Screw drive for a vehicle steering drive and vehicle steering drive

Abstract

The invention relates to a spindle drive for a vehicle steering drive and a vehicle steering drive. The invention relates to a spindle drive comprising a spindle having an external thread on which a spindle nut is guided by means of an internal thread, one of the two components, namely the spindle and the spindle nut, being rotatable about an axis of rotation and causing a corresponding translational movement of the other during rotation, for this purpose, the other component is guided along the axis of rotation via a sliding bearing. The sliding bearing portion is established between the sliding surfaces of the two bearing portions, in which the first bearing portion is provided on the other component side and the second bearing portion is provided on the stationary member side. In this case, the first bearing part is designed as a projection, which projects transversely to the axis of rotation into another bearing part, which is designed as a recess in cross section. In addition, the recess surrounds the protrusion from both sides in a cross-section in a direction of rotation about the axis of rotation.

Description

Technical Field

[0001] The present invention relates to a screw drive for a vehicle steering gear, the screw drive comprising a screw having an external thread, a screw nut guided on the external thread by an internal thread, wherein one of the two components, the screw and the screw nut, is rotatable about an axis of rotation and, upon rotation, causes a corresponding translational movement of the other component through the mutual engagement of the external and internal threads. To this end, the other component is guided along the axis of rotation via a sliding bearing so as to be axially displaceable relative to a stationary component, and wherein the sliding bearing is formed between sliding surfaces of two bearing parts, a first bearing part being arranged on the other component side and a second bearing part being arranged on the stationary component side. Furthermore, the present invention relates to a vehicle steering gear having at least one screw drive. Background Art

[0002] Screw drives are used in a variety of fields to convert rotational motion into translational motion and vice versa. Typically, in a screw drive, a spindle nut is guided with an internal thread on an external thread of a spindle, wherein the conversion between rotational motion and translational motion is achieved by the mutual interaction of the internal and external threads.

[0003] WO 2018 / 014902 A1 discloses a spindle drive for adjusting the height of a vehicle structure. In this spindle drive, a spindle nut is guided on an external thread of a spindle at an internal thread, wherein the spindle drive is specifically designed as a ball screw drive in that the internal and external threads are coupled via rolling elements in the form of balls located therebetween. The spindle nut is supported in a housing via a thrust bearing so as to be rotatable about an axis of rotation, wherein the rotation of the spindle nut is converted into a corresponding translational movement of the spindle along the axis of rotation by the mutual interaction of the external and internal threads. The spindle is guided in the housing so as to be axially movable, wherein the guidance is implemented via a plurality of sliding bearings, each of which is constructed between two sliding surfaces facing each other. In each of the sliding bearings, one sliding surface is designed on a first bearing part, which is formed by a respective tube section of the housing, while the other sliding surface is defined on a second bearing part, which is formed by a sliding bearing ring connected to the threaded spindle in a rotationally fixed manner. Summary of the Invention

[0004] Based on the aforementioned prior art, the object of the present invention is now to provide a spindle drive in which a reliable mode of operation is achieved while having a design that is as compact as possible.

[0005] This object is achieved based on the preamble of claim 1 in conjunction with its distinguishing features. The subsequent dependent claims each describe advantageous developments of the invention. Furthermore, a vehicle steering gear having at least one spindle drive according to the invention is the subject of claim 12.

[0006] According to the present invention, a screw drive includes a screw having an external thread, and a screw nut guided on the external thread by means of an internal thread. Of the two components, the screw and the screw nut, one component is rotatable about a rotational axis, and upon rotation, the interaction of the external and internal threads causes corresponding translational motion of the other component. To this end, the other component is guided along the rotational axis via a sliding bearing so as to be axially movable relative to a component. The sliding bearing is formed between sliding surfaces of two bearing portions, of which a first bearing portion is provided on the other component side, and a second bearing portion is provided on the stationary component side.

[0007] Therefore, the screw drive according to the present invention comprises a screw and a spindle nut, which are operatively connected to each other via a thread. The spindle nut is equipped with an internal thread, which runs on the external thread of the spindle. Of these components, namely the spindle nut and the spindle, one of the components (i.e., either the spindle nut or the spindle) can rotate about an axis of rotation, while the other component, namely the spindle or the spindle nut, can move translationally along the axis of rotation. The interaction of the internal and external threads converts a rotation of one component into a corresponding translational movement of the other component along the axis of rotation, wherein the corresponding direction of rotation of one component, based on the helical direction of the thread, also defines the axial direction of the corresponding movement. "Axial" in the sense of the present invention refers to an orientation along the axis of rotation about which one of the two components, namely the spindle and the spindle nut, can rotate.

[0008] The internal and external threads can be engaged with each other by interlocking threads, but the screw drive according to the invention particularly preferably has rolling elements that couple the internal and external threads to each other in a form-fitting manner. More particularly preferably, these rolling elements are embodied as balls, so that the screw drive according to the invention is designed as a ball screw drive.

[0009] The translationally movable component is guided axially on the stationary component during its movement, wherein this guidance is implemented via a sliding bearing. In particular, the sliding bearing supports the translationally movable component solely on the stationary component, but within the scope of the invention, at least one further bearing can optionally be provided, which can also be designed as a sliding bearing or can also be realized as a rolling bearing.

[0010] In a screw drive, a sliding bearing is realized between sliding surfaces that are designed to face each other and enable sliding movement in the axial direction via the sliding surfaces in order to achieve a corresponding translational movement of the other component relative to the stationary component. The sliding surfaces are each designed on a bearing part, wherein a first bearing part is provided on the other component side and a second bearing part is provided on the stationary component side.

[0011] By means of a sliding bearing formed in this manner, a direct guidance of the other component on the stationary component can be achieved. For this purpose, the first bearing part is then arranged rigidly, that is, rotationally fixed and axially immovable, on the other component, while the second bearing part is rigidly attached to the stationary component. Alternatively, however, an indirect guidance of the other component on the stationary component can also be achieved via the sliding bearing by rigidly attaching at least one of the bearing parts to another component, which is directly or indirectly fastened to the other component or the stationary component. Therefore, arranging the corresponding bearing part on the "side" of the other component or the stationary component means, within the meaning of the present invention, that the corresponding bearing part is rigidly attached directly or indirectly to the other component or the stationary component.

[0012] In order to achieve axially movable guidance of a component that is relatively fixed to another component over the entire axial range of movement of the other component, it is preferred that one of the bearing parts and the associated sliding surface are designed to have an axial extension in the direction of translation that is sufficient for permanent guidance.

[0013] The stationary component, on the side of which the second bearing part is arranged, is in particular a component which is arranged rotationally and translationally stationary with respect to another component.

[0014] The spindle drive according to the present invention is preferably designed for use in a vehicle steering gear, in particular a steering gear for a commercial vehicle. The spindle drive according to the present invention is particularly designed to convert a rotational drive motion into a translational output motion in a vehicle steering gear.

[0015] The present invention now includes the following technical teaching: one of the two bearing parts is designed as a protrusion in cross section, which protrudes transversely to the rotational axis into the other bearing part, which is designed as a recess in cross section. Furthermore, the recess extends from both sides in the cross section in the direction of rotation about the rotational axis, surrounding the recess. In other words, the bearing part that implements the sliding bearing is designed as a protrusion and a recess in cross section, wherein the protrusion engages in the recess transversely to the rotational axis and is surrounded by the recess from both sides in the direction of rotation about the rotational axis.

[0016] This design of the screw drive has the advantage that, in addition to axially displacing the other component on the stationary component, the sliding bearing also provides for securing the other component against rotation relative to the stationary component, thereby preventing the other component from rotating and thus ensuring the proper functioning of the screw drive. To convert a rotation of one component into a corresponding translational movement of the other component, the other component is permanently secured against rotation. Because, according to the present invention, one of the bearing parts of the sliding bearing is designed as a protrusion that engages transversely into a recess formed by the other bearing part and is also enclosed on both sides by the recess in the direction of rotation about the axis of rotation, a positive locking effect prevents rotation of one bearing part relative to the other bearing part, ultimately securing the other component in a positively locking manner on the stationary component, also in the direction of rotation. By shifting this anti-rotational protection to the region of the sliding bearing, this aspect can be achieved in a compact manner.

[0017] A “cross section” of the respective bearing part within the meaning of the present invention is a section of the respective bearing part having a section plane extending transversely to the axis of rotation, ie, orthogonally to the axis of rotation.

[0018] Within the scope of the invention, the depression is designed in particular in the form of a notch, ie the depth of the depression is preferably smaller than its extension in the direction of rotation.

[0019] According to one embodiment of the invention, the elevation is convexly rounded in cross section, wherein in combination therewith the depression is preferably concavely rounded in cross section. As an alternative, the elevation is V-shaped in cross section, wherein in combination therewith the depression is also V-shaped in cross section. In both cases, when one bearing part is twisted relative to the other bearing part, planar contact occurs between the elevation and the depression in both rotational directions.

[0020] Particularly preferably, the ridge is designed symmetrically in cross section and about the highest point of its cross section. As an alternative to this, but in particular as a supplement to this, the recess is preferably designed symmetrically in cross section and about the lowest point of its cross section.

[0021] According to one design option of the present invention, the elevation and depression are designed to fit together in cross section. Consequently, the cross-sectional geometry of the elevation follows that of the depression, and vice versa. This has the advantage that the depression can rest against the elevation over a large area in both rotational directions.

[0022] Another embodiment of the present invention is that the elevation in its highest region in cross section and / or the depression in its deepest region in cross section are each provided with a groove-like recess. This reduces the risk of linear contact between the depression and elevation due to tolerances.

[0023] In a further development of the invention, the respective sliding surface is formed on a coating applied to the respective support part. In this case, the respective support part is thus provided with a coating, which then also forms the respective sliding surface. By selecting the appropriate material for the coating, a suitable sliding surface can be easily formed in the respective area using a disordered particle structure.

[0024] As an alternative to the aforementioned variants of the invention, the respective sliding surfaces are formed on an element fastened to the respective support part. This also allows for the realization of suitable sliding surfaces by appropriate material selection of the separate element. The ordered particle structure for realizing the respective sliding surface is then formed by the separate element, which preferably exists as a support shell. Alternatively, however, the use of a film as the separate element is also conceivable.

[0025] According to one design option of the present invention, the second bearing portion is formed by a section of the inner periphery of the stationary component, wherein this section of the inner periphery protrudes into the interior space defined by the stationary component and within which the spindle nut and the spindle are accommodated. Depending on the specific design, a bearing portion designed as a depression or a bearing portion designed as a protrusion is thus formed on the section of the inner periphery of the stationary component according to the present invention. Preferably, the section of the inner periphery extends axially completely over the axial range of motion to be exhibited, wherein the depression or protrusion formed in the cross section is then also formed axially completely over this section.

[0026] According to one embodiment of the present invention (which is implemented here as an alternative to the aforementioned design options, but preferably also as a supplement), the first bearing portion is formed by a section of the outer periphery of another component that is rigidly connected to another component. In this case, either a bearing portion designed as a protrusion or a bearing portion designed as a depression is formed on the section of the outer periphery. In combination with the aforementioned design options, the additional component is then also accommodated, in particular, within the interior of the stationary component. Preferably, the additional component is at least partially cylindrical, with the section then being formed on the cylindrical portion of the additional component. More preferably, the additional component is an adjusting element of a vehicle steering gear.

[0027] In the screw drive according to the present invention, the screw is preferably rotatable and, when it rotates, the interaction of the external and internal threads causes a corresponding translational movement of the screw nut. However, within the scope of the present invention, it is also possible to choose the opposite configuration, in which the screw nut is rotatable and, when rotated, causes a corresponding translational movement of the screw.

[0028] The screw drive is particularly designed so that the first bearing portion is designed as a raised portion and the second bearing portion is designed as a recessed portion. Therefore, in this case, the raised portion is designed on the other component side, while the recessed portion is realized on the side of the fixed component.

[0029] In a development of the invention, the stationary component is the housing, so that the other component can be designed in a reliable manner to be guided in an axially displaceable manner while being locked in rotation.

[0030] The present invention also provides a vehicle steering gear comprising at least one spindle drive, wherein the at least one spindle drive is designed according to one or more of the aforementioned variants. The at least one spindle drive is preferably used to convert a rotational drive motion of an adjusting actuator into a translational adjusting motion of an adjusting element. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] The advantageous embodiment of the invention to be explained below is shown in the accompanying drawings. In the drawings:

[0032] Figure 1 shows a sectional view of a vehicle steering gear in the region of a spindle drive according to an embodiment of the present invention;

[0033] Figure 2 Shown Figure 1 Detailed view of the screw transmission according to the present invention;

[0034] Figure 3shows a sectional view of a vehicle steering gear in the region of a spindle drive according to a further possible embodiment of the present invention;

[0035] Figure 4 Shown Figure 3 A detailed view of a screw drive according to the present invention; and

[0036] Figure 5 A sectional view of a vehicle steering gear is shown in the region of a spindle drive according to a further embodiment of the present invention. DETAILED DESCRIPTION

[0037] Depend on Figure 1 A cross-sectional view of a region of a vehicle steering mechanism 1 is shown, which may specifically be a steering mechanism for a commercial vehicle. The vehicle steering mechanism 1 comprises a component 2, which is an adjusting element 3 of the vehicle steering mechanism 1. The adjusting element 3 can be axially displaced within the vehicle steering mechanism 1 in order to perform a corresponding adjusting movement. To this end, the adjusting element 3 is coupled to a spindle drive 4, which is designed according to an embodiment of the present invention and includes a spindle nut 6 in addition to a spindle 5.

[0038] In the vehicle steering gear 1 , a spindle 5 can rotate about an axis of rotation 7 . The spindle 5 is provided with an external thread 8 , on which a spindle nut 6 is guided by an internal thread 9 . The spindle drive 4 is designed as a ball screw drive in that a plurality of rolling elements (not shown here) in the form of balls are positioned between the external thread 8 and the internal thread 9 . These rolling elements each provide a positive-locking coupling between the spindle 5 and the spindle nut 6 . The balls positioned therebetween convert the rotation of the spindle 5 into an axial movement of the spindle nut 6 , which is rotationally fixed, along the axis of rotation 7 .

[0039] In the present case, the spindle nut 6 is accommodated in the receiving bore 10 in the adjusting element 3, wherein the adjusting element 3 and the spindle nut 6 are rigidly fastened to one another, i.e., they are firmly connected to one another both in the direction of rotation about the rotation axis 7 and axially along the rotation axis 7. In this case, the spindle nut 6 can be pressed into the receiving bore 10 of the adjusting element 3, for example.

[0040] When jointly performing an axial movement with a movement direction that depends on the rotation direction of the threaded spindle 5, the spindle nut 6 and the adjusting element 3 are jointly guided axially on a stationary component 11, which is a housing 12. The adjusting element 3 is accommodated together with the spindle nut 6 and the threaded spindle 5 in an interior space 13 defined by the housing 12. The axially movable guidance is achieved between the housing 12 and the adjusting element 3 via a sliding bearing 14, which is located at the housing 12. Figure 2 is shown in more detail in .

[0041] As in Figure 2 As can be seen in the figure, the sliding bearing 14 is formed between sliding surfaces 15 and 16, which are formed on a coating applied to bearing parts 17 and 18 of the sliding bearing 14. In this case, the bearing part 17 is designed in cross section as a ridge 19, which is provided on the outer circumference of the cylindrical section of the adjusting element 3. This ridge 19 gives the cylindrical section of the adjusting element 3 a cam-like shape in this region, with the ridge 19 protruding transversely to the axis of rotation 7 in the direction of a depression 20, which is designed as a depression of the bearing part 18 on the housing 12 side, on a section 21 of the inner circumference of the housing 12 that protrudes into the interior 13.

[0042] The cross-sectional shape of the two bearing portions 17 and 18 allows, on the one hand, axial guidance of the adjusting element 3 and, consequently, the spindle nut 6 on the housing 12 via the sliding surfaces 15 and 16 . Furthermore, the adjusting element 3 and the spindle nut 6 are secured against rotation relative to the housing 12 on the sliding bearing 14 by the bearing portion 18 designed as a recess 20 extending from both sides in the direction of rotation of the adjusting element 3 and the spindle nut 6 about the axis of rotation 7 and encompassing the bearing portion 17 designed as a projection 19 . The projection 19 and the recess 20 thus prevent, by interacting with each other, a relative rotation of the adjusting element 3 and, consequently, the spindle nut 6 relative to the housing 12 about the axis of rotation 7 in a form-fitting manner.

[0043] As especially in Figure 2 As can be seen in the figure, the elevation 19 and the depression 20 are designed as mating parts in cross section, the elevation 19 being convexly rounded, while the depression 20 is concavely rounded as a mating part therewith. Furthermore, a groove-like recess 22 is introduced into the elevation 19 in the highest region of the elevation in cross section, which contributes to the formation of a planar contact between the sliding surfaces 15 and 16.

[0044] also, Figure 3 A sectional view of a vehicle steering gear 23 is also shown, which has a screw drive 24 according to another design possibility of the present invention. Here, the vehicle steering gear 23 and also the screw drive 24 are respectively largely similar to the above-mentioned Figure 1 and Figure 2 Corresponding to a variant of Figure 1 and Figure 2The difference from the embodiment of the invention is that the sliding bearing 25 is now designed differently, via which the adjusting element 3 and the spindle nut 6 are guided in an axially displaceable manner relative to the housing 12. Figure 4 As can be seen in FIG, the ridges 26 and recesses 27 of the support parts 28 and 29 of the sliding support 25 are now each designed as a V-shaped fitting in cross section. In addition, there is no groove-shaped recess on the ridge 26 side. In addition, according to Figure 3 and Figure 4 The feasible design solutions are all in accordance with Figure 1 and Figure 2 The variants of , therefore, are referred to the description thereof.

[0045] at last, Figure 5 A sectional view of a vehicle steering gear 30 with a spindle drive 31 according to another embodiment of the invention is also shown. Here, the vehicle steering gear 30 and the spindle drive 31 are also largely identical to the embodiment according to the invention. Figure 1 and Figure 2 The only difference is that the sliding bearing 32 for guiding the adjusting element 3 and the spindle nut 6 axially relative to the housing 12 has, in addition to the bearing part 17, a bearing part 33, in which the sliding surface 16 is formed by a bearing shell 34 fastened to the bearing part 33. Figure 5 Implementation and basis of Figure 1 and Figure 2 The variants of , therefore, are referred to the description thereof.

[0046] By means of the embodiment according to the invention, a spindle drive can be provided in each case in which a reliable mode of operation is achieved with a design that is as compact as possible.

[0047] List of reference numerals (part of the description)

[0048] 1Vehicle steering transmission mechanism

[0049] 2 components

[0050] 3 regulatory elements

[0051] 4-screw drive

[0052] 5 screws

[0053] 6 screw nuts

[0054] 7 rotation axes

[0055] 8 external thread

[0056] 9 internal thread

[0057] 10 receiving holes

[0058] 11 Fixed components

[0059] 12 shell

[0060] 13Interior Space

[0061] 14 Sliding support part

[0062] 15 sliding surface

[0063] 16 sliding surface

[0064] 17 Supporting part

[0065] 18 Supporting part

[0066] 19 bulge

[0067] 20 recessed portion

[0068] Section 21

[0069] 22 concavities

[0070] 23 Vehicle steering transmission mechanism

[0071] 24 screw drive

[0072] 25 sliding support part

[0073] 26 bulge

[0074] 27 Depression

[0075] 28 supporting part

[0076] 29 supporting part

[0077] 30 Vehicle steering transmission mechanism

[0078] 31 Screw drive device

[0079] 32 sliding support part

[0080] 33 supporting part

[0081] 34 support shell

Claims

1. A spindle drive (4; 24; 31) for a vehicle steering gear (1; 23; 30), comprising a spindle (5) having an external thread (8), on which a spindle nut (6) is guided by an internal thread (9), wherein: Of the two components, namely a threaded spindle (5) and a threaded nut (6), one of the components is rotatable about an axis of rotation (7) and, during rotation, causes a corresponding translational movement of the other component by the mutual cooperation of an external thread (8) and an internal thread (9), the other component being guided for this purpose via a sliding bearing (14; 25; 32) along the axis of rotation (7) in an axially movable manner relative to a stationary component (11), wherein the sliding bearing (14; 25; 32) is formed between sliding surfaces (15, 16) of two bearing parts (17, 18; 28, 29; 17, 33), of which the first bearing part (17; 28) is The invention relates to a support portion (17; 28) provided on the other component side, and a second support portion (18; 29; 33) provided on the fixed component (11) side, characterized in that, of the two support portions (17, 18; 28, 29; 17, 33), one support portion (17; 28) is designed as a raised portion (19; 26) in cross section, the raised portion protruding transversely to the rotation axis (7) into the other support portion (18; 29; 33) designed as a recessed portion (20; 27) in cross section, and the recessed portion (20; 27) extends from both sides in the cross section in the direction of rotation about the rotation axis (7) to surround the raised portion (19; 26).

2. The screw transmission device (4; 24; 31) according to claim 1, characterized in that The raised portion (19; 26) is designed to be convexly rounded or V-shaped in cross section.

3. The screw transmission device (4; 24; 31) according to claim 1 or 2, characterized in that The depression (20; 27) is designed to be concavely rounded or V-shaped in cross section.

4. The screw drive (4; 24; 31) according to any one of claims 1 to 3, characterized in that The raised portion (19; 26) and the recessed portion (20; 27) are designed as fitting parts relative to each other in cross section.

5. The screw drive (4; 31) according to any one of the preceding claims, characterized in that The elevation (19) is provided in its highest region in cross section and / or the depression is provided in its deepest region in cross section with a respective groove-like recess (22).

6. The screw drive (4; 24; 31) according to any one of the preceding claims, characterized in that The respective sliding surface (15; 16) is formed on a coating applied to the respective support part (17; 18; 28; 29; 33) or on an element fastened to the respective support part (22).

7. The screw drive (4; 24; 31) according to any one of the preceding claims, characterized in that The second bearing portion (18; 29; 33) is formed by a section (21) of the inner periphery of the stationary component (11), wherein the section (21) of the inner periphery projects into an interior space (13) defined by the stationary component (11) and in which the spindle nut (6) and the spindle (5) are accommodated.

8. The screw drive (4; 24; 31) according to any one of the preceding claims, characterized in that The first bearing portion (17; 28) is formed by a section of the outer periphery of the further component (2) which is rigidly connected to the further part.

9. The screw drive (4; 24; 31) according to any one of the preceding claims, characterized in that The threaded spindle (5) is rotatable and, when it rotates, causes a corresponding translational movement of the spindle nut (6) through the interaction of the external thread (8) and the internal thread (9).

10. The screw drive (4; 24; 31) according to any one of the preceding claims, characterized in that The first supporting portion (17; 28) is designed as a raised portion (19; 26), while the second supporting portion (18; 29; 33) is designed as a recessed portion (20; 27).

11. The screw drive (4; 24; 31) according to any one of the preceding claims, characterized in that The stationary component (11) is a housing (12).

12. Vehicle steering transmission (1; 23; 30), comprising at least one screw drive (4; 24; 31) according to any one or more of claims 1 to 11.

Images