Towbar for motor vehicles

Abstract

Trailer coupling for motor vehicles, comprising an adjusting mechanism (3) by means of which a ball rod (4) provided at its free end with a coupling ball (5) can be adjusted from a rest position to an operating position and vice versa by means of a pivoting movement and a rotational movement of the ball rod (4) can be superimposed on this pivoting movement, and a drive unit (2) comprising an electric motor (6), a nut unit (7) and a drive spindle (8) which is connected to the adjusting mechanism (3) via a coupling element (9).the end of the ball rod (4) facing it is connected, characterized by a spherical cap (33) with a recess (34) through which the drive spindle (8) can be moved out of and into a drive housing (10) of the drive unit (2), wherein the coupling element (9) is always located outside the drive housing (10) which is closed around the drive spindle (8) by means of the spherical cap (33), by means of which spherical cap (33) the tensile stress acting on the nut unit (7) when the drive spindle (8) is drawn into the drive housing (10) can be transferred to the adjusting mechanism (3) by means of which spherical cap (33) the tensile stress acting on the nut unit (7) can be transferred to the adjusting mechanism (3) by the outer surface (35) of the spherical cap (33) coming into at least partial contact with the adjusting mechanism (3).

Description

[0001] The invention relates to a trailer coupling for motor vehicles, with an adjusting mechanism by means of which a ball rod provided with a coupling ball at its free end can be adjusted by a pivoting movement from a rest position to an operating position and vice versa and a rotary movement of the ball rod can be superimposed on this pivoting movement, and with a drive unit which includes an electric motor, a nut unit and a drive spindle which is connected via a coupling member to the adjusting mechanism or to the end of the ball rod facing it.

[0002] Such a trailer coupling is described, for example, in DE 10 2004 051 976 A1.

[0003] During operation of such trailer couplings for motor vehicles, in addition to tensile and compressive stresses, shock loads often occur when adjusting the ball bar, which are passed on from the adjusting mechanism or the ball bar to the drive unit.

[0004] The invention is based on the object of developing the trailer coupling for motor vehicles described at the outset in such a way that the mechanical stresses on the drive unit occurring due to the operation of the trailer coupling and due to shock loads are reduced.

[0005] For this purpose, the invention proposes a spherical cap with a recess through which the drive spindle can be moved out of and into a drive housing of the drive unit, wherein the coupling element is always located outside the drive housing closed around the drive spindle by means of the spherical cap, by means of which spherical cap the tensile stress acting on the nut unit when the drive spindle is retracted into the drive housing can be diverted to the adjusting mechanism in that the spherical cap comes into at least partial contact with the adjusting mechanism with its outer surface. Accordingly, such tensile stresses cannot lead to undue mechanical loads on the drive unit. The adjusting mechanism is usually suitable for absorbing such loads due to its design. The drive unit can therefore be designed for lower mechanical loads.

[0006] A particularly lightweight design for the drive unit can be achieved if its drive housing is made of plastic.

[0007] The transmission of even large forces from the spherical cap to the adjusting mechanism is possible if the spherical cap is made of a metallic material, e.g. steel.

[0008] According to an advantageous embodiment of the trailer coupling according to the invention, its nut unit has a support by means of which the tensile load absorbed by a spindle nut of the nut unit when the drive spindle is retracted into the drive housing is transferred to the spherical cap. The tensile load acting on the spindle nut is thus transferred from the spindle nut via the support and the spherical cap to the adjusting mechanism.

[0009] The support of the nut unit is advantageously designed as a steel support in order to increase the loads that can be transmitted.

[0010] According to a further advantageous embodiment, the compressive stress absorbed by the spindle nut of the nut unit when the drive spindle is driven out of the drive housing can also be diverted to the adjusting mechanism by means of the carrier. For this purpose, the carrier can advantageously be pivotally mounted in a housing of the adjusting mechanism by means of a pivot bearing. Such a pivot bearing can consist, in a structurally and mechanically simple manner, of two pivot pins arranged diametrically opposite one another on the carrier. These pivot pins are held in recesses in the carrier on the one hand and project through openings in the drive housing that are aligned with the recesses in the carrier into associated receptacles in the housing of the adjusting mechanism.

[0011] The pivot pins can be screwed or pressed into the carrier.

[0012] The nut unit advantageously includes an axial bearing located between the spindle nut and the support. This absorbs the axial forces that occur when the drive spindle retracts. This axial bearing also absorbs the maximum shock loads of up to 68 kN that occur during operation, which are caused by vibration or impacts when a trailer is attached. The design of this axial bearing is determined accordingly.

[0013] Advantageously, the nut unit includes a radial bearing which is arranged on the inner circumferential surface of the carrier and by means of which the spindle nut is in turn radially mounted.

[0014] Furthermore, in an advantageous embodiment, the nut unit of the trailer coupling according to the application has an additional axial bearing arranged in the inner cavity of the spherical cap. This additional axial bearing can absorb the axial forces when the spindle is extended. The shock loads mentioned in connection with the first-mentioned axial bearing do not have to be borne by this second axial bearing, since this second axial bearing is supported directly on the carrier.

[0015] If the spherical cap rests directly against the carrier with its ring surface facing the spindle nut, a direct flow of force between the spherical cap and the carrier is possible, whereby all axial loads can then be absorbed by the carrier.

[0016] A correct spatial arrangement of the spherical cap in relation to the nut unit can be realized in a technically and structurally simple manner if the spherical cap is centered in relation to the nut unit by means of a radial step formed on the annular surface of the carrier facing it.

[0017] The carrier of the nut unit advantageously supports the two axial bearings.

[0018] The additional axial bearing arranged in the cavity of the spherical cap is expediently designed for considerably lower loads than the axial bearing arranged between the carrier and the spindle nut, since the aforementioned first axial bearing does not have to absorb shock loads, etc.

[0019] The spindle nut of the nut unit expediently has an external toothing, which in an advantageous embodiment is realized by means of a gear wheel that is slipped or pressed onto the spindle nut.

[0020] In order to prevent any jamming between the spindle nut and the drive spindle while maintaining an advantageous clearance between the spindle nut and the drive spindle, it is advantageous if the spindle nut has two plain bearings by means of which the drive spindle can be centered with respect to the nut unit, wherein these plain bearings can preferably be arranged on the two axial end sections of the spindle nut.

[0021] The plain bearings can alternatively center the drive spindle via its outer diameter or via its thread flanks.

[0022] A compact design of the drive unit can be achieved if the drive spindle and the electric motor are spaced apart from each other in the radial direction and arranged parallel to each other.

[0023] This can be achieved with comparatively little technical construction effort if a planetary gear with planetary gears driven by the output pinion of the electric motor and a ring gear which is driven by the planetary gears on its inner circumference and is in driving connection with the nut unit of the drive spindle on its outer circumference is arranged between an output pinion of the electric motor and the nut unit of the drive spindle.

[0024] The drive housing, which houses the electric motor and drive spindle, is advantageously divided into a main part, in which the electric motor is fixed, preferably screwed, and an end cap facing the actuating mechanism, from which the coupling element of the drive spindle protrudes. This can significantly simplify assembly.

[0025] In an alternative embodiment, the end cap of the drive housing can be made of a metallic cast material and formed in one piece with the spherical cap.

[0026] The ring gear of the planetary gear can advantageously be mounted at the transition between the main part and the end cap of the drive housing, wherein bearing points should preferably be provided both on the main part and in the end cap, by means of which the ring gear can be mounted in the radial direction.

[0027] The drive connection between the ring gear and the spindle nut can be realized in a technically and structurally inexpensive manner if the ring gear of the planetary gear is in drive connection with the external toothing of the spindle nut by means of its external toothing.

[0028] The planetary gears of the planetary gear can advantageously be mounted in the drive housing using dowel pins.

[0029] The output pinion of the electric motor can expediently be designed with two teeth, in which case the planetary gear advantageously has two planetary gears.

[0030] To increase mechanical stability, it is advantageous if a free tip of the output pinion of the electric motor is rotatably mounted on the end cap.

[0031] According to an advantageous embodiment of the trailer coupling according to the invention, the force absorption of the nut unit is effected via the drive spindle, wherein the nut unit is designed to absorb shock loads of up to 68 kN.

[0032] In the following, the invention is explained in more detail using an embodiment with reference to the drawing.

[0033] They show: Fig. 1 a side view of an embodiment of a trailer coupling for motor vehicles according to the invention; Fig. 2 a view of the Fig. 1 shown embodiment of the trailer coupling according to the invention in the direction of arrow B in Fig. 1; Fig. 3 a sectional view “AA” in Fig. 2; Fig. 4 a sectional view of an embodiment of a drive unit of the trailer coupling for motor vehicles according to the invention; Fig. 5 an exploded view of the Fig. 4 shown drive unit; and Fig. 6 an exploded view of a modified embodiment of a spindle nut of the Fig. 4 and Fig. 5 shown drive unit of the trailer coupling according to the invention.

[0034] One in Fig. 1 shows an embodiment of a trailer coupling 1 according to the invention, shown in a side view, comprising a drive unit 2, an adjusting mechanism 3 and a ball rod 4 which, in cooperation between the drive unit 2 and the adjusting mechanism 3, can be subjected to a pivoting movement and a rotational movement superimposed thereon, at the free end of which a coupling ball 5 is arranged which serves for engagement with coupling members on the trailer side.

[0035] The ball bar 4 of the trailer coupling 1 is connected to the adjusting mechanism 3 and the drive unit 2 at its end opposite the coupling ball 5.

[0036] The drive unit 2 has an electric motor 6, a nut unit 7 and a drive spindle 8, which is provided at its end facing the adjusting mechanism 3 or the ball rod 4 with a coupling member 9, by means of which the drive spindle 8 and thus the drive unit 2 is in driving connection with the adjusting mechanism 3 or the ball rod 4.

[0037] The drive spindle 8 and the electric motor 6 are arranged parallel and spaced from one another and are housed in a two-part drive housing 10. The drive housing 10 includes a main part 11 and an end cap 12 arranged on the side of the drive housing 10 facing the adjusting mechanism 3 or the ball rod 4. The main part 11 of the drive housing 10 and its end cap 12 are made, for example, from a suitable plastic. The electric motor 6 is fixed or screwed into the main part 11 of the drive housing 10 by means of suitable screws 13. To control or regulate the electric motor 6, an electronics unit 14 is provided on the side of the electric motor 6 facing away from the adjusting mechanism 3 and is also housed in the drive housing 10.

[0038] An output pinion 15 of the electric motor 6, provided on the side of the same facing away from the electronics unit 14, is designed with two teeth and is rotatably mounted at its free tip 16 by a suitable bearing in the end cap 12.

[0039] The output pinion 15 of the electric motor 6 meshes with two planetary gears 18, 19 of a planetary gear 20. The two planetary gears 18, 19 of the planetary gear 20 are rotatably mounted and fixed to the housing within the drive housing 10 of the drive unit 2 by means of locating pins 21, 22. The two planetary gears 18, 19 mesh with an internal toothing 23 of a ring gear 24, which is located at the transition between the main part 11 and the end cap 12 of the drive housing 10. The ring gear 24 is radially mounted on three bearing points each in the main part 11 and in the end cap 12. On its outer circumferential surface, the ring gear 24 of the planetary gear 20 is provided with an external toothing 25, which meshes with an external toothing 26 of a spindle nut 27 of the nut unit 7.The spindle nut 27 has a gear ring 28 having its external toothing 26, a cylinder section 29 projecting from the side facing away from the coupling member 9 of the drive spindle 8, and a cylinder section 30 projecting from the side of the gear ring 28 facing the coupling member 9 of the drive spindle 8, wherein the cylinder sections 29, 30 have a smaller diameter than the gear ring 28.

[0040] With its cylinder section 29 pointing away from the coupling member 9 of the drive spindle 8, the spindle nut 27 sits in a plain bearing 31 which is fixed in the main part 11 of the drive housing 10.

[0041] The spindle nut 27 of the nut unit 7 is in threaded engagement with the drive spindle 8. The drive spindle 8, in the retracted state into the drive housing 10, is arranged with the section of its threaded section 32 facing away from its coupling member 9 within the main part 11 of the drive housing 10. Its coupling member 9 protrudes from the end cap 12 of the drive housing 10, wherein the end cap 12 is closed in the area associated with the threaded section 32 of the drive spindle 10 adjoining the coupling member 9 of the drive spindle 8 by means of a spherical cap 33 which has a central recess 34 through which the threaded section 32 of the drive spindle 8 can be moved out of the drive housing 10 and into the drive housing 10. On its outer surface 35, the spherical cap is shaped such that it can make flat contact with a section of the adjusting mechanism 3 lying opposite it, as can best be seen from Fig. 3. This can be a section of the housing 36 of the adjusting mechanism 3, or, as in Fig. 3, a receiving member 37 arranged accordingly on the adjusting mechanism 3.

[0042] By means of the spherical cap 33, the tensile stress acting on the nut unit 7 when the drive spindle 8 is retracted into the drive housing 10 can be diverted to the adjusting mechanism 3. This ensures that such loads do not have to be absorbed by the drive housing 10 of the drive unit 2 or by the drive unit 2.

[0043] In addition to the spindle nut 27 and the spherical cap 33, the nut unit 7 includes a steel support 38 which is cylindrical and is provided on part of its inner circumferential surface with a radial bearing 39 in which the cylinder section 30 of the spindle nut 27 projecting towards the coupling member 9 of the drive spindle 8 is rotatably mounted. The steel support has two diametrically opposed recesses 40, 41 which, together with pivot pins not shown in the figures which are screwed or pressed into them and which extend through openings 42, 43 in the end cap 12 of the drive housing 10 which are aligned with the recesses 40, 41 and are pivotably mounted in corresponding receiving sections of the adjusting mechanism 3 (not shown in the figures), form a pivot bearing for the steel support 38, by means of which the steel support 38 is pivotally connected to the adjusting mechanism 3 or its housing 36.

[0044] An axial bearing 44 is arranged between the steel support 38 on the one hand and the gear ring 28 of the spindle nut 27 on the other. This axial bearing 44 serves to absorb the axial forces when the drive spindle 8 is retracted. Furthermore, this axial bearing 44 absorbs the maximum shock loads of up to 68 kN that occur during operation of the motor vehicle due to vibration and / or impacts when a trailer is attached. Therefore, this axial bearing 44 is designed to be relatively large.

[0045] The forces occurring under corresponding loads are diverted to the adjusting mechanism 3 via the axial bearing 44 and the steel beam 38 via its pivot bearings 40, 41, 42, 43.

[0046] The spherical cap 33 sits with its annular surface 45 facing the spindle nut 27 directly on the end face of the steel support 38 facing it. For this purpose, the steel support 38 has a radial step 46 on its end wall facing the spherical cap 33, by means of which the spherical cap 33 is centered with respect to the steel support 38 and thus with respect to the nut unit 7.

[0047] By means of the steel support 38, the tensile stress absorbed by the spindle nut 27 of the nut unit 7 when the drive spindle 8 is retracted into the drive housing 10 can be transferred to the spherical cap 33, by means of which these stresses can be further dissipated to the adjusting mechanism 3. Furthermore, by means of the steel support 38, the compressive stresses absorbed by the spindle nut 27 of the nut unit 7 when the drive spindle 8 is expelled from the drive housing 10, as well as the stresses occurring during shock loads, can be dissipated to the adjusting mechanism via the pivot bearing.

[0048] The spindle nut 27 can be designed as a single piece with the gear ring 28 forming its external toothing. Alternatively, the spindle nut 27 can be provided with a pinion gear that is either attached or pressed onto it.

[0049] The spindle nut 27 has in the Fig.6, each of the axial end sections of the drive spindle 8 has a sliding bearing 49, 50, by means of which the drive spindle 8 is centered with respect to the spindle nut 27 or the nut unit 7. This allows the optimal play between the internal thread of the spindle nut 27 and the external thread of the drive spindle for the operation of the nut unit 7 or the drive spindle 8 to be achieved without the operation of the nut unit 7 or the drive spindle 8 being impaired due to impact loads, canting, or the like.

[0050] The plain bearings 49, 50 can center the drive spindle 8 via its outer diameter or via its thread flanks.

Claims

[1] Trailer coupling for motor vehicles, with an adjusting mechanism (3), by means of which a ball rod (4) provided with a coupling ball (5) at its free end can be adjusted by a pivoting movement from a rest position to an operating position and vice versa, and a rotary movement of the ball rod (4) can be superimposed on this pivoting movement, and with a drive unit (2) which includes an electric motor (6), a nut unit (7) and a drive spindle (8) which is connected via a coupling member (9) to the adjusting mechanism (3) or to the end of the ball rod (4) facing it, characterized bya spherical cap (33) with a recess (34) through which the drive spindle (8) can be moved out of and into a drive housing (10) of the drive unit (2), wherein the coupling member (9) is always located outside the drive housing (10) closed around the drive spindle (8) by means of the spherical cap (33), by means of which spherical cap (33) the tensile stress acting on the nut unit (7) when the drive spindle (8) is pulled into the drive housing (10) can be diverted to the adjusting mechanism (3) in that the spherical cap (33) comes into at least partial contact with the adjusting mechanism (3) with its outer surface (35). [2] Trailer coupling according to claim 1, the drive housing (10) of which is made of plastic. [3] Trailer coupling according to claim 1 or 2, the spherical cap (33) of which is made of a metallic material, e.g. steel. [4] Trailer coupling according to one of claims 1 to 3, the nut unit (7) of which has a support (38) by means of which the tensile stress absorbed by a spindle nut (27) of the nut unit (7) when the drive spindle (8) is pulled into the drive housing (10) can be transferred to the spherical cap (33). [5] Trailer coupling according to claim 4, wherein the support (38) of the nut unit (7) is designed as a steel support (38). [6] Trailer coupling according to claim 4 or 5, by means of whose support (38) the compressive stress absorbed by the spindle nut (27) of the nut unit (7) when the drive spindle (8) is driven out of the drive housing (10) can be diverted to the adjusting mechanism (3). [7] Trailer coupling according to one of claims 4 to 6, the carrier (8) of which is pivotally mounted on a housing (36) of the adjusting mechanism (3) by means of a pivot bearing (40, 41, 42, 43). [8] Trailer coupling according to claim 7, in which the pivot bearing (40, 41, 42, 43) of the carrier (38) consists of two pivot pins arranged diametrically opposite one another on the carrier (38), which are held on the one hand in recesses (40, 41) of the carrier (38) and project through openings (42, 43) of the drive housing (10) aligned with the recesses (40, 41) of the carrier (38) into receptacles assigned to them in the housing (36) of the actuating mechanism (3). [9] Trailer coupling according to claim 8, wherein the pivot pins of the pivot bearing (40, 41, 42, 43) of the carrier (38) are screwed or pressed into the carrier (38). [10] Trailer coupling according to one of claims 4 to 9, the nut unit (7) of which has an axial bearing (44) arranged between the spindle nut (27) and the carrier (38). [11] Trailer coupling according to one of claims 4 to 10, the nut unit (7) of which has a radial bearing (39) which is arranged on the inner circumferential surface of the carrier (38) and by means of which the spindle nut (27) is radially mounted. [12] Trailer coupling according to one of claims 10 or 11, the nut unit (7) of which has a further axial bearing (48) which is arranged in an inner cavity (47) of the spherical cap (33). [13] Trailer coupling according to one of claims 4 to 12, the spherical cap (33) of which bears directly against the carrier (38) with its annular surface (45) facing the spindle nut (27). [14] Trailer coupling according to claim 13, the spherical cap (33) of which is centred with respect to the nut unit (7) by means of a radial step (46) formed on the annular surface of the support (38) facing it. [15] Trailer coupling according to one of claims 12 to 14, wherein the support (38) of the nut unit (7) supports the two axial bearings (44, 48) thereof. [16] Trailer coupling according to one of claims 12 to 15, in which the further axial bearing (48) arranged in the cavity (47) of the spherical cap (33) is designed for considerably lower stresses than the axial bearing (44) arranged between the carrier (38) and the spindle nut (27). [17] Trailer coupling according to one of claims 4 to 16, wherein the spindle nut (27) of the nut unit (7) has an external toothing (26). [18] Trailer coupling according to claim 17, wherein the spindle nut (27) of the nut unit (7) is provided with a pinion gear which is attached or pressed on. [19] Trailer coupling according to one of claims 4 to 18, in which the spindle nut (27) is preferably provided at its axial end sections with a sliding bearing (49, 50) by means of which the drive spindle (8) can be centered with respect to the nut unit (7). [20] Trailer coupling according to claim 19, wherein the plain bearings (49, 50) of the spindle nut (27) are designed such that they center the drive spindle (8) via its outer diameter. [21] Trailer coupling according to claim 19, wherein the plain bearings (49, 50) of the spindle nut (27) are designed such that they center the drive spindle (8) via its thread flanks. [22] Trailer coupling according to one of claims 1 to 21, in which the drive spindle (8) and the electric motor (6) are spaced apart from one another in the radial direction and arranged parallel to one another. [23] Trailer coupling according to one of claims 1 to 22, in which a planetary gear (20) with planetary gears (18, 19) driven by the output pinion (15) of the electric motor (6) and a ring gear (24) driven on its inner circumference by the planetary gears (18, 19) and in driving connection with the nut unit (7) of the drive spindle (8) is arranged between an output pinion (15) of the electric motor (6) and the nut unit (7) of the drive spindle (8). [24] Trailer coupling according to one of claims 1 to 23, the drive housing (10) in which the electric motor (6) and the drive spindle (8) are accommodated, has a main part (11) in which the electric motor (6) is screwed, and an end cap (12) facing the adjusting mechanism (2), from which the coupling member (9) of the drive spindle (8) protrudes. [25] Trailer coupling according to claim 24, wherein the end cap (12) of the drive housing (10) is made of a metallic cast material and is formed in one piece with the spherical cap (33). [26] Trailer coupling according to claim 24 in conjunction with claim 23 or claim 25 in conjunction with claim 23, in which the ring gear (24) of the planetary gear (20) is mounted in the radial direction at the transition between the main part (11) and the end cap (12) of the drive housing (10), preferably on three bearing points in each case in the main part (11) and in the end cap (12). [27] Trailer coupling according to one of claims 24 to 26, each in conjunction with claim 23 and with claim 4, in which the ring gear (24) of the planetary gear (20) is in driving connection with the external toothing (26) of the spindle nut (27) by means of its external toothing (25). [28] Trailer coupling according to one of claims 23, 26 and 27, in which the planetary gears (18, 19) of the planetary gear (20) are mounted fixedly to the housing by means of dowel pins (21, 22). [29] Trailer coupling according to one of claims 23, 26 to 28, in which the output pinion (15) of the electric motor (6) is designed with two teeth and the planetary gear (20) has two planet wheels (18, 19). [30] Trailer coupling according to one of claims 23, 26 to 29, in which a free tip (16) of the output pinion (15) of the electric motor (6) is rotatably mounted on the end cap (12). [31] Trailer coupling according to one of claims 1 to 30, in which the force absorption of the nut unit (7) takes place via the drive spindle (8) and the nut unit (7) is designed to absorb shock loads of up to 68 kN.

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