Planetary gearbox of micro electric tool
Through the shared internal ring design of the two-stage planetary wheel system, the problem of excessive gear box volume in micro power tools is solved, high reduction ratio and high torque output are achieved, and transmission accuracy and reliability are improved.
Patent Information
- Application Number
- CN202510723178.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-05-30
- Publication Date
- 2025-07-22
AI Technical Summary
Traditional planetary gear boxes mostly use a single-stage transmission structure, which makes it difficult to reduce the size of the gear boxes, cannot adapt to the narrow installation space of micro-power tools, and is difficult to achieve high speed reduction ratio.
The design of a two-stage planetary gear train is adopted to combine the internal gear ring, copper sleeve, gasket and cylindrical flange and other structures to achieve multi-stage reduction and high integration, enhance structural rigidity, and reduce vibration and friction.
It realizes the medium-to-high reduction ratio and high torque output of micro power tools, reduces noise, improves transmission accuracy and reliability, and adapts to the needs of narrow spaces.
Smart Images
Figure CN120351284A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of gearboxes, and particularly to a planetary gearbox for a micro electric tool. Background Art
[0002] At present, gearboxes are mostly used as speed reducers, which are transmission mechanisms used to reduce the rotational speed and increase the torque. One end of it is usually connected to an electric motor, and the other end is connected to a workpiece. A planetary gearbox usually includes parts such as a sun gear, planetary gears, an internal gear ring, a planetary carrier, and planetary pin shafts. Power is input through the sun gear connected to the electric motor, and drives the rotation of the planetary carrier connected to the planetary gears through meshing with the planetary gears, and then the power is transmitted to the next-stage planetary gear train or output assembly.
[0003] With the continuous development of technologies in the field of electric tools, various types of electric tools have been widely used in all walks of life of humans. For current electric tools, in order to achieve the purpose of outputting appropriate rotational speed and torque of the workpiece, a gearbox needs to be arranged between the electric motor and the workpiece for speed reduction and torque increase. Traditional planetary gearboxes mostly adopt a single-stage transmission structure. To meet the high reduction ratio requirement, it is necessary to increase the gear module or the diameter of the gear ring, resulting in difficulty in further reducing the volume of the gearbox and difficulty in adapting to the narrow installation space of micro electric tools. Summary of the Invention
[0004] (I) Technical Problems to be Solved The purpose of the present invention is to solve the problem that traditional planetary gearboxes mostly adopt a single-stage transmission structure. To meet the high reduction ratio requirement, it is necessary to increase the gear module or the diameter of the gear ring, resulting in difficulty in further reducing the volume of the gearbox and difficulty in adapting to the narrow installation space of micro electric tools, and to propose a planetary gearbox for a micro electric tool.
[0005] (II) Technical Solutions The technical solutions of the present invention for solving the above technical problems are as follows: A planetary gearbox for a micro electric tool includes a housing. An electric motor shaft and an output shaft are rotatably connected to the inner side of the housing. An internal gear ring is arranged on the inner side of the housing. A first-stage planetary gear train and a second-stage planetary gear train which are connected to each other are arranged on the inner side of the internal gear ring. The first-stage planetary gear train is arranged outside the electric motor shaft. The second-stage planetary gear train is arranged on the output shaft. A torque sensor is fixedly connected to the inner side of the housing.
[0006] On the basis of the above technical solutions, the present invention can also be improved as follows.
[0007] Preferably, the first-stage planetary gear train includes a copper sleeve, a first-stage sun gear, a top plate, three first-stage planetary gears, three first-stage planetary gear shafts, and a first-stage planetary carrier. A copper sleeve is fixedly connected to the outer side of the motor shaft, a first-stage sun gear is fixedly connected to the outer side of the copper sleeve, three first-stage planetary gears are meshed with the outer side of the first-stage sun gear, all three first-stage planetary gears are meshed with the inner side of the internal gear ring, first-stage planetary gear shafts are fixedly connected to the inner sides of all three first-stage planetary gears, the outer sides of all three first-stage planetary gear shafts are rotatably connected to the first-stage planetary carrier, the top plate is fixedly connected to the inner side of the internal gear ring, and the first-stage sun gear is rotatably connected to the inner side of the top plate.
[0008] Preferably, the second-stage planetary gear train includes a second-stage sun gear, three second-stage planetary gears, and three second-stage planetary gear shafts. The second-stage sun gear is fixedly connected to the inner side of the first-stage planetary carrier, three second-stage planetary gears are meshed with the outer side of the second-stage sun gear, all three second-stage planetary gears are meshed with the inner side of the internal gear ring, second-stage planetary gear shafts are fixedly connected to the inner sides of all three second-stage planetary gears, and the outer sides of all three second-stage planetary gear shafts are rotatably connected to the inner side of the output shaft.
[0009] Preferably, a spacer is sleeved on the outer side of the second-stage sun gear and is located between the first-stage planetary carrier and the second-stage planetary gears.
[0010] Preferably, a cylindrical flange is provided on the second-stage sun gear.
[0011] Preferably, the internal gear ring is arranged in a thin-walled cylindrical structure.
[0012] (III) Advantageous Effects Compared with the prior art, the technical solution of the present application has the following beneficial technical effects: 1. By providing an internal gear ring, a first-stage planetary gear train, and a second-stage planetary gear train, the two-stage planetary gear trains share the internal gear ring, which has a high integration degree and a small volume, is suitable for miniature tools, realizes a high reduction ratio through multi-stage reduction, significantly improves the output torque, the internal gear ring enhances the structural rigidity, reduces vibration, ensures smooth gear meshing, and improves the transmission accuracy and reliability.
[0013] 2. By providing a spacer, the second-stage planetary gear shafts are avoided from the planetary gear shaft holes on the first-stage planetary carrier, making the rotation of the second-stage planetary gear train smoother; at the same time, direct contact between the second-stage planetary gear shafts and the first-stage planetary carrier is avoided, eliminating the friction caused by their relative movement, improving the efficiency of the gearbox, and reducing the noise of the gearbox.
[0014] 3. By providing a cylindrical flange, the second-stage sun gear is firmly press-fitted into the central hole of the first-stage planetary carrier by means of the cylindrical flange. When rotating, this structure has a large frictional force, can transmit a larger torque, and plays a role in preventing slipping.
[0015] 4. In the present invention, the internal gear ring is set as a thin-walled cylindrical structure to increase the flexibility of the internal gear itself. This structure can achieve good effects of buffering impact and making the load distribution among the planet gears uniform. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 is a schematic diagram of the overall structure of the present invention; Figure 2 is a schematic diagram of the front sectional structure of the present invention; Figure 3 is a schematic diagram of the relative positional relationship of the internal components inside the outer housing of the present invention; Figure 4 is a schematic diagram of the relative positional relationship between the outer housing and the internal gear ring of the present invention; Figure 5 is a schematic diagram of the relative positional relationship between the first-stage planet carrier and the cylindrical flange of the present invention.
[0017] In the figure: 1. Motor shaft; 2. Copper sleeve; 3. First-stage sun gear; 4. Torque sensor; 5. Top plate; 6. First-stage planet gear; 7. First-stage planet gear shaft; 8. First-stage planet carrier; 9. Gasket; 10. Internal gear ring; 11. Second-stage sun gear; 12. Second-stage planet gear; 13. Second-stage planet gear shaft; 14. Output shaft; 15. Outer housing; 16. Cylindrical flange. DETAILED DESCRIPTION OF THE EMBODIMENTS
[0018] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.
[0019] In the embodiment, given by Figures 1-5 a planetary gearbox of a micro electric tool includes an outer housing 15. The inner side of the outer housing 15 is rotatably connected with a motor shaft 1 and an output shaft 14. An internal gear ring 10 is arranged on the inner side of the outer housing 15. A first-stage planetary gear train and a second-stage planetary gear train are connected to each other inside the internal gear ring 10. The first-stage planetary gear train is arranged outside the motor shaft 1, and the second-stage planetary gear train is arranged on the output shaft 14. A torque sensor 4 is fixedly connected to the inner side of the outer housing 15.
[0020] With the above settings, the motor shaft 1 is driven by an external motor to rotate, driving the sun gear of the first-stage planetary gear train. The planetary gears of the first-stage planetary gear train revolve around the sun gear and mesh with the fixed internal gear ring 10. The power is transmitted to the sun gear of the second-stage planetary gear train through the planet carrier, completing the first-stage deceleration and increasing the torque. The second-stage planetary gear train repeats a similar process, with its planetary gears meshing with the same internal gear ring 10, driving the output shaft 14 through the second-stage planet carrier, further decelerating and amplifying the torque. The internal gear ring 10 bears the reaction force of gear meshing due to the fixed connection. The torque sensor 4 inside it detects the torque change in real time, feeds back the load state, and the output shaft 14 transmits the final low-speed and high-torque power to the tool head to complete the operation task. The two-stage planetary gear trains share the fixed internal gear ring 10, with high integration and small volume, suitable for micro tools. The multi-stage deceleration achieves a high reduction ratio, significantly enhancing the output torque. The internal gear ring 10 enhances the structural rigidity, reduces vibration, ensures smooth gear meshing, and improves the transmission accuracy and reliability. It should be noted that the torque sensor 4 cooperates with the outer housing 15 to fix the internal gear ring 10 so that it cannot rotate, and there is a clearance fit between the internal gear ring 10 and the outer housing 15; when the load distribution among the planetary gears is uneven, the internal gear ring 10 can generate a small radial displacement to achieve the purpose of automatic position adjustment, thereby equalizing the loads among the planetary gears.
[0021] Referring to Figures 2-3 , wherein, the first-stage planetary gear train includes a copper sleeve 2, a first-stage sun gear 3, a top plate 5, three first-stage planetary gears 6, three first-stage planetary gear shafts 7 and a first-stage planet carrier 8. A copper sleeve 2 is fixedly connected to the outer side of the motor shaft 1, a first-stage sun gear 3 is fixedly connected to the outer side of the copper sleeve 2, three first-stage planetary gears 6 are meshed with the outer side of the first-stage sun gear 3, all three first-stage planetary gears 6 are meshed with the inner side of the internal gear ring 10, a first-stage planetary gear shaft 7 is fixedly connected to the inner side of each of the three first-stage planetary gears 6, the outer sides of the three first-stage planetary gear shafts 7 are all rotatably connected to the first-stage planet carrier 8, a top plate 5 is fixedly connected to the inner side of the internal gear ring 10, and the first-stage sun gear 3 is rotatably connected to the inner side of the top plate 5; With the above structural arrangement, the motor shaft 1 is fixedly connected to the first-stage sun gear 3 through the copper sleeve 2. The copper sleeve 2 serves as a wear-resistant intermediate member, reducing the direct friction loss between the motor shaft 1 and the first-stage sun gear 3, and enhancing the coaxiality at the same time. The first-stage sun gear 3 is axially positioned through the top plate 5 to ensure its stable meshing with the three first-stage planet gears 6. The first-stage sun gear 3 drives the three first-stage planet gears 6 to rotate around their own first-stage planet gear shafts 7. At the same time, due to the meshing with the fixed internal gear ring 10, the first-stage planet gears 6 are forced to revolve along the inner side of the internal gear ring 10. The revolving motion of the first-stage planet gears 6 is transmitted to the first-stage planet carrier 8 through the first-stage planet gear shafts 7, driving the first-stage planet carrier 8 to rotate (as the input of the second-stage planetary gear train). The first-stage planet gear shafts 7 are fixedly connected to the first-stage planet gears 6, but the outer sides of the shafts are rotatably connected to the first-stage planet carrier 8. Sliding or rolling bearings are used to reduce the frictional resistance during the revolution of the planet gears. The top plate 5 and the copper sleeve 2 jointly restrict the axial displacement of the first-stage sun gear 3, preventing abnormal meshing caused by gear skew. Among them, the copper sleeve 2 isolates the direct contact between the motor shaft 1 and the first-stage sun gear 3, reducing metal wear, extending the life of the motor shaft 1, and avoiding transmission jamming caused by machining errors at the same time. The three first-stage planet gears 6 are circumferentially distributed, and the load is evenly distributed through the linkage between the first-stage planet gear shafts 7 and the first-stage planet carrier 8, avoiding single-point overload and improving the reliability of the gear system.
[0022] Referring to Figures 2-3 , wherein the second-stage planetary gear train includes a second-stage sun gear 11, three second-stage planet gears 12, and three second-stage planet gear shafts 13. The second-stage sun gear 11 is fixedly connected to the inner side of the first-stage planet carrier 8. The outer side of the second-stage sun gear 11 meshes with the three second-stage planet gears 12. The three second-stage planet gears 12 are all meshed with the inner side of the internal gear ring 10. The inner sides of the three second-stage planet gears 12 are all fixedly connected to the second-stage planet gear shafts 13. The three second-stage planet gear shafts 13 are all rotatably connected to the inner side of the output shaft 14; With the above structural arrangement, the rotation of the first-stage planet carrier 8 drives the second-stage sun gear 11 fixedly connected to its inner side to rotate synchronously, forming the input power for the second-stage speed reduction. The second-stage sun gear 11 drives the three second-stage planet gears 12 to rotate around the second-stage planet gear shafts 13. At the same time, due to the meshing with the fixed internal gear ring 10, the second-stage planet gears 12 are forced to revolve along the inner side of the internal gear ring 10. The second-stage planet gear shafts 13 are rotatably connected to the inner side of the output shaft 14, and the revolving motion is converted into the rotation of the output shaft 14 through the second-stage planet gear shafts 13, completing the second-stage speed reduction and outputting high torque. The reaction forces of the first-stage and second-stage planetary gear trains both act on the fixed internal gear ring 10. The torque sensor 4 simultaneously senses the double-stage load through the internal gear ring 10 to realize the torque monitoring of the entire transmission chain.
[0023] Referring to Figures 2-3 , wherein a spacer 9 is sleeved on the outer side of the second-stage sun gear 11 and is located between the first-stage planet carrier 8 and the second-stage planet gear 12; With the above structural arrangement, the function of the gasket 9 is to keep the secondary planet gear shaft 13 away from the three planet gear shaft holes on the primary planet carrier 8, making the rotation of the secondary planetary gear train smoother; at the same time, it avoids the direct contact between the secondary planet gear shaft 13 and the primary planet carrier 8, eliminates the friction caused by their relative movement, improves the efficiency of the gearbox, and reduces the noise of the gearbox.
[0024] Referring to Figure 5 , in which, a cylindrical flange 16 is provided on the secondary sun gear 11; With the above structural arrangement, the secondary sun gear 11 is firmly press-fitted into the central hole of the primary planet carrier 8 by means of the cylindrical flange 16. When this structure rotates, the frictional force is large, which can transmit a larger torque and play a role in preventing slippage.
[0025] Referring to Figure 4 , in which, the internal gear ring 10 is arranged as a thin-walled cylindrical structure; With the above structural arrangement, on the premise of ensuring the strength of the internal gear ring 10, the internal gear ring 10 is arranged as a thin-walled cylindrical structure to increase the flexibility of the internal gear itself. This structure can achieve the good effects of buffering impact and making the load distribution among the planet gears uniform, which can be explained by the load distribution uniformity coefficient Kp among the planet gears: Theoretically, the load distribution among the planet gears is uniform, that is, the Kp value is 1. Assuming that the number of planet gears is 3 and the Kp is 1, each planet gear receives a tangential force of 100 N. When the Kp is 1.2, the forces on the three planet gears are 120 N, 120 N, and 60 N, which indicates that the forces on two planet gears will increase, resulting in a reduction in the service life of the planet gears. Generally, in a planetary gear transmission without a load sharing mechanism, when the number of planet gears is 3, the load distribution non-uniformity coefficient Kp among the planet gears = 1.35 - 1.45. By adopting a thin-walled structure for the internal gear ring, through the force deformation and small radial displacement of the internal gear ring, the load distribution can be made more uniform, and the Kp value can be reduced to 1.1, which reduces the maximum force on the planet gear by 0.185 - 0.241, and improves the service life of the planet gear.
[0026] It should be noted that in this article, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the term "comprising", "including" or any other variant thereof is intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising a..." does not exclude the existence of additional identical elements in the process, method, article or device comprising the element.
[0027] Although embodiments of the present invention have been shown and described, those of ordinary skill in the art will appreciate that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. A planetary gearbox for a micro electric tool, characterized in that, It includes a housing (15). The motor shaft (1) and the output shaft (14) are rotatably connected to the inner side of the housing (15). An internal gear ring (10) is arranged on the inner side of the housing (15). A first-stage planetary gear train and a second-stage planetary gear train which are connected to each other are arranged on the inner side of the internal gear ring (10). The first-stage planetary gear train is arranged outside the motor shaft (1), and the second-stage planetary gear train is arranged on the output shaft (14). A torque sensor (4) is fixedly connected to the inner side of the housing (15).
2. A planetary gearbox for a micro electric tool according to claim 1, characterized in that: The first-stage planetary gear train includes a copper sleeve (2), a first-stage sun gear (3), a top plate (5), three first-stage planetary gears (6), three first-stage planetary gear shafts (7) and a first-stage planet carrier (8). The copper sleeve (2) is fixedly connected to the outside of the motor shaft (1). The first-stage sun gear (3) is fixedly connected to the outside of the copper sleeve (2). Three first-stage planetary gears (6) are meshed with the outside of the first-stage sun gear (3). The three first-stage planetary gears (6) are all meshed with the inner side of the internal gear ring (10). The inner sides of the three first-stage planetary gears (6) are all fixedly connected with the first-stage planetary gear shafts (7). The outside of the three first-stage planetary gear shafts (7) are all rotatably connected to the first-stage planet carrier (8). The top plate (5) is fixedly connected to the inner side of the internal gear ring (10). The first-stage sun gear (3) is rotatably connected to the inner side of the top plate (5).
3. The planetary gearbox of a micro electric tool according to claim 2, characterized in that: The second-stage planetary gear train includes a second-stage sun gear (11), three second-stage planetary gears (12) and three second-stage planetary gear shafts (13). The second-stage sun gear (11) is fixedly connected to the inner side of the first-stage planet carrier (8). Three second-stage planetary gears (12) are meshed with the outside of the second-stage sun gear (11). The three second-stage planetary gears (12) are all meshed with the inner side of the internal gear ring (10). The inner sides of the three second-stage planetary gears (12) are all fixedly connected with the second-stage planetary gear shafts (13). The three second-stage planetary gear shafts (13) are all rotatably connected to the inner side of the output shaft (14).
4. A planetary gearbox for a micro electric tool according to claim 3, characterized in that: A gasket (9) located between the first-stage planet carrier (8) and the second-stage planetary gear (12) is sleeved on the outside of the second-stage sun gear (11).
5. A planetary gearbox for a micro electric tool according to claim 2, characterized in that: A cylindrical flange (16) is provided on the second-stage sun gear (11).
6. The planetary gearbox of a micro electric tool according to claim 1, characterized in that: The internal gear ring (10) is arranged as a thin-walled cylindrical structure.