WO2018131758A1

WO2018131758A1 - Power transmission apparatus

Info

Publication number: WO2018131758A1
Application number: PCT/KR2017/005733
Authority: WO
Inventors: 정창현
Original assignee: 한화테크윈주식회사
Priority date: 2017-01-10
Filing date: 2017-06-01
Publication date: 2018-07-19
Also published as: KR20180082230A

Abstract

Disclosed is a power transmission apparatus. The present invention comprises: a first rotating shaft; a drive part that is installed on the first rotating shaft and rotates the first rotating shaft; a second rotating shaft that is disposed inside the first rotating shaft, and is connected to the first rotating shaft and thus rotates when the drive part is operated; a first rotating body that is installed on the second rotating shaft and rotates together with the second rotating shaft; a first rotation detecting part that detects the rotation of the first rotating body; and a stopper part that is disposed between the first rotation detecting part and either the first rotating body or the second rotating shaft to limit the radius of rotation of the second rotating shaft.

Description

Power train

The present invention relates to a device, and more particularly to a power transmission device.

In general, power trains are used in a variety of industries. For example, the power transmission device may be used in joints, drivers, and turntables in the semiconductor field. The power transmission device is used for power cables, signal cables, etc. to drive a variety of devices. Such a cable or the like may be disposed outside or inside the power train. At this time, the power transmission device may generate a rotating object in accordance with the operation of the internal components. Due to such an object, the cable or the like is twisted, and if such an operation is repeated, the cable or the like may be broken.

Various structures can be used in the power transmission device to solve the above problems. For example, by attaching a sensor to determine the relative position between the components of the power transmission device or by installing a separate structure, such as a power transmission device can limit the rotation angle.

The power transmission device as described above is specifically disclosed in Korean Patent Publication No. 2015-011253 (name of the invention: brake device for robot joint module, Applicant: Auto Power Co., Ltd.).

Embodiments of the present invention seek to provide a power transmission device.

According to an aspect of the present invention, a first rotating shaft, a driving unit installed on the first rotating shaft to rotate the first rotating shaft, and disposed inside the first rotating shaft, connected to the first rotating shaft to operate the driving unit. A second rotating shaft rotating at a time, a first rotating body installed on the second rotating shaft and rotating together with the second rotating shaft, a first rotation detecting unit sensing a rotation of the first rotating body, and the first rotation The power transmission device may include a stopper part disposed between one or all of the second rotation shafts and the first rotation sensing unit to limit a rotation radius of the second rotation shaft.

Embodiments of the present invention can effectively prevent the twisting of the inner cable or the like by effectively limiting the rotation range. Embodiments of the present invention can prevent damage or damage due to excessive rotation by no longer rotating after a certain number of rotations.

1 is a cross-sectional perspective view showing a part of a power transmission device according to an embodiment of the present invention.

2 is a cross-sectional view showing the power transmission device shown in FIG.

3 is a partial perspective view showing an embodiment of the stopper portion of the power transmission device shown in FIG.

4 is a partial perspective view showing a power transmission device according to another embodiment.

The stopper may include a rotating member installed on one of the first rotating body and the second rotating shaft, a locking member having a variable position depending on the rotation of the rotating member, and a locking member installed on the rotation detecting unit. It may include a guide for guiding the rotation and linear motion of the.

The locking member may include a first body part installed to rotate and linearly move the guide part, and a locking protrusion protruding from the first body part.

In addition, the locking protrusions may be provided in plural, and the plurality of locking protrusions may be arranged to be spaced apart from each other by a predetermined interval on the outer surface of the first body part.

In addition, a groove or a hole may be formed in the rotating member so that the locking protrusion is inserted.

In addition, a plurality of grooves or holes may be formed in the rotating member so as to be spaced apart from each other.

The locking member may include a first body part installed to rotate and linearly move the guide part, and a first gear tooth formed to protrude from an outer surface of the first body part.

In addition, the rotating member may include the second body portion and a second gear protruding from the second body portion toward the locking member.

In addition, at least two or more second gear teeth may form one second gear teeth group, and a plurality of second gear teeth groups may be provided, and the plurality of second gear teeth groups may be arranged to be spaced apart from each other.

In addition, the guide unit may further include an elastic unit disposed between the locking member and the rotation sensing unit.

The invention will become apparent with reference to the embodiments described below in detail in conjunction with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but will be implemented in various forms, and only the present embodiments are intended to complete the disclosure of the present invention, and the general knowledge in the art to which the present invention pertains. It is provided to fully convey the scope of the invention to those skilled in the art, and the present invention is defined only by the scope of the claims. Meanwhile, the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. In this specification, the singular also includes the plural unless specifically stated otherwise in the phrase. As used herein, “comprises” and / or “comprising” refers to the presence of one or more other components, steps, operations and / or elements. Or does not exclude additions. Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. The terms are only used to distinguish one component from another.

1 is a cross-sectional perspective view showing a part of a power transmission device according to an embodiment of the present invention. 2 is a cross-sectional view showing the power transmission device shown in FIG. 3 is a partial perspective view showing an embodiment of the stopper portion of the power transmission device shown in FIG.

1 to 3, the power transmission device 100 includes a housing 111, a first rotating shaft 112, a driving unit 120, a reduction gear 131, a second rotating shaft 132, a brake 133, The first encoder 140, the driver 151, the second encoder 160, the stopper unit 170, the sensor unit 181, the alarm unit 182, and the cover 183 may be included.

The housing 111 may form an appearance. In this case, a space may be formed in the housing 111, and various parts or components may be disposed in the housing 111.

The first rotation shaft 112 may be disposed inside the housing 111. In this case, a hollow may be formed in the first rotation shaft 112 and a second rotation shaft 132 may be inserted. The first rotation shaft 112 may be formed in the form of a shaft.

The driving unit 120 may be disposed between the first rotation shaft 112 and the housing 111. In this case, the driving unit 120 may be in the form of a motor. For example, the driving unit 120 may include a rotor 121 disposed on the first rotation shaft 112 and a stator 122 disposed to surround the outer surface of the rotor 121. At this time, the rotor 121 may be formed in the form of a permanent magnet, the stator 122 may be in the form of an electromagnet. The stator 122 may be disposed to be spaced apart from the outer surface of the rotor 121 and may be fixed to the housing 111.

The reducer 131 may be connected to the first rotation shaft 112. In this case, the first rotating shaft 112 may be penetrated inside the reducer 131. The reducer 131 may reduce the torque of the first rotating shaft 112 that rotates according to the driving of the driving unit 120 and transmit the decelerated torque to the second rotating shaft 132. The reducer 131 as described above may be formed in various forms. For example, the reducer 131 may be a reducer in the form of a harmonic drive. In another embodiment, the reduction gear 131 may be a reduction gear including a planetary gear. In this case, the reducer 131 is not limited to the above, and may include all shapes and structures connected to the first rotating shaft 112 to reduce the torque and then transfer the reduced speed to the second rotating shaft 132. However, hereinafter, the speed reducer 131 will be described in detail with reference to a case including a harmonic drive reducer for convenience of description. In this case, although not shown in detail with respect to the reducer 131 in FIGS. 2 and 3, the harmonic drive reducer is the same as a general harmonic drive reducer, and thus a detailed description thereof will be omitted.

The second rotation shaft 132 may be disposed inside the first rotation shaft 112. At this time, the second rotation shaft 132 may be hollow formed therein. Cables such as a power cable and a signal cable may pass through the second rotation shaft 132.

An external device may be connected to one end of the second rotation shaft 132. In this case, the external device may be an object such as a robot arm, a part of the robot, a rotating stage, or the like. In this case, the second rotation shaft 132 may transmit the rotational force to the external device.

The brake 133 may be disposed on the first rotation shaft 112. In this case, the first rotation shaft 112 may be disposed to penetrate the brake 133. The brake 133 may receive a signal from the outside to slow down the rotation of the first rotating shaft 112 or stop the first rotating shaft 112. In this case, the brake 133 may adjust the rotation of the first rotation shaft 112 by contacting the first rotation shaft 112.

The first encoder 140 may be connected to the second rotation shaft 132 to measure the rotation speed of the second rotation shaft 132. In detail, the first encoder 140 may include a first rotating body 141 and a first rotation detecting unit 142. The first rotating body 141 may be connected to the second rotating shaft 132 and rotate together when the second rotating shaft 132 rotates. The first rotation sensing unit 142 may be connected to and fixed to at least one of a part of the second encoder 160, the brake 133, the housing 111, and the cover 183. The first rotating body 141 as described above may be formed in various forms. For example, the first rotating body 141 may include a magnet. The first rotation detecting unit 142 may detect the rotation of the first rotating body 141. In particular, when the first rotating body 141 includes a magnet, the first rotation detecting unit 142 detects a change in a magnetic field that is variable when the first rotating body 141 rotates to rotate the first rotating body 141. The degree can be measured. The first encoder 140 as described above is not limited to the above, and may include all devices and structures connected to the second rotation shaft 132 to sense the rotation speed of the second rotation shaft 132. However, hereinafter, the first rotating body 141 will be described in detail with reference to the case of the magnet for convenience of description.

The driver 151 may be connected to the driver 120 to control the driver 120. In this case, the driver 151 may be installed to be fixed to the housing 111.

The second encoder 160 may be connected to the first rotation shaft 112 to measure the rotation speed of the first rotation shaft 112. In this case, the second encoder 160 may include a second rotating body 161 and a second rotation detecting unit 162. In this case, the second rotating body 161 may be connected to the first rotating shaft 112 to rotate together with the first rotating shaft 112 when the first rotating shaft 112 rotates. In addition, the second rotation detecting unit 162 detects the rotation angle (or rotation speed) of the second rotation body 161 when the second rotation body 161 rotates (or the rotation angle of the first rotation shaft 112). Number of revolutions) can be detected. In this case, since the second rotation body 161 and the second rotation detection unit 162 are the same as or similar to the first rotation body 141 and the first rotation detection unit 142 described above, a detailed description thereof will be omitted. .

The stopper unit 170 may be disposed on either the first encoder 140 or the second rotation shaft 132. In this case, the stopper unit 170 may limit the rotation angle of the second rotation shaft 132.

In detail, the stopper part 170 may include a rotating member 171, a locking member 172, a guide part 173, and an elastic part 174.

The rotating member 171 may be installed on one of the second rotating shaft 132 or the first rotating body 141 to rotate together when one of the second rotating shaft 132 or the first rotating body 141 is rotated. At this time, as an embodiment, the first rotating member 171 may be integrally formed with one of the second rotating shaft 132 or the first rotating member 141. In another embodiment, the first rotating member 171 is formed separately from one of the second rotating shaft 132 or the first rotating member 141 to be coupled to one of the second rotating shaft 132 or the first rotating member 141. It is also possible. In this case, a groove (not shown) or a hole 171a may be formed in the first rotating member 171 so that a part of the locking member 172 is inserted into and in contact with the first rotating member 171. Hereinafter, for convenience of description, the rotating member 171 is installed on the first rotating body 141, the rotating member 171 is formed separately from the first rotating body 141, and a hole 171a is formed therein. The case will be described in detail.

A plurality of holes 171a may be formed in the rotating member 171 as described above. In this case, the plurality of holes 171a may be disposed to be spaced apart from each other by a predetermined interval. In particular, a rib 171b is formed between the adjacent holes 171a to be in contact with a part of the locking member 172.

The locking member 172 may rotate and linearly move in the guide unit 173 by selectively contacting the rotating member 171 of the first rotating body 141 during rotation. The locking member 172 may include a first body portion 172a and a locking protrusion 172b. In this case, the guide part 173 may be inserted into the first body part 172a. In addition, the locking protrusion 172b may protrude from an outer surface of the first body portion 172a and may be provided in plural. In this case, the plurality of locking protrusions 172b may be arranged to be spaced apart from each other along the outer surface of the first body portion 172a. In particular, the plurality of locking projections 172b may be disposed on the outer surface of the first body portion 172a to be spaced apart from each other by a predetermined interval. The plurality of locking protrusions 172b as described above may be disposed in the first body 172a to be sequentially inserted into the holes 171a of the rotating member 171 when the rotating member 171 rotates. That is, each locking protrusion 172b may be inserted into each hole 171a of the rotating member 171 when the rotating member 171 rotates.

The guide part 173 may be disposed in the first rotation detecting part 142. In this case, the guide unit 173 may be arranged to face outward from the center of the first rotation detecting unit 142. Threads may be formed on the outer surface of the guide part 173 so that the first body part 172a rotates and linearly moves. In this case, a screw thread may be formed on the inner surface of the first body portion 172a.

The elastic part 174 may provide a restoring force to the locking member 172 when the locking member 172 linearly moves the guide 173. In this case, the elastic unit 174 may be disposed between the locking member 172 and the first rotation detecting unit 142. In particular, the elastic portion 174 may be in the form of a coil spring in which the guide portion 173 is disposed. In another embodiment, the elastic part 174 is formed of an elastic material, and may include a cylindrical member in which the guide part 173 is inserted therein. However, hereinafter, the elastic unit 174 will be described in detail with reference to a case including the coil spring for convenience of description.

The elastic portion 174 may be provided in plurality. For example, the elastic portion 174 may include a first elastic portion 174a and a second elastic portion 174b which are disposed to face each other with respect to the locking member 172. In this case, the first elastic part 174a may provide a restoring force to the locking member 172 when the locking member 172 moves in the first direction. The second elastic part 174b may provide a restoring force to the locking member 172 when the locking member 172 moves in the second direction opposite to the first direction. In addition, the elastic part 174 may prevent the locking member 172 from moving due to vibration or the like by applying a preload to the locking member 172 during or after the movement of the locking member 172.

The sensor unit 181 may grasp the position of the locking member 172. In this case, the sensor unit 181 may measure the position of the locking member 172 in real time, and when the locking member 172 linearly moves the guide unit 173, the locking member 172 may move. It may be detected whether the locking member 172 has reached the end of the displacement. For example, the sensor unit 181 may detect whether the locking member 172 has reached a position where it can no longer linearly move. In this case, the sensor unit 181 may have various forms. For example, the sensor unit 181 may include various types of sensors capable of detecting the position of the locking member 172 such as a contact sensor, an ultrasonic sensor, a laser sensor, an optical sensor, a linear scale, and the like.

The alarm unit 182 may warn an external user through light, sound, or the like based on the result detected by the sensor unit 181.

The cover 183 may be coupled to the housing 111. In this case, the cover 183 may be disposed at the side of the first encoder 140 to be coupled to the housing 111 to shield the first encoder 140 from the outside. In addition, the cover 183 may be provided with a transparent window (not shown) to check the position of the stopper 170. In this case, the transparent window may be formed of a material that can transmit light.

Meanwhile, referring to the operation of the power transmission device 100 as described above, when a signal is first applied to the driver 151, the driver 151 may operate the driving unit 120. In this case, current is applied to the stator 122 so that the rotor 121 may rotate. In addition, the first rotation shaft 112 may rotate in accordance with the rotation of the rotor 121.

Rotation of the first rotary shaft 112 may be transmitted to the second rotary shaft 132 through the reducer 131 to rotate the second rotary shaft 132. In addition, the rotation of the first rotating shaft 112 may rotate the second rotating body 161, the second rotation detecting unit 162 may detect the rotation of the second rotating body (161).

As described above, the first rotating body 141 may be rotated according to the rotation of the second rotating shaft 132. In this case, the first rotation detecting unit 142 may be in a stopped state.

When the first rotating body 141 rotates, the rotating member 171 may rotate together with the first rotating body 141. In this case, the rotating member 171 may apply a force to the locking protrusion 172b by contacting the locking protrusion 172b. In detail, when the rotating member 171 rotates, the locking protrusion 172b may be inserted into the hole 171a to collide with the rib 171b. In addition, when the rib 171b passes through the lower surface of the locking member 172, the first body portion 172a without the locking protrusion 172b passes, so that the locking member 172 and the rotating member 171 interfere with each other. You can't.

In this case, when the protrusion 172b and the rib 171b collide with each other, the first body 172a may linearly move while rotating the guide 173. For example, when the rotating member 171 rotates in the clockwise direction in FIG. 3, the first body part 172a may linearly move in the right direction of FIG. 3 along the guide part 173. On the other hand, when the rotating member 171 rotates in the counterclockwise direction in FIG. 3, the first body part 172a may linearly move in the left direction of FIG. 3 along the guide part 173. At this time, the above-described exercise is not limited to this, but may be implemented in reverse.

As described above, when the first body portion 172a linearly moves the guide portion 173, the elastic portion 174 in the linear movement direction may be compressed. For example, when the first body portion 172a moves to the right side of FIG. 3, the first elastic portion 174a may be compressed. Also, the second elastic portion 174b in which the first body portion 172a moves to the left side of FIG. 3 may be compressed. In this case, the opposite elastic portion 174 may be stretched. The elastic portion 174 that is tensioned or compressed as described above may provide a restoring force to the first body portion 172a during linear movement of the first body portion 172a.

On the other hand, the stopper portion 170 that operates as described above may not be a problem in normal cases. Specifically, when the power transmission device 100 moves in the designed range (for example, the set angle range, etc.), the stopper unit 170 may have little influence on the operation of the power transmission device 100.

On the other hand, when the power transmission device 100 is out of the designed range, the stopper unit 170 may stop the rotation of the second rotation shaft 132. In detail, the locking member 172 moves along the guide portion 173 as the second rotation shaft 132 rotates. The locking member 172 may reach the end of the guide portion 173. In this case, when the elastic part 174 is no longer compressed or the locking member 172 contacts the first rotation sensing unit 142, the locking member 172 linearly guides the guide unit 173 without further rotating. You may not be able to exercise.

In this case, the locking protrusion 172b may be inserted into the hole 171a to be in contact with the rib 171b. In this case, the first rotating body 141 may not be able to rotate any more, and the second rotating shaft 132 may no longer rotate. In addition, the external device connected to the second rotating shaft 132 may not rotate anymore. In this case, the driver 151 may recognize that the load applied to the driver 120 increases and may stop the driver 120. Alternatively, the brake 133 may be operated to stop the rotation of the first rotation shaft 112. In another embodiment, when the locking member 172 reaches the position as described above, the sensor unit 181 may stop the operation of the driving unit 120 and operate the brake 133.

The sensor unit 181 may detect the position of the locking member 172 when the locking member 172 reaches the position as described above. At this time, the alarm unit 182 may inform the external user that the power transmission device 100 has reached the boundary of the set range through light, sound, etc. based on the result detected by the sensor unit 181. have.

The cable as described above may be inserted into the second rotation shaft 132, and may be connected to each component such as the driving unit 120 through the cover 183. In this case, when the first rotary shaft 112 and the second rotary shaft 132 rotates out of the design range, the cable inserted into the second rotary shaft 132 continuously rotates according to the rotation of the second rotary shaft 132. May occur. In particular, as each end of the cable is fixed, a plurality of cables may be entangled with each other or excessive twist may be applied to the ends of the cables, as the second rotation shaft 132 is rotated. In this case, the cable may be broken or broken, thereby causing a short circuit. However, as described above, when the operation of the driving unit 120 is stopped or the second rotating shaft 132 is no longer rotated and rotates in the design range, the first rotating shaft 112 and the second rotating shaft 132 rotate beyond the designed range. You can't. In this case, the cable inside the second rotary shaft 132 may not rotate any more.

On the other hand, the transmission window may be in a state in which a scale or the like is recorded so as to check the rotation amount and the rotation direction of the second rotation shaft 132 according to the position of the locking member 172. In addition, in addition to the above case, a scale or the like may be recorded in the first rotating body 141 and the first guide part 173 so as to check the rotation amount and the rotation direction of the second rotating shaft 132. In this case, by reading the scale overlapping with the locking member 172, the user can check the degree of rotation of the second rotary shaft 132.

Therefore, the power transmission device 100 can limit the operating range through a simple configuration and structure. The power transmission device 100 may physically limit the rotation of 360 degrees or more to prevent the cable inside the power transmission device 100 from being twisted.

Referring to FIG. 4, the power transmission device (not shown) includes a housing (not shown), a first rotating shaft (not shown), a driver (not shown), a reducer (not shown), a second rotating shaft 232, and a brake (not shown). H), a first encoder 240, a driver (not shown), a second encoder (not shown), a stopper portion 270, a sensor portion 281, an alarm unit (not shown) and a cover (not shown) can do. In this case, the housing, the first rotary shaft, the drive unit, the reducer, the second rotary shaft 232, the brake, the first encoder 240, the driver, the second encoder, the sensor unit 281, the alarm unit And since the cover is the same as or similar to that described above, a detailed description thereof will be omitted.

The stopper part 270 may include a rotating member 271, a locking member 272, a guide part 273, and an elastic part 274.

The rotating member 271 may include a second body portion 271a and a second gear tooth 271b. The second body portion 271a is formed integrally with one of the second rotating shaft 232 or the first rotating body 241 or is formed separately to be coupled to one of the second rotating shaft 232 or the first rotating body 241. can do. The second gear teeth 271b may protrude from the second body portion 271a toward the locking member 272. In this case, the second gear 271b may be formed along the outer surface of the second body portion 271a. In another embodiment, at least two or more second gear teeth 271b may form one second gear teeth group. In this case, a plurality of second gear teeth groups may be provided, and the plurality of second gear teeth groups may be arranged on the second body part 271a to be spaced apart from each other. Hereinafter, for convenience of description, the second gear 271b will be described in detail with reference to a case in which the second gear group is formed.

The locking member 272 may be installed at the guide part 273 to rotate and linearly move. The locking member 272 may include a first body portion 272a and a first gear tooth 272b. In this case, the first body portion 272a may be installed to be rotatable in the guide portion 273. The first gear 272b may be formed on a portion or the front surface of the first body portion 272a. Hereinafter, for convenience of description, the first gear 272b will be described in detail with reference to a case where the first gear 272b is formed on the entire outer surface of the first body portion 272a.

The guide part 273 may be disposed in the first rotation detecting part 242. In this case, a hole may be formed in the first rotation detecting unit 242 so that the guide part 273 is installed.

The elastic part 274 may be disposed in the guide part 273 to maintain the position of the locking member 272 during the movement of the locking member 272. At this time, since the elastic portion 274 is the same as or similar to that described above, a detailed description thereof will be omitted.

On the other hand, looking at the operation of the power transmission device, according to the operation of the drive unit may be sequentially transmitted to the first rotary shaft, the reducer and the second rotary shaft 232. In this case, the first rotating body 241 may rotate according to the rotation of the second rotating shaft 232, and the rotating member 271 may rotate together with the first rotating body 241.

When the rotating member 271 rotates, the second gear teeth group may sequentially contact the first gear teeth 272b. In this case, the second gear teeth 271b of each second gear teeth group may contact the first gear teeth 272b while rotating. In this case, a force is applied to the first gear 272b and the first body 272a may rotate. The first body portion 272a may linearly move in the same or similar manner as described above while rotating in the guide portion 273. In this case, when the first body part 272a reaches both ends of the guide part 273 or the elastic part 274 is completely compressed, the first body part 272a may not rotate any more and may not linearly move.

In this case, at least a portion of the first gear 272b and at least a portion of the second gear 271b may be arranged to overlap each other. In particular, at least a portion of the first gear 272b and the second gear 271b may overlap each other within the moving range of the locking member 272. Accordingly, the first gear 272b and the second gear 271b may be in contact with each other.

As described above, when the locking member 272 moves and stops, the second rotation shaft 232 may stop without further rotation. In this case, at least one of the driver and the brake may stop the operation of the driving unit or stop the rotation of the first rotation shaft.

In addition, as described above, when the locking member 272 is no longer moved, the sensor unit 281 may detect the locking member 272, and the alarm unit may emit an alarm to the outside. The drive unit may stop.

The user may check at least one of the rotation direction and the rotation amount of the second rotation shaft 232 through the transmission window of the cover. In this case, the method of checking at least one of the rotation direction and the rotation amount of the second rotation shaft 232 is the same or similar to that described above, and thus the detailed description thereof will be omitted.

Therefore, the power transmission device can limit the operating range through a simple configuration and structure. The power train may physically limit the rotation of 360 degrees or more to prevent the cable inside the power train from being twisted.

Although the present invention has been described in connection with the above-mentioned preferred embodiments, it is possible to make various modifications or variations without departing from the spirit and scope of the invention. Accordingly, the appended claims will include such modifications and variations as long as they fall within the spirit of the invention.

According to an embodiment of the present invention, by providing a power transmission device that can limit the operation angle, can be installed in a joint structure for transmitting power installed in a robot, etc., an industrial robot, a traveling robot, including the joint structure, Embodiments of the present invention can be applied to a robot field such as a humanoid.

Claims

A first rotating shaft;

A driving unit installed on the first rotation shaft to rotate the first rotation shaft;

A second rotation shaft disposed inside the first rotation shaft and connected to the first rotation shaft to rotate when the driving unit is operated;

A first rotating body installed on the second rotating shaft and rotating together with the second rotating shaft;

A first rotation sensing unit sensing a rotation of the first rotating body; And

And a stopper unit disposed between one of the first rotating body or the second rotating shaft and the first rotation detecting unit to limit a radius of rotation of the second rotating shaft.
The method of claim 1,

The stopper portion,

A rotating member installed on one of the first rotating body or the second rotating shaft;

A catching member whose position varies according to the rotation of the rotating member; And

And a guide part installed in the rotation detecting part to guide rotation and linear motion of the locking member.
The method of claim 2,

The locking member,

A first body part installed to allow the guide part to rotate and linearly move; And

And a locking protrusion formed to protrude from the first body portion.
The method of claim 3, wherein

The locking projection is provided with a plurality,

The plurality of locking projections are arranged on the outer surface of the first body portion spaced apart from each other by a predetermined distance.
The method of claim 3, wherein

The rotating member is a power transmission device formed with a groove or a hole so that the engaging projection.
The method of claim 5, wherein

And a plurality of grooves or holes formed in the rotating member to be spaced apart from each other.
The method of claim 2,

The locking member,

A first body part installed to allow the guide part to rotate and linearly move; And

And a first gear formed to protrude from an outer surface of the first body part.
The method of claim 7, wherein

The rotating member,

Second body portion; And

And a second gear projecting from the second body portion toward the locking member.
The method of claim 8,

At least two or more second gear teeth form one second gear teeth group, and a plurality of second gear teeth groups are provided.

The plurality of second gear group is arranged to be spaced apart from each other.
The method of claim 2,

And an elastic part disposed on the guide part and disposed between the locking member and the rotation sensing part.
The method of claim 10,

The elastic portion is provided with a plurality,

And the plurality of elastic parts are disposed to face each other with respect to the rotating member.