Electric impact tools

Abstract

The present invention relates to an electric impact tool, which includes: an outer rotor motor, which includes a rotor assembly and a stator; a main shaft; a reduction mechanism, which includes a gearbox rear cover and a transmission gear set located within the gearbox rear cover; the transmission gear set is used to reduce the rotational force of the rotor shaft of the rotor assembly and transmit it to the main shaft; and an impact mechanism, wherein the main shaft drives the impact mechanism to generate an impact force; wherein the stator is sleeved on the outer periphery of the gearbox rear cover, the rotor assembly is rotatably connected to the outer periphery of the gearbox rear cover via a rotor front bearing, and the stator at least partially overlaps axially with the rotor front bearing and the transmission gear set. In the electric impact tool of the present invention, the rear portion of the stator can at least partially overlap axially with the rotor front bearing, and the front portion of the stator can at least partially overlap axially with the transmission gear set, which is conducive to the axial miniaturization design of the electric impact tool, so that it can be used in scenarios with small axial space.

Description

Technical Field

[0001] The present invention relates to electric tools, in particular to an electric impact tool. Background Art

[0002] An electric wrench or electric screwdriver mainly includes a motor, a transmission mechanism, an impact mechanism and an output shaft arranged in sequence along the axial direction. The overall volume is relatively large, and it is not convenient to operate the electric wrench or electric screwdriver in a narrow space.

[0003] Existing electric wrenches and screwdrivers primarily achieve structural compactness by reducing the size of their internal components. For example, this approach reduces the axial length of the motor while increasing its outer diameter to maintain power, or by reducing the width of components like bearings and gears. This approach, while reducing component size, can compromise their functionality, limiting the extent to which electric tools can become compact. Summary of the Invention

[0004] In view of the above-mentioned defects in the prior art, an object of the present invention is to provide an electric impact tool, which optimizes the structure and assembly position of the outer rotor assembly to make the electric impact tool more compact in the axial direction.

[0005] To this end, the present invention provides the following technical solutions.

[0006] The present invention provides an electric impact tool, comprising:

[0007] An outer rotor motor comprising a rotor assembly and a stator;

[0008] spindle;

[0009] a speed reduction mechanism comprising a gearbox rear cover and a transmission gear set located within the gearbox rear cover; the transmission gear set is used to reduce the rotational force of the rotor shaft of the rotor assembly and transmit it to the main shaft;

[0010] An impact mechanism, wherein the main shaft drives the impact mechanism to generate an impact force;

[0011] The stator is sleeved on the outer periphery of the gearbox rear cover, the rotor assembly is rotatably connected to the outer periphery of the gearbox rear cover via a rotor front bearing, and the stator at least partially overlaps axially relative to the rotor front bearing and the transmission gear set.

[0012] Preferably, the electric impact tool is an impact wrench or an impact driver, which has a rotating state and an impact state; the electric impact tool further comprises an output shaft;

[0013] The impact mechanism includes a striking block for applying a rotational driving force to the output shaft or periodically impacting the output shaft in a rotational direction.

[0014] Preferably, the outer rotor motor is located at the rear of the gearbox rear cover.

[0015] Preferably, the outer wall of the gearbox rear cover is provided with a first boss and a second boss in sequence from back to front, the rotor front bearing is sleeved on the first boss, and the stator is sleeved on the second boss.

[0016] Preferably, the inner wall of the gearbox rear cover is provided with a first groove, and the main shaft is rotatably connected to the first groove via a main shaft bearing; the main shaft bearing and the stator at least partially overlap in the axial direction.

[0017] Preferably, the rotor assembly includes a rotor shell and a plurality of rotor magnets, wherein the plurality of rotor magnets are evenly spaced apart along a circumferential direction of the rotor shell.

[0018] Preferably, the rotor shell includes a bottom wall and an annular side wall, the plurality of rotor magnets are embedded in the inner wall of the annular side wall, and the stator is at least partially located in the rotor shell.

[0019] Preferably, a second groove is provided on a side of the rotor shell facing the gearbox rear cover, and the rotor front bearing is embedded in the second groove.

[0020] Preferably, a sun gear portion is provided at one end of the rotor shaft;

[0021] The transmission gear set includes planetary gears and an inner ring gear that mesh with each other. The inner ring gear is connected to the rear cover of the gear box, and the planetary gears are meshed with the sun gear part.

[0022] Preferably, one end of the main shaft is provided with a first concave cavity extending in the axial direction and a second concave cavity extending in the radial direction, the end of the rotor shaft provided with a sun gear part is inserted into the first concave cavity, the planetary gear is partially inserted into the second concave cavity and the two are connected by a planetary pin.

[0023] The present invention has the following technical effects:

[0024] The present invention provides an electric impact tool, in which an outer rotor motor is assembled on the outer periphery of the rear cover of a gear box. The rear part of the stator can at least partially overlap with the front bearing of the rotor in the axial direction, and the front part of the stator can at least partially overlap with the transmission gear set in the axial direction. The axial space inside the electric impact tool is fully utilized, making the axial structure of the electric impact tool more compact, which is conducive to the axial miniaturization design of the electric impact tool, so that it can be used in application scenarios with smaller axial space. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 A cross-sectional view of the structure of the electric impact tool of the present invention;

[0026] Figure 2 for Figure 1 Enlarged view of point A in the middle;

[0027] Figure 3 A partial structural cross-sectional view of the electric impact tool of the present invention;

[0028] Figure 4 An exploded view of a local structure of the electric impact tool of the present invention;

[0029] Figure 5 Schematic diagram of the assembly structure of the outer rotor motor, gearbox rear cover and inner gear ring of the present invention;

[0030] Figure 6 Schematic diagram of the assembly structure of the stator and the gearbox rear cover of the present invention;

[0031] Figure 7 A cross-sectional view of the assembly structure of the impact mechanism and the main shaft of the present invention;

[0032] Figure 8 It is a schematic diagram of the three-dimensional structure of the electric impact tool of the present invention.

[0033] Description of Reference Numerals

[0034] 100. Electric impact tools;

[0035] 1. Outer rotor motor; 11. Rotor assembly; 111. Rotor shaft; 1111. Sun gear unit; 112. Rotor front bearing; 113. Rotor housing; 1131. Bottom wall; 11311. Second groove; 1132. Annular side wall; 114. Rotor magnet; 115. Rotor rear bearing; 12. Stator; 13. Fan;

[0036] 2. Main shaft; 21. First concave cavity; 22. Second concave cavity; 23. Protrusion; 24. Second concave hole;

[0037] 3. Speed ​​reduction mechanism; 31. Gearbox rear cover; 311. First boss; 312. Second boss; 313. First groove; 321. Planetary gear; 322. Internal gear ring; 323. Planetary pin; 324. Circlip; 33. Gearbox front cover;

[0038] 4. Impact mechanism; 41. Striking block; 411. Guide hole; 42. Steel ball; 43. Spring;

[0039] 5. Output shaft; 51. First concave hole; 52. First stopper;

[0040] 61. Spindle bearing; 62. Bushing; 7. Gasket; 81. First housing; 82. Second housing; 91. Light; 92. Lampshade; 93. Reversing lever; 94. Switch; 95. Control panel. DETAILED DESCRIPTION

[0041] To make the technical solutions and beneficial effects of the present invention more clearly understood, the following is a detailed description by listing specific embodiments. Unless otherwise defined, the technical and scientific terms used herein have the same meanings as those in the technical field to which this application belongs.

[0042] In the description of the present invention, unless otherwise expressly defined, the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "height", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise" and the like to indicate directions or positional relationships are based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of simplifying the description of the present invention, and do not indicate that the device or element referred to must have a specific direction, be constructed and operate in a specific direction, and should not be understood as a limitation to the present invention.

[0043] In this disclosure, the terms "first" and "second" are used solely for descriptive clarity and should not be construed as indicating the relative importance of the features indicated or the quantity of the technical features indicated. Therefore, a feature specified as "first" or "second" may explicitly include at least one such feature. In the description of this disclosure, "plurality" means at least two, and "several" means at least one, unless expressly specified otherwise.

[0044] In the present invention, unless otherwise expressly defined, the terms "installed," "connected," "connect," "fixed," and "disposed" should be understood broadly. For example, "connection" can mean fixed connection, removable connection, or integral molding; it can be mechanical or electrical; it can be direct or indirect through an intermediary; it can also refer to internal communication between two components or the interaction between two components. Those skilled in the art will understand the specific meanings of these terms in the present invention based on the specific circumstances.

[0045] In the present invention, unless otherwise clearly defined, when a first feature is “on,” “above,” “above,” “above,” “below,” “below,” or “below” a second feature, the first feature and the second feature may be in direct contact, or the first feature and the second feature may be in indirect contact via an intermediate medium. Moreover, when a first feature is “on,” “above,” or “above” a second feature, it may mean that the first feature is directly above or obliquely above the second feature, or simply means that the horizontal height of the first feature is higher than the horizontal height of the second feature. When a first feature is “below,” “below,” or “below” a second feature, it may mean that the first feature is directly below or obliquely below the second feature, or simply means that the horizontal height of the first feature is lower than the horizontal height of the second feature.

[0046] The terms "front", "back", "left", "right", "up" and "down" mentioned in this invention are all in the Figure 1 and Figure 8 The markings in the table shall prevail.

[0047] The following is based on Figures 1 to 8 The electric impact tool of the present invention will be described in detail.

[0048] In this embodiment, if Figures 1 to 4 As shown, the electric impact tool 100 includes an outer rotor motor 1, a spindle 2, a reduction mechanism 3, and an impact mechanism 4. The outer rotor motor 1 includes a rotor assembly 11 and a stator 12, with the rotor assembly 11 located outside the stator 12. The reduction mechanism 3 includes a gearbox rear cover 31 and a transmission gear set located within the gearbox rear cover 31. When the electric impact tool 100 is in operation, the rotational force generated by the rotor shaft 111 is reduced by the transmission gear set, which then transmits the reduced rotational force to the spindle 2. The spindle 2 drives the impact mechanism 4 to generate an impact force, causing the electric impact tool 100 to perform an impact operation.

[0049] In this embodiment, if Figures 2 to 6 As shown, the stator 12 is sleeved on the outer periphery of the gearbox rear cover 31, and the rotor assembly 11 is rotatably connected to the outer periphery of the gearbox rear cover 31 through the rotor front bearing 112. The stator 12 and the rotor front bearing 112 at least partially overlap in the axial direction, and the stator 12 and the transmission gear set at least partially overlap in the axial direction.

[0050] By adopting the above technical solution, the outer rotor motor 1 is assembled on the outer periphery of the gear box rear cover 31, and the rear part of the stator 12 can at least partially overlap with the rotor front bearing 112 in the axial direction, and the front part of the stator 12 can at least partially overlap with the transmission gear set in the axial direction, thereby fully utilizing the axial space within the electric impact tool 100, making the axial structure of the electric impact tool 100 more compact, which is conducive to the axial miniaturization design of the electric impact tool 100, so that it can be used in scenarios with smaller axial space.

[0051] It should be understood that the axial overlapping structure of the stator 12 relative to the rotor front bearing 112 and the transmission gear set is not limited to this. The stator 12 and the rotor front bearing 112 can be completely overlapped in the axial direction and the stator 12 and the transmission gear set can be partially overlapped in the axial direction, or the stator 12 and the rotor front bearing 112 can be partially overlapped in the axial direction and the stator 12 and the transmission gear set can be completely overlapped in the axial direction.

[0052] In one embodiment, if Figures 1 to 3 As shown, the electric impact tool 100 is an impact wrench or impact driver, which has a rotation state and an impact state. The electric impact tool 100 also includes an output shaft 5, and the impact mechanism 4 includes a striking block 41, which is used to apply a rotational driving force to the output shaft 5 or periodically impact the output shaft 5 in the rotational direction.

[0053] Specifically, if Figure 2 and Figure 7 As shown, the impact mechanism 4 includes a striking block 41, a steel ball 42 and a spring 43. One end of the spring 43 abuts against the striking block 41 and the other end is connected to the main shaft 2. The striking block 41 is an annular structure and is provided with a through hole (not shown in the figure). The main shaft 2 is provided with a protrusion 23 at one end facing the output shaft 5, and the output shaft 5 is provided with a first recessed hole 51 at one end facing the main shaft 2. After the main shaft 2 passes through the through hole of the striking block 41, the protrusion 23 is inserted into the first recessed hole 51. The shaft body of the main shaft 2 is provided with two second recessed holes 24, the striking block 41 is provided with a guide hole 411, and the steel ball 42 is embedded in the second recessed hole 24 and the guide hole 411. The output shaft 5 is provided with two first stops 52 at one end facing the striking block 41, and two second stops (not shown in the figure) are provided at one end facing the output shaft 5. The first stop 52 and the second stop are matched one by one in the circumferential direction of the output shaft 5.

[0054] The operating principle of the electric impact tool 100 is similar to that of a conventional impact wrench or impact screwdriver. When the reaction force of the workpiece applied to the output shaft 5 is less than or equal to a preset value, the rotor shaft 111 of the outer rotor motor 1 reduces the speed through the transmission gear set to drive the main shaft 2 to rotate. The main shaft 2 drives the striking block 41 to rotate. Under the abutment of the first stop 52 and the second stop, the striking block 41 drives the output shaft 5 to rotate synchronously. At this time, the electric impact tool 100 is in a rotating state. When the reaction force of the workpiece applied to the output shaft 5 is greater than the preset value, the output shaft 5 does not rotate because the first stop 52 of the output shaft 5 exerts a large circumferential resistance on the second stop of the striking block 41 during the rotation of the striking block 41. At this time, the striking block 41 rotates while moving axially backward under the cooperation of the steel ball 42 and the guide hole 411 of the striking block 41. At the same time, the striking block 41 that moves backward compresses the spring 43 until the second stop of the striking block 41 moves backward to the point where it is out of circumferential contact with the first stop 52. The striking block 41 is rotated. The striking block 41 rotates and the spring 43 rebounds, wherein the striking block 41 rotates so that the second stopper of the striking block 41 circumferentially hits the first stopper 52 of the output shaft 5, and the rebound of the spring 43 causes the striking block 41 to axially impact the end face of the output shaft 5. At this time, the electric impact tool 100 is in an impact state. After the impact is completed, the striking block 41 and the output shaft 5 are reset to wait for the next impact. The striking block 41 rotates to the next position and impacts the output shaft 5 again. Finally, the electric impact tool 100 periodically impacts the output shaft 5 in the rotation direction through the impact mechanism 4.

[0055] In one embodiment, if Figure 4 and Figure 5 As shown, the outer rotor motor 1 is located at the rear of the gear box rear cover 31 to facilitate the assembly of the outer rotor motor 1 and the gear box rear cover 31, thereby avoiding the outer rotor motor 1 being too large due to the assembly of the outer rotor motor 1 and the gear box rear cover 31, which is not conducive to the miniaturization design of the electric impact tool 100.

[0056] In one embodiment, if Figure 2 、 Figure 4 and Figure 6 As shown, the outer wall of the gear box rear cover 31 is provided with a first boss 311 and a second boss 312 in sequence from the back to the front. Figure 2 As shown, the rotor front bearing 112 is sleeved on the first boss 311, as shown in FIG. Figure 2 、 Figure 5 and Figure 6 As shown, the stator 12 is sleeved onto the second boss 312. During assembly, the rotor assembly 11 and stator 12 are first assembled into the outer rotor motor 1, and then the outer rotor motor 1 is mounted on the gearbox rear cover 31. By defining the position and size of the first boss 311 and the second boss 312, the assembly position of the rotor assembly 11 and stator 12 is defined, facilitating a compact structure while reducing assembly difficulty.

[0057] Further, if Figure 2 As shown, the outer diameter of the first boss 311 is smaller than the outer diameter of the second boss 312 , so as to facilitate the assembly of the rotor assembly 11 and the stator 12 .

[0058] In one embodiment, if Figure 2 and Figure 4 As shown, the inner wall of the gear box rear cover 31 is provided with a first groove 313, the main shaft bearing 61 is embedded in the first groove 313, and the main shaft 2 is rotatably connected to the first groove 313 through the main shaft bearing 61. Figure 2 As shown, the spindle bearing 61 and the stator 12 at least partially overlap in the axial direction to further reduce the axial size of the electric impact tool 100. Furthermore, the first groove 313 partially overlaps with the second boss 312 in the axial direction, so that the spindle bearing 61 and the stator 12 partially overlap in the axial direction.

[0059] Further, if Figure 2 As shown, the first groove 313 partially overlaps with the first boss 311 in the axial direction, so that the spindle bearing 61 can also partially overlap with the rotor front bearing 112 in the axial direction, thereby further facilitating the compactness of the electric impact tool 100 in the axial direction.

[0060] In one embodiment, if Figure 2 and Figure 4 As shown, the rotor assembly 11 includes a rotor shell 113 and a plurality of rotor magnets 114 . All the rotor magnets 114 are evenly spaced apart along the circumference of the rotor shell 113 . The rotor assembly 11 has a simple and compact structure.

[0061] Further, if Figure 2 and Figure 4 As shown, the rotor shell 113 includes a bottom wall 1131 and an annular side wall 1132. All rotor magnets 114 are embedded in the inner wall of the annular side wall 1132. The stator 12 is at least partially located in the rotor shell 113. The outer rotor motor 1 has a simple overall structure and is compact in the axial direction.

[0062] Further, if Figure 2 and Figure 4 As shown, a second groove 11311 is provided on the side of the rotor shell 113 facing the gear box rear cover 31, and the inner wall of the rotor front bearing 112 is sleeved on the first boss 311 of the gear box rear cover 31 and its outer wall is embedded in the second groove 11311, which is convenient for assembly and can further contribute to the compactness of the electric impact tool 100 in the axial direction.

[0063] In one embodiment, if Figure 4 As shown, one end of the rotor shaft 111 is provided with a sun gear portion 1111. Figure 2 and Figure 4 As shown, the transmission gear set includes intermeshing planetary gears 321 and an inner ring gear 322. The inner ring gear 322 is clipped into the gearbox rear cover 31 and secured by a retaining spring 324. There are three planetary gears 321, all of which mesh with the sun gear unit 1111. Thus, when the rotor shaft 111 rotates, the sun gear unit 1111 drives the planetary gears 321 to rotate, reducing the output speed of the rotor shaft 111 through the planetary gears 321.

[0064] Further, if Figure 7 As shown, one end of the main shaft 2 is provided with a first concave cavity 21 extending in the axial direction and a second concave cavity 22 extending in the radial direction, and the first concave cavity 21 and the second concave cavity 22 are connected. Figure 2 and Figure 3 As shown, the rotor shaft 111 is provided with one end of the sun gear portion 1111 inserted into the first concave cavity 21 , and the planetary gear 321 is partially inserted into the second concave cavity 22 and the two are connected by a planetary pin 323 , and the main shaft 2 is driven to rotate by the planetary gear 321 .

[0065] In one embodiment, if Figure 4 As shown, the outer rotor motor 1 further includes a fan 13 for heat dissipation.

[0066] In one embodiment, if Figure 2 and Figure 8 As shown, the reduction mechanism 3 also includes a gearbox front cover 33, which is assembled with the gearbox rear cover 31 to form a cavity. The main shaft 2, the transmission gear set, and the impact mechanism 4 are accommodated in the cavity, and the output shaft 5 is rotatably connected to the through hole of the gearbox front cover 33 through the shaft sleeve 62.

[0067] Further, if Figure 2 As shown, the gearbox front cover 33 is an aluminum part, and a gasket 7 is provided between the gearbox front cover 33 and the striking block 41 . The gasket 7 is used to reduce the friction generated between the striking block 41 and the gearbox front cover 33 during movement.

[0068] In one embodiment, if Figure 3 and Figure 8 As shown, the electric impact tool 100 further includes a first housing 81 and a second housing 82 , which are connected to form an outer shell of the electric impact tool 100 to accommodate internal components thereof.

[0069] Further, if Figure 2 As shown, the rotor shaft 111 of the rotor assembly 11 is rotatably connected to the outer housing of the electric impact tool 100 through a rotor rear bearing 115 .

[0070] In one embodiment, if Figure 1 and Figure 8As shown, an outer shell of the electric impact tool 100 is provided with a lighting lamp 91 and a lampshade 92 . The lighting lamp 91 is used for lighting, and the lampshade 92 is provided on the outer periphery of the lighting lamp 91 to prevent dust.

[0071] In one embodiment, if Figure 1 and Figure 8 As shown, a reversing lever 93 is provided on the outer housing of the electric impact tool 100 , and the reversing lever 93 is moved to switch the rotation direction of the outer rotor motor 1 .

[0072] In one embodiment, if Figure 1 and Figure 8 As shown, a switch 94 is provided on the outer housing of the electric impact tool 100 , and the switch 94 is used to control the opening and closing of the electric impact tool 100 .

[0073] In one embodiment, if Figure 1 and Figure 8 As shown, a control panel 95 is provided on the outer shell of the electric impact tool 100. The control panel 95 is used to adjust the rotation speed, torque or select a mode (such as selecting a reverse self-stop mode).

[0074] It should be understood that the above embodiments are exemplary and are not intended to encompass all possible implementations of the claims. Various modifications and variations may be made to the above embodiments without departing from the scope of this disclosure. Similarly, the various technical features of the above embodiments may be arbitrarily combined to form additional embodiments of the present invention that may not be explicitly described. Therefore, the above embodiments merely illustrate several implementations of the present invention and do not limit the scope of protection of the patent of this invention.

Claims

1. An electric impact tool, characterized in that: The electric impact tool (100) comprises: An outer rotor motor (1) comprising a rotor assembly (11) and a stator (12); spindle (2); A speed reduction mechanism (3) comprising a gearbox rear cover (31) and a transmission gear set located within the gearbox rear cover (31); the transmission gear set is used to reduce the rotational force of the rotor shaft (111) of the rotor assembly (11) and transmit it to the main shaft (2); An impact mechanism (4), wherein the main shaft (2) drives the impact mechanism (4) to generate an impact force; The stator (12) is sleeved on the outer periphery of the gearbox rear cover (31), the rotor assembly (11) is rotatably connected to the outer periphery of the gearbox rear cover (31) via a rotor front bearing (112), and the stator (12) at least partially overlaps with the rotor front bearing (112) and the transmission gear set in the axial direction.

2. The electric impact tool according to claim 1, wherein The electric impact tool (100) is an impact wrench or an impact screwdriver, which has a rotation state and an impact state; the electric impact tool (100) further comprises an output shaft (5); The impact mechanism (4) includes an impact block (41) for applying a rotational driving force to the output shaft (5) or periodically impacting the output shaft (5) in a rotational direction.

3. The electric impact tool according to claim 1, wherein The outer rotor motor (1) is located at the rear of the gear box rear cover (31).

4. The electric impact tool according to claim 1, wherein The outer wall of the gearbox rear cover (31) is provided with a first boss (311) and a second boss (312) in sequence from rear to front, the rotor front bearing (112) is sleeved on the first boss (311), and the stator (12) is sleeved on the second boss (312).

5. The electric impact tool according to claim 1, wherein A first groove (313) is provided on the inner wall of the gearbox rear cover (31), and the main shaft (2) is rotatably connected to the first groove (313) via a main shaft bearing (61); the main shaft bearing (61) and the stator (12) at least partially overlap in the axial direction.

6. The electric impact tool according to any one of claims 1 to 5, characterized in that: The rotor assembly (11) includes a rotor shell (113) and a plurality of rotor magnets (114). The plurality of rotor magnets (114) are evenly spaced apart along the circumference of the rotor shell (113).

7. The electric impact tool according to claim 6, wherein: The rotor shell (113) comprises a bottom wall (1131) and an annular side wall (1132); the plurality of rotor magnets (114) are embedded in the inner wall of the annular side wall (1132); and the stator (12) is at least partially located in the rotor shell (113).

8. The electric impact tool according to claim 6, wherein: A second groove (11311) is provided on a side of the rotor shell (113) facing the gear box rear cover (31), and the rotor front bearing (112) is embedded in the second groove (11311).

9. The electric impact tool according to any one of claims 1 to 5, characterized in that: A sun gear portion (1111) is provided at one end of the rotor shaft (111); The transmission gear set comprises planetary gears (321) and an inner gear ring (322) meshing with each other, the inner gear ring (322) is connected to the gear box rear cover (31), and the planetary gears (321) mesh with the sun gear part (1111).

10. The electric impact tool according to claim 9, wherein One end of the main shaft (2) is provided with a first concave cavity (21) extending in the axial direction and a second concave cavity (22) extending in the radial direction; one end of the rotor shaft (111) provided with a sun gear portion (1111) is inserted into the first concave cavity (21); the planetary gear (321) is partially inserted into the second concave cavity (22) and the two are connected via a planetary pin (323).

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