Planetary gear with improved bearing flange
The planetary gear's innovative two-part bearing flange design addresses the challenge of absorbing radial forces and reduces manufacturing costs, enabling effective force absorption and increased gear reduction ratios.
Patent Information
- Application Number
- JP2024568995
- Authority / Receiving Office
- JP · JP
- Patent Type
- Applications
- Current Assignee / Owner
- Priority Date
- 2022-05-27
- Filing Date
- 2023-05-26
- Publication Date
- 2025-05-30
AI Technical Summary
Existing planetary gears face challenges in providing a cost-effective and easy-to-manufacture solution for the output shaft bearing, particularly in absorbing radial forces effectively.
The planetary gear features a bearing flange composed of multiple parts, including a first ring gear side bearing flange part integrally formed with the ring gear and a second output side bearing flange part as a separate component, which are rotatably and fixedly connected. This configuration allows for the arrangement of two bearings at a certain axial distance, effectively absorbing large radial forces.
This design enhances the ability to absorb radial forces on the output shaft, allows for the use of different materials for the bearing flange parts, reduces manufacturing costs, and enables the creation of larger gear reduction ratios or wider planetary gears.
Smart Images
Figure 2025516907000001_ABST
Abstract
Description
Technical Field
[0001] The present application relates to a planetary gear comprising a ring gear, at least one gear stage, and a bearing flange for supporting an output shaft.
[0002] An essential problem of such a planetary gear is to ensure a safe bearing for the output shaft of the gear. In particular, the radial forces acting on the output shaft must also be absorbed.
[0003] WO 2021 / 075217 A1 discloses an electric motor with a planetary gear attached thereto. For this purpose, a motor holder is provided, which is screwed onto the electric motor. The ring gear of the planetary gear is connected to the motor holder via a plug-in connection. On the side of the ring gear opposite the motor, a bearing holder for holding a bearing for the output shaft of the planetary gear is integrally formed. The bearing of the output shaft is fully supported by the bearing holder. There is no contact between the bearing and the ring gear or the motor mounting part. The bearing holder is further connected to the planetary gearbox via a plug connection. In addition, the motor mounting part, the hollow gear wheel and the bearing holder are screwed to each other by several screws.
[0004] DE 10 2018 204 051 A1 also shows a geared motor comprising an electric motor and a planetary gear attached to the electric motor by mounting screws. The ring gear of the planetary gear forms part of the gearbox housing. In addition, the planetary gear comprises a bearing plate integrally formed with the ring gear. The output shaft is supported by two sliding bearings mounted axially spaced apart on the bearing plate.
[0005] From DE 10 2005 052 008 A1, an epicyclic gear with an input shaft, one or two gear stages, and a multi-component housing is known. The housing includes a housing part for mounting the output shaft. The input shaft includes a sun gear, also called a sun wheel. The housing part for mounting the output shaft is designed with a first bearing seat for supporting the ring gear side bearing and a second bearing seat for supporting the output side bearing. Thereby, both bearings of the output shaft, namely, the ring gear side bearing and the output side bearing, are accommodated in the housing part. The outer ring of the ring gear side bearing is arranged adjacent to the ring gear. The plurality of housing parts are connected to each other by screws. The screws pass between the outside of the housing and the tooth part of the ring gear within the gearbox housing. The ring gear tooth part is designed as an internal tooth part on the gearbox housing and engages with the epicyclic gear.
[0006] U.S. Patent No. 5,240,462 describes another epicyclic gear. The epicyclic gear includes an input shaft on which a sun gear is arranged, a ring gear, a plurality of planet gears that mesh with the sun gear and the ring gear, and a housing. The planet gears are rotatably mounted on a planet shaft. The planet shaft is connected to a carrier integrally formed with the output shaft. The output shaft is rotatably mounted in the housing by two bearings. The housing is formed from a plurality of components and includes side plates, a central flange, and a housing cylinder. One bearing of the output shaft is mounted on the central flange, and the other bearing of the output shaft is mounted on the side plate. The central flange is screwed into the housing cylinder on which the ring gear is also placed by screws. The side plates are connected to the central flange by screws. The housing cylinder does not contact the two bearings for supporting the output shaft.
Summary of the Invention
[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 output shaft bearing of the gear, regardless of the material used for the planetary gear.
[0008] This problem is solved by the features of independent claim 1. Thus, in a planetary gear comprising a ring gear, at least one gear stage, and a bearing flange for mounting an output shaft, the bearing flange is composed of a plurality of parts, the bearing flange comprises at least a first ring gear side bearing flange part and a second output side bearing flange part, the first ring gear side bearing flange part is integrally formed with the ring gear, and the second output side bearing flange part is formed as a separate component and is rotatably and fixedly connected to the first ring gear side bearing flange part. With such a configuration, the problem of the present invention can be solved.
[0009] The bearing flange surrounds the bearing provided for radially supporting the output shaft from the outside and supports it from the inside. The bearing flange of the present invention is designed with a plurality of parts. Preferably, each bearing flange part surrounds the bearing provided for mounting the output shaft at least partly from the outside in the radial direction or supports it at least partly from the inside. The first ring gear side bearing flange part can be designed as an annular disk. The annular disk is adjacent to the ring gear, for example, to the cylindrical part of the ring gear. The second output side bearing flange part can have the same outer contour as the first output side bearing flange part as the first ring gear side bearing flange part and can also be designed as a cylinder. With the two-part design of the bearing flange, the two bearings provided for the output shaft can be arranged at a certain axial distance from each other. Thereby, a large radial force applied to the output shaft can be absorbed. With the design of two parts or a plurality of parts of the bearing flange, different materials can be used for the two bearing flange parts. Thereby, various material combinations of the two bearing flange parts become possible. As a result, in particular, costs are saved and the two bearing flange parts can 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 matter of the claims.
[0011] In a preferred embodiment of the present invention, the ring gear may be sintered. In terms of the ring gear being made of a sintered material, cost-effective manufacturing is possible while maintaining a high level of accuracy. To achieve the required accuracy, it is necessary to press the sintered parts into a mold under high pressure. Since this is only possible up to a specific length of the part, sintered metal parts can only be configured with a limited maximum length. With the two-part design of the bearing flange, the length of the ring gear formed integrally with the first ring gear side bearing flange part can be designed to be longer, thereby allowing several planetary gear stages for higher reduction ratios, or wider planetary gears for transmitting higher torques, to be arranged within the ring gear. Thus, by arranging the bearings on the two-part bearing flange, even a ring gear made of a sintered material can support the output shaft by two bearings arranged at a predetermined axial distance from each other.
[0012] Advantageously, the first ring gear side bearing flange part and the second output side bearing flange part can be rotatably fixed by a screw connection. Screw connections are, in fact, possible with all materials. Particularly with regard to sintered parts, alternative connection methods such as welding, gluing, or pressing are disadvantageous and complex to implement. In addition, screw connections can be separated and reassembled without leaving residues.
[0013] To prevent the screw connection of the two bearing flange parts from loosening from the outside, at least one through hole can be formed in the first ring gear side bearing flange part, and at least one blind hole can be formed in the second output side bearing flange part that cooperates with the through hole to accommodate the screw. In another design, the bore of the second output side bearing flange part can also be designed as a through hole. Therefore, the screw connection part is not guided into the gearbox housing along the ring gear, but is arranged at the end of the ring gear of the first ring gear side flange part. The screw connection is to insert the screw through the through hole of the ring gear side bearing flange part and screw it into the blind hole of the second output side bearing flange part. Therefore, one or more screws are oriented from the inside (from the ring gear side) to the outside (output side). When assembling the planetary gear, the connection of the two bearing flange parts cannot be loosened from the outside. Nevertheless, as an option, it is possible to disassemble the gearbox and loosen the screw connection non-destructively from the inside of the ring gear. In a simple design of the screw connection, preferably, the blind hole can be provided with a screw. Alternatively, it is also possible to design the blind hole without a screw. In this case, the screw is a self-tapping type.
[0014] To ensure that the output shaft can be securely mounted on the bearing flange, the bearing flange comprises a first ring gear side bearing seat and a second output side bearing seat, and the first ring gear side bearing seat and the second output side bearing seat may be arranged spaced apart from each other in the axial direction of the output shaft. Due to the spacing of the bearings arranged on the two bearing seats, according to the principle of the lever, a larger radial force can be absorbed by the output shaft.
[0015] In this case, it is preferable that the first ring gear side bearing seat is formed on both the first ring gear side bearing flange portion and the second output side bearing flange portion. Preferably, the second output side bearing flange portion forms a stop portion for the bearing disposed on the first bearing seat. Thereby, the manufacturing tolerances of the two bearing flange portions can be easily compensated. Since the bearing can also be pushed into the bearing seat, the tolerance of the bearing can be compensated by pushing the bearing to a predetermined size. The bearing seat on the bearing of the second output side bearing flange portion can have an interference fit. Therefore, the first ring gear side bearing flange portion and the second output side bearing flange portion can be centered and integrated with each other, facilitating the assembly of both components. Also, the bearing seat is easy to machine. The existing manufacturing tolerances of the bearing seat in the first ring gear side bearing flange portion and / or the second output side bearing flange portion can be reduced by post-processing such as turning, drilling, milling or grinding.
[0016] The second output side bearing seat is preferably formed on the second output side bearing flange portion. Since the two bearing seats are formed on two different components which are the two bearing flange portions, good machining of the two bearing seats is possible.
[0017] In yet another advantageous embodiment, the first ring gear side bearing for the output shaft is disposed on the first ring gear side bearing seat, and the second output side bearing for the output shaft is disposed on the second output side bearing seat. The first bearing and the second bearing are preferably designed such that the radial force is absorbed by the second output side bearing in particular. Thereby, the first ring gear side bearing can be made smaller than the second output side bearing. Thereby, the screw connection of the two bearing flange portions can be arranged radially between the first ring gear side bearing and the ring gear diameter. Thus, even in a small gearbox with a diameter of less than 100 mm that requires a bearing on the output side and the output shaft is strengthened by torque, the installation space required for providing an additional screw connection can be ensured.
[0018] The second output-side bearing seat is preferably arranged as axially close as possible to the axial end on the opposite side of the first ring gear-side bearing flange part, so as to achieve the maximum possible distance between the first ring gear-side bearing seat and the second output-side bearing seat, and thus between the first ring gear-side bearing and the second output-side bearing.
[0019] In yet another advantageous embodiment, it is provided that the first ring gear-side bearing has a smaller diameter than the second output-side bearing. Thus, a threaded connection part can be provided inside the ring gear, so that the installation space on the outer periphery of the hollow space can be reduced, and the ring gear can be enlarged to increase the reduction ratio.
[0020] In another embodiment, the planetary gear can be designed as a multi-stage gear, and the ring gear covers at least two first output-side gear stages. With the multi-stage gear, a higher reduction ratio can be achieved.
[0021] In order to achieve a particularly compact design of the planetary gear, the ring gear can be designed to form part of the gearbox housing.
[0022] Preferably, the wall thickness of the ring gear or the gearbox housing is less than 20% of the outer radius of the gearbox housing, preferably less than 15%, particularly preferably less than 10%. Due to the small wall thickness, the gear diameter of the ring gear can be made as large as possible, enabling a larger gear reduction ratio. A larger gear reduction ratio can also be achieved in additional stages, but this increases the overall length of the gearbox and reduces the efficiency.
[0023] Advantageously, at least one through hole in the first ring gear-side bearing flange part can be provided with a step or chamfer, and the through hole has a larger diameter on the ring gear side. Thereby, the screw head of the screw is axially received in the through hole of the first ring gear-side bearing flange part and is substantially flush with the ring gear-side end face of the bearing flange in the axial direction. This eliminates the need for additional installation space for the screw head.
[0024] Preferably, a seal is disposed between the first ring gear side bearing flange portion and the second output side bearing flange portion. The seal is preferably designed as an O-ring. The seal firmly seals the first ring gear side bearing flange portion and the second output side bearing flange portion, and in particular, prevents liquid or gas from entering between the two.
[0025] In yet another advantageous embodiment, the second output side bearing flange portion is made of aluminum. This provides advantages in terms of the cost and weight of the planetary gear.
[0026] To securely connect the two bearing flange portions, the first ring gear side bearing flange portion and the second output side bearing flange portion may be screwed together with at least four, preferably eight, screws.
[0027] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Brief Description of the Drawings
[0028]
Figure 1
[0029] Detailed Description of the Invention
[0030] The planetary gear 1 includes an input shaft 2 and a ring gear 3, and a first gear stage 4 and a second gear stage 5 are disposed within the ring gear 3. Each of the two gear stages 4, 5 includes a central sun gear 6 that engages with at least one planetary gear 7. Each planetary gear 7 is provided with external teeth that engage with the internal teeth of the ring gear 3. In addition, the planetary gear 1 includes an output shaft 8. As is apparent from FIG. 1, the ring gear 3 forms a part of the gearbox housing 24.
[0031] Figure 1 shows a two-stage planetary gear 1. It is also possible to design the planetary gear as a multi-stage planetary gear. In a planetary gear with more than two stages, the ring gear covers at least the first two output-side gear stages. Although the efficiency of the planetary gear decreases at each stage, a higher gear reduction can be achieved using multiple stages of gears.
[0032] The output shaft 8 is mounted by the first ring gear side bearing 9 and the second output side bearing 10. The two bearings 9, 10 are held by a bearing flange 11. The bearing flange 11 is designed with multiple parts and is designed with two parts in the illustrated embodiment, comprising 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 designed integrally with the ring gear 3. Thus, the ring gear 3 and the first bearing flange part 12 are integrally formed. As shown in Figure 1, the first bearing flange part 12 extends in the direction of the central axis M of the planetary gear 1 from the peripheral surface of the ring gear 3. The bearing flange part 12 has a central recess for receiving the output shaft 8 and the first bearing 9. The second bearing flange part 13 is designed as a separate component. The second output side bearing flange part 13 is preferably made of aluminum.
[0033] Two bearing seats 14, 15, namely the first ring gear side bearing seat 14 and the second output side bearing seat 15, are formed on the bearing flange 11. The first ring gear side bearing seat 14 is formed by the first bearing flange part 12 integrally formed with the ring gear 3 and the second bearing flange part 13. In this case, a first shoulder 16 for forming an axial stop portion of the outer ring of the first ring gear side bearing 9 is formed on the second output side bearing flange part 13. The second output side bearing seat 15 is formed on the second output side bearing flange part 13. A second shoulder 17 for forming an axial stop portion of the outer ring of the second output side bearing 10 is formed on the second output side bearing flange part 13. The two bearings 9, 10 are arranged with an axial spacing from each other. Thereby, a large radial force applied to the output shaft 8 can be absorbed.
[0034] The ring gear 3 is preferably formed of a sintered material together with the integrally formed first bearing flange portion 12. For this reason, the ring gear 3 and the first bearing flange portion 12 are produced by sintering, that is, sintering treatment. Sintered metal components can only constitute a limited maximum length. In the illustrated embodiment, since the bearing flange 11 is designed with two parts, the first ring gear side bearing flange portion 12 designed integrally with the ring gear 3 and the second output side bearing flange portion 13 designed as another component, it is possible to secure the necessary axial interval between the two bearing seats 14, 15 formed in the bearing flange 11 while using a sintered ring gear.
[0035] In the illustrated embodiment, the two bearings 9, 10 are designed such that the radial force is particularly absorbed by the second output side bearing 10. This means that the first ring gear side bearing 9 can be made smaller, and the first ring gear side bearing 9 has an outer diameter smaller than that of the second output side bearing 10.
[0036] The second output side bearing flange portion 13 is rotatably fixed to the first ring gear side bearing flange portion 12. In the illustrated embodiment, the connection in the rotatably fixed connection is realized by a screw connection. For this reason, the first ring gear side bearing flange portion 12 is provided with at least one through hole 18. In the second output side bearing flange portion 13, at least one blind hole 19 for receiving the screw 20 in cooperation with the through hole 18 in the first bearing flange portion 12 is formed. The advantage of the screw connection is that the screw connection can be separated and reassembled without leaving residues. In addition, screw connection is possible with substantially all materials. Alternative connection methods such as welding, adhesion or pressing are disadvantageous and expensive to implement, especially for sintered components.
[0037] The screw connection is preferably created by at least four, preferably eight screws. Accordingly, the first bearing flange portion 12 is provided with at least four, preferably eight through holes, and the second bearing flange portion 12 is provided with at least four, preferably eight blind holes, each interacting with one through hole of the first bearing flange portion 12 to receive a screw. Accordingly, the screws 20 are oriented from the inside (i.e., the ring gear side) towards the outside (i.e., the output side). Accordingly, the screw connection is not visible from the outside and cannot be accessed. For this reason, when assembling the planetary gear 1, the screw connection cannot be loosened from the outside. However, it is also selectively possible to disassemble the planetary gear 1 and non-destructively loosen the screw connection from the inside of the ring gear.
[0038] As described above, the first ring gear side bearing 9 has a smaller diameter on the output side than the second output side bearing 10. Thereby, a screw connection can be arranged radially between the first bearing 9 and the ring gear diameter. Thereby, it is not necessary to screw-connect to the outside of the ring gear 3, and a screw running axially in the gearbox housing 24 is also unnecessary. Accordingly, the installation space on the outer periphery of the ring gear 3 can be reduced, and the ring gear can be enlarged and the gear reduction ratio can be increased. In the embodiment shown in FIG. 1, the wall thickness of the gearbox housing 24 is less than 15%. The wall thickness depends inter alia on the size of the gearbox housing, the torque transmitted, and the housing material used.
[0039] In the illustrated embodiment, the through holes 18 of the first ring gear side bearing flange portion 12 are designed with an enlarged diameter. On the output side, the through holes have a smaller diameter. Thereby, a shoulder is created in the through hole 18. Thereby, the screw head 21 can be axially accommodated in the through hole 18. Accordingly, the screw head 21 of the screw 20 is substantially in the same plane as the ring gear side end face 22 of the bearing flange 11 and abuts against the shoulder of the through hole 18. Thereby, an additional installation space for the screw head 21 is not required.
[0040] Preferably, at least one or each of the blind holes 19 has a thread. Alternatively, the blind hole 19 may be designed without a screw. In this case, the screw 20 is a self-tapping type.
[0041] The seal 23 is preferably disposed at the interface surface of the bearing flange 11 composed of two parts between the first bearing flange portion 12 and the second bearing flange portion 13. In the illustrated embodiment, the seal 23 is designed as an O-ring.
Explanation of Reference Numerals
[0042] 1…Planet gear, 2…Input shaft, 3…Ring gear, 4…First gear stage, 5…Second gear stage, 6…Sun gear, 7…Planet gear, 8…Output shaft, 9…First ring gear side bearing, 10…Second output side bearing, 11…Bearing flange, 12…First ring gear side bearing flange portion, 13…Second output side bearing flange portion, 14…First output side bearing seat, 15…Second output side bearing seat, 16…First shoulder, 17…Second shoulder, 18…Through hole, 19…Blind hole, 20…Screw, 21…Screw head, 22…Ring gear side end face of the bearing flange, 23…Seal, 24…Gearbox housing, M…Central axis of the planet gear.
Claims
1. A planetary gear (1) comprising a ring gear (3), at least one gear stage (4, 5), and a bearing flange (11) for mounting an output shaft (8), wherein the bearing flange (11) is designed as a plurality of parts and has at least 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 integrally with the ring gear (3), the second output side bearing flange part (13) is formed as a separate component, and is rotatably fixedly connected to the first ring gear side bearing flange part (12), characterized in that the planetary gear (1).
2. The planetary gear (1) according to claim 1, characterized in that the ring gear (3) is sintered.
3. The planetary gear (1) according to claim 1 or 2, characterized in that the first ring gear side bearing flange part (12) and the second output side bearing flange part (13) are rotatably fixed to each other by a screw connection.
4. The planetary gear (1) according to any one of claims 1 to 3, characterized in that at least one through hole (18) is formed in the first ring gear side bearing flange part (12), and at least one blind hole (19) for receiving a screw (20) in cooperation with the through hole (18) is formed in the second output side bearing flange part (13).
5. The planetary gear (1) according to any one of claims 1 to 4, characterized in that the bearing flange (11) has a first ring gear side bearing seat (14) and a second output side bearing seat (15), and the first ring gear side bearing seat (14) and the second output side bearing seat (15) are arranged axially spaced apart from each other with respect to the output shaft (8).
6. The 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 the second output side bearing flange part (13).
7. The planetary gear (1) according to claim 5 or 6, characterized in that the second output side bearing seat (15) is formed in the second output side bearing flange part (13).
8. A first ring gear side bearing (9) for the output shaft (8) is arranged on the first ring gear side bearing seat (14), and a second output side bearing (10) for the output shaft (8) is arranged on the second output side bearing seat (15). The planetary gear (1) according to any one of claims 5 to 7, characterized in that.
9. The planetary gear (1) according to claim 8, characterized in that the first ring gear side bearing (9) has a diameter smaller than that of the second output side bearing (10).
10. The planetary gear (1) according to any one of claims 1 to 9, characterized in that the planetary gear (1) is designed in multiple stages, and the ring gear (3) covers at least two of the first output side gear stages (4, 5).
11. The planetary gear (1) according to any one of claims 1 to 10, characterized in that the ring gear (3) forms a part of the gearbox housing (24).
12. The planetary gear (1) according to any one of claims 1 to 11, characterized in that the wall thickness of the ring gear (3) is less than 20% of the outer radius of the gearbox housing (24), preferably less than 15%, particularly preferably less than 10%.
13. The planetary gear (1) according to any one of claims 4 to 12, characterized in that at least one through hole (18) of the first ring gear side bearing flange portion (12) is provided with a step or chamfer, and the through hole (18) has a larger diameter on the ring gear side.
14. The planetary gear (1) according to any one of claims 1 to 13, characterized in that a seal (23) is arranged between the first ring gear side bearing flange portion (12) and the second output side bearing flange portion (13).
15. The planetary gear (1) according to any one of claims 1 to 14, characterized in that the second output side bearing flange portion (13) is made of aluminum.
16. The planetary gear (1) according to any one of claims 1 to 15, characterized in that the first ring gear side bearing flange portion (12) and the second output side bearing flange portion (13) are screwed together by at least four screws (20), preferably eight screws (20).