Multi-stage planetary gearbox comprising two ring gears

Abstract

The present invention relates to a planetary gearbox comprising at least two gear stages, a drive-side ring gear, and an output-side ring gear, wherein ring gear teeth of the output-side ring gear and ring gear teeth of the drive-side ring gear are formed coaxially with an axis of the planetary gearbox, wherein at least one of the gear stages is associated with the drive-side ring gear and one of the gear stages is associated with the output-side ring gear, and each gear stage comprises a sun gear, at least one planet gear, and a planet carrier, wherein the at least one planet gear meshes with the sun gear and with the associated ring gear teeth of the drive-side ring gear or of the output-side ring gear, and is rotatably mounted on the planet carrier about a planet gear axis that is fixed in position relative to the planet carrier, wherein the drive-side ring gear is stationary, and the output-side ring gear forms an output of the planetary gearbox. According to the invention, the drive-side ring gear forms the planet carrier of the gear stage associated with the output-side ring gear.

Description

[0001] Multi-stage planetary gearbox with two ring gears

[0002] The present invention relates to a planetary gear unit according to the preamble of claim 1.

[0003] A planetary gear system of this type comprises at least two gear stages, a drive-side ring gear and an output-side ring gear, wherein a ring gear toothing of the output-side ring gear and a ring gear toothing of the drive-side ring gear are formed coaxially to an axis of the planetary gear system, wherein at least one of the gear stages is assigned to the drive-side ring gear and one of the gear stages is assigned to the output-side ring gear, and each gear stage comprises a sun gear, at least one planet gear and a planet carrier, wherein the at least one planet gear meshes with the sun gear and the associated ring gear toothing of the drive-side ring gear or the output-side ring gear and is rotatably mounted on the planet carrier about a planet gear axis that is fixed relative to the planet carrier, wherein the drive-side ring gear is stationary and the output-side ring gear forms an output of the planetary gear system.

[0004] A planetary gear of this type is known, for example, from US 2003 / 220169 A1. This type of planetary gear is intended for applications requiring a small and lightweight planetary gear with high torque generation. Nevertheless, the known planetary gear exhibits a relatively large dimension, particularly in one axial direction.

[0005] The object of the present invention is therefore to provide a planetary gear unit which offers a further improvement with regard to the required installation space and the possible torque generation.

[0006] The problem is solved by the features of independent claim 1. Accordingly, a solution to the problem according to the invention exists if the drive-side ring gear forms the planet carrier of the gear stage associated with the output-side ring gear. The drive-side ring gear and the planet carrier of the gear stage associated with the output-side ring gear need not necessarily be formed integrally. The drive-side ring gear can also be connected to the planet carrier of the gear stage associated with the output-side ring gear only in a rotationally fixed manner.

[0007] The solution according to the invention allows the planetary gear to be designed more compactly, thereby reducing the required installation space relative to the required torque generation. The planet gear axis associated with each planet gear is a geometric axis around which the respective planet gear rotates.

[0008] Advantageous embodiments of the present invention are the subject of the dependent claims. In a preferred embodiment of the present invention, the inner radius of the ring gear teeth of the output-side ring gear is larger than the inner radius of the ring gear teeth of the input-side ring gear. Due to the larger inner radius of the ring gear teeth of the output-side ring gear, a higher gear ratio and a higher torque can be generated in the gear stage associated with the output-side ring gear than in the gear stage(s) associated with the input-side ring gear. Preferably, the input-side ring gear and the output-side ring gear each have a constant inner radius for their respective ring gear teeth. This simplifies the manufacturing of the planetary gear set.

[0009] Preferably, the ratio of the inner radius of the ring gear teeth of the output-side ring gear to the inner radius of the ring gear teeth of the input-side ring gear is greater than 1.05 and is preferably in the range of 1.05 to 2, more preferably in the range of 1.2 to 1.7. In these ranges, an advantageous ratio of the gear ratios of the respective gear stages is obtained with respect to the required installation space of the planetary gear.

[0010] Furthermore, preferably, the radial distance of the planet gear axis of the at least one planet gear of the gear stage associated with the output-side ring gear from the axis is smaller than the inner radius of the ring gear teeth of the input-side ring gear. This enables a compact design. For this purpose, the input-side ring gear can have a radially inwardly directed projection on which the at least one sun gear of the gear stage associated with the output-side ring gear is rotatably mounted.

[0011] In a particularly preferred embodiment of the present invention, the output-side ring gear comprises a hollow cylinder which encompasses or encloses the input-side ring gear in a radial direction to the axis, at least along a section of the axis. Preferably, the hollow cylinder forms the output. This enables a compact design.

[0012] Preferably, the hollow cylinder is radially mounted on the drive-side ring gear. This provides stable mounting of the output-side ring gear while still allowing for a compact design of the planetary gear set. More preferably, the hollow cylinder is mounted on the drive-side ring gear by means of rolling bearings, particularly preferably by means of ball bearings. Also preferably, the output-side ring gear, its toothed section, and the hollow cylinder are formed integrally, or the hollow cylinder and its toothed section are formed as separate components, with the hollow cylinder and its toothed section being rotationally connected to each other. The integral output-side ring gear provides particularly reliable power transmission.In contrast, with the hollow cylinder as a separate component, the hollow cylinder can be made from a lighter material than the ring gear teeth of the output-side ring gear, which reduces the weight of the planetary gear.

[0013] In a preferred embodiment, the hollow cylinder forms the output of the planetary gear.

[0014] Furthermore, preferably the outer diameter of the ring gear teeth of the output-side ring gear is less than or equal to the outer diameter of the hollow cylinder. This results in a compact design of the planetary gear.

[0015] According to a preferred embodiment, in successive gear stages in one output direction, the planet carrier of the front gear stage is rotationally fixed to the sun gear of the rear gear stage or is integrally formed. This enables a simple and compact design of the planetary gear set and the coupling of the gear stage associated with the input-side ring gear, which is the last gear stage in the output direction, with the gear stage associated with the output-side ring gear.

[0016] In a preferred embodiment, the planetary gear has at least three, preferably at least four, and particularly preferably five gear stages associated with the drive-side ring gear. This results in an advantageous gear ratio.

[0017] According to a preferred embodiment, the gear stage associated with the output-side ring gear has a support disk, wherein the at least one planet gear is arranged between the support disk and the input-side ring gear and is rotatably mounted on the input-side ring gear and the support disk about the planet gear axis, the planet gear axis being fixed relative to the input-side ring gear and relative to the support disk. This results in a stable structure of the gear stage associated with the output-side ring gear.

[0018] In a further preferred embodiment, each gear stage comprises at least three planet gears, wherein each gear stage preferably comprises three or four planet gears, and further preferably the gear stage associated with the output-side ring gear comprises four planet gears and the gear stage(s) associated with the input-side ring gear comprises three planet gears. This results in a stable and reliable torque transmission through the planetary gear set.

[0019] According to a preferred embodiment, the maximum diameter of the pallet gear perpendicular to the axis is less than 25 mm. The advantages of the aforementioned embodiments are particularly relevant at such diameters.

[0020] Furthermore, the invention relates to a drive device with a planetary gear according to one of the embodiments of the planetary gear described above and an electric motor which forms a drive of the planetary gear.

[0021] According to one embodiment of the drive device, the electric motor drives the sun gear of a first gear stage in the output direction.

[0022] According to another embodiment of the drive device, the drive device is designed as a wheel drive. The planetary gear is particularly suitable for such a drive.

[0023] According to another embodiment of the drive device, the drive device is designed as an articulated drive for robots. The planetary gear is particularly suitable for such a drive.

[0024] Two exemplary embodiments of a planetary gear according to the invention are explained in more detail below with reference to drawings.

[0025] The drawings show:

[0026] Figure 1: an axial longitudinal section through a first embodiment of a planetary gear unit according to the invention in a first position of the gear stages and an uncut electric motor as drive,

[0027] Figure 2: an axial longitudinal section through the first embodiment of the planetary gear according to the invention in a second position of the gear stages and the uncut electric motor as drive,

[0028] Figure 3: an axial longitudinal section through a second embodiment of a planetary gear according to the invention in a first position of the gear stages and an uncut electric motor as drive, Figure 4: an axial longitudinal section through the second embodiment of the planetary gear according to the invention in a second position of the gear stages and the uncut electric motor as drive.

[0029] In the following illustrations, identical parts are labelled with the same reference symbols. If a figure contains reference symbols that are not explicitly addressed in the corresponding figure description, reference is made to previous or subsequent figure descriptions.

[0030] Figures 1 and 2 show axial longitudinal sections through a first embodiment of the planetary gear 1 according to the invention and an uncut electric motor 2 as a drive, wherein the gear stages of the planetary gear 1 are shown in different positions in Figures 1 and 2. The first embodiment is a planetary gear 1 with a drive-side ring gear 3 and an output-side ring gear 4, wherein a ring gear toothing of the output-side ring gear 4 and a ring gear toothing of the drive-side ring gear 3 are formed coaxially with an axis 5 of the planetary gear 1. The planetary gear 1 comprises six gear stages, wherein five of the gear stages are assigned to the drive-side ring gear 3 and one of the gear stages to the output-side ring gear 4.Each gear stage comprises a sun gear 6, at least one planet gear 7, and a planet carrier 8, wherein the at least one planet gear 7 meshes with the associated sun gear 6 and the associated ring gear teeth of the input-side ring gear 3 or the output-side ring gear 4 and is rotatably mounted on the planet carrier β about a planet gear axis 9 that is fixed relative to the planet carrier 8. In the illustrated first embodiment of the planetary gear, the gear stages associated with the input-side ring gear 3 comprise three planet gears 7, and the gear stages associated with the output-side ring gear 4 comprise four planet gears 7. The planetary gear 1 is designed such that the input-side ring gear 3 is stationary, and the output-side ring gear 4 forms an output of the planetary gear 1.According to the invention, the drive-side ring gear 3 forms the planet carrier 8 of the gear stage associated with the output-side ring gear 4. For this purpose, in the illustrated embodiment, the drive-side ring gear 4 has a radially inwardly directed projection 10 on which the planet carriers 8 of the gear stage associated with the output-side ring gear 4 are rotatably mounted.

[0031] In the exemplary embodiment, with successive gear stages 11 in an output direction, the planet carrier 8 of the front gear stage is integrally formed with the sun gear 7 of the rear gear stage, wherein the sun gear 7 of the first gear stage in the output direction 11 is driven by the electric motor 2. Furthermore, the inner radius 12 of the ring gear teeth of the output-side ring gear 4 is larger than the inner radius 13 of the ring gear teeth of the input-side ring gear 3, wherein the inner radius 12 of the ring gear teeth of the output-side ring gear 4 and the inner radius 13 of the ring gear teeth of the input-side ring gear 3 are constant. According to the first embodiment, the ratio of the inner radius 12 of the ring gear teeth of the output-side ring gear 4 to the inner radius 13 of the ring gear teeth of the input-side ring gear 3 is in the range of 1.2 and 1.7.Furthermore, the radial distance of the planet gear axis 9 of the planet gears 7 of the gear stage assigned to the output-side ring gear 4 from the axis 5 is smaller than the inner radius 13 of the ring gear teeth of the input-side ring gear 3.

[0032] In addition, the output-side ring gear 4 comprises a hollow cylinder 14, which encompasses the input-side ring gear 3 in a radial direction to the axis 5 at least along a section of the axis 5, wherein the hollow cylinder 14 is radially mounted on the input-side ring gear 3 by means of ball bearings 15. The output-side ring gear 4 is formed integrally from the hollow gear teeth of the output-side ring gear and the hollow cylinder 14, wherein an outer diameter 16 of the hollow gear teeth of the output-side ring gear 4 is smaller than an outer diameter 17 of the hollow cylinder 14. The hollow cylinder 14 forms the output of the planetary gear 1.

[0033] Furthermore, the gear stage associated with the output-side ring gear 4 has a support disc 18, wherein the planet gears 7 of the gear stage associated with the output-side ring gear 4 are arranged between the support disc 18 and the input-side ring gear 3, as planet carriers 8 of the gear stage associated with the output-side ring gear 4, and are rotatably mounted on the input-side ring gear 3 and the support disc 18 about the respective planet gear axes 9.

[0034] Furthermore, the maximum diameter of the pallet gear perpendicular to axis 5 according to the first embodiment is less than 25 mm.

[0035] Figures 3 and 4 show axial longitudinal sections through a second embodiment of a planetary gear 1 according to the invention and an uncut electric motor 2 as a drive, wherein the gear stages of the planetary gear 1 are shown in different positions in Figures 3 and 4. The second embodiment differs from the first embodiment in that the hollow cylinder 14 and the ring gear teeth of the output-side ring gear 4 are designed as separate components, wherein the hollow cylinder 14 and the ring gear teeth of the output-side ring gear 4 are rotationally fixed to one another. List of

[0036] 1 planetary gear

[0037] 2 electric motors

[0038] 3 Drive-side ring gear

[0039] 4 Output-side ring gear

[0040] 5-axis

[0041] 6 Sun wheel

[0042] 7 planetary gear

[0043] 8 planetary carriers

[0044] 9 planetary gear axle

[0045] 10 lead

[0046] 11. Drive direction

[0047] 12 Inner radius of the ring gear teeth of the output-side ring gear

[0048] 13 Inner radius of the ring gear teeth of the drive-side ring gear

[0049] 14 hollow cylinders

[0050] 15 ball bearings

[0051] 16 Outer diameter of the ring gear teeth of the output-side ring gear

[0052] 17 Outer diameter of the hollow cylinder

[0053] 18 Support disc

Claims

Claims 1. Planetary gear (1) with at least two gear stages, a drive-side ring gear (3) and a driven-side ring gear (4), wherein a ring gear toothing of the driven-side ring gear (4) and a ring gear toothing of the drive-side ring gear (3) are formed coaxially to an axis (5) of the planetary gear (1), wherein at least one of the gear stages is assigned to the drive-side ring gear (3) and one of the gear stages is assigned to the driven-side ring gear (4) and each gear stage is a sun gear (6) comprises at least one planet gear (7) and a planet carrier (8), wherein the at least one planet gear (7) meshes with the sun gear (6) and the associated ring gear teeth of the drive-side ring gear (3) or the output-side ring gear (4) and is rotatably mounted on the planet carrier (8) about a planet gear axis (9) that is fixed relative to the planet carrier (8), wherein the drive-side ring gear (3) is stationary and the output-side ring gear (4) forms an output of the planetary gear (1), characterized in that the drive-side ring gear (3) forms the planet carrier (8) of the gear stage associated with the output-side ring gear (4).

2. Planetary gear (1) according to claim 1 , characterized in that an inner radius (12) the ring gear teeth of the output-side ring gear (4) larger than an inner radius (13) the ring gear toothing of the drive-side ring gear (3) is formed.

3. Planetary gear (1) according to claim 2, characterized in that the ratio of the inner radius (12) of the ring gear teeth of the output-side ring gear (4) to the inner radius (13) of the ring gear teeth of the input-side ring gear (3) is greater than 1.05 and preferably in the range of 1.05 and 2, more preferably in the range of 1.2 and 1.

7.

4. Planetary gear (1) according to one of claims 2 or 3, characterized in that a radial distance of the planet gear axis (9) of the at least one planet gear (7) the distance from the axis (5) to the output-side ring gear (4) is smaller than the inner radius (13) of the ring gear teeth of the input-side ring gear (3).

5. Planetary gear (1) according to one of claims 1 to 4, characterized in that the output-side ring gear (4) comprises a hollow cylinder (14) which encompasses the input-side ring gear (3) in a radial direction to the axis (5) at least along a section of the axis (5).

6. Planetary gear (1) according to claim 5, characterized in that the hollow cylinder (14) is radially mounted on the drive-side ring gear (3), preferably by means of rolling bearings, more preferably by means of ball bearings (15).

7. Planetary gear (1) according to claim 5 or 6, characterized in that the output-side ring gear (4) is formed integrally with the ring gear teeth of the output-side ring gear (4) and the hollow cylinder (14) or the hollow cylinder (14) and the ring gear teeth of the output-side ring gear (4) are formed as separate components, wherein the hollow cylinder (14) and the ring gear teeth of the output-side ring gear (4) are rotationally connected to each other.

8. Planetary gear (1) according to one of claims 5 to 7, characterized in that the hollow cylinder (14) forms the output.

9. Planetary gear (1) according to one of claims 5 to 8, characterized in that an outer diameter (16) of the ring gear toothing of the output-side ring gear (4) is less than or equal to an outer diameter (17) of the hollow cylinder (14).

10. Planetary gear (1) according to one of claims 1 to 9, characterized in that, in the case of successive gear stages in an output direction (11), the planet carrier (8) of the front gear stage is rotationally fixed to the sun gear (6) of the rear gear stage or is integrally formed.

11. Planetary gear (1) according to one of claims 1 to 10, characterized in that the planetary gear (1) has at least three, preferably at least four, particularly preferably five gear stages associated with the drive-side ring gear (3).

12. Planetary gear (1) according to one of claims 1 to 11, characterized in that the gear stage associated with the output-side ring gear (4) has a support disk (18), wherein the at least one planet gear (7) is arranged between the support disk (18) and the input-side ring gear (3) and is rotatably mounted on the input-side ring gear (3) and the support disk (18) about the planet gear axis (9), wherein the planet gear axis (9) is stationary relative to the input-side ring gear (3) and relative to the support disk (18).

13. Planetary gear (1) according to any one of claims 1 to 12, characterized in that each gear stage comprises at least three planet gears (7), wherein each gear stage preferably comprises three or four planet gears (7), wherein the gear stage associated with the output-side ring gear (4) preferably comprises four planet gears (7) and the gear stage(s) associated with the drive-side ring gear (3) comprise three planet gears (7).

14. Planetary gear (1) according to one of claims 1 to 13, characterized in that a maximum diameter of the planetary gear perpendicular to the axis (5) is less than 25 mm.

15. Drive device comprising a planetary gear (1) according to one of claims 1 to 14 and an electric motor (2) which forms a drive of the planetary gear (1).

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