Planetary gear with improved bearing flange

Abstract

The present invention relates to a planetary gear comprising a ring gear, at least one gear stage and a bearing flange for the mounting of an output shaft. The problem addressed by the present invention is that of providing such a planetary gear that the gears known from the prior art are improved and in particular provide a solution which is cost-effective and simple to produce for the mounting of the output shaft of the gear. For this purpose, it is provided according to the invention that the bearing flange is of multi-part design and has at least a first bearing flange part on the ring-gear side and a second bearing flange part on the output side, wherein the first bearing flange part is formed integrally with the ring gear and the second bearing flange part is designed as a separate component and is connected nonrotatably to the first bearing flange part.

Description

[0001] Planetary gear with improved bearing flange

[0002] The present patent application relates to a planetary gear comprising a ring gear, at least one gear stage and a bearing flange for supporting an output shaft.

[0003] A key function of such a planetary gear is to ensure the secure mounting of the gearbox's output shaft. In particular, it must also absorb radial forces acting on the output shaft.

[0004] An electric motor with a planetary gear attached to it is known from WO 2021 / 075217 A1. For this purpose, a motor mount is provided which is screwed to the electric motor. The ring gear of the planetary gear is connected to the motor mount via a plug connection. On the side of the ring gear opposite the motor, there is a one-piece bearing mount which houses a bearing for the output shaft of the planetary gear. The bearing for the output shaft is completely housed in the bearing mount. There is no contact between the bearing and the ring gear or the motor mount. The bearing mount is also connected to the planetary gear via a plug connection. In addition, the motor mount, the ring gear, and the bearing mount are screwed together using several screws.

[0005] DE 10 2018 204 051 A1 also shows a geared motor with an electric motor and a planetary gear unit, which is attached to the electric motor by means of fastening screws. The ring gear of the planetary gear unit forms part of the gear housing. Furthermore, the planetary gear unit has a bearing plate formed integrally with the ring gear unit. The output shaft is mounted in two plain bearings, which are mounted in the bearing plate at an axial distance from each other.

[0006] DE 10 2005 052 008 A1 discloses a planetary gear unit with an input shaft, one or two gear stages, and a multi-part housing. The housing comprises a housing part for supporting an output shaft. The input shaft comprises the sun gear toothing and is also called a sun gear. Formed in the housing part for supporting the output shaft are a first bearing seat for supporting a ring gear bearing and a second bearing seat for supporting an output bearing. Both bearings of the output shaft, i.e., the ring gear bearing and the output bearing, are thus accommodated in the housing part. The outer ring of the ring gear bearing is arranged adjacent to the ring gear. The housing parts are connected to one another by screws. The screws run inside the gear unit, between a housing outer side and a ring gear toothing.The ring gear teeth are formed as internal teeth on the gear housing and mesh with the planet gears. US Pat. No. 5,240,462 A describes another planetary gear. The planetary gear comprises an input shaft on which a sun gear is arranged, a ring gear, several planet gears that mesh with the sun gear and the ring gear, and a housing. The planet gears are rotatably mounted on planetary shafts. The planetary shafts are connected to a carrier that is integrally formed with an output shaft. The output shaft is rotatably mounted in the housing by two bearings. The housing is constructed in several parts and comprises a side plate, a center flange, and a housing cylinder. One of the output shaft bearings is mounted in the center flange, the other output shaft bearing is mounted in the side plate. The center flange is bolted to the housing cylinder, in which the ring gear is also formed, by means of screws.The side plate is connected to the center flange by bolts. The housing cylinder has no contact with the two bearings supporting the output shaft.

[0007] The object of the present invention is to provide a planetary gear as described above which improves the gears known from the prior art and in particular provides a cost-effective and easy-to-manufacture solution for the bearing of the output shaft of the gear, regardless of the materials used in the planetary gear.

[0008] This object is achieved by the features of independent claim 1. Accordingly, in a planetary gear comprising a ring gear, at least one gear stage and a bearing flange for supporting an output shaft, an inventive solution to the object is provided if the bearing flange is designed in several parts and has at least a first, ring gear-side bearing flange part and a second, output-side bearing flange part, wherein the first, ring gear-side bearing flange part is designed in one piece with the ring gear and the second, output-side bearing flange part is designed as a separate component and is connected in a rotationally fixed manner to the first, ring gear-side bearing flange part.

[0009] The bearing flange surrounds the bearings provided for supporting the output shaft in the radial direction from the outside or supports the bearings from the inside. The bearing flange of the present invention is designed in several parts. Preferably, each of the individual bearing flange parts at least partially surrounds the bearings provided for supporting the output shaft in the radial direction from the outside or at least partially supports the bearings from the inside. The first bearing flange part on the ring gear side can be designed as an annular disc. The annular disc adjoins, for example, a cylindrical part of the ring gear. The second, output-side bearing flange part can have the same outer contour as the first bearing flange part on the ring gear side and can also be designed as a cylinder. The two-part design of the bearing flange ensures that two bearings provided for supporting the output shaft can be arranged at a certain axial distance from one another.This allows for the absorption of larger radial forces on the output shaft. The two-part or multi-part design of the bearing flange allows for different materials to be used for the two bearing flange components. This allows for various material combinations for the two bearing flange components. This leads to cost savings, among other things, and also allows the two bearing flange components to be more easily designed according to their different loads and the required force absorption of the two components.

[0010] Advantageous embodiments of the present invention are the subject of the subclaims.

[0011] In a preferred embodiment of the present invention, it can be provided that the ring gear is sintered. Because the ring gear is made of a sintered material, cost-effective production with simultaneous high precision is possible. In order to achieve this precision, the sintered parts must be pressed into a mold under high pressure. This is only possible up to a certain component length, which is why sintered metal components can only have a limited maximum length. Due to the two-part design of the bearing flange, the ring gear, which is formed integrally with the first ring gear-side bearing flange part, can be designed longer, whereby several planetary gear stages for a higher reduction ratio or wider planet gears for transmitting higher torques can be arranged in the ring gear.The arrangement of the bearings in the two-part bearing flange enables the output shaft to be supported by two bearings arranged at a certain or predetermined axial distance from one another, even in the case of a ring gear made of sintered material.

[0012] Advantageously, it can also be provided that the first bearing flange part on the ring gear side and the second bearing flange part on the output side are connected to each other in a rotationally fixed manner by means of a screw connection. A screw connection is possible with virtually all materials. Especially with sintered components, alternative joining methods such as welding, gluing, or pressing are disadvantageous and complex to implement. Furthermore, a screwed connection can be separated and reconnected without leaving any residue.

[0013] In order to prevent the screw connection between the two bearing flange parts from coming loose from the outside, it can be provided that at least one through-bore is formed in the first, ring gear-side bearing flange part, and at least one blind hole is formed in the second, output-side bearing flange part, which cooperates with the through-bore to accommodate a screw. In an alternative design variant, the hole in the second, output-side bearing flange part can also be designed as a through-bore. The screw connection is therefore not guided along the ring gear in a gear housing, but is arranged at the end of the ring gear in the first, ring gear-side flange part. For the screw connection, the screw is pushed through the through-bore in the ring gear-side bearing flange part and screwed into the blind hole in the second, output-side bearing flange part.The screws are therefore oriented from the inside, from the ring gear side, outwards, towards the output side. Loosening the connection between the two bearing flange parts is not possible from the outside when the planetary gear is assembled. However, it is optionally possible to disassemble the gear and loosen the screw connection from the inside of the ring gear without causing any damage. In a simple design of the screw connection, it can preferably also be provided that the blind hole has a thread. Alternatively, it is also possible for the blind hole to be designed without a thread. In this case, the screws are self-tapping.

[0014] To enable secure mounting of the output shaft in the bearing flange, the bearing flange can further be provided with a first bearing seat on the ring gear side and a second bearing seat on the output side, wherein the first bearing seat on the ring gear side and the second bearing seat on the output side are arranged at a distance from one another in the axial direction of the output shaft. By spacing the bearings arranged in the two bearing seats, larger radial forces can be absorbed by the output shaft according to the lever principle.

[0015] In this case, the first bearing seat on the ring gear side is preferably formed in both the first bearing flange part on the ring gear side and in the second bearing flange part on the output side. The second bearing flange part on the output side preferably forms a stop for the bearing arranged in the first bearing seat. This makes it easy to compensate for manufacturing tolerances of the two bearing flange parts. The bearing can also be pressed into the bearing seat, whereby the bearing tolerance can be compensated by pressing it in to size. The bearing seat on the bearing of the second bearing flange part on the output side can have a clearance fit. The first bearing flange part on the ring gear side and the second bearing flange part on the output side are thus mutually centered when brought together, which simplifies the assembly of the two components. Furthermore, easy machining of the bearing seat is possible.Existing manufacturing tolerances of the bearing seat in the first ring gear-side bearing flange part and / or on the second, output-side bearing flange part can preferably be reduced by post-machining, such as turning, drilling, milling, or grinding. The second, output-side bearing seat is preferably formed in the second, output-side bearing flange part. Since the two bearing seats are formed on two different components, the two bearing flange parts, good machining of the two bearing seats is possible.

[0016] In yet another advantageous embodiment, a first, ring gear-side bearing for the output shaft is arranged on the first, ring gear-side bearing seat, and a second, output-side bearing for the output shaft is arranged on the second, output-side bearing seat. The first bearing and the second bearing are preferably designed such that, in particular, radial forces are absorbed by the second, output-side bearing. As a result, the first, ring gear-side bearing can be smaller than the second, output-side bearing. This makes it possible for the screw connection between the two bearing flange parts to be arranged radially between the first, ring gear-side bearing and the ring gear diameter.In this way, despite the bearing required on the output side and the torque-related stronger output shaft, it is possible to find the necessary installation space to provide an additional screw connection even for small gearboxes with a diameter of less than 100 mm.

[0017] Preferably, the second, output-side bearing seat is arranged as far as possible at the axial end opposite the first, ring gear-side bearing flange part in order to achieve the greatest possible distance between the first, ring gear-side bearing seat and the second, output-side bearing seat and thus the first, ring gear-side bearing and the second, output-side bearing.

[0018] Yet another advantageous embodiment provides for the first bearing on the ring gear side to have a smaller diameter than the second bearing on the output side. The screw connection can therefore be located inside the ring gear, allowing the installation space in the outer circumference of the cavity to be reduced, which in turn allows for a larger ring gear with a higher reduction ratio.

[0019] In a further embodiment, the planetary gear can be designed with multiple stages, with the ring gear covering at least the first two output-side gear stages. A higher reduction ratio can be achieved with a multi-stage gear.

[0020] To achieve a particularly compact design of the planetary gear, the ring gear can be provided as part of a gear housing. The wall thickness of the ring gear or the gear housing is preferably less than 20%, preferably less than 15%, and particularly preferably less than 10% of the outer radius of the gear housing. A thin wall thickness allows the tooth diameter of the ring gear to be as large as possible, thereby enabling a larger reduction ratio of the gear. A larger reduction ratio could also be achieved with additional stages, but this would increase the overall length of the gear and reduce efficiency.

[0021] Advantageously, the at least one through-hole in the first, ring gear-side bearing flange part can also be provided with a step or a chamfer, wherein the through-hole has a larger diameter on the ring gear side. This allows a screw head of the screw to be received axially within the through-hole in the first, ring gear-side bearing flange part and to be substantially axially flush with the ring gear-side end face of the bearing flange. This avoids the need for additional installation space for the screw head.

[0022] Preferably, a seal is arranged between the first bearing flange part on the ring gear side and the second bearing flange part on the output side. The seal is preferably designed as an O-ring. The seal tightly seals the first bearing flange part on the ring gear side and the second bearing flange part on the output side, thereby preventing, in particular, the penetration of liquids or gases between the two parts.

[0023] In yet another advantageous embodiment, the second, output-side bearing flange part can be made of aluminum. This leads to advantages in terms of the cost and weight of the planetary gear.

[0024] In order to obtain a secure connection between the two bearing flange parts, it can be provided that the first, ring gear-side bearing flange part and the second, output-side bearing flange part are screwed together by means of at least four screws, preferably by means of eight screws.

[0025] In the following, an embodiment of the present invention is explained in more detail with reference to a drawing.

[0026] Fig. 1 shows a section through a planetary gear 1 according to the invention. The planetary gear 1 comprises an input shaft 2 and a ring gear 3, in which a first gear stage 4 and a second gear stage 5 are arranged. Each of the two gear stages 4, 5 comprises a central sun gear 6, which meshes with at least one planet gear 7. Each of the planet gears 7 is provided with external teeth that mesh with internal teeth of the ring gear 3. The planetary gear 1 also has an output shaft 8. As can be clearly seen in Fig. 1, the ring gear 3 forms part of a gear housing 24.

[0027] Fig. 1 shows a two-stage planetary gear unit 1. It is also possible to implement the planetary gear unit as a multi-stage planetary gear unit. In planetary gear units with more than two stages, the ring gear covers at least the first two output-side gear stages. A multi-stage gear unit allows for a higher reduction ratio. However, the efficiency of the planetary gear unit decreases with each stage.

[0028] The output shaft 8 is supported by a first, ring gear-side bearing 9 and a second, output-side bearing 10. The two bearings 9, 10 are accommodated in a bearing flange 11. The bearing flange 11 is formed in several parts, in the illustrated embodiment in two parts, and comprises a first, ring gear-side bearing flange part 12 and a second, output-side bearing flange part 13. The first, ring gear-side bearing flange part 12 is formed in one piece with the ring gear 3. The ring gear 3 and the first bearing flange part 12 are therefore formed as a single component. As shown in Fig. 1, the first bearing flange part extends

[0029] 12, extending from the circumferential surface of the ring gear 3 toward a central axis M of the planetary gear 1. The bearing flange part 12 has a central recess for accommodating the output shaft 8 and the first bearing 9. The second bearing flange part 13 is formed as a separate component. Preferably, the second, output-side bearing flange part 13 is made of aluminum.

[0030] Two bearing seats 14, 15 are formed in the bearing flange 11, a first bearing seat 14 on the ring gear side and a second bearing seat 15 on the output side. The first, ring gear side bearing seat 14 is formed by the first bearing flange part 12, which is formed integrally with the ring gear 3, and by the second bearing flange part 13. In the second, output side bearing flange part

[0031] 13, a first shoulder 16 is formed, which forms an axial stop for the outer ring of the first, ring gear-side bearing 9. The second, output-side bearing seat 15 is formed in the second, output-side bearing flange part 13. A second shoulder 17 is formed in the second, wear-side bearing flange part 13, which forms an axial stop for the outer ring of the second, output-side bearing 10. The two bearings 9, 10 are arranged at an axial distance from one another. This makes it possible to absorb larger radial forces on the output shaft 8.

[0032] The ring gear 3, with the first bearing flange part 12 formed integrally therewith, is preferably made of a sintered material. The ring gear 3 and the first bearing flange part 12 are therefore sintered, i.e. manufactured using a sintering process. Sintered metal components can only have a limited maximum length. Because the bearing flange 11 is formed in multiple parts, two parts in the illustrated embodiment, with the first, ring gear-side bearing flange part 12 formed integrally with the ring gear 3, and the second, output-side bearing flange part 13 formed as a separate component, it is possible to use a sintered ring gear and still ensure the required axial distance between the two bearing seats 14, 15 formed in the bearing flange 11.

[0033] In the illustrated embodiment, the two bearings 9, 10 are designed so that radial forces, in particular, are absorbed by the second, output-side bearing 10. As a result, the first, ring gear-side bearing 9 can be smaller and has a smaller outer diameter than the second, output-side bearing 10.

[0034] The second, output-side bearing flange part 13 is connected in a rotationally fixed manner to the first, ring gear-side bearing flange part 12. In the illustrated embodiment, the rotationally fixed connection is realized by means of a screw connection. For this purpose, the first, ring gear-side bearing flange part 12 has at least one through-bore 18. At least one blind hole 19 is formed in the second, output-side bearing flange part 13, which cooperates with the through-bore 18 in the first bearing flange part 12 to receive a screw 20. The advantages of a screw connection are that the screw connection can be separated and reconnected without leaving any residue. In addition, a screw connection is possible with virtually all materials. Alternative joining methods such as welding, gluing, or pressing are disadvantageous and complex to implement, particularly with sintered components.

[0035] The screw connection is preferably created by means of at least four and preferably eight screws. Accordingly, the first bearing flange part 12 then has at least four, preferably eight through-bores, and the second bearing flange part 12 has at least four, preferably eight blind bores, which each interact with one of the through-bores in the first bearing flange part 12 to accommodate the screws. The screws 20 are therefore oriented from the inside, i.e. from the ring gear side, to the outside, i.e. towards the output side. The screw connection is therefore not visible or accessible from the outside. This means that it is not possible to loosen the screw connection from the outside when the planetary gear set 1 is in the assembled state. However, it is optionally possible to dismantle the planetary gear set 1 and to loosen the screw connection from the inside of the ring gear without causing any damage.

[0036] As described above, the first bearing 9 on the ring gear side has a smaller diameter than the second bearing 10 on the output side. This allows the screw connection to be arranged radially between the first bearing 9 and the ring gear diameter. This eliminates the need for screw connections on the outside of the ring gear 3 or screws running axially in the gear housing 24. The required installation space in the outer circumference of the ring gear 3 is thereby reduced, which in turn allows for a larger ring gear with a larger reduction ratio. The wall thickness of the gear housing 24 is less than 15% in the embodiment shown in Figure 1. The wall thickness depends, among other things, on the size of the gear housing, the torque to be transmitted and the housing material used.

[0037] In the illustrated embodiment, the through-bore 18 in the first bearing flange part 12 is designed with an enlarged diameter on the ring gear side. On the output side, the through-bore has a smaller diameter. As a result, a shoulder is formed in the through-bore 18. This allows a screw head 21 to be received axially within the through-bore 18. The screw head 21 of the screw 20 is therefore essentially axially flush with the end face 22 of the bearing flange 11 on the ring gear side and rests against the shoulder in the through-bore 18. This avoids the need for additional installation space for the screw head 21.

[0038] Preferably, the at least one blind hole 19, or each blind hole 19, has a thread. Alternatively, the blind hole(s) 19 can also be designed without a thread. In this case, the screw(s) 20 are designed to be self-tapping.

[0039] Preferably, a seal 23 is arranged at the interface of the two-part bearing flange 11, i.e., between the first bearing flange part 12 and the second bearing flange part 13. In the illustrated embodiment, the seal 23 is designed as an O-ring.

[0040] List of reference symbols

[0041] 1 planetary gear

[0042] 2 input shaft

[0043] 3 ring gear

[0044] 4 first gear stage

[0045] 5 second gear stage

[0046] 6 Sun gear

[0047] 7 Planetary gear

[0048] 8 Output shaft

[0049] 9 first, ring gear side bearing

[0050] 10 second, output-side bearing

[0051] 11 Bearing flange

[0052] 12 first, ring gear side bearing flange part

[0053] 13 second, output-side bearing flange part

[0054] 14 first, ring gear side bearing seat

[0055] 15 second, output-side bearing seat

[0056] 16 first shoulder

[0057] 17 second shoulder

[0058] 18 through hole

[0059] 19 Blind hole drilling

[0060] 20 screw

[0061] 21 screw head

[0062] 22 ring gear side face of the bearing flange

[0063] 23 Seal

[0064] 24 Gearbox housing

[0065] M central axis of the planetary gear

Claims

Claims: Planetary gear (1) comprising a ring gear (3), at least one gear stage (4, 5) and a bearing flange (11) for supporting an output shaft (8), characterized in that the bearing flange (11) is formed in multiple parts and has at least a first, ring gear-side bearing flange part (12) and a second, output-side bearing flange part (13), wherein the first, ring gear-side bearing flange part (12) is formed integrally with the ring gear (3) and the second, output-side bearing flange part (13) is formed as a separate component and is rotationally fixed to the first, ring gear-side bearing flange part (12). Planetary gear (1) according to claim 1, characterized in that the ring gear (3) is sintered. Planetary gear (1) according to claim 1 or 2, characterized in that the first bearing flange part (12) on the ring gear side and the second bearing flange part (13) on the output side are connected to each other in a rotationally fixed manner by means of a screw connection.A planetary gear (1) according to at least one of the preceding claims, characterized in that at least one through bore (18) is formed in the first, ring gear-side bearing flange part (12) and at least one blind bore (19) cooperating with the through bore (18) for receiving a screw (20) is formed in the second, output-side bearing flange part (13). A planetary gear (1) according to at least one of the preceding claims, characterized in that the bearing flange (11) has a first, ring gear-side bearing seat (14) and a second, output-side bearing seat (15), wherein the first ring gear-side bearing seat (14) and the second, output-side bearing seat (15) are spaced apart from each other in the axial direction of the output shaft (8).Planetary gear (1) according to claim 5, characterized in that the first, ring gear-side bearing seat (14) is formed in the first, ring gear-side bearing flange part (12) and in the second, output-side bearing flange part (13). Planetary gear (1) according to one of claims 5 or 6, characterized in that the second, output-side bearing seat (15) is formed in the second, output-side bearing flange part (13). A planetary gear (1) according to any one of claims 5 to 7, characterized in that a first ring-gear-side bearing (9) for the output shaft (8) is arranged at the first ring-gear-side bearing seat (14) and a second output-side bearing (10) for the output shaft (8) is arranged at the second output-side bearing seat (15). A planetary gear (1) according to claim 8, characterized in that the first ring-gear-side bearing (9) has a smaller diameter than the second output-side bearing (10). A planetary gear (1) according to at least one of the preceding claims, characterized in that the planetary gear (1) is designed as a multi-stage gear and the ring gear (3) covers at least the first two output-side gear stages (4, 5). A planetary gear (1) according to at least one of the preceding claims, characterized in that the ring gear (3) forms part of a gear housing (24).A planetary gear (1) according to at least one of the preceding claims, characterized in that the wall thickness of the ring gear (3) is less than 20%, preferably less than 15%, particularly preferably less than 10% of the outer radius of the gear housing (24). A planetary gear (1) according to any one of claims 4 to 12, characterized in that the at least one through-hole (18) in the first, ring-gear-side bearing flange part (12) is provided with a step or a chamfer, wherein the through-hole (18) has a larger diameter on the ring-gear side. A planetary gear (1) according to at least one of the preceding claims, characterized in that a seal (23) is arranged between the first, ring-gear-side bearing flange part (12) and the second, output-side bearing flange part (13).A planetary gear (1) according to at least one of the preceding claims, characterized in that the second, output-side bearing flange part (13) is made of aluminum. A planetary gear (1) according to at least one of the preceding claims, characterized in that the first, ring gear-side bearing flange part (12) and the second, output-side bearing flange part (13) are screwed together by means of at least four screws (20), preferably by means of eight screws (20).

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