JP2017177233A - Joint driving device and multi-axial manipulator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a joint driving device and a multi-axial manipulator capable of reducing weights of joints without compromising a loadable weight, as well as reducing a weight of the whole device.SOLUTION: A joint driving device for driving joints connecting adjacent link members with each other, drives a link member to be driven using a driving power provided to a drive shaft disposed in a root-side link member, and comprises: a drive power transmission drive means for transmitting the drive power to a succeeding joint; and a switch means for switching between a drive and a stop of the link member to be driven by the drive power transmission drive means. The drive power transmission drive means is constituted of a differential gear mechanism.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a joint drive device and a multi-axis manipulator suitable for being applied to a robot that performs predetermined work in a factory or the like.

  Multi-axis manipulators are classified into two types depending on the driving method. One is a multi-axis manipulator in which one actuator (motor, power cylinder, etc.) is arranged at each joint. According to such a multi-axis manipulator, it is possible to perform fine position control quickly with high output. For example, a 3-axis manipulator typified by a scalar robot in the industrial field and a 6-axis industrial robot correspond to this. When mass production, high-precision machining, high-precision assembly, etc. are performed in a factory, It's being used. The other is that a slim transmission has been achieved by allocating power transmission parts such as wires and pneumatic tubes to each joint in an antagonistic manner, moving them to the manipulator base, and moving the motor to the base of the manipulator. An axis manipulator. This multi-axis manipulator is considered to be effective because the joints can be made compact and high output can be obtained when arranging multi-joints such as hands at a short pitch. For example, in medical use, a small manipulator is inserted into a patient and is used as an instrument for performing surgery.

  In recent years, the use of multi-axis manipulators has increased in human society, such as the development of assist-type manipulators that are worn by humans and assist humans in bending their joints. In addition, in the mechatronics industry other than manipulators, there are companies that organize more than 10,000 transport robots moving around in warehouses. This robot has a mechanism that, when transported, enters under a shelf containing goods and conveys it by lifting the shelf.

  Patent Document 1 discloses a robot joint unit and a robot that are small and lightweight and can improve the output torque of a joint. In the joint unit described in Patent Document 1, in a joint that uses two motors to achieve two-degree-of-freedom driving, the motor is arranged inside the gear corresponding to the internal gear and the sun gear of the differential gear mechanism. It has the function of differentially controlling the revolution and rotation of planetary gears. When two motors are rotated, the torque extracted from the planet carrier is the sum of the torques output from the two motors, so it is very powerful.

Japanese Patent No. 5327312 JP 2011-218500 A

Shigeo Hirose, “Wire Interference Driven Articulated Manipulator”, Journal of the Society of Instrument and Control Engineers, Vol. 26, no. 11 Arai Hirohiko, “Controllability of non-holonomic three-degree-of-freedom manipulators with non-driven joints”, Journal of the Robotics Society of Japan, 1996 No. 5, Vol. 14

  However, since the conventional multi-axis manipulators described above, such as scalar robots and 6-axis industrial robots, have motors attached to the joints, the weights of the motors must be supported by the joints. Since the total manipulator weight is applied to the joint portion, the possible load weight decreases as the number of joints increases.

  Non-Patent Document 1 discloses a mechanism that drives a motor installed in a base portion through a pulley and a wire that is antagonistically arranged around the pulley in order to solve the problem of restriction of the possible load weight of the manipulator. Has been. However, in this case, the wire length of the joints after the second joint has a problem that the path length changes depending on the rotation angle of the root side joint. Even if this change in path length is canceled using a path length compensation unit such as that described in Patent Document 2, the number of motors in the wire drive manipulator is the same as the number of joints. As the number of units to be adjusted increases, the overall weight increases, and it is considered that the loadable weight of the transfer robot equipped with the manipulator is pressed.

  Furthermore, Non-Patent Document 2 discloses a manipulator that controls the joint angle with a single motor. This manipulator is designed to bend the joint using the inertial force generated during rotation by opening the brake unit attached to each joint between the base and the tip when driving the motor attached to the base joint. It is. When the joint reaches the target angle due to the inertial force, the brake unit is placed in a restrained state, the joint is bent, and the entire manipulator is controlled by performing this operation a plurality of times. Such a mechanism uses sliding of an object due to inertial force and tries to obtain driving force with inertial force. Therefore, a running section to increase the inertial force is necessary, and the joint in a narrow space accompanying it is necessary. However, it has a light and simple structure, but its functions and behavioral conditions are limited. Also, increasing inertia (mass) to increase joint torque creates a dilemma with the goal of weight reduction.

The present invention solves the above-mentioned problems of the prior art, and its purpose is as follows:
It is an object of the present invention to provide a joint driving device and a multi-axis manipulator that can reduce the weight of the joint portion, press the possible load weight, and reduce the weight of the entire device.

  Another object of the present invention is to provide a joint drive device and a multi-axis manipulator capable of maintaining a high rotational torque and performing fine posture control even when the number of drive motors is reduced.

  According to the present invention, the joint drive device that drives the joint portion that connects adjacent link members drives the driven link member with the drive force supplied to the drive shaft provided in the root side link member, and the drive force Driving force transmission driving means for transmitting the power to the next joint, and switching means for switching between driving and stopping of the driven link member by the driving force transmission driving means. The driving force transmission driving means is composed of a differential gear mechanism.

  The driving force transmission driving means for driving the driven link member with the driving force supplied to the driving shaft provided on the root side link member and transmitting this driving force to the next joint portion is composed of a differential gear mechanism. As a result, the weight of the joint portion can be reduced, the possible load weight can be reduced, and the weight of the entire apparatus can be reduced. Even when the number of drive motors is reduced, high rotational torque is maintained and fine attitude control is possible.

  The driving force transmission driving means includes a planetary gear including a sun gear located at the center, a planetary gear arranged in mesh with the sun gear, a planet carrier on which a rotation shaft of the planetary gear is mounted, and an internal gear meshed with the planetary gear. It is preferable that a gear mechanism is provided, one end of the driven link member functions as a planet carrier, and the internal gear functions as an output shaft that transmits a driving force to the next joint. Thereby, the weight of the whole apparatus can be reduced without reducing the weight of the joint part and pressing the possible load weight. Even when the number of drive motors is reduced, high rotational torque is maintained and fine attitude control is possible.

  The switching means includes a shaft having one end fixed to the root side link member, a gear rotatably mounted on the shaft, and a clutch mechanism mounted on the other end of the shaft, and the clutch mechanism is in a released state. Preferably, the gear is configured to be rotatable, and a gear-shaped portion that meshes with the gear is provided on the outer periphery of one end of the driven link member. Thereby, the operation of the driven link member can be controlled with a simple configuration.

  It is preferable that the drive shaft and the shaft of the sun gear are connected via a pair of bevel gears to be transmitted. Thereby, the rotation direction can be changed by a predetermined angle, for example, 90 degrees.

  According to the present invention, the multi-axis manipulator is a multi-axis manipulator having a plurality of joints, and a joint driving unit that drives a driving force supply unit that supplies a driving force and a joint that connects adjacent link members. And a tip end mechanism that is driven by power transmitted through the joint drive device. The joint drive device uses the driving force supplied to the drive shaft provided on the root side link member to drive the driven link member. Driving force transmission driving means for driving and transmitting this driving force to the next joint part, and switching means for switching between driving and stopping of the driven link member by the driving force transmission driving means, A planetary gear including a sun gear located at the center, a planetary gear arranged in mesh with the sun gear, a planet carrier mounted with a rotation shaft of the planetary gear, and an internal gear meshing with the planetary gear With a configuration and is configured so that one end of the driven link member acts as a planet carrier, the internal gear serves as an output shaft for transmitting the driving force to the next joint.

  Thereby, the weight of the whole apparatus can be reduced without reducing the weight of the joint part and pressing the possible load weight. Even when the number of drive motors is reduced, high rotational torque is maintained and fine attitude control is possible.

  The switching means includes a shaft having one end fixed to the root side link member, a gear rotatably mounted on the shaft, and a clutch mechanism mounted on the other end of the shaft, and the clutch mechanism is in a released state. Preferably, the gear is configured to be rotatable, and a gear-shaped portion that meshes with the gear is provided on the outer periphery of one end of the driven link member.

  It is preferable that the drive shaft and the shaft of the sun gear are connected via a pair of bevel gears to be transmitted.

  The driving force supply means is preferably arranged at the first joint of the root portion. Thereby, the fine attitude | position of a multi-axis manipulator can be controlled with one motor.

  According to the present invention, the driving force transmission driving means for driving the driven link member with the driving force supplied to the driving shaft provided in the root side link member and transmitting the driving force to the next joint portion is the differential gear. Using a mechanism, for example, a planetary gear mechanism, one end of the driven link member functions as a planet carrier, and the internal gear functions as an output shaft that transmits driving force to the next joint. Each link member is attached with a subsequent link member and a clutch mechanism that restrains and releases torque that transmits rotational power to the tip end mechanism, thereby reducing the weight of the joint portion and pressing the possible load weight. And the weight of the entire apparatus can be reduced. Even when the number of drive motors is reduced, high rotational torque is maintained and fine attitude control is possible.

It is sectional drawing which shows schematically the structure of the joint drive device which concerns on one Embodiment of this invention. It is sectional drawing which shows schematically the structure of the joint drive device in the modification of embodiment of FIG. It is a perspective view which shows roughly the structure of the multi-axis manipulator using the joint drive device of FIG. It is sectional drawing which shows schematically the structure of the 1st joint part of the multi-axis manipulator of FIG. It is sectional drawing which shows schematically the structure of the front-end | tip mechanism part of the multi-axis manipulator of FIG. It is a top view which shows roughly the transmission state (the 1) of the multi-axis manipulator using the joint drive device of FIG. It is a top view which shows roughly the transmission state (the 2) of a multi-axis manipulator using the joint drive device of FIG.

  Hereinafter, a joint drive device according to an embodiment of the present invention and a multi-axis manipulator using the joint drive device will be described.

  FIG. 1 schematically shows the configuration of a joint drive device according to an embodiment of the present invention.

  As shown in the figure, the joint drive device 100 of this embodiment includes a root side link member 10, a drive shaft 20, a driven link member 30, a drive force transmission drive means 40, and a switching means 50. ing.

  A base side or other link member is rotatably connected to the base side of the base side link member 10, and a drive shaft 20 and an input side sprocket 21 are provided on the tip side. A switching means 50 is disposed on the distal end side of the root side link member 10.

  The drive shaft 20 is rotatably provided at the distal end portion 10a of the root side link member 10 via a bearing. An input side sprocket 21 is provided at the end of the drive shaft 20, and an input side chain C <b> 1 is attached to the input side sprocket 21. A driving force is input to the drive shaft 20 from the root side of the root side link member 10 via the input side chain C1.

  Driving force transmission driving means 40 is provided on the base side of the driven link member 30. The driven link member 30 is connected to the root side link member 10 via the driving force transmission driving means 40. A gear-shaped portion 31 is provided on the outer periphery of the end portion 30 a on the root side of the driven link member 30. The gear portion 31 is configured to mesh with the gear 52 of the switching means 50.

  The drive force transmission drive means 40 drives the driven link member 30 with the drive force supplied to the drive shaft 20 provided on the root side link member 10 and transmits the drive force to the next joint portion. . The driving force transmission driving means 40 meshes with the planetary gear 42, the sun gear 41 located at the center, the planetary gear 42 arranged to mesh with the sun gear 41, the planet carrier 43 that supports the rotation shaft of the planetary gear 42, and the planetary gear 42. A planetary gear mechanism including an internal gear 44 is provided. The planet carrier 43 is constituted by an end portion 30 a on the root side of the driven link member 30. The internal gear 44 is configured to function as an output shaft that transmits driving force to the next joint.

  The switching unit 50 switches between driving and stopping of the driven link member 30 by the driving force transmission driving unit 40. The switching means 50 includes a shaft 51 having one end fixed to the base side link member 10, a gear 52 rotatably mounted on the shaft 51 via a bearing, and a clutch mechanism mounted on the other end of the shaft 51. 53. For example, a non-excitation differential brake is mounted on the clutch mechanism 53. When the clutch mechanism 53 is in the released state, the gear 52 is rotatable, and when the clutch mechanism 53 is in the restrained state, the rotation of the gear 52 is restricted. Further, the gear 52 is configured to mesh with the gear-shaped portion 31 of the driven link member 30. In a state where the rotation of the gear 52 is restricted, the rotation of the driven link member 30 is suppressed.

  As described above, the joint drive device 100 includes the root side link member 10, the drive shaft 20, the driven link member 30, the drive force transmission drive means 40, and the switching means 50. The driving force transmission driving means 40 includes a planetary gear mechanism, the root-side end 30a of the driven link member 30 functions as the planet carrier 43, and the internal gear 43 is an output shaft that transmits the driving force to the next joint portion. Is configured to function as In the joint drive device 100 of the present embodiment, the drive shaft 20 and the rotation shaft of the sun gear 41 are integrally formed coaxially.

  FIG. 2 schematically shows the structure of a joint drive device 100A in a modification of the embodiment of FIG.

  As shown in the figure, the joint drive device 100A includes a root side link member 10, a drive shaft 20, a driven link member 30, a drive force transmission drive means 40, a switching means 50, and a pair of bevel gears. 60 (60a and 60b). In this joint drive device 100A, the configuration excluding the pair of bevel gears 60 (60a and 60b) is the same as the configuration of the joint drive device 100 described above, and thus detailed description thereof is omitted.

  The bevel gear 60a is fixed to the drive shaft 20, the bevel gear 60b is fixed to the rotating shaft 41a of the sun gear 41, and the pair of bevel gears 60a and 60b are used at a predetermined angle (for example, 90 degrees). Rotational motion can be transmitted between the two shafts engaged, that is, the root side link member 10 and the driven link member 30 are disposed at an angle of 90 degrees with each other, and the rotational drive direction is changed by 90 degrees.

  As described above, in the joint drive devices 100 and 100A according to the embodiment of the present invention and the modification thereof, the drive force transmission drive means 40 uses the planetary gear mechanism, and the root side of the driven link member 30 is The end 30a functions as the planet carrier 43, and the internal gear 44 is configured to function as an output shaft that transmits driving force to the next joint. The switching means 40 for switching between driving and stopping of the driven link member 30 by the driving force transmission driving means 40 is attached to a shaft 51 having one end fixed to the root side link member 10 and to the shaft 51 so as to be rotatable. The gear 52 and the clutch mechanism 53 attached to the other end of the shaft 51 are configured such that the gear 52 is rotatable when the clutch mechanism 53 is in the released state, and the base side of the driven link member 30 A gear-like portion 31 that meshes with the gear 52 is provided on the outer periphery of the end portion 30a. Thereby, the weight of the whole apparatus can be reduced without reducing the weight of the joint part and pressing the possible load weight. Further, even when the number of drive motors is reduced, high rotational torque can be maintained and fine attitude control can be performed.

  FIG. 3 schematically shows a configuration of a multi-axis manipulator 200 having four joint portions using a joint driving device. FIG. 4 schematically shows the configuration of the first joint portion 220 of the multi-axis manipulator 200, and FIG. 5 schematically shows the configuration of the tip mechanism portion 260.

  As shown in FIG. 3, the multi-axis manipulator 200 includes a motor 210 as a driving force supply means for supplying a driving force, a first joint portion 220, a second joint portion 230, and a third joint portion 240. And a fourth joint part 250, a tip part mechanism 260, and a control means (not shown). Here, the 2nd joint part 230, the 3rd joint part 240, and the 4th joint part 250 are comprised using the joint drive device 100, and this is the same as that of the structure shown in FIG. The control unit is configured to control the switching operation of the switching unit 50.

  As shown in FIG. 4, the motor 210 is fixed to the base portion 211. The rotation shaft of the motor 210 is inserted through the base portion 211 and connected to the link member 213 via the bearing 212. A transmission sprocket 214 is attached to the end of the rotating shaft of the motor 210, and the transmission sprocket 214 is driven by the motor 210.

  The first joint portion 220 includes a base portion 211, a bearing 212, a link member 213, a transmission sprocket 214, and a switching unit 50. A gear-shaped portion 213 b is provided on the outer periphery of the end portion 213 a on the root side of the link member 213. The gear portion 213b is configured to mesh with the gear 52 of the switching means 50. A chain 215 is connected to the transmission sprocket 214, and power is transmitted to the second joint portion 230, which is the next joint, via the chain 215. Similarly, power transmission from the second joint portion 230 to the third joint portion 240 and from the third joint portion 240 to the fourth joint portion 250 is also performed via the chain. Note that the link member 213 in the first joint portion 220 becomes the root side link member 10 with respect to the second joint portion 230. Similarly, the driven link member 30 in the second joint portion 230 becomes the root side link member 10 with respect to the third joint portion 240. The same applies to the next joint.

  The tip end mechanism 260 includes a hand, scissors, a cutter, or the like, and has a structure capable of performing various operations. The power transmitted by the chain from the fourth joint portion 250 is converted into rotational torque by the sprocket 261 and transmitted to the tip end mechanism 260 via the shaft 262. At this time, the clutch mechanism 263 fixed to the driven link member 30 controls the rotation of the shaft 262 to restrict the transmission of power to the tip mechanism 260 and the switching control of the release, so that the hand of the tip portion mechanism 260 and the scissors Or a cutter or the like is controlled.

  Next, operations of the joint driving device 100 and the multi-axis manipulator 200 in the present embodiment will be described with reference to FIGS.

  Hereinafter, the case where the 3rd joint part 240 is driven is demonstrated. First, when the clutch mechanism 53 and the clutch mechanism 263 other than the third joint portion 240 cannot be rotated, and the motor 210 is rotated, the rotation of the motor 210 is performed through the transmission sprocket 214 and the chain 215 to the next joint (second joint). 2 joints 230) as rotation. At this time, since the clutch mechanism 53 is in a restrained state, the gear 52 cannot rotate and the link member 213 is restrained. Therefore, all the torque is transmitted to the second joint portion 230 via the transmission sprocket 214 and the chain 215. In the second joint portion 230, the rotational torque from the first joint portion is transmitted via the input side sprocket 21, and is transmitted to the sun gear 41 attached to the same shaft as the input side sprocket 21. Torque from the sun gear 41 is transmitted to the planetary gear 42. At this time, the clutch mechanism 53 connected to the end 30a on the root side of the driven link member 30 which is the planet carrier 43 of the planetary gear 42 is connected. Since it is restrained, the driven link member 30 cannot rotate, and the planet carrier 43 cannot rotate. As a result, the planetary gear 42 rotates and its rotation is transmitted to the internal gear 44, and is transmitted to the third joint 240 via the output side chain C 2 by the output side sprocket 22 attached to the internal gear 44. The third joint 240 also rotates the sun gear 41 in the same manner, but the driven link member 30 that is a planet carrier is free because the clutch mechanism 53 is in a released state. Therefore, the rotational torque of the sun gear 41 can revolve the planetary gear 42 to rotate the driven link member 30 or rotate the internal gear 44. Similarly, the internal gear 44 transmits power to the sun gear 41 of the fourth joint portion 250.

  In the fourth joint part 250, the clutch mechanism 53 cannot rotate as in the second joint part 23, so that the driven link member 30 cannot rotate and power is transmitted to the tip part mechanism 260. However, the tip end mechanism 260 is not transmitted to the tip end mechanism 260 and is in a fixed state because the clutch mechanism 263 is in a restrained state and the shaft 262 cannot rotate. As a result, the joints after the third joint part 240 and the tip part mechanism 260 are all in a restrained state, so that only the third joint part 240 can rotate. With the above driving method, it is possible to freely rotate the joint of the driven link member 30 in a state where the clutch mechanism 53 can rotate in the forward direction and the reverse direction. If the clutch mechanisms 53 of all joints other than the clutch mechanism 263 of the tip end mechanism 260 cannot rotate, it is possible to transmit power to the tip end mechanism 260. Moreover, it is possible to freely change the transmission torque of each joint by changing the number of teeth of each differential gear mechanism.

  As described above, the multi-axis manipulator 200 includes the motor 210, the first joint portion 220, the second joint portion 230, the third joint portion 240, the fourth joint portion 250, and the distal end portion. A mechanism 260 and control means (not shown) are provided. The second joint part 230, the third joint part 240, and the fourth joint part 250 are configured using the joint driving device 100. Thereby, the weight of the whole apparatus can be reduced without reducing the weight of the joint part and pressing the possible load weight. Even when the number of drive motors is reduced, high rotational torque is maintained and fine attitude control is possible.

  In the joint drive devices 100 and 100A described above, the switching unit 50 has been described as being configured with the shaft 51, one end of which is fixed to the root side link member 10, the gear 52, and the clutch mechanism 53. The present invention is not limited to this. Other switching means may be used.

  Moreover, although the multi-axis manipulator 200 described above has been described as having four joints, the present invention is not limited to this.

  Further, in the above-described multi-axis manipulator 200, the second joint unit 230, the third joint unit 240, and the fourth joint unit 250 have been described as being configured using the joint driving device 100. Is not limited to this. Any of these joint portions may use the joint drive device 100A. The joint driving device 100A can also be used for the first joint portion 220 and the tip portion mechanism 260.

  All the embodiments described above are illustrative of the present invention and are not intended to be limiting, and the present invention can be implemented in other various modifications and changes. Therefore, the scope of the present invention is defined only by the claims and their equivalents.

  The joint drive device and multi-axis manipulator of the present invention can be used for a robot that performs a predetermined work in a factory or the like.

DESCRIPTION OF SYMBOLS 10 Root side link member 20 Drive shaft 21 Input side sprocket 22 Output side sprocket 30 Driven link member 30a End part 31 and 213b Gear-like part 40 Driving force transmission drive means 41 Sun gear 41a Rotating shaft 42 Planetary gear 43 Planetary carrier 44 Engagement Internal gear 50 Switching means 51 Shaft 52 Gear 53, 263 Clutch mechanism 60, 60a, 60b Bevel gear 100, 100A Joint drive device 200 Multi-axis manipulator 210 Motor 211 Base 212 Bearing 213 Link member 214 Transmission sprocket 215 Chain 220 1st Joint part 230 second joint part 240 third joint part 250 fourth joint part 260 tip part mechanism 261 sprocket 262 shaft C1 input side chain C2 output side chain

Claims (8)

A joint drive device that drives a joint part that connects adjacent link members,
Driving force transmission driving means for driving the driven link member with the driving force supplied to the driving shaft provided on the root side link member and transmitting the driving force to the next joint part;
Switching means for switching between driving and stopping of the driven link member by the driving force transmission driving means;
The joint drive device according to claim 1, wherein the drive force transmission drive means comprises a differential gear mechanism.   The driving force transmission drive means includes a sun gear located at the center, a planetary gear arranged in mesh with the sun gear, a planet carrier on which a rotation shaft of the planetary gear is mounted, and an internal gear meshed with the planet gear. And one end of the driven link member functions as the planet carrier, and the internal gear functions as an output shaft that transmits the driving force to the next joint. The joint drive device according to claim 1.   The switching means includes a shaft having one end fixed to the root side link member, a gear rotatably mounted on the shaft, and a clutch mechanism mounted on the other end of the shaft, and the clutch mechanism The gear is configured to be rotatable in a released state, and a gear-shaped portion that meshes with the gear is provided on an outer periphery of one end of the driven link member. Or the joint drive device of 2.   The joint drive device according to claim 2 or 3, wherein the drive shaft and the shaft of the sun gear are connected via a pair of bevel gears to be transmitted. A multi-axis manipulator having a plurality of joints,
Driving force supplying means for supplying driving force;
A joint drive device for driving a joint part connecting adjacent link members;
A tip portion mechanism driven by the power transmitted through the joint drive device,
The joint driving device drives a driven link member with a driving force supplied to a driving shaft provided on a root side link member, and transmits the driving force to the next joint portion; and the driving Switching means for switching between driving and stopping of the driven link member by the force transmission driving means,
The driving force transmission drive means includes a sun gear located at the center, a planetary gear arranged in mesh with the sun gear, a planet carrier on which a rotation shaft of the planetary gear is mounted, and an internal gear meshed with the planet gear. And one end of the driven link member functions as the planet carrier, and the internal gear functions as an output shaft that transmits the driving force to the next joint. A multi-axis manipulator characterized by that.   The switching means includes a shaft having one end fixed to the root side link member, a gear rotatably mounted on the shaft, and a clutch mechanism mounted on the other end of the shaft, and the clutch mechanism The gear is configured to be rotatable in a released state, and a gear-shaped portion that meshes with the gear is provided on an outer periphery of one end of the driven link member. The multi-axis manipulator described in 1.   The multi-axis manipulator according to claim 5 or 6, wherein the drive shaft and the shaft of the sun gear are connected and transmitted via a pair of bevel gears.   The multi-axis manipulator according to any one of claims 5 to 7, wherein the driving force supply means is disposed at a first joint of a root portion.

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