Patent ID: 12259025

DETAILED DESCRIPTION

FIG.1shows a schematic representation of an actuator for a steering device of a motor vehicle, specifically for a rear-wheel steering system.

The actuator is provided with an electric motor1and has a roller screw drive3arranged in a housing2, which is rotatably mounted in the housing2by means of bearings4,5arranged axially spaced apart from one another. An axially displaceable threaded spindle6is part of a thrust rod7penetrating the housing2.

The housing2is split transversely to the thrust rod into housing parts8,9. The first bearing4is associated with the first housing part8and the second bearing5is associated with the second housing part9.

An adjusting nut10penetrated by the thrust rod7is screwed into a thread11of the first housing part8. The first bearing4is supported or mounted on an end-side supporting surface12of the adjusting nut10. An axial bearing distance between the two bearings4,5is set by screwing the adjusting nut10into the thread11.

In the exemplary embodiment, the adjusting nut10is screwed into a threaded bore13of the first housing part8which is arranged coaxially to the thrust rod and forms the thread11. On the end face thereof facing the first bearing4, the adjusting nut10is provided with a radial rim14having the supporting surface12.

In the exemplary embodiment, the bearings4,5are formed by axial angular contact roller bearings15, the tapered raceways17of which are inclined to a plane arranged transversely to the spindle axis.

The adjusting nut10has a tapered supporting surface12adapted to the axial angular contact roller bearing15as a support for the axial angular contact roller bearing.

The detail enlargements inFIGS.2and7show an enlarged view of the roller screw drive3, which is formed by a planetary roller screw drive19in the exemplary embodiment. Planetary rollers20mesh with the groove profiles21thereof on the one hand with groove profiles22of a nut23and on the other hand with a thread24of the threaded spindle6.

A rotationally driven planetary roller carrier25accommodates the planetary rollers20in the pockets26thereof distributed over the circumference. The planetary roller carrier25is mounted on the housing2on the one hand by means of the axial angular contact roller bearings15,16and on the other hand by means of axial roller bearings27, which are arranged between the planetary roller carrier25and the nut23.

The planetary roller carrier25has a sleeve element28that engages around the nut23and flanges29arranged on both axial sides, which are connected to the sleeve element28in a non-rotatable and axially displaceable manner with respect to one another. One of the axial roller bearings27is arranged between the flanges29and the nut23, and one of the axial angular contact roller bearings15is arranged between the flanges29and the housing2.

The electric motor1mentioned at the outset drives the planetary roller carrier25of the planetary roller screw drive19via a belt drive37(FIGS.1,2). Under the rotation thereof, the planetary rollers20orbit the threaded spindle6and roll off the threaded spindle6and the nut23. The rolling of the planetary rollers20causes the nut23to rotate relative to the threaded spindle6and to the planetary roller carrier25. The thrust rod7is displaced axially in this way.

FIGS.3and4clearly show the first housing part8, which has a first housing edge30located transversely to the spindle axis and the second housing part9thereof has a second housing edge31located transversely to the spindle axis, which rest against one another, as can be clearly seen inFIG.2.

FIGS.5and6show two examples of a screw lock, by means of which the adjusting nut10is secured in place on the first housing part8. The screw lock according toFIG.5is carried out by a thread lock32between the first housing part8and the adjusting nut10, and according toFIG.6is formed by a material connection36by means of a coating33of the screw thread34of the adjusting nut10.

In the case of the thread lock32, a special thread35is pressed into a longitudinal groove that is made in the screw thread34.

In the case of the coating33, a central thread portion of the screw thread34is coated.

FIG.7shows a further enlargement of a section ofFIG.1, specifically in the area of the first bearing4, that is the axial angular contact roller bearing15. The running disks40,41thereof and the set of rollers42arranged between the running disks can be clearly seen. A mean bearing diameter dLcircumscribes a circular path that forms a reference line on an end face43of the running disk40facing the adjusting nut10, from which a distance “x” can be measured in the axial direction to the second edge of the housing edge31, as is explained in more detail below.

The setting of a desired axial preload of the planetary roller screw drive19can be carried out in a simple manner with the proposed actuator. The planetary roller screw drive19is inserted with the two axial angular contact roller bearings15into the second housing part9(FIG.4). The axial angular contact roller bearing15as the second bearing is inserted in the intended bearing point thereof of the second housing part9. The other axial angular contact roller bearing15as the first bearing4is also mounted. Both axial angular contact roller bearings15are arranged on both sides of the flanges29of the planetary roller carrier25.

An axial load is now introduced, which is transmitted from the first bearing4—axial angular contact roller bearing15—via the planetary roller screw drive19to the second bearing5—thus the other axial angular contact roller bearing15. This axial load is so great that a desired preload force is set. An axial load distance “X” is now measured (FIG.4) starting from the reference line, which is formed as a circular path with the mean bearing diameter “dL” of the axial angular contact roller bearing15on the side of the bearing disk40thereof facing the adjusting nut10, up to the second housing edge31of the second housing part9.

The adjusting nut10can now be screwed into the first housing part8(FIG.3) and an axial adjustment distance can be measured, starting from a circular reference line on the tapered supporting surface12of the adjusting nut10, with the mean bearing diameter “dL” of the axial angular contact roller bearing15. Starting from this reference line, the axial adjustment distance to the first housing edge30of the first housing part8is set (seeFIG.3). The adjusting nut10is screwed in until the axial adjustment distance has reached the amount “x”.

A securing in place of the adjusting nut10in the first housing part8reliably maintains the preload once it has been set during operation of the actuator. Finally, the two housing parts8,9can be assembled and the actuator can be completed.

The reference lines on the tapered supporting surface12and on the bearing disk40are in the same place in the axial direction after assembly is complete and coincide. The housing edges30,31of the two housing parts8,9are also in the same place in the axial direction after assembly is complete and coincide. As a result, the adjustment distance and the load distance “X” are of the same amount.

The two housing parts8,9can now be screwed together.

After assembly, the desired axial preload force is set on the roller screw drive.

LIST OF REFERENCE SYMBOLS

1Electric motor2Housing3Roller screw drive4First bearing5Second bearing6Threaded spindle7Thrust rod8First housing part9Second housing part10Adjusting nut11Thread12Adjusting nut supporting surface13Threaded bore14Radial rim15Axial angular contact roller bearing17Tapered raceway19Planetary roller screw drive20Planetary rollers21Groove profile22Groove profile23Nut24Thread25Planetary roller carrier26Pockets27Axial roller bearings28Sleeve element29Flange30First housing edge31Second housing edge32Thread lock33Coating34Screw thread35Thread36Material connection37Belt drive38Bearing supporting surface40Running disk41Running disk42Roller setdLMean bearing diameter