DE102021103448A1 - spindle drive - Google Patents

Abstract

The invention comprises a spindle drive (1), the spindle drive (1) being designed as a planetary roller screw drive (2), which has a threaded spindle nut (3), a threaded spindle (4), a plurality of planetary roller bodies (5) with a planetary roller body profile (6) and at least comprises two planetary guide rings (7), with the planetary screw drive (2) converting a rotational movement into a translatory movement, in that the threaded spindle (4) is arranged concentrically in the planetary guide rings (7) and the threaded spindle nut (3), with the planetary guide rings (7) facing each other of the threaded spindle (4) and the planetary rolling bodies (5) are rotatably mounted about their respective planetary rolling body axis (8) in the planetary guide rings (7) and inside and in the threaded spindle nut (3), the planetary rolling body profile (6) of the planetary rolling body (5) with the threaded spindle (4) meshes, so that a rotation of the threaded spindle (4) causes a rotation of the planetary rolling elements (5). causes its planetary roller body axis (8) and a rotation of the planetary roller bodies (5) around the threaded spindle (4), the planetary guide rings (7) and the threaded spindle nut 3 being arranged such that they can rotate relative to one another via a first group of roller bearings (11) and the planetary guide rings (7) has a second group of roller bearings (12) on their respective outer end faces remote from the threaded spindle nut (3), the first group of roller bearings (11) and the second group of roller bearings (12) being designed as angular needle bearings.

Description

The invention relates to a spindle drive, the spindle drive being designed as a planetary roller screw drive, which comprises a threaded spindle nut, a threaded spindle, a plurality of planetary roller bodies with a planetary roller body profile, and at least two planetary guide rings, with the planetary roller screw drive converting a rotational movement into a translatory movement by the threaded spindle is arranged concentrically in the planetary guide rings and the threaded spindle nut, the planetary guide rings being rotatable relative to the threaded spindle and the planetary roller bodies being mounted rotatably about their respective planetary roller body axis in the planetary guide rings and inside and the threaded spindle nut, the planetary roller body profile of the planetary roller bodies meshing with the threaded spindle, so that a Rotation of the threaded spindle, rotation of the planetary rollers about their planetary roller axis and rotation of the planetary rollers about di e threaded spindle causes.

Spindle drives, such as planetary screw drives, have been state of the art for many years and are used, for example, in DD 0277308 A5 described. There is a continuing need to simplify the design of such planetary screw drives and to reduce the complexity of the components and thus the manufacturing costs.

In the light of the previously known state of the art, it is therefore the object of the subject matter of the invention to provide a spindle drive that can be produced at low cost.

This object is achieved by a spindle drive, the spindle drive is designed as a planetary roller screw drive, which comprises a threaded spindle nut, a threaded spindle, a plurality of planetary roller bodies with a planetary roller body profile, and at least two planetary guide rings, with the planetary roller screw drive converting a rotational movement into a translatory movement by the threaded spindle is arranged concentrically in the planetary guide rings and the threaded spindle nut, the planetary guide rings being rotatable relative to the threaded spindle and the planetary roller bodies being mounted rotatably about their respective planetary roller body axis in the planetary guide rings and inside and the threaded spindle nut, the planetary roller body profile of the planetary roller bodies meshing with the threaded spindle, so that a Rotation of the threaded spindle, a rotation of the planetary rolling elements about their planetary rolling element axis and a rotation of the planetary rolling elements causes the threaded spindle, the planetary guide rings and the threaded spindle nut being arranged such that they can be rotated relative to one another via a first group of roller bearings, and the planetary guide rings have a second group of roller bearings on their respective outer end faces facing away from the threaded spindle nut, the first group of roller bearings and the second group of roller bearings are designed as angular needle bearings.

This achieves the advantage that the spindle drive according to the invention has roller bearings of the same type, as a result of which the spindle drive according to the invention has a reduced component complexity and can therefore be implemented very cost-effectively.

It was also shown that a total of four angular needle bearings can generate enough friction torque to operate the spindle drive in order to keep the efficiency of the entire unit below 50%. The necessary frictional torque can be adjusted in particular by a geometric adjustment of the second group of roller bearings, for example a larger diameter of the angular needle bearings, longer needles or steeper angles.

First, the individual elements of the claimed subject matter of the invention are explained in the order in which they are mentioned in the set of claims, and particularly preferred configurations of the subject matter of the invention are described below.

A spindle drive converts with the help of a threaded spindle and a threaded spindle nut, which are geared to one another in such a way that they convert a rotational movement of the threaded spindle or the spindle nut into a linear movement of the threaded spindle or the threaded nut.

In its simplest form, a spindle drive can be formed from a threaded spindle and a threaded spindle nut, with the thread of the threaded spindle meshing directly in a corresponding internal thread of the threaded spindle nut, with sliding friction occurring here along the meshing thread flanks and consequently comparatively high friction losses comes. In order to minimize these friction losses, planetary roller screw drives were developed in which planetary roller bodies are arranged between the threaded spindle and the threaded spindle nut, so that a rolling or rolling movement is realized on the meshing thread flanks, which leads to significantly better efficiency of the spindle drive mechanics. Basically, planets also change rolling screw drives convert a rotary movement into a translational movement and usually vice versa.

The main components of a planetary roller screw drive are usually a threaded spindle, a threaded spindle nut, planetary roller bodies and planetary guide rings, with the planetary roller bodies with a planetary roller body thread being held in a threaded spindle nut with two planetary guide rings and rotating around the threaded spindle in an axially parallel manner and without axial displacement, as a result of which the threaded spindle nut moves linearly in relation to the threaded spindle . Both the threaded spindle and the threaded spindle nut usually have a multiple, identical profile with a flank angle of preferably 90°.

In principle, a planetary screw drive can be driven via the threaded spindle or via the threaded spindle nut.

The hollow-cylindrical threaded spindle nut has the function of accommodating the threaded spindle and the planetary roller bodies. The threaded spindle and the threaded spindle nut are rotatably mounted in relation to one another. The threaded spindle nut also has the function of protecting the inside of the rolling element gear from mechanical influences, as well as dust and other dirt.

A further function of the threaded spindle nut can also be to allow mechanical coupling to an actuator drive, in particular an electric motor or hydraulic actuator.

To improve rigidity and positioning accuracy under load, a planetary screw drive can be preloaded. This can be achieved, for example, by forming the spindle nut in two parts and clamping the two halves of the threaded spindle nut against one another.

Furthermore, a threaded spindle nut can also have the function of adjusting the planetary roller screw drives without play. There is a threaded spindle nut spacer ring of the right thickness between the two spindle nut halves.

The threaded spindle nut can be designed in one piece or in two parts, in which case the threaded spindle nut comprises a first spindle nut half and a second spindle nut half. The first spindle nut half and the second spindle nut half are preferably of essentially identical design.

The coupling of an electromotive actuator drive to the threaded spindle nut can be implemented, for example, via a feather key connection on the outer diameter of the threaded spindle nut. In principle, it is also possible to drive the planetary guide rings via an electric motor actuator drive.

The planetary roller body has at least one profile on its outer peripheral surface. In the case of a planetary roller screw drive, this profiling of the planetary roller body can be designed as a planetary roller body thread. Planetary rolling bodies preferably have a cylindrical three-dimensional shape, the length of the planetary rolling body being greater than the diameter of the planetary rolling body. A cylindrical planetary rolling body has a planetary rolling body axis, which can also be referred to as the axis of rotation of the planetary rolling body. The planetary roller bodies are preferably of essentially identical design.

The planetary rolling bodies can have planetary rolling body bearing elements at both ends for positioning and rotatably mounting a planetary rolling body in or on a planetary guide ring. The planetary rolling body bearing elements can be designed in particular as bearing journals, which are mounted in corresponding bearing bores of the planetary guide rings.

A planetary roller screw drive usually has at least two planetary guide rings, which have the function of defining the radial position of the planetary roller bodies relative to one another within the spindle nut and of supporting the planetary roller bodies so that they can rotate about their longitudinal axis.

For this purpose, a planetary guide ring has, in particular, bearing points on or in which complementary bearing elements of the planetary roller bodies are rotatably accommodated. It is particularly preferred that the bearing points of a planetary guide ring are formed as bearing bores and the bearing elements of the planetary roller bodies are formed as bearing journals complementary thereto, so that the bearing journals are rotatably accommodated in the bearing bores. The bearing points are preferably arranged equidistantly along the circumference of the planetary guide ring, so that the planetary rolling elements are evenly distributed between the spindle nut and the spindle.

A planetary guide ring can be formed integrally with the spindle nut or configured as a separate component from the spindle nut. If the planetary guide ring is designed as a component separate from the spindle nut, the planetary guide ring can be made of a metallic material, ceramic material or be formed from a plastic.

The planetary guide rings are preferably of essentially identical design. In addition to the bearing and positioning of the planetary rolling elements, the planetary rolling element guide ring also prevents coarse dirt from penetrating into the spindle nut.

The roller bearings have an inner ring and an outer ring as well as rolling elements which are held between them and mounted in a rolling manner.

The inner ring can be made of a metallic and/or ceramic material. In principle, it is conceivable to design the inner ring in one piece or in multiple pieces, in particular in two pieces.

The rolling bodies can roll within the rolling bearing, in particular on the inner ring raceway of the inner ring. For this purpose, the surface of the inner ring raceway can advantageously be designed to be correspondingly abrasion-resistant, for example also by means of a corresponding surface treatment method and/or by applying a corresponding additional layer of material.

The inner ring raceway can be flat or profiled. A profiled design of the inner ring raceway can be used, for example, to guide the rolling elements on the inner ring raceway. On the other hand, a planar formation of the inner ring raceway can, for example, allow a certain axial displaceability of the rolling elements on the inner ring raceway.

The inner ring raceway can have a profile for receiving and/or guiding rolling bodies. As a result, the rolling bodies are guided, for example, in a defined manner in or on the inner ring raceway. Furthermore, the axial and radial force absorption of the roller bearing can be influenced by the geometric design of the profiled inner ring raceway.

The outer ring can be made of a metallic and/or ceramic material. In principle, it is conceivable to design the outer ring in one piece or in multiple pieces, in particular in two pieces.

The rolling bodies can roll within the rolling bearing, in particular on the outer ring raceway of the outer ring. For this purpose, the surface of the outer ring raceway can advantageously be designed to be abrasion-resistant, for example by means of a corresponding surface treatment process and/or by applying a corresponding additional layer of material.

The outer ring raceway can be flat or profiled. A profiled design of the outer ring raceway can be used, for example, to guide the rolling elements on the outer ring raceway. On the other hand, a planar shape of the outer ring raceway can, for example, allow a certain axial displaceability of the rolling elements on the outer ring raceway.

The outer ring raceway can have a profile to accommodate and/or guide rolling bodies. As a result, the rolling bodies are guided, for example, in a defined manner in or on the outer ring raceway. Furthermore, the axial and radial force absorption of the roller bearing can also be influenced by the geometric design of the profiled outer ring raceways.

The rolling elements are in the form of a roller. They roll on the raceways of the roller bearing and have the task of transferring the force acting on a roller bearing from the outer ring to the inner ring and vice versa

Rolling elements can be guided and spaced apart in a cage or by rolling element spacers. In principle, it is also conceivable to design a roller bearing without a cage, which is also referred to as a full complement roller bearing. In full complement rolling bearings, adjacent rolling elements can contact each other.

The first group of roller bearings and the second group of roller bearings has needle rollers as rolling elements. Needle rollers of rolling bearings are designed geometrically as circular cylinders, which have a very large length in relation to the diameter of the rolling element. As a rule, one speaks of a needle roller when the length/diameter ratio of a circular-cylindrical roller is >2.5. Particularly compact roller bearings, so-called needle bearings, can be implemented using needle rollers.

In angular needle bearings, the axes of rotation of the needle rollers are at an angle to the axis of rotation of the inner ring or the outer ring, with the axes of rotation of the needle rollers intersecting at a point on the axis of rotation of the inner ring or the outer ring. Angular needle bearings can be single-row or multi-row.

A roller bearing can have a cage, with the cage guiding the rolling elements. The cage is designed in such a way that the rolling element balls and/or the rolling element rollers are spaced apart from one another so that, for example, the friction and heat development of the rolling elements is kept as low as possible. Furthermore, the cage keeps the rolling element balls and/or rolling element rollers at a fixed distance when rolling towards each other, whereby an even load distribution can be achieved. The cage can be made in one piece or in several pieces.

It is also preferred that only identical angular needle bearings are present within the first group of roller bearings and/or only identical angular needle bearings are present within the second group of roller bearings, as a result of which the component complexity and the manufacturing costs of the spindle drive can be further reduced.

In this context, it is also preferable that the first group of roller bearings includes exactly two angular needle bearings and/or the second group of roller bearings includes exactly two angular needle bearings.

A further reduction in components within the spindle drive can also be achieved in an advantageous manner in that an outer ring of the first group of roller bearings is designed monolithically with one of the planetary guide rings. In this context, an inner ring of the first group of roller bearings can also be designed monolithically with the threaded spindle nut in a preferred manner. According to a further preferred embodiment of the invention, an inner ring of the second group of roller bearings can be formed monolithically with one of the planetary guide rings.

In order to be able to provide protection against mechanical and/or chemical influences and a connection to an electric motor drive, the planetary guide rings can preferably have a planetary carrier which connects the axially spaced planetary guide rings to one another, forming an annular space that accommodates the threaded spindle nut. In this context, for reasons of simple assembly of the spindle drive, it can be preferred that the planetary carrier is designed as a component separate from the planetary guide rings.

The spindle drive is preferably configured for use in a rear-axle steering system of a motor vehicle.

The invention will be explained in more detail below with reference to figures without restricting the general inventive idea. The figures are only of a schematic nature and serve exclusively for understanding the invention. The same elements are provided with the same reference numbers. The different features of the various exemplary embodiments can also be freely combined with one another within what is technically feasible.

• 1 den erfindungsgemäßen Spindeltrieb in einer schematischen Querschnittsansicht.

It shows:

• 1 the spindle drive according to the invention in a schematic cross-sectional view.

the 1 shows an embodiment of the spindle drive 1 according to the invention. The spindle drive 1 is designed as a planetary roller screw drive 2, which includes the threaded spindle nut 3, the threaded spindle 4, a plurality of planetary roller bodies 5 with a planetary roller body profile 6, and at least two planetary guide rings 7.

The planetary screw drive 2 converts a rotational movement into a translational movement. This is explained in more detail below. The threaded spindle 4 is arranged concentrically in the planetary guide rings 7 and the threaded spindle nut 3 . The two planetary guide rings 7 , which are of essentially identical design, can be rotated relative to the threaded spindle 4 . The planetary roller bodies 5 in turn are rotatably mounted about their respective planetary roller body axis 8 in the planetary guide rings 7 and inside and the threaded spindle nut 3 . The planetary rolling element profile 6 of the planetary rolling elements 5 meshes with the corresponding profile of the threaded spindle 4, so that a rotation of the threaded spindle 4 causes a rotation of the planetary rolling elements 5 about its planetary rolling element axis 8 and a rotation of the planetary rolling elements 5 about the threaded spindle 4.

The planetary guide rings 7 and the threaded spindle nut 3 are arranged such that they can be rotated in relation to one another via a first group of roller bearings 11, and the planetary guide rings 7 also have a second group of roller bearings 12 on their respective outer end faces facing away from the threaded spindle nut 3, via which the planetary roller screw drive 2 can be rotated relative to a Connection structure is stored.

How from the 1 is clearly visible, the first group of roller bearings 11 and the second group of roller bearings 12 are designed as angular needle bearings. In the embodiment of the invention shown, only identical angular needle bearings are present within the first group of roller bearings 11 and only identical angular needle bearings are present within the second group of roller bearings 12 . The first group of roller bearings 11 includes exactly two angular needle bearings and / the second group of roller bearings 12 also includes exactly two angular needle bearings.

One or all of the outer rings 14 of the first group of roller bearings 11 can be formed monolithically with one of the planetary guide rings 7, but this is not the case 1 is shown. It is also conceivable that one or all of the inner rings 15 of the first group of roller bearings 11 is formed monolithically with the threaded spindle nut 3 . Finally, one or all of the inner rings 16 of the second group of roller bearings 11 can also be formed monolithically with one of the planetary guide rings 7 .

The planetary guide rings 7 have a planetary carrier 17 which connects the axially spaced planetary guide rings 7 to one another, forming an annular space 18 accommodating the threaded spindle nut 3 . The planetary carrier 17 is designed as a component separate from the planetary guide rings 7 .

The spindle drive 1 is configured for use in a rear-axle steering system of a motor vehicle.

The invention is not limited to the embodiments shown in the figures. The foregoing description is therefore not to be considered as limiting but as illustrative. The following patent claims are to be understood in such a way that a mentioned feature is present in at least one embodiment of the invention. This does not exclude the presence of other features. If the patent claims and the above description define 'first' and 'second' feature, this designation serves to distinguish between two similar features without establishing a ranking.

Reference List

1

spindle drive

2

planetary screw drive

3

lead screw nut

4

lead screw

5

planetary rolling elements

6

Planetary rolling element profiling

7

planetary wear rings

8th

planetary roller axis

11

first group of rolling bearings

12

second group of rolling bearings

14

outer ring

15

inner ring

16

inner ring

17

planet carrier

18

annulus

QUOTES INCLUDED IN DESCRIPTION

This list of documents cited by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent Literature Cited

• DD 0277308 A5 [0002]

Claims (9)

Spindle drive (1), the spindle drive (1) is designed as a planetary roller screw drive (2), which has a threaded spindle nut (3), a threaded spindle (4), a plurality of planetary roller bodies (5) with a planetary roller body profile (6), and at least two planetary guide rings ( 7), wherein the planetary roller screw drive (2) converts a rotational movement into a translational movement by the threaded spindle (4) being arranged concentrically in the planetary guide rings (7) and the threaded spindle nut (3), the planetary guide rings (7) opposite the threaded spindle ( 4) are rotatable and the planetary roller bodies (5) are rotatably mounted about their respective planetary roller body axis (8) in the planetary guide rings (7) and inside and in the threaded spindle nut (3), the planetary roller body profile (6) of the planetary roller bodies (5) being connected to the threaded spindle ( 4) meshes, so that a rotation of the threaded spindle (4) a rotation of the planetary rolling elements (5) to their planetary rolling bodies rperachse (8) and a rotation of the planetary rolling elements (5) around the threaded spindle (4), whereby the planetary guide rings (7) and the threaded spindle nut 3 are arranged to rotate against each other via a first group of roller bearings (11) and the planetary guide rings (7) on has a second group of roller bearings (12) on its respective outer end faces facing away from the threaded spindle nut (3), characterized in that the first group of roller bearings (11) and the second group of roller bearings (12) are designed as angular needle bearings. spindle drive, after claim 1 , characterized in that within the first group of roller bearings (11) exclusively identical angular needle bearings and / or within the second group of roller bearings (12) exclusively identical angular needle bearings are present. Spindle drive according to one of the preceding claims, characterized in that the first group of roller bearings (11) comprises exactly two angular needle bearings and/or the second group of roller bearings (12) comprises exactly two angular needle bearings. Spindle drive according to one of the preceding claims, characterized in that an outer ring (14) of the first group of roller bearings (11) is designed monolithically with one of the planetary guide rings (7). Spindle drive according to one of the preceding claims, characterized in that an inner ring (15) of the first group of roller bearings (11) is formed monolithically with the threaded spindle nut (3). Spindle drive according to one of the preceding claims, characterized in that an inner ring (16) of the second group of roller bearings (11) is designed monolithically with one of the planetary guide rings (7). Spindle drive according to one of the preceding claims, characterized in that the planetary guide rings (7) have a planet carrier (17) which connects the axially spaced planetary guide rings (7) to one another, forming an annular space (18) which accommodates the threaded spindle nut (3). Spindle drive according to one of the preceding claims, characterized in that the planetary carrier (17) is designed as a component separate from the planetary guide rings (7). Spindle drive according to one of the preceding claims, characterized in that the spindle drive (1) is configured for use in a rear-axle steering system of a motor vehicle.

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