Coaxial speed reducer

Abstract

The application provides a coaxial speed reducer, which comprises a speed reduction planetary gear set (100), a differential (200) and a planet carrier (300), the speed reduction planetary gear set comprises a first sun gear (110), an inner ring gear (120) and a plurality of first planet gears (130), each first planet gear is respectively provided with a first gear part (131) and a second gear part (132) with a pitch circle diameter smaller than that of the first gear part (131), the differential comprises a second sun gear (210, 210A), a plurality of second planet gears (220, 220A), a third sun gear (230) and a plurality of third planet gears (240, 240A), the first gear part, the second gear part and the third sun gear are all helical gears with the same helical direction. Therefore, the cost can be controlled, and the NVH performance, durability and transmission efficiency can be improved.

Description

Technical Field

[0001] This application relates to a coaxial speed reducer. Background Technology

[0002] Consider a coaxial reducer comprising a reduction planetary gear set, a differential, and a planet carrier, wherein both the reduction planetary gear set and the differential are mounted on the planet carrier. The differential employs spur planetary gears to achieve a compact axial space. Furthermore, the reduction planetary gear set adopts an NW-type structure, i.e., it uses stepped planetary gears, which have a first gear section meshing with the sun gear and a second gear section meshing with the internal ring gear.

[0003] Furthermore, the planetary carrier is rotatably supported on the housing using angular contact ball bearings (ACBBs). To ensure the service life of the angular contact ball bearings, it is desirable to minimize the axial force acting on the planetary carrier from the entire gear system, preferably to make this axial force zero.

[0004] Since the differential uses spur planetary gears, in order to ensure that the axial force acting on the planet carrier is zero, the axial force of the reduction planetary gear set must be zero. At this time, the helix angles of the first and second gear sections of the stepped planetary gears of the reduction planetary gear set must satisfy the following relationship (1).

[0005] Relation (1):

[0006] Where, β P11 It is the helix angle of the first gear, β P12 It is the helix angle of the second gear, Z. P11 Z is the number of teeth in the first gear section. P12 Z is the number of teeth in the second gear section. S1 It is the number of teeth on the sun gear of the reduction planetary gear set, m nP12 It is the normal module of the second gear section, m nS1 It is the normal module of the sun gear in the reduction planetary gear set.

[0007] Under the condition that the above relationship (1) is satisfied, the helix angle β of the second gear is P12 It will be very small, usually 12~15°.

[0008] In this situation, because the helix angle of the second gear and its meshing internal gear ring is small, the overlap between them is reduced, leading to poorer NVH performance. To ensure the overlap, the tooth width of the second gear needs to be increased. Increasing the tooth width of the second gear will cause the following problems.

[0009] ① This will cause the positional error of the planetary bores on the planet carrier, which support the planetary pins (used for mounting the stepped planetary gears), to worsen due to the increased distance, which is detrimental to NVH performance.

[0010] ② The increased length of the planetary gear pins leads to a decrease in the stiffness of the planetary gear pins, which will also affect NVH performance and durability.

[0011] ③ The increased distance between the two needle roller bearings installed between the stepped planetary gear and the planetary pin creates a blank area without needle roller support, which is not conducive to gear meshing and will also affect NVH performance and durability.

[0012] ④ The increased weight of the stepped planetary gears leads to an increase in the overall weight of the coaxial reducer, resulting in increased costs.

[0013] ⑤ The extended manufacturing cycle of gears and the machining time of planetary holes on the planetary carrier reduce manufacturing feasibility and lead to increased costs.

[0014] ⑥ The increased contact area between the second gear and the internal gear ring leads to a decrease in transmission efficiency. Utility Model Content

[0015] This application was made in response to the deficiencies of the prior art. The purpose of this application is to provide a coaxial reducer that can control costs and improve NVH performance, durability, and transmission efficiency.

[0016] To achieve the above objectives, the present application may adopt the following technical solutions.

[0017] This application provides a coaxial speed reducer, including a reduction planetary gear set, a differential, and a planet carrier. Both the reduction planetary gear set and the differential are mounted on the planet carrier. The reduction planetary gear set includes: a first sun gear mounted inside the planet carrier; an internal ring gear sleeved on the outside of the planet carrier; and a plurality of first planet gears respectively disposed around the first sun gear and mounted on the planet carrier via multiple first planetary pins. Each first planet gear has a first gear portion and a second gear portion with a pitch circle diameter smaller than that of the first gear portion. The first gear portion meshes with the first sun gear, and the second gear portion meshes with the internal ring gear. The differential includes: a second sun gear mounted in the planet carrier with its axis aligned with the axis of the first sun gear; a plurality of second planet gears respectively disposed around the second sun gear and mounted on the planet carrier by a plurality of second planet gear pins, and respectively meshing with the second sun gear; a third sun gear mounted in the planet carrier with its axis aligned with the axis of the first sun gear; and a plurality of third planet gears respectively disposed around the third sun gear and mounted on the planet carrier by a plurality of third planet gear pins, and respectively meshing with the third sun gear, wherein the first gear section, the second gear section, and the third sun gear are all helical gears with the same helical direction.

[0018] In one alternative embodiment, the helix angles of the first gear section, the second gear section, and the third sun gear satisfy the following relationship:

[0019]

[0020] Where, β P11 It is the helix angle of the first gear, β P12 It is the helix angle of the second gear, β S3 Z is the helix angle of the third sun gear. S1 Z is the number of teeth on the first sun gear. R Z is the number of teeth on the internal gear ring. P11 Z is the number of teeth in the first gear section. P12 Z is the number of teeth in the second gear section. S3 The number of teeth on the third sun gear is m. nS1 It is the normal modulus of the first sun gear, m nP12 It is the normal module of the second gear section, m nS3 It is the normal module of the third sun gear.

[0021] In another alternative embodiment, the input shaft connected to the first sun gear, the first output shaft connected to the second sun gear, and the second output shaft connected to the third sun gear are rotatably supported on the housing by bearings. The first output shaft extends outward from the hollow interior of the input shaft to the planet carrier, and the input shaft, the first output shaft, and the second output shaft extend outward from the planet carrier in opposite directions.

[0022] In another alternative, the helix angle of the second gear is greater than 15°.

[0023] In another alternative embodiment, each of the plurality of third planetary gears has a third gear portion and a fourth gear portion, each of the third gear portions meshing with each of the plurality of second planetary gears, and each of the fourth gear portions meshing with the third sun gear.

[0024] In another alternative, thrust needle roller bearings or thrust sliding bearings are respectively installed between the two end faces of each of the third planetary gears and the planet carrier.

[0025] In another alternative, the second sun gear is either a spur gear or a helical gear.

[0026] In another alternative, thrust needle roller bearings or thrust sliding bearings are respectively installed between the two end faces of each of the first planetary gears and the planet carrier.

[0027] In another alternative, the planetary carrier is rotatably supported to the housing using angular contact ball bearings.

[0028] In another alternative, the power input from the first sun gear is transmitted to the planet carrier via the plurality of first planet gears, then to the second sun gear via the plurality of second planet gears, and simultaneously to the third sun gear via the plurality of third planet gears.

[0029] By adopting the above technical solution, a coaxial reducer that can control costs and improve NVH performance, durability and transmission efficiency can be provided. Attached Figure Description

[0030] Figure 1 This is a cross-sectional schematic diagram showing a coaxial reducer according to an embodiment of the present application.

[0031] Figure 2 It shows Figure 1 A three-dimensional schematic diagram of a coaxial reducer, in which the diagram of structures such as the planetary carrier is omitted.

[0032] Figure 3It shows Figure 1 Another three-dimensional schematic diagram of the coaxial reducer, in which the diagram of the planetary carrier and other structures is omitted.

[0033] Figure 4 It shows Figure 1 A schematic diagram showing the meshing relationship of the gears in the differential of a coaxial reducer.

[0034] Figure 5 This is a perspective schematic diagram of a coaxial reducer according to a modified embodiment of the present application, which is related to... Figure 3 The corresponding diagram omits illustrations of structures such as the planetary carrier.

[0035] Explanation of reference numerals in the attached figures

[0036] 1. Coaxial reducer;

[0037] 100 reduction planetary gear set;

[0038] 110 First sun gear; 111 Input shaft; 120 Internal gear ring; 130 First planet gear; 131 First gear section; 132 Second gear section; 135 First planet gear pin; 136, 137 Thrust needle roller bearings; 138 Needle roller bearing;

[0039] 200 Differential; 210, 210A Second Sun Gear; 211 First Output Shaft; 212 Thrust Needle Roller Bearing; 220, 220A Second Planetary Gears; 225 Second Planetary Gear Pin; 230 Third Sun Gear; 231 Second Output Shaft; 232 Bearing; 240, 240A Third Planetary Gears; 241, 241A Third Gear Section; 242 Fourth Gear Section; 245 Third Planetary Gear Pin;

[0040] 300 Planetary carrier; 301, 302 Angular contact ball bearings; 303 First end plate; 304 Second end plate; 305 Peripheral wall; 306 Intermediate plate;

[0041] A: Axial direction; A1: One side of the axial direction; A2: The other side of the axial direction; C: Circumferential direction. Detailed Implementation

[0042] The specific embodiments of this application will be described in detail below with reference to the accompanying drawings. It should be understood that these specific descriptions are only for teaching those skilled in the art how to implement this application, and are not intended to exhaustively describe all possible methods of this application, nor to limit the scope of this application.

[0043] In this application, unless otherwise specified, "axial" and "circumferential" refer to the axial and circumferential directions of the coaxial reducer, respectively. "One side of the axial direction" corresponds to... Figure 1 The left side of the "axial other side" corresponds to Figure 1 On the right side of the middle.

[0044] The coaxial reducer of one embodiment of this application will be described below with reference to the accompanying drawings.

[0045] like Figure 1 As shown, a coaxial reducer 1 according to an embodiment of this application includes a reduction planetary gear set 100, a differential 200, and a planet carrier 300, wherein the reduction planetary gear set 100 and the differential 200 are both mounted on the same planet carrier 300.

[0046] like Figure 1 As shown, the planetary carrier 300 has a first end plate 303 located on one axial side A1, a second end plate 304 located on the other axial side A2, a generally cylindrical peripheral wall 305 connecting the first end plate 303 and the second end plate 304, and an intermediate plate 306 located on the axial side A between the first end plate 303 and the second end plate 304. Through holes are provided at the center of the first end plate 303, the second end plate 304, and the intermediate plate 306 for the input shaft 111, the first output shaft 211, and the second output shaft 231 (described later) to extend outward from the planetary carrier 300. Furthermore, a reduction planetary gear set 100 is mounted between the first end plate 303 and the intermediate plate 306, and a differential 200 is mounted between the second end plate 304 and the intermediate plate 306. Additionally, the planetary carrier 300 is rotatably supported on an outer housing (not shown) by angular contact ball bearings 301 and 302.

[0047] like Figures 1 to 3 As shown, the reduction planetary gear set 100 includes: a first sun gear 110, which is mounted inside the planet carrier 300; an input shaft 111 connected to the first sun gear 110 is a hollow cylindrical shaft extending axially to one side A1 and rotatably supported on an outer housing (not shown) by bearings (not shown); an internal gear ring 120, which is sleeved on the outside of the planet carrier 300 and fixed to the outer housing (not shown); and a plurality of first planet gears 130, which are respectively arranged around the first sun gear 110. It should be noted that in the various figures, only one first planet gear 130 is shown for ease of observation, but there may be, for example, three first planet gears 130. Of course, the number of first planet gears 130 is not limited to three; there may be more than three, for example, four to six. The same applies to the second planet gear 220, the third planet gear 240, and 240A, which will be described later.

[0048] like Figure 1As shown, a plurality of first planetary gears 130 are respectively mounted on the planet carrier 300 via a plurality of first planetary gear pins 135. One end of each first planetary gear pin 135 is fixed to a first end plate 303, and the other end passes through a through hole in an intermediate plate 306 and is fixed to a second end plate 304. Furthermore, needle roller bearings 138 are respectively installed between each first planetary gear 130 and each first planetary gear pin 135, thereby rotatably supporting each first planetary gear 130 on its respective first planetary gear pin 135. Figure 1 Only one needle roller bearing 138 is shown, but two needle roller bearings 138 can also be provided, that is, one needle roller bearing 138 is provided for the first gear part 131 and the second gear part 132 described later.

[0049] In addition, such as Figure 1 As shown, thrust needle roller bearings 136 and 137 are respectively installed between the two end faces of each first planetary gear 130 and the planet carrier 300, and more specifically, between the two end faces of each first planetary gear 130 and the first end plate 303 and the intermediate plate 306. Thus, the thrust needle roller bearings 136 and 137 can be used to bear the axial force acting on each first planetary gear 130, thereby preventing excessive wear of each first planetary gear 130. Alternatively, thrust sliding bearings can be installed between the two end faces of each first planetary gear 130 and the planet carrier 300 to replace the thrust needle roller bearings 136 and 137.

[0050] like Figure 1 and Figure 2 As shown, each of the first planetary gears 130 has a first gear portion 131 and a second gear portion 132 with a pitch circle diameter smaller than that of the first gear portion 131. The first gear portion 131 meshes with the first sun gear 110, and the second gear portion 132 meshes with the internal gear ring 120. Furthermore, the first sun gear 230, the first gear portion 131, the second gear portion 132, and the internal gear ring 120 are all helical gears, and the helix directions of the first sun gear 230, the first gear portion 131, the second gear portion 132, and the internal gear ring 120 are opposite. Since the first gear portion 131 meshes with the first sun gear 110, their helix angles are the same. Since the second gear portion 132 meshes with the internal gear ring 120, their helix angles are the same.

[0051] When torque is input from the input shaft 111 to the first sun gear 110, since the internal gear ring 120 is fixed, the multiple first planet gears 130, driven by the first sun gear 110, rotate around the axis (i.e., the central axis) of each first planet gear pin 135 while revolving around the axis of the first sun gear 110, thereby driving the planet carrier 300 to rotate around the axis of the first sun gear 110.

[0052] like Figure 1 and Figure 3As shown, the differential 200 includes: a second sun gear 210, which is mounted in the planet carrier 300 and whose axis is aligned with the axis of the first sun gear 110; a plurality of second planet gears 220, which are respectively disposed around the second sun gear 210 and are respectively mounted on the planet carrier 300 by means of a plurality of second planet gear pins 225 and respectively mesh with the second sun gear 210; a third sun gear 230, which is mounted in the planet carrier 300 and whose axis is aligned with the axis of the first sun gear 110; and a plurality of third planet gears 240, which are respectively disposed around the third sun gear 230 and are respectively mounted on the planet carrier 300 by means of a plurality of third planet gear pins 245 and respectively mesh with the third sun gear 230.

[0053] like Figure 1 and Figure 3 As shown, the second sun gear 210 is a spur gear. A first output shaft 211 connected to the second sun gear 210 extends from the interior of the hollow input shaft 111 outwards from the planet carrier 300. After extending from the planet carrier 300, the first output shaft 211 is rotatably supported on an outer housing (not shown) by a bearing (not shown). Furthermore, a thrust needle roller bearing 212 is installed between the end face of the axial side A1 of the second sun gear 210 and the planet carrier 300 to absorb the axial force acting on the second sun gear 210. Alternatively, a thrust sliding bearing can be installed between the end face of the axial side A1 of the second sun gear 210 and the planet carrier 300 to replace the thrust needle roller bearing 212.

[0054] like Figure 1 and Figure 3 As shown, the third sun gear 230 is a helical gear, and the second output shaft 231 connected to the third sun gear 230 extends outward from the planet carrier 300 in the opposite direction A2. That is, the input shaft 111 and the first output shaft 211 extend outward from the planet carrier 300 in opposite directions as the second output shaft 231. In addition, the second output shaft 231 is rotatably supported on an outer housing (not shown) by means of a bearing 232.

[0055] like Figure 3 As shown, each of the plurality of second planetary gears 220 is a spur gear, just like the second sun gear 210. Furthermore, although not shown, the two ends of each second planetary gear pin 225 supporting each second planetary gear 220 are fixed to the intermediate plate 306 and the second end plate 304 of the planet carrier 300, respectively.

[0056] like Figure 3 and Figure 4As shown, multiple third planetary gears 240, multiple second planetary gears 220, and multiple first planetary gears 130 are staggered in the circumferential direction C. Furthermore, although not shown, the two ends of each third planetary gear pin 245 supporting each third planetary gear 240 are fixed to the intermediate plate 306 and the second end plate 304 of the planet carrier 300, respectively.

[0057] Furthermore, each third planetary gear 240 has a third gear portion 241 and a fourth gear portion 242. Each third gear portion 241 meshes with each second planetary gear 220, and therefore, each third gear portion 241 and each second planetary gear 220 are spur gears. Each fourth gear portion 242 meshes with each third sun gear 230, and therefore, each fourth gear portion 242 and each third sun gear 230 are helical gears, and the helix directions of each fourth gear portion 242 and the third sun gear 230 are opposite, while the helix angles are equal. Although not shown in the figure, thrust needle roller bearings or thrust sliding bearings are respectively installed between the two end faces of each third planetary gear 240 and the planet carrier 300, and more specifically between the two end faces of each third planetary gear 240 and the intermediate plate 306 and the second end plate 304, to withstand the axial force acting on each third planetary gear 240.

[0058] As previously described, the power input from the input shaft 111 drives the planet carrier 300 to rotate. Driven by the planet carrier 300, multiple second planet gears 220 rotate on their own axes around the second planet gear pins 225 and revolve around the second sun gear 210, thereby causing the second sun gear 210 to rotate around its own axis. Additionally, driven by the planet carrier 300, multiple third planet gears 240 rotate on their own axes around the third planet gear pins 245 and revolve around the third sun gear 230, thereby causing the third sun gear 230 to rotate around its own axis.

[0059] In a coaxial reducer 1 according to an embodiment of this application, by setting the third sun gear 230 as a helical gear, the axial force acting on the planet carrier 300 can be generated by the third sun gear 230 and the third planet gear 240 meshing with it. Moreover, by making the helix directions of the first gear portion 131, the second gear portion 132, and the third sun gear 230 the same, the axial force generated on the differential 200 side is balanced with the axial force generated on the reduction planetary gear set 100 side, and the axial force acting on the planet carrier of the entire gear system is zero. Therefore, by adopting the coaxial reducer 1 according to an embodiment of this application, it is not necessary for the helix angles of the first gear portion 131 and the second gear portion 132 of the first planet gear 130 to satisfy the above-mentioned relationship (1). As a result, the design freedom of the helix angles of the first gear portion 131 and the second gear portion 132 of the first planet gear 130, especially the second gear portion 132, is increased, and a coaxial reducer that can control costs and is beneficial to improving NVH performance, durability, and transmission efficiency can be provided.

[0060] The inventors of this application have further discovered that by making the helix angles of the first gear section 131, the second gear section 132, and the third sun gear 230 satisfy the following relationship (2), the axial force acting on the planet carrier of the entire gear system can be zero.

[0061] Relation (2):

[0062]

[0063] Where, β P11 It is the helix angle β of the first gear section 131. P12 It is the helix angle β of the second gear section 132. S3 It is the helix angle of the third sun gear at 230 degrees, Z. S1 It is the number of teeth on the first sun gear, Z. R It is the number of teeth on the internal gear ring 120, Z. P11 Z is the number of teeth in the first gear section 131. P12 It is the number of teeth in the second gear section 132, Z S3 It is the number of teeth on the third sun gear, 230, m. nS1 It is the normal module of the first sun gear 110, m nP12 It is the normal module of the second gear section 132, m nS3 It is the normal module of the third sun wheel 230.

[0064] As mentioned above, under the condition that relation (1) is satisfied, the helix angle β of the second gear is P12 It will be very small, usually 12~15°. However, according to an embodiment of the coaxial reducer 1 of this application, when the above relationship (2) is satisfied, the helix angle of the second gear part 132 can be set to an angle greater than 15°, for example, 30°.

[0065] According to an embodiment of the coaxial reducer 1 of this application, by setting the helix angle of the second gear section 132 to a larger helix angle, it is not necessary to increase the tooth width of the second gear section 132 to ensure the contact ratio, thereby eliminating the problems of deterioration of NVH performance and durability, increased cost and reduced transmission efficiency caused by increasing the tooth width.

[0066] Furthermore, by setting the third sun gear 230 as a helical gear, the same load capacity can be achieved with a smaller tooth width compared to the spur gear scheme.

[0067] Therefore, the coaxial reducer 1 according to an embodiment of this application can have a lighter weight, a more compact axial space, and a more competitive cost due to its smaller size.

[0068] The specific technical solutions of this application have been described in detail above. However, this application is not limited to the above technical solutions, and various modifications that can be conceived by those skilled in the art are of course included within the scope of this application. Examples are given below.

[0069] I. In one embodiment of the coaxial reducer of this application, a structure in which the second sun gear 210 is a spur gear has been described as an example, but it is not limited thereto. Figure 5 As shown in the coaxial reducer of a modified example of this application, the second sun gear 210A can also be configured as a helical gear. In this case, the second planet gear 220A meshing with the second sun gear 210A and the third gear portion 241A of the third planet gear 240A meshing with the second planet gear 220A are also configured as helical gears. The helical direction of the second sun gear 210A can be the same as or opposite to that of the third sun gear 230.

[0070] II. In one embodiment of the coaxial reducer of this application, the structure in which each third planetary gear 240 has a third gear portion 241 and a fourth gear portion 242 is described as an example, but it is not limited to this. It can also be configured as follows: each third planetary gear 240 has only a fourth gear portion 242, and each fourth gear portion 242 meshes with the third sun gear 230.

Claims

1. A coaxial reducer, characterized in that, It includes a reduction planetary gear set, a differential, and a planet carrier, wherein the reduction planetary gear set and the differential are both mounted on the planet carrier. The reduction planetary gear set includes: a first sun gear mounted inside the planet carrier; an internal gear ring sleeved on the outside of the planet carrier; and a plurality of first planet gears respectively disposed around the first sun gear and mounted on the planet carrier by means of a plurality of first planet pins. Each first planet gear has a first gear portion and a second gear portion with a pitch circle diameter smaller than that of the first gear portion. The first gear portion meshes with the first sun gear, and the second gear portion meshes with the internal gear ring. The differential includes: a second sun gear mounted within the planet carrier with its axis aligned with the axis of the first sun gear; a plurality of second planet gears respectively disposed around the second sun gear and mounted on the planet carrier via a plurality of second planetary pins, each meshing with the second sun gear; a third sun gear mounted within the planet carrier with its axis aligned with the axis of the first sun gear; and a plurality of third planet gears respectively disposed around the third sun gear and mounted on the planet carrier via a plurality of third planetary pins, each meshing with the third sun gear. The first gear section, the second gear section, and the third sun gear are all helical gears, and their helical directions are the same.

2. The coaxial reducer according to claim 1, characterized in that, The helix angles of the first gear section, the second gear section, and the third sun gear satisfy the following relationship: Where, β P11 It is the helix angle of the first gear, β P12 It is the helix angle of the second gear, β S3 Z is the helix angle of the third sun gear. S1 Z is the number of teeth on the first sun gear. R Z is the number of teeth on the internal gear ring. P11 Z is the number of teeth in the first gear section. P12 Z is the number of teeth in the second gear section. S3 The number of teeth on the third sun gear is m. nS1 It is the normal module of the first sun gear, m nP12 It is the normal module of the second gear section, m nS3 It is the normal module of the third sun gear.

3. The coaxial reducer according to claim 1, characterized in that, The input shaft connected to the first sun gear, the first output shaft connected to the second sun gear, and the second output shaft connected to the third sun gear are rotatably supported on the housing by bearings. The first output shaft extends outward from the interior of the hollow input shaft to the planetary carrier, and the input shaft, the first output shaft, and the second output shaft extend outward from the planetary carrier in opposite directions.

4. The coaxial reducer according to claim 1, characterized in that, The helix angle of the second gear is greater than 15°.

5. The coaxial reducer according to claim 1, characterized in that, Each of the plurality of third planetary gears has a third gear portion and a fourth gear portion. Each third gear portion meshes with each of the plurality of second planetary gears, and each fourth gear portion meshes with the third sun gear.

6. The coaxial reducer according to claim 5, characterized in that, Thrust needle roller bearings or thrust sliding bearings are respectively installed between the two end faces of each of the third planetary gears and the planet carrier.

7. The coaxial reducer according to claim 1, characterized in that, The second sun gear is either a spur gear or a helical gear.

8. The coaxial reducer according to claim 1, characterized in that, Thrust needle roller bearings or thrust sliding bearings are respectively installed between the two end faces of each of the first planetary gears and the planet carrier.

9. The coaxial reducer according to claim 1, characterized in that, The planetary carrier is rotatably supported to the outer shell using angular contact ball bearings.

10. The coaxial reducer according to any one of claims 1 to 9, characterized in that, The power input from the first sun gear is transmitted to the planet carrier via the plurality of first planet gears, then to the second sun gear via the plurality of second planet gears, and simultaneously to the third sun gear via the plurality of third planet gears.

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