JP2010014177A - Eccentric rocking type gear transmission device - Google Patents

Abstract

A transmission device capable of fixing a motor to a gear that does not rotate eccentrically among an external gear and an internal gear.
A transmission device includes an internal gear, an external gear that meshes with the internal gear, and a carrier that supports the external gear. A crankshaft 14 and a subshaft 38 are supported on the carrier 12. An eccentric body 20 that engages with the external gear 8 and rotates eccentrically is fixed to the crankshaft 14. The torque of the motor is transmitted from the pinion 24 to the crankshaft 14 via the second ring gear 28 and the sub shaft 38, and the external gear 8 is eccentrically rotated. As the carrier 12 rotates, the sub shaft 38 moves around the axis CL. Even if the sub shaft 38 moves relative to the pinion 24 that transmits torque, the engagement of the pinion 24 and the sub shaft 38 is maintained via the second ring gear 28. Therefore, the transmission device 100 can fix the motor to the internal gear 6.
[Selection] Figure 1

Description

  The present invention relates to an eccentric oscillating gear transmission in which one of an internal gear and an external gear meshed with the internal gear rotates eccentrically with respect to the other.

  There is known an eccentric oscillating gear transmission that achieves a predetermined speed ratio by either one of an internal gear and an external gear meshing with the internal gear rotating eccentrically with respect to the other. The present specification mainly describes a gear transmission in which an external gear rotates eccentrically. Hereinafter, for the sake of simplicity, the “eccentric oscillating gear transmission” may be referred to as “eccentric oscillating transmission” and more simply “transmission”.

  In the type of transmission device in which the external gear rotates eccentrically, the external gear that rotates eccentrically is supported by the carrier so that it can rotate eccentrically. The carrier is rotatably supported coaxially on the internal gear. In this transmission device, when the internal gear is fixed to another device, the carrier corresponds to an “output shaft”. When the carrier is fixed to another device, the internal gear corresponds to the “output shaft”. For example, when the transmission device is applied to a robot joint, when the internal gear is fixed to the base arm of the robot, the carrier is fixed to the tip arm as an output shaft. Alternatively, the carrier may be fixed to the base arm of the robot, and in this case, the internal gear is fixed to the distal arm as an output shaft. Which of the internal gear and the carrier is fixed to another device depends on the use of the transmission device. In the transmission device of the type in which the internal gear rotates eccentrically, the internal gear is supported by the carrier so that it can rotate eccentrically, and the carrier is supported by the external gear so that it can rotate coaxially. In a transmission device in which the internal gear rotates eccentrically, one of the carrier and the external gear is fixed to the other device, and the other corresponds to the “output shaft”.

  For example, Patent Document 1 discloses a transmission device in which an external gear rotates eccentrically. The transmission device includes a sub-shaft (referred to as “input shaft” in Patent Document 1) having an input gear that engages with a pinion of a motor and receives a driving force from the pinion, and an input formed on the sub-shaft. A plurality of crankshafts (referred to as "eccentric body shafts" in Patent Document 1) having a shaft gear and an eccentric body for eccentricizing the external gear, and at least one of the plurality of crankshafts, An eccentric body shaft gear for receiving power from the crankshaft, a transmission gear for transmitting the rotation of the input shaft gear to the eccentric body shaft gear, and a carrier are provided. The subshaft and the plurality of crankshafts are rotatably supported by the carrier. A motor that applies torque to the transmission is fixed to a motor mounting body fixed to the carrier.

JP 2007-278355 A

In a normal gear transmission, the motor is fixed to another device, so that the motor is disposed immovably with respect to the housing of the transmission. In short, the motor is fixed to the transmission housing (including the case where the motor is fixed via another member).
On the other hand, in the case of an eccentric oscillating transmission device, the internal gear may be fixed to another device or the carrier may be fixed to another device depending on the application. That is, in this type of transmission, both the internal gear and the carrier can be a “housing” or an “output shaft”. Therefore, in this type of transmission, the motor may be preferably fixed to the internal gear, or may be preferably fixed to the carrier. However, in the transmission device disclosed in Patent Document 1, since the sub shaft engaged with the pinion of the motor moves around the carrier axis as the carrier rotates, the motor is fixed to the internal gear. The position of the pinion and the sub shaft changes. That is, the transmission device of Patent Document 1 cannot fix the motor to the internal gear.
This specification discloses the transmission which can fix a motor to the gear which does not rotate eccentrically among an external gear and an internal gear.

  A transmission gear disclosed in the present specification is a ring gear that meshes with a gear of a sub shaft so that the torque of the motor can be transmitted even if the sub shaft moves around the axis of the carrier as the carrier rotates. Is introduced. The torque of the motor is transmitted to this ring gear. In this transmission, the torque of the motor is transmitted to the sub-shaft via the ring gear while the sub-shaft moves around the carrier axis. Even if the positional relationship between the motor and the sub shaft changes as the carrier rotates, the engagement between the motor and the sub shaft is maintained through the ring gear. Therefore, this transmission can fix the motor to the internal gear.

  The invention disclosed in this specification can be embodied in an eccentric oscillation gear transmission in which either an internal gear or an external gear meshing with the internal gear rotates eccentrically with respect to the other. The transmission includes a carrier, a plurality of crankshafts, a first ring gear, a second ring gear, and at least one subshaft. The carrier is rotatably supported coaxially on the other of the internal gear and the external gear (that is, a gear that does not rotate eccentrically). A plurality of crankshafts are rotatably supported on the carrier. An eccentric body and an input gear that are engaged with one of an internal gear and an external gear and eccentrically rotate are fixed to each of the plurality of crankshafts. That is, the carrier supports one of the internal gear and the external gear (that is, the gear that rotates eccentrically) via the crankshaft so that it can rotate eccentrically. The first ring gear meshes with the input gears of the plurality of crankshafts. The second ring gear is arranged coaxially with the first ring gear and meshes with a pinion gear that transmits the torque of the motor. A first intermediate gear meshing with the first ring gear and a second intermediate gear meshing with the second ring gear are fixed to the sub shaft. Hereinafter, a transmission device in which the external gear rotates eccentrically will be described, but the present invention is also applicable to a transmission device in which the internal gear rotates eccentrically.

  According to the above transmission device, the torque of the motor is transmitted from the pinion gear to the second ring gear. Further, the torque of the motor is transmitted from the second ring gear to the crankshaft through the sub shaft and the first ring gear, and eccentrically rotates the external gear. As the carrier rotates, the sub-shaft transmits the motor torque from the second ring gear to the crankshaft while moving around the carrier axis. That is, even if the sub shaft moves relative to the pinion gear that transmits the torque of the motor, the engagement between the pinion gear and the sub shaft is maintained via the second ring gear. That is, this transmission device can fix the motor to the internal gear.

  In this transmission, the first ring gear is preferably an internal ring gear having teeth formed on the inner peripheral surface, and the second ring gear is preferably an external ring gear having teeth formed on the outer peripheral surface. . When the center through hole is provided in the carrier, the second ring gear can be supported on the carrier by the bearing even if the center through hole is made as large as possible. The torque of the motor can be evenly transmitted from the second ring gear to the plurality of crankshafts.

  On the other hand, in this transmission, the first ring gear is an external ring gear with teeth formed on the outer peripheral surface, and the second ring gear is an internal ring gear with teeth formed on the inner peripheral surface. Is also preferable. In this case, even if the center through hole of the carrier is made as large as possible, the second ring gear can be supported by the carrier with the bearing, and the torque of the motor is evenly transmitted from the second ring gear to the plurality of crankshafts. can do.

  The transmission device preferably includes the same number of subshafts as the crankshaft. The torque of the motor is transmitted from the plurality of sub shafts to the plurality of crank shafts. The plurality of crankshafts receive torque equally from the plurality of subshafts. Therefore, this transmission can transmit torque evenly to the crankshaft, and as a result, the external gear can be smoothly eccentrically rotated.

  According to the technique of the present specification, an eccentric oscillating gear transmission capable of fixing a motor to a gear that does not rotate eccentrically among an external gear and an internal gear can be realized.

Below, the characteristic of the ring gear of an Example is described.
(1) The second intermediate gear of the sub-shaft 38 for transmitting the torque from the pinion gear 24 to the crankshaft 14 while the pinion gear 24 to which the motor torque is input meshes with the second ring gear 28 (228). 40 meshes with the second ring gear 28 (228). With such a configuration, the sub shaft 38 can move around the carrier axis CL while maintaining the engagement between the pinion gear 24 and the sub shaft 38. That is, the motor can be fixed to the internal gear 6 (case 2).
(2) The first ring gear 42 (242) is disposed between the pair of bearings 16 that support the crankshaft 14, and the second ring gear 28 (228) is disposed at the end of the crankshaft 14. Yes. With such a configuration, the central through hole 50 is provided in the shaft center of the transmission device 100 (200), the motor is disposed on the outer side in the axial direction of the crankshaft 14, and the motor torque is smoothly transmitted to the crankshaft 14. can do.
(3) A plurality of sub shafts 38 are rotatably supported by the carrier 12 (212). A plurality of sub-shafts 38 and a plurality of crankshafts 14 are alternately arranged at equal intervals around the axis CL of the carrier 12 (212).

(First embodiment)
With reference to FIGS. 1-3, the transmission apparatus 100 (eccentric oscillation type gear transmission) of 1st Example is demonstrated. FIG. 1 is a cross-sectional view of the transmission device 100 in a plane including the axis CL. FIG. 2 is a cross-sectional view of the transmission device 100 when viewed along line II-II in FIG. FIG. 3 is a plan view of the transmission device 100 when viewed from the right side of FIG. 1. 1 is a cross-sectional view taken along line I-I in FIG.

  The gear transmission 100 includes a case 2 in which a plurality of internal teeth pins 4 are arranged on the inner periphery, a carrier 12, and two external gears 8. The plurality of internal teeth pins 4 are arranged along the inner periphery of the case 2 with the axis of the pins parallel to the axis CL of the transmission device 100. The case 2 and the plurality of internal teeth pins 4 constitute an internal gear 6. Each of the two external gears 8 meshes with the internal gear 6. The number of teeth of the internal gear 6 (the number of internal teeth pins 4) and the number of teeth of the external gear 8 are slightly different.

  The carrier 12 is rotatably supported by the case 2 via a pair of angular ball bearings 10. The carrier 12 is disposed coaxially with the internal gear 6, and its axis coincides with the axis CL of the transmission device 100. The carrier 12 supports the three crankshafts 14 and the three subshafts 38 in a rotatable manner. Each crankshaft 14 is disposed parallel to the axis CL, and is supported by the carrier 12 via a pair of tapered roller bearings 16. Each of the sub shafts 38 is disposed in parallel with the axis CL, and is supported by the carrier 12 via a pair of deep groove ball bearings 32. The three crankshafts 14 and the three subshafts 38 are alternately arranged at equal intervals around the axis CL of the transmission device 100. The carrier 12 is provided with a central through hole 50 penetrating in the axial direction at the axial center thereof.

  In FIG. 2, the symbol D <b> 1 indicates the diameter of a circle formed by connecting the axis of each sub shaft 38 around the axis CL of the transmission device 100. Hereinafter, the diameter D1 may be referred to as PCD (Pitch Circle Diameter) of the sub shaft 38. Reference numeral D <b> 2 indicates the diameter of a circle formed by connecting the axis of each crankshaft 14 around the axis line CL of the transmission device 100. Hereinafter, the diameter D2 may be referred to as PCD of the crankshaft 14. The PCD (D1) of the sub shaft 38 is larger than the PCD (D2) of the crankshaft 14.

  Two eccentric bodies 20 and one input gear 22 are fixed to each crankshaft 14. Each of the two eccentric bodies 20 is engaged with a hole provided in each of the two external gears 8 via a needle roller bearing 18. In addition, illustration of the needle roller bearing 18 is abbreviate | omitted in FIG. The two external gears 8 rotate eccentrically around the axis CL while meshing with the internal gear 6 as the crankshaft 14 rotates.

  A first intermediate gear 34 and a second intermediate gear 40 are fixed to each sub shaft 38. The first intermediate gear 34 meshes with a first ring gear 42 described later, and the second intermediate gear 40 meshes with a second ring gear 28 described later.

As shown in FIG. 2, the first ring gear 42 is disposed so as to surround the three input gears 22 and the three first intermediate gears 34. The first ring gear 42 is an internal gear ring gear in which spur teeth are formed on the inner periphery. The first ring gear 42 is disposed coaxially with the axis CL of the transmission device 100. The first ring gear 42 meshes with the three input gears 22 and the three first intermediate gears 34.
The first ring gear 42 is not supported via a bearing. This is based on the following two reasons. The first ring gear 42 is sandwiched between the two external gears 8, and therefore its movement in the axial direction is restricted. Further, the first ring gear 42 meshes with the three input gears 22 and the three first intermediate gears 34 arranged at equal intervals around the axis line CL of the transmission device 100, and thereby, in the radial direction thereof. Movement is restricted.

  As shown in FIG. 3, the second ring gear 28 is disposed so as to be inscribed in the three second intermediate gears 40. The second ring gear 28 is an externally toothed ring gear having spur teeth formed on the outer periphery. The second ring gear 28 is rotatably supported near the end portion of the carrier 12 via the ball bearing 30. The second ring gear 28 is also arranged coaxially with the axis CL of the transmission device 100. That is, the second ring gear 28 and the first ring gear 42 described above are arranged coaxially. The second ring gear 28 meshes with the three second intermediate gears 40 and the pinion gear 24 fixed to the output shaft 26 of a motor (not shown) 60.

The operation of the transmission device 100 will be described. The torque of the motor is transmitted to the second ring gear 28 via the pinion gear 24. Torque is transmitted from the second ring gear 28 to the three sub shafts 38 via the second intermediate gear 40. Further, torque is transmitted from the sub shaft 38 to the first ring gear 42 via the first intermediate gear 34. Torque is transmitted from the first ring gear 42 to the three crankshafts 14 via the input gear 22. When the three crankshafts 14 rotate, the eccentric gear 20 causes the external gear 8 to rotate eccentrically around the axis CL while meshing with the internal gear 6. The number of teeth of the external gear 8 and the number of teeth of the internal gear 6 are slightly different, and when the eccentric body 20 makes one rotation, that is, when the external gear 8 moves around the axis CL once, the external gear. The carrier 12 rotates by an angle corresponding to a difference in the number of teeth between the internal gear 6 and the internal gear 6. One rotation of the crankshaft 14 is decelerated to an angle corresponding to the difference in the number of teeth between the external gear 8 and the internal gear 6.
Further, in the transmission device 100, the PCD (D 1) of the sub shaft 38 is larger than the PCD (D 2) of the crankshaft 14, and therefore, between the first intermediate gear 34 and the input gear 22 via the first ring gear 42. The rotational speed is reduced. In this way, the transmission device 100 can achieve a high reduction ratio.
When the case 2 is fixed to another device (for example, the base side arm of the robot), the carrier 12 corresponds to the output shaft. In this case, a member to be rotated (for example, an arm on the front end side of the robot) is fixed to the carrier 12. Conversely, when the carrier 12 is fixed to another device, the case 2 corresponds to the output shaft, and a member to be rotated is fixed to the case 2.

The advantages of the transmission device 100 will be described. As described above, the carrier 12 rotates relative to the case 2 (that is, the internal gear 6). That is, as the carrier 12 rotates, the three sub shafts 38 supported by the carrier 12 move around the axis CL. The second intermediate gear 40 of the sub shaft 38 moves around the second ring gear 28 while rotating. Since the torque of the motor 60 is transmitted from the pinion gear 24 to the sub shaft 38 via the second ring gear 28, the positional relationship between the sub shaft 38 and the pinion gear 24 is allowed to change. That is, the transmission device 100 can fix the motor to the case 2.
In the transmission device 100, the pinion gear 24 and the second intermediate gear 40 mesh with the second ring gear 28 at different positions in the axial direction. Therefore, even if the second intermediate gear 40 moves around the axis CL, that is, even if the positional relationship between the pinion gear 24 and the second intermediate gear 40 changes, they do not interfere with each other.

  The transmission device 100 can also fix the motor to the carrier 12. FIG. 4 shows the transmission device 100 in which the motor 60 is attached to the carrier 12. The cross section of the transmission device 100 in FIG. 4 is the same as the cross section of FIG. Therefore, illustration of some codes is omitted. Reference numeral 62 in the drawing represents a driven member that the transmission device 100 drives. The driven member 62 is, for example, a robot arm. The driven member 62 is fixed to the carrier 12. The motor 60 is fixed to the carrier 12 via a driven member 62. Thus, the transmission device 100 can be applied to both fixing the motor to the internal gear 6 (case 2) and fixing to the carrier 12 without changing the arrangement of the gears.

  Another advantage of the transmission device 100 will be described. The transmission device 100 includes the first and second ring gears 42 and 28, so that the motor can be disposed at a position offset in the radial direction from the axis of the carrier 12. Thus, the transmission device 100 can be provided with a large central through hole 50 in the axis of the carrier 12 without being obstructed by the motor. The axis of the carrier 12 corresponds to the axis CL of the transmission device 100. The first ring gear 42 is disposed between the pair of tapered roller bearings 16 that support the crankshaft 14, and the second ring gear 28 is disposed at the end of the crankshaft 14. By providing the first and second ring gears 42 and 28 arranged in such a manner, the transmission 100 can arrange the motor axially outside the end of the crankshaft 14 and at the same time, Torque can be transmitted to the crankshaft 14 from between the pair of tapered roller bearings 16. Since torque can be transmitted to the crankshaft 14 from between the pair of tapered roller bearings 16, the crankshaft 14 can be smoothly rotated without receiving a biased load. Thereby, transmission loss can be suppressed. The transmission device 100 can provide the center through hole 50 in the carrier 12 without being obstructed by the motor, and can suppress torque transmission loss.

  In addition, the transmission device 100 employs an internal ring gear as the first ring gear 42 and employs an external ring gear as the second ring gear 28. By combining the internal ring gear and the external ring gear in this way, the deep groove ball bearing 30 that supports the second ring gear 28 can be mounted on the carrier 12 even if the center through hole 50 of the carrier 12 is made as large as possible. It is possible to secure a space to be arranged in Since the second ring gear 28 can be supported by the bearing, the torque of the motor can be evenly transmitted from the second ring gear 28 to the plurality of crankshafts 14.

  Furthermore, torque is transmitted from the plurality of sub-shafts 38 to the plurality of crankshafts 14 via the first ring gear 42, so that torque is evenly transmitted to each crankshaft (that is, transmission loss is suppressed). To contribute).

Other characteristics of the transmission device 100 are listed.
The two external gears 8 have through-holes formed in the shaft center, and cylindrical members 52 having both ends connected to the carrier 12 are disposed in the through-holes. An oil seal 54 is disposed between the case 2 and the carrier 12. A seal cap 56 is disposed in a hole in the carrier 12 for inserting the crankshaft 14. The cylindrical member 52, the oil seal 54, and the seal cap 56 seal the lubricant inside the case 2.
The two eccentric bodies 20 fixed to each of the crankshafts 14 eccentrically rotate with a phase difference of 180 degrees. That is, the two external gears 8 are eccentrically rotated with a phase difference of 180 degrees. The two external gears 8 are in contact with the inner periphery of the internal gear 6 with a phase difference of 180 degrees. As a result, a good balance of forces acting between the internal gear 6 and the carrier 12 is maintained.

(Second embodiment)
With reference to FIGS. 5-7, the transmission apparatus 200 (eccentric oscillation type gear transmission) of 2nd Example is demonstrated. FIG. 5 is a sectional view in a plane including the axis CL of the transmission device 200. 6 is a cross-sectional view of the transmission device 200 when viewed along the line VI-VI in FIG. FIG. 7 is a plan view of the transmission device 200 as viewed from the right side of FIG. FIG. 5 is a cross-sectional view taken along line VV in FIG.
5-7, the same code | symbol is attached | subjected to the same components as the power transmission apparatus 100 shown in FIGS. 1-3. The parts different from the transmission device 100 are denoted by three-digit symbols. The description of the same components as the transmission device 100 is omitted. The last two digits of the three-digit code indicate corresponding parts in the transmission device 100.

  In the transmission device 200, the carrier 212, the first ring gear 242, the second ring gear 228, and the deep groove ball bearing 230 are different from the components of the transmission device 100. The carrier 212 is different from the transmission device 100 in the position at which the second ring gear 228 is supported. The ball bearing 230 is different from the transmission device 100 in the mounting position on the carrier 212.

The first ring gear 42 of the first embodiment is an internal ring gear having a flat tooth formed on the inner peripheral surface, whereas the first ring gear 242 of the second embodiment is a flat tooth on the outer peripheral surface. Is a ring gear with external teeth formed. That is, the first ring gear 242 is disposed so as to be inscribed in the three input gears 22 and the three first intermediate gears 34. The first ring gear 242 meshes with the three input gears 22 and the three first intermediate gears 34.
The second ring gear 28 of the first embodiment is an external ring gear with spur teeth formed on the outer peripheral surface, whereas the second ring gear 228 of the second embodiment is spur teeth on the inner peripheral surface. Is a ring gear of an internal tooth formed. That is, the second ring gear 228 is disposed so as to surround the three second intermediate gears 40 and the pinion gear 24 and meshes with these gears.
Similarly to the first embodiment, the second ring gear can be obtained by combining the outer ring first ring gear 242 and the inner ring second ring gear 228 even if the center through hole 50 of the carrier 12 is made as large as possible. A space for arranging the deep groove ball bearing 30 supporting 228 in the carrier 12 can be secured. Since the second ring gear 28 can be supported by the bearing, the torque of the motor can be evenly transmitted from the second ring gear 28 to the plurality of crankshafts 14.

Further, in the transmission device 100 of the first embodiment, the PCD (D1) of the sub-shaft 38 is larger than the PCD (D2) of the crankshaft 14, whereas in the transmission device 200 of the second embodiment, the sub-shaft 38 The PCD (D3) of the shaft 38 is smaller than the PCD (D4) of the crankshaft 14. If each shaft is arranged in this manner, the rotational speed is reliably reduced between the first intermediate gear 34 and the input gear 22 via the first ring gear 242.
In addition, the operations and functions of the first and second ring gears 242 and 228 are the same as those of the first and second ring gears 42 and 28 of the first embodiment.

  Specific examples of the present invention have been described in detail above, but these are merely examples and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes of the specific examples illustrated above.

The transmission device 100 (200) of the embodiment is a type in which the external gear 8 rotates eccentrically. The present invention can also be applied to a transmission device in which the internal gear is eccentrically oscillated.
The transmission device 100 (200) of the embodiment preferably includes a plurality of sub-shafts 38. However, if transmission device 100 (200) includes at least one sub-shaft, the motor can be fixed to a gear that does not rotate eccentrically among the internal gear and the external gear.
Further, the first ring gear 42 of the first embodiment and the second ring gear 228 of the second embodiment may be combined. Similarly, the second ring gear 28 of the first embodiment and the first ring gear 242 of the second embodiment may be combined.

  The technical elements described in this specification or the drawings exhibit technical usefulness alone or in various combinations, and are not limited to the combinations described in the claims at the time of filing. In addition, the technology exemplified in this specification or the drawings achieves a plurality of objects at the same time, and has technical utility by achieving one of the objects.

Sectional drawing of the transmission of 1st Example is shown. Sectional drawing along the II-II line | wire of FIG. 1 is shown. The top view of a transmission device when it sees from the right side of FIG. 1 is shown. Sectional drawing of the transmission which fixed the motor to the carrier is shown. Sectional drawing of the transmission of 2nd Example is shown. Sectional drawing along the VI-VI line of FIG. 5 is shown. The top view of a transmission device when it sees from the right side of FIG. 5 is shown.

Explanation of symbols

2: Case 4: Internal tooth pin 6: Internal gear 8: External gear 12: Carrier 14: Crankshaft 20: Eccentric body 22: Input gear 24: Pinion gear 28, 228: Second ring gear 34: First intermediate Gear 38: Subshaft 40: Second intermediate gear 42, 242: First ring gear 60: Motor 100, 200: Transmission

Claims (4)

An eccentric oscillating gear transmission in which any one of an internal gear and an external gear meshing with the internal gear rotates eccentrically with respect to the other,
A carrier rotatably supported coaxially on the other of the internal gear and the external gear;
An eccentric body that engages with one of the internal gear and the external gear and the input gear is fixed, and a plurality of crankshafts that are rotatably supported by the carrier,
A first ring gear meshing with input gears of a plurality of crankshafts;
A second ring gear disposed coaxially with the first ring gear and meshing with a pinion gear that transmits torque of the motor;
At least one sub-shaft to which a first intermediate gear meshing with the first ring gear and a second intermediate gear meshing with the second ring gear are fixed;
An eccentric oscillating gear transmission characterized by comprising:   2. The ring gear according to claim 1, wherein the first ring gear is a ring gear having inner teeth formed on an inner peripheral surface, and the second ring gear is a ring gear having outer teeth formed on an outer peripheral surface. Gear transmission.   The first ring gear is a ring gear having outer teeth formed on an outer peripheral surface, and the second ring gear is a ring gear having inner teeth formed on an inner peripheral surface. Gear transmission.   The gear transmission according to any one of claims 1 to 3, comprising the same number of sub-shafts as the crankshaft.

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