred embodiment, it is here and preferably such that, viewed in cross section, the guide-tube-side formation 16 and the spindle-nut-side counter-formation 17 are part of a circumferential, closed contour. In principle, this can also apply only to one of the two formations 16, 17.The configuration of the spindle nut 9 is of very particular importance in the exemplary embodiment shown and preferred to this extent. It is first of all essential that the spindle nut 9 is arranged in the spindle nut tube 14, here and preferably at one end of the spindle nut tube 14. This ensures that the spindle drive can be moved apart as far as physically possible.Of interest is the fact that the spindle nut 9 protrudes radially through at least one opening 20 in the spindle nut tube 14 and that the protruding part 9 aof the spindle nut 9 provides at least a part of the counter-formation 17 on the spindle nut side for the anti-rotation means. FIG. 3 further shows that here and preferably the part 9 aof the spindle nut 9 radially protruding through the opening 20 extends laterally, i.e. perpendicularly to a radial direction, beyond the edge 20 aof the opening 20. This can be realized best by configuring the spindle nut 9 as a plastic injection-molded part and by injection-molding the spindle nut 9 together with the spindle nut-side counter-molding 17 for the anti-rotation prevention into or onto the spindle nut tube 14 in the plastic injection-molding process. In this context, it is conceivable for the spindle nut tube 14 to be inserted into an injection mold and for the spindle nut 9 to be produced together with the spindle nut-side counter-molding 17 in a single injection molding process.In this context, it is also conceivable that the spindle nut 9 is injection molded on the one hand from a first plastic material and the at least one spindle nut-side counter-molding 17 is injection molded on the other hand from a second plastic material. The second plastic material is preferably softer than the first plastic material in order to improve the damping properties of the interaction of the two formations 16, 17.Finally, it should be pointed out that the guide tube 15 is made of plastic in a particularly preferred embodiment. This is possible above all in that, due to the wedge-like interaction of the formations 16, 17 associated with one another, a considerable part of the twisting moments can be supported by a radial force component.

Claims

Spindle drive for an adjusting element (1) of a motor vehicle, wherein a drive unit (2) and a spindle-spindle nut gear (3) which is connected downstream of the drive unit (2) in terms of drive technology are provided for generating linear drive movements, wherein the spindle-spindle nut gear (3) has a spindle (8) and a spindle nut (9) which meshes with the spindle, wherein the spindle drive has two drive sections (10, 11) which, in the case of a motor adjustment, run telescopically one inside the other, wherein the spindle (8) is assigned to one drive section (10) and the spindle nut (9) is assigned to the other drive section (11), wherein the two drive sections (10, 11) are coupled in a manner transmitting rotation torque in the sense of a rotation prevention means, wherein, in the case of the motor adjustment, the spindle nut (9) runs along the spindle axis (7) within a guide tube (15) of the spindle-side drive section (10) and is secured against rotation with respect to the guide tube (15), wherein, viewed in cross section, at least one formation (16) within the guide tube (15) is or can be brought into torque-transmitting engagement with an associated counter formation (17) in the region of the spindle nut (9) for the anti-rotation prevention, and the two formations (16, 17) associated with one another interact in a wedge-like manner for this torque transmission, forming a radial force component, characterized in that, viewed in cross section, the formation (16) on the guide tube side and / or the counter formation (17) on the spindle nut side is or are designed to be at least partially curved, and in that two connections (12, 13) are provided for diverting the linear drive movements, in that one connection (12) is connected to the drive section (10) on the spindle side and the other connection (13) is connected to the drive section (11) on the spindle nut side.Spindle drive according to claim 1, characterised in that the anti-rotation device and the corresponding torque-transmitting engagement are provided in both rotational directions.Spindle drive according to claim 1 or 2, characterised in that, as seen in cross-section, the formation (16) on the guide tube side or the counter formation (17) on the spindle nut side is designed convexly and in that correspondingly the counter formation (17) on the spindle nut side or the formation (16) on the guide tube side is designed concavely.Spindle drive according to one of the preceding claims, characterized in that, as seen in cross section, the guide-tube-side formations (16) and / or the spindle-nut-side counter formations (17) are configured to be flat in such a way that the resultant wedge angle is below 50°, preferably below 45°.Spindle drive according to one of the preceding claims, characterized in that a plurality of guide-tube-side formations (16) and a plurality of spindle-nut-side formations (17) are provided.Spindle drive according to claim 5, characterised in that the guide tube-side formations (16) and / or the spindle nut-side counter formations (17) are arranged uniformly distributed around the spindle axis (7).Spindle drive according to one of the preceding claims, characterized in that, as seen in cross section, the formation (16) on the guide tube side and / or the counter formation (17) on the spindle nut side is or are closed, preferably in that, as seen in cross section, the formation (16) on the guide tube side and / or the counter formation on the spindle nut side is or are part of a circumferential, closed contour.Spindle drive according to one of the preceding claims, characterized in that the spindle nut (9) is connected to the spindle nut-side connection (12) via a spindle nut tube (14), and in that the spindle nut tube (14) runs at least partially in the guide tube (15) of the spindle-side drive section (10), preferably in that the spindle nut (9) is arranged in the spindle nut tube (14), preferably at one end of the spindle nut tube (14).Spindle drive according to one of the preceding claims, characterized in that the spindle nut (9) projects radially through at least one opening (20) in the spindle nut tube (14), and in that the projecting part of the spindle nut (9) provides at least a part of the spindle nut-side formation (16) for the anti-rotation means, preferably in that the part of the spindle nut (9) projecting through the opening (20) extends laterally beyond the edge (20a) of the opening (20).Spindle drive according to one of the preceding claims, characterized in that the spindle nut (9) is designed as a plastic injection-moulded part and in that the spindle nut (9) and the spindle nut-side shaping (16) are injection-moulded or injection-moulded into or onto the spindle nut tube (14) in the plastic injection-moulding process for the anti-rotation protection.

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