PLANETARY ROLLER SCREW DRIVE

Abstract

A planetary roller screw drive for an actuator of a rear-axle steering system of a motor vehicle, including a planetary roller support which accommodates the planetary rollers and is connected to a drive sleeve for rotation therewith, which drive sleeve is driven rotatably about the screw spindle and is mounted rotatably on a machine part by an axial angular contact roller bearing which is arranged coaxially with respect to the drive sleeve and of which the rollers are in rolling contact with angled-bearing raceways which are inclined with respect to a plane arranged transversely with respect to the axis of rotation of the drive sleeve.

Claims

1. A planetary roller screw drive, comprising: a nut arranged on a screw spindle; planetary rollers having a planetary groove profile arranged between the screw spindle and the nut and which mesh via the planetary groove profile with a nut-side groove profile and, with a thread profile of the screw spindle; a planetary roller support having pockets, which are arranged distributed over a circumference thereof and in which the planetary rollers are rotatably mounted about respective planetary roller axes thereof; a drive sleeve that is rotatably driven about a spindle axis of the screw spindle and which is connected for conjoint rotation with the planetary roller support and is rotatably mounted on a machine part by a bearing; wherein the bearing comprises an axial angular contact roller bearing arranged coaxially with the drive sleeve and having rollers in rolling contact with angled-bearing raceways that are arranged inclined with respect to a plane arranged transverse to the spindle axis which coincides with a rotation axis of the drive sleeve.

2. The planetary roller screw drive according to claim 1, wherein the drive sleeve includes a sleeve and an angled-bearing disc which is arranged in a rotationally fixed manner in the sleeve and which has the inclined angled-bearing raceway.

3. The planetary roller screw drive according to claim 2, wherein the angled-bearing disc is arranged in the sleeve with play in an axial direction.

4. The planetary roller screw drive according to claim 3, wherein the nut is axially mounted on the drive sleeve by an axial roller bearing.

5. The planetary roller screw drive according to claim 4, wherein the nut is axially mounted by the axial roller bearing on the angled-bearing disc, which on an end face facing away from the angled-bearing raceway, includes an axial bearing raceway of the axial roller bearing.

6. The planetary roller screw drive according to claim 5, wherein the planetary roller support is firmly connected to the angled-bearing disc on a receptacle of the angled-bearing disc, and the receptacle is arranged radially within the angled-bearing raceway.

7. The planetary roller screw drive according to claim 1, further comprising a second axial angular contact roller bearing such that there are two of the axial angular contact roller bearings, each arranged on one end face of the drive sleeve.

8. An actuator for a rear-axle steering system of a motor vehicle, comprising the planetary roller screw drive according to claim 1, a push rod having ends that face away from one another and are configured for articulation of rear wheels of the motor vehicle, and the screw spindle is part of the push rod.

9. The actuator according to claim 8, further comprising an electric motor, and a belt drive having a toothed belt which loops around a motor pinion of the electric motor and the drive sleeve.

10. The actuator according to claim 9, further comprising a housing which forms the machine part, and the belt drive with the motor pinion and the planetary roller screw drive are arranged in the housing.

11. A planetary roller screw drive, comprising: a screw spindle; a nut arranged on the screw spindle via a plurality of planetary rollers, each having a planetary groove profile that meshes with a nut-side groove profile of the nut and with a thread profile of the screw spindle; a planetary roller support having pockets distributed over a circumference thereof and in which the planetary rollers are rotatably mounted about respective planetary roller axes thereof; a drive sleeve that is rotatably drivable about a spindle axis of the screw spindle and which is connected for conjoint rotation with the planetary roller support; a machine part on which the drive sleeve and is rotatably supported by a bearing; wherein the bearing comprises an axial angular contact roller bearing arranged coaxially with the drive sleeve and having rollers in rolling contact with angled-bearing raceways that are connected to or located on the machine part and the drive sleeve that are arranged inclined with respect to a plane arranged transverse to the spindle axis.

12. The planetary roller screw drive according to claim 11, wherein the drive sleeve includes a sleeve and an angled-bearing disc which is rotationally fixed to the sleeve and which has one of the inclined angled-bearing raceways.

13. The planetary roller screw drive according to claim 12, wherein the angled-bearing disc is arranged in the sleeve with play in an axial direction.

14. The planetary roller screw drive according to claim 13, wherein the nut is axially supported on the drive sleeve by an axial roller bearing.

15. The planetary roller screw drive according to claim 14, wherein the nut is axially mounted by the axial roller bearing on the angled-bearing disc, which on an end face facing away from the angled-bearing raceway, includes an axial bearing raceway of the axial roller bearing.

16. The planetary roller screw drive according to claim 15, wherein the planetary roller support is firmly connected to the angled-bearing disc on a receptacle of the angled-bearing disc, and the receptacle is arranged radially within the angled-bearing raceway of the angled-bearing disc.

17. The planetary roller screw drive according to claim 11, further comprising a second axial angular contact roller bearing such that there are two of the axial angular contact roller bearings, each arranged on one end face of the drive sleeve.

18. The planetary roller screw drive according to claim 17, wherein the axial contact roller bearings are inclined in opposite directions.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The disclosure is explained in more detail below with reference to an exemplary embodiment shown in three figures. In the figures:

[0023] FIG. 1 shows a planetary roller screw drive in longitudinal section

[0024] FIG. 2 shows an actuator of a rear-axle steering system of a motor vehicle;

[0025] FIG. 3 shows a section from FIG. 2.

DETAILED DESCRIPTION

[0026] The planetary roller screw drive shown in FIG. 1 is provided with a nut 2 arranged on a screw spindle 1. Planetary rollers 3 are distributed over the circumference of the screw spindle 1 between the screw spindle 1 and the nut 2. The planetary rollers 3 mesh, on the one hand, with their planetary groove profile 4 with a nut-side groove profile 5 and, on the other hand, with a thread profile 6 of the screw spindle 1 that is wound helically around the spindle axis.

[0027] This planetary roller screw drive also has a planetary roller support 7 having pockets 8, which are arranged distributed over the circumference and in which the planetary rollers 3 are rotatably mounted about their planetary roller axis. The figure clearly shows bearing journals 9 which are formed at the axial ends of the planetary rollers 3 and which engage in bearing pockets 10 of the planetary roller support 7.

[0028] The planetary roller support 7 is connected for conjoint rotation with a drive sleeve 11 that is rotatably driven about a spindle axis of the screw spindle 1. The drive sleeve 11 is rotatably mounted on a machine part 12, merely indicated here, by means of an axial angular contact roller bearing 13 arranged coaxially with the drive sleeve 11, the cylindrical rollers 14 of which are in rolling contact with angled-bearing raceways 15, 19 which are inclined with respect to a transverse plane arranged transverse to the axis of rotation of the drive sleeve.

[0029] The machine part 12 is fixed to the frame and, in the exemplary embodiment, is designed as a housing, as is clearly shown in FIG. 2.

[0030] The nut 2 is axially mounted on the drive sleeve 11 by means of an axial roller bearing 17. The axial roller bearing 17 only transmits axial bearing forces and enables radial play between the screw spindle 1, the planetary rollers 3 and the nut 2 on the one hand and the drive sleeve 11 on the other hand. The axial roller bearing 17 has two discs 20, 21 which are each provided with an axial bearing raceway 22, 23 of the axial roller bearing 17 on their mutually facing end faces. One disc 20 is supported on the drive sleeve 11 and the other disc 21 is supported on the nut 2.

[0031] The drive sleeve 11 has a sleeve 24, in each of the end-face ends of which an angled-bearing disc 25 is inserted in a rotationally fixed manner. On their end faces facing away from one another, the two angled-bearing discs 25 are provided with the angled-bearing raceways 15 of the axial angular contact roller bearing 13. The axial bearing raceways 22 of the axial roller bearings 17 can alternatively be formed on the mutually facing end faces of the angled-bearing discs 25; in this case the discs can be omitted.

[0032] The sleeve 24 is designed at its outer circumference in a central portion as a toothed belt wheel 16, around which a toothed belt of a belt drive is looped.

[0033] The planetary roller support 7 is received at both axial ends in central receptacles 26 of the two angled-bearing discs 25, said central receptacles being arranged radially inside the angled-bearing raceway 15, and is firmly connected to the angled-bearing discs 25. The receptacle 26 can be designed as a central opening in the angled-bearing disc 25, for example to be cylindrical like a bore.

[0034] The planetary roller support 7 is provided at each of its axial ends with a connecting piece 18 which is firmly inserted into said receptacle 26 so that the drive force can be transmitted properly from the drive sleeve 11 to the planetary roller support 7. For the purpose of configuring a bearing play, it can be useful if, on the one hand, there is a rotationally fixed connection between the sleeve 24 and the two angled-bearing discs 25, and, on the other hand, an axial play of the at least one angled-bearing disc 25 in the sleeve 24 is possible. A bearing play of the axial angular contact roller bearing 13 between the machine part 12 and the drive sleeve 11 can be configured on the outside by means of adjustment means (not shown) on the sides of the machine part 12. Owing to the angled-bearing disc 25 with axial play, an axial play of the axial roller bearing 17 between the nut 2 and the drive sleeve 11 is configured at the same time.

[0035] In the exemplary embodiment according to FIG. 1, the planetary roller screw drive is provided with two axial angular contact roller bearings 13 each arranged on one of the end faces of the drive sleeve 11. This planetary roller screw drive is useful when axial loads of the same magnitude are to be expected in both axial directions, and enables the use of structurally identical axial angular contact roller bearings, such that economically favorable production is possible.

[0036] FIG. 2 shows an actuator of a rear-axle steering system of a motor vehicle with the planetary roller screw drive described above, which is arranged in the machine part, designed as a housing 27, of the actuator. This actuator is provided with a push rod 28, the ends of which facing away from one another are designed for the articulation of rear wheels of the motor vehicle and are guided out of the housing 27. In the exemplary embodiment, the ends of the push rod 28 are provided with fork-like link heads 29. The ends of the push rod 28 which protrude from the housing 27 are encased by bellows collars and covered in the figure. The screw spindle 1, arranged in the housing 27, of the planetary roller screw drive forms a central portion of the push rod 28. The push rod 28 can have two push rod parts which are arranged axially one behind the other and between which the screw spindle 1 is arranged and firmly connected to the two push rod parts. Alternatively, the push rod parts and the screw spindle can be connected to one another in one piece.

[0037] The actuator has an electric motor 30 and a belt drive 31, which is shown in detail in FIG. 3. A toothed belt 32 loops around a motor pinion 33 of the electric motor 30 as well as the drive sleeve 11, not shown here. The belt drive, the motor pinion 33 and the planetary roller screw drive are accommodated in the housing 27.

LIST OF REFERENCE SIGNS

[0038] 1 Screw spindle

[0039] 2 Nut

[0040] 3 Planetary roller

[0041] 4 Planetary groove profile

[0042] 5 Nut-side groove profile

[0043] 6 Thread profile

[0044] 7 Planetary roller support

[0045] 8 Pocket

[0046] 9 Bearing journal

[0047] 10 Bearing pocket

[0048] 11 Drive sleeve

[0049] 12 Machine part

[0050] 13 Axial angular contact roller bearing

[0051] 14 Roller

[0052] 15 Angled-bearing raceway

[0053] 16 Toothed belt wheel

[0054] 17 Axial roller bearing

[0055] 18 Connecting piece

[0056] 19 Angled-bearing raceway

[0057] 20 Disc

[0058] 21 Disc

[0059] 22 Axial bearing raceway

[0060] 23 Axial bearing raceway

[0061] 24 Sleeve

[0062] 25 Angled-bearing disc

[0063] 26 Central receptacle

[0064] 27 Housing

[0065] 28 Push rod

[0066] 29 Link head

[0067] 30 Electric motor

[0068] 31 Belt drive

[0069] 32 Toothed belt

[0070] 33 Motor pinion