Patent Description:
Generally, planetary gear devices are widely used as a transmission device.

The planetary gear device includes a ring gear, a sun gear disposed in the center of the ring gear, a plurality of planet gears that are arranged between the ring gear and the sun gear and engaged with the ring gear and the sun gear, and a carrier in which the plurality of planet gears are disposed.

The planetary gear device may transmit power in a variety of ways. For example, in the case of using the sun gear as an input, when the carrier is fixed, a reverse deceleration output is implemented through the ring gear. Conversely, when the sun gear is used as the input and the ring gear is fixed, a forward deceleration output is implemented through the carrier.

In addition, in the case of using the carrier as the input, when the sun gear is fixed, a forward acceleration output is implemented through the ring gear, whereas when the ring gear is fixed, the forward acceleration output is implemented through the sun gear.

In addition, in the case of using the ring gear as the input, when the sun gear is fixed, a forward deceleration output is implemented through the carrier, whereas when the carrier is fixed, the reverse acceleration output is implemented through the sun gear.

As described above, the planetary gear device may implement four outputs, that is, a forward acceleration output, a forward deceleration output, a reverse acceleration output, and a reverse deceleration output with one input.

However, the planetary gear device of the related art has a structure in which an input part and an output part are disposed in the same straight line on opposite sides of planetary gear device. Therefore, although the size of the planetary gear device itself is small, there is a problem that the size of the planetary gear transmission device including the input part and the output part is large.

<CIT> proposes that a fixed internal gear holds planet gears rollably around a sun gear. A movable internal gear is continuously/integrally provided with an output part for transmitting a generated torque to the outside. A housing is fixed to a motor case of a motor and accommodates the sun gear, the planet gears, the fixed internal gear, and the movable internal gear. A ring spring is provided between the fixed internal gear and the housing; when the magnitude of a force applied to the fixed internal gear is equal to or less than a preset threshold value, the ring spring limits the fixed internal gear to rotate around a revolving shaft J1, and when the magnitude of the force applied to the fixed internal gear exceeds the preset threshold value, the ring spring permits the fixed internal gear to rotate around the revolving shaft J1.

The above information is presented as background information only to assist with an understanding of the following description. No determination has been made, and no assertion is made, as to whether any of the above might be applicable as prior art.

Aspects of the present application are to address at least the above-mentioned problems and/or disadvantages and to provide at least the advantages described below. Accordingly, an aspect of the present application is to provide a planetary gear transmission device capable of reducing a size by disposing an input part and an output part together on one side of a planetary gear device, and a robot having the same.

In accordance with an aspect, a planetary gear transmission device is provided. The planetary gear transmission device includes a planetary gear device including a sun gear, a ring gear, a plurality of planet gears, and a carrier supporting the plurality of planet gears, a motor configured to generate a rotational force input to the planetary gear device, the motor including a motor shaft and a motor body supporting the motor shaft, a fixing bracket formed to fix any one of the sun gear, the ring gear, or the carrier of the planetary gear device to prevent rotation, and a recursive rotation bracket provided with the motor and fixed to any one of the sun gear, the ring gear, or the carrier of the planetary gear device, which is not fixed by the fixing bracket, wherein the recursive rotation bracket is formed so that the motor shaft of the motor is connected to any one of the sun gear, the ring gear, or the carrier of the planetary gear device, to which the fixing bracket and the recursive rotation bracket are not fixed, and wherein when any one of the sun gear, the ring gear, or the carrier of the planetary gear device connected to the motor shaft is rotated by the motor shaft, the motor body is rotated by the recursive rotation bracket and the rotational force of the motor shaft is output through the recursive rotation bracket.

The ring gear of the planetary gear device may be fixed to the fixing bracket, the recursive rotation bracket may be fixed to the carrier, the motor shaft of the motor may be connected to the sun gear, and the rotational force of the motor may be output to an outside through the recursive rotation bracket fixed to the carrier.

The sun gear of the planetary gear device may be fixed to the fixing bracket, the recursive rotation bracket may be fixed to the carrier, the motor shaft of the motor may be connected to the ring gear, and the rotational force of the motor may be output to an outside through the recursive rotation bracket fixed to the carrier.

The carrier of the planetary gear device may be fixed to the fixing bracket, the recursive rotation bracket may be fixed to the ring gear, the motor shaft of the motor may be connected to the sun gear, and the rotational force of the motor may be output to an outside through the recursive rotation bracket fixed to the ring gear.

In accordance with another aspect, a robot is provided. The robot includes a main body, a moving member disposed to rotate at a predetermined angle with respect to the main body, and a planetary gear transmission device according to the previously described aspect disposed between the main body and the moving member and allowing the moving member to rotate at a predetermined angle with respect to the main body, wherein the fixing bracket is fixed to the main body ; the moving member is fixed to any one of the motor or the recursive rotation bracket; and when any one of the sun gear, ring gear, or the carrier of the planetary gear device connected to the motor shaft is rotated by the motor shaft, the motor and the moving member are rotated by the recursive rotation bracket.

Other aspects, advantages, and salient features will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses various embodiments.

With the planetary gear transmission device according to an embodiment having the above-described structure, the size of the planetary gear transmission device may be reduced compared to the planetary gear transmission device of the related art in which the input part and the output part are disposed on opposite sides of the planetary gear device interposed therebetween.

The above and other aspects, features, and advantages of certain embodiments will be more apparent from the following description taken in conjunction with the accompanying drawings, in which:.

The following description with reference to the accompanying drawings is provided to assist in a comprehensive understanding of various embodiments of the as defined by the claims.

The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding. Accordingly, it should be apparent to those skilled in the art that the following description of various embodiments is provided for illustration purpose only and not for the purpose of limiting the scope, which is defined by the appended claims.

The terms 'first', 'second', etc. may be used to describe diverse components, but the components are not limited by the terms. The terms may only be used to distinguish one component from the others. For example, without departing from the scope of the invention, a first component may be referred to as a second component, and similarly, a second component may also be referred to as a first component.

The terms used in embodiments may be construed as commonly known to those skilled in the art unless otherwise defined.

Further, the terms 'leading end', 'rear end', 'upper side', 'lower side', 'top end', 'bottom end', etc. used herein are defined with reference to the drawings. However, the shape and position of each component are not limited by the terms.

Hereinafter, certain embodiments of a planetary gear transmission device will be described in detail with reference to the accompanying drawings.

<FIG> is a view illustrating a planetary gear device of the related art.

Referring to <FIG>, a planetary gear device <NUM> may include a sun gear <NUM> disposed to rotate at the center of the planetary gear device <NUM>, a plurality of planet gears <NUM> that revolve around the sun gear <NUM> like a planet, a ring gear <NUM> disposed on the outer periphery of the plurality of planet gears <NUM>, and a carrier <NUM> in which the plurality of planet gears <NUM> are disposed.

In the planetary gear device <NUM> as described above, when any one of the sun gear <NUM>, the ring gear <NUM>, and the carrier <NUM> is fixed and a rotation force is input to another of the sun gear <NUM>, the ring gear <NUM>, and the carrier <NUM>, a rotational force of which the speed is changed may be output through the other of the sun gear <NUM>, the ring gear <NUM>, and the carrier <NUM>.

For example, when the ring gear <NUM> is fixed and the sun gear <NUM> is rotated by a motor, the rotation reduced by the planetary gear device <NUM> is output through the carrier <NUM>.

In detail, in the case that the sun gear <NUM> is coupled to a motor shaft (not illustrated) of the motor, when the motor shaft rotates, the sun gear <NUM> rotates integrally with the motor shaft.

When the sun gear <NUM> rotates, the plurality of planet gears <NUM> meshed with the sun gear <NUM>, in the case of <FIG>, four planet gears <NUM> are rotated by the sun gear <NUM>. At this time, the plurality of planet gears <NUM> are inscribed in the ring gear <NUM> having teeth formed on the inner circumferential surface. Accordingly, the plurality of planet gears <NUM> revolve around the sun gear <NUM> along the ring gear <NUM> while being rotated by the sun gear <NUM>.

Because the plurality of planet gears <NUM> are disposed on the carrier <NUM>, the carrier <NUM> is rotated based on the sun gear <NUM> when the plurality of planet gears <NUM> revolve. The carrier <NUM> rotates by decelerating at a predetermined gear ratio compared to the rotation speed of the motor shaft. In this case, the gear ratio of the planetary gear device <NUM> is S/(S + R). Here, S is the number of teeth of the sun gear <NUM>, and R is the number of teeth of the ring gear <NUM>.

<FIG> is a perspective view illustrating a planetary gear transmission device according to an embodiment, and <FIG> is a cross-sectional view illustrating a planetary gear transmission device according to an embodiment. <FIG> is a cross-sectional view illustrating the planetary gear transmission device of <FIG> taken along line °-° according to an embodiment. <FIG> is a perspective view illustrating a planetary gear device used in a planetary gear transmission device according to an embodiment according to an embodiment. <FIG> is a perspective view illustrating a recursive rotation bracket of the planetary gear transmission device of <FIG> according to an embodiment.

Referring to <FIG>, a planetary gear transmission device <NUM> according to an embodiment includes a planetary gear device <NUM>, a motor <NUM>, a fixing bracket <NUM>, and a recursive rotation bracket <NUM>.

The planetary gear device <NUM> includes a sun gear <NUM>, a plurality of planet gears <NUM>, a ring gear <NUM>, and a carrier <NUM> supporting the plurality of planet gears <NUM>. The planetary gear device <NUM> is the same as or similar to the planetary gear device <NUM> of the related art illustrated and described in <FIG>; therefore, a detailed description thereof is omitted.

However, the planetary gear device <NUM> according to an embodiment is different from the planetary gear device <NUM> of the related art illustrated in <FIG> in that it includes a plurality of protrusions <NUM> provided on the outer circumferential surface of the ring gear <NUM> as illustrated in <FIG>.

The motor <NUM> is formed to generate a rotational force that is input to the planetary gear device <NUM>. The motor <NUM> includes a motor shaft <NUM> and a motor body <NUM>.

The motor body <NUM> may be formed to support the rotation of the motor shaft <NUM>. A rotor (not illustrated) and a stator (not illustrated) may be provided inside the motor body <NUM> to rotate the motor shaft <NUM>. A speed reducer (not illustrated) may be disposed inside the motor body <NUM>.

For example, as the motor <NUM>, a reducer-integrated motor in which a reducer is built in the motor body <NUM> may be used. For example, the reducer may reduce the rotation of the motor <NUM> by <NUM>/<NUM>. In the case of the planetary gear transmission device <NUM> according to an embodiment, a reducer integrated motor is used. In addition, a servo motor may be used as the motor <NUM>.

The fixing bracket <NUM> is formed to fix the planetary gear device <NUM>. In detail, the fixing bracket <NUM> is formed to fix any one of the sun gear <NUM>, the ring gear <NUM>, and the carrier <NUM> of the planetary gear device <NUM> to prevent rotation. Accordingly, a part of the planetary gear device <NUM> fixed by the fixing bracket <NUM>, that is, any one of the sun gear <NUM>, the ring gear <NUM>, and the carrier <NUM> of the planetary gear device <NUM>, which is fixed by the fixing bracket <NUM>, is not rotated when the motor shaft <NUM> rotates.

For example, in the case where the ring gear <NUM> of the planetary gear device <NUM> is fixed to the fixing bracket <NUM>, when the motor shaft <NUM> of the motor <NUM> rotates, the ring gear <NUM> is not rotated and only the sun gear <NUM> and the plurality of planet gears <NUM> are rotated.

The recursive rotation bracket <NUM> may be disposed on the motor <NUM>. The recursive rotation bracket <NUM> is formed such that any one of the sun gear <NUM>, the ring gear <NUM>, and the carrier <NUM>, which is not fixed by the fixing bracket <NUM>, of the planetary gear device <NUM> is fixed to the recursive rotation bracket <NUM>.

In addition, the recursive rotation bracket <NUM> is formed such that the motor shaft <NUM> of the motor <NUM> transmits the rotational force to the other one among the sun gear <NUM>, the ring gear <NUM>, and the carrier <NUM> of the planetary gear device <NUM> that is not fixed to the fixing bracket <NUM> and the recursive rotation bracket <NUM>.

Therefore, when the motor shaft <NUM> rotates, any one of the sun gear <NUM>, the ring gear <NUM>, and the carrier <NUM> of the planetary gear device <NUM> connected to the motor shaft <NUM> rotates, so that another one of the sun gear <NUM>, the ring gear <NUM>, and the carrier <NUM> of the planetary gear device <NUM> in which the recursive rotation bracket <NUM> is disposed is rotated.

Then, because the recursive rotation bracket <NUM> is rotated, the motor body <NUM>, that is, the motor <NUM> disposed in the recursive rotation bracket <NUM> is rotated. In other words, the recursive rotation bracket <NUM> is rotated by a certain angle by the rotation of the motor shaft <NUM>, and thereby the motor <NUM> itself is rotated at the certain angle.

On the other hand, the rotational force of the motor shaft <NUM> is output through the recursive rotation bracket <NUM>. In other words, an output part may be disposed on the recursive rotation bracket <NUM>. Alternatively, the output part may be disposed on the motor <NUM> fixed to the recursive rotation bracket <NUM>.

Because the motor <NUM> is fixed to the recursive rotation bracket <NUM>, the motor <NUM> rotates in the same manner as the recursive rotation bracket <NUM>.

Hereinafter, various examples in which any one of the sun gear <NUM>, the ring gear <NUM>, and the carrier <NUM> of the planetary gear device <NUM> is used as any one of a fixing part to fix the planetary gear device <NUM>, an input part to which the rotational force of the motor <NUM> is input, and an output part through which the rotational force passing through the planetary gear device <NUM> is output will be described in detail.

First, the case in which the ring gear <NUM> of the planetary gear device <NUM> is fixed, the sun gear <NUM> is used as the input part, and the carrier <NUM> is used as the output part will be described in detail with reference to <FIG>, <FIG>, <FIG>, and <FIG>.

The fixing bracket <NUM> may be formed to fix the ring gear <NUM> of the planetary gear device <NUM>. Therefore, when the motor shaft <NUM> rotates, the ring gear <NUM> disposed on the fixing bracket <NUM> is not rotated. The fixing bracket <NUM> may include a receiving portion <NUM> and an extending portion <NUM>.

The receiving portion <NUM> may include a circular insertion groove <NUM> into which the ring gear <NUM> of the planetary gear device <NUM> is inserted. The diameter of the insertion groove <NUM> of the receiving portion <NUM> may be formed to correspond to the outer diameter of the planetary gear device <NUM>, that is, the outer diameter of the ring gear <NUM>.

When a plurality of protrusions <NUM> are formed on the outer circumferential surface of the planetary gear device <NUM>, that is, on the outer circumferential surface of the ring gear <NUM>, a plurality of grooves <NUM> corresponding to the plurality of protrusions <NUM> of the planetary gear device <NUM> may be provided around the insertion groove <NUM>.

A step portion <NUM> may be provided at the bottom of the insertion groove <NUM>. The step portion <NUM> may be formed as a circular groove having a diameter less than the diameter of the insertion groove <NUM>. The width of the step portion <NUM> may be determined to stably support the ring gear <NUM>. The depth of the step portion <NUM> may be determined so that the tips of a plurality of shafts <NUM> protruding from the carrier <NUM> do not touch the bottom of the step portion <NUM>.

A bearing groove <NUM> may be provided in the center of the step portion <NUM>. A bearing <NUM> for supporting one end of an adapter <NUM> in which the sun gear <NUM> is disposed may be disposed in the bearing groove <NUM>.

The extending portion <NUM> may extend from the outer circumferential surface of the receiving portion <NUM> and may be formed to be fixed to another part on which the fixing bracket <NUM> is disposed. For example, when the planetary gear transmission device <NUM> according to an embodiment is applied to a head joint of a robot (see <FIG>), the extending portion <NUM> of the fixing bracket <NUM> may be fixed to a main body of the robot.

The recursive rotation bracket <NUM> may be disposed to rotate integrally with the carrier <NUM>. In the case of this embodiment, the recursive rotation bracket <NUM> is not directly fixed to the carrier <NUM>, but is fixed to the opposite side of the plurality of planet gears <NUM> disposed on the carrier <NUM>. In detail, the carrier <NUM> and the recursive rotation bracket <NUM> may be disposed to support both ends of the plurality of planet gears <NUM>.

To this end, the carrier <NUM> may be formed in a disk shape and provided with a plurality of through holes <NUM> corresponding to the plurality of planet gears <NUM>. For example, when the planetary gear device <NUM> includes four planet gears <NUM>, four through holes <NUM> are formed in the carrier <NUM>.

A center hole <NUM> through which the adapter <NUM> to be described later passes may be formed in the center of the carrier <NUM>. The plurality of through holes <NUM> may be formed around the center hole <NUM> of the carrier <NUM> at predetermined intervals.

A shaft hole 23a may be formed in the center of each of the plurality of planet gears <NUM>.

The motor <NUM> may be disposed on the recursive rotation bracket <NUM> to transmit power to the sun gear <NUM>.

The recursive rotation bracket <NUM> may include a planetary gear fixing portion <NUM> and a motor fixing portion <NUM>. The planetary gear fixing portion <NUM> and the motor fixing portion <NUM> may be formed to form a substantially right angle. Therefore, the recursive rotation bracket <NUM> may be formed in an approximately L-shape.

The planetary gear fixing portion <NUM> may be provided with a plurality of fixing holes <NUM> corresponding to the plurality of planet gears <NUM> and an adaptor hole <NUM> through which the adapter <NUM> connected to the motor shaft <NUM> passes. The plurality of fixing holes <NUM> may be formed around the adapter hole <NUM> at predetermined intervals.

The adapter <NUM> may be formed to connect the sun gear <NUM> and the motor shaft <NUM> to transmit the power of the motor shaft <NUM> to the sun gear <NUM>.

A connecting plate <NUM> may be disposed at the front end of the motor shaft <NUM>. The connecting plate <NUM> may be coupled to the front end of the motor shaft <NUM> so as to rotate integrally with the motor shaft <NUM>. The connecting plate <NUM> may be formed in a substantially disk shape and have a plurality of fastening holes <NUM> provided around the motor shaft <NUM>. Female threads may be formed in the plurality of fastening holes <NUM>.

The adapter <NUM> may be coupled to the sun gear <NUM>, and may be fixed to the connecting plate <NUM> coupled to the motor shaft <NUM>. The adapter <NUM> may include a base portion <NUM> and a shaft portion <NUM> protruding perpendicularly from the center of the base portion <NUM>.

The base portion <NUM> may be formed in a disk corresponding to the connecting plate <NUM> of the motor <NUM>, and may have a plurality of fixing holes <NUM> formed around the shaft portion <NUM> at predetermined intervals. Accordingly, when a plurality of bolts <NUM> are fastened to the plurality of fastening holes <NUM> of the connecting plate <NUM> through the plurality of fixing holes <NUM>, the adapter <NUM> is fixed to the connecting plate <NUM>.

The shaft portion <NUM> may extend vertically from the center of the base portion <NUM>, and the sun gear <NUM> may be coupled to the shaft portion <NUM>. A shaft hole 22a into which the shaft portion <NUM> is inserted may be provided in the center of the sun gear <NUM>. Accordingly, the sun gear <NUM> may rotate integrally with the shaft portion <NUM>.

The front end of the shaft portion <NUM> may be supported by the bearing <NUM> disposed at the bottom of the receiving portion <NUM> of the fixing bracket <NUM>.

Accordingly, when the motor shaft <NUM> rotates, the connecting plate <NUM> is rotated, and when the connecting plate <NUM> rotates, the adapter <NUM> rotates integrally with the connecting plate <NUM>. When the adapter <NUM> rotates, the sun gear <NUM> fixed to the shaft portion <NUM> of the adapter <NUM> rotates integrally with the adapter <NUM>.

The recursive rotation bracket <NUM>, the plurality of planet gears <NUM>, and the carrier <NUM> may be integrally fixed by the plurality of shafts <NUM>. To this end, each of the plurality of shafts <NUM> may include a head portion 29a formed at one end of the shaft <NUM> and a ring groove 29b formed at the other end thereof. The head portion 29a may be formed to have a diameter larger than the diameter of the shafts <NUM>. The ring groove 29b may be formed as a groove having a predetermined depth along the outer circumferential surface of the shafts <NUM> so that a snap ring 29c is inserted into the ring groove 29b.

Accordingly, when the plurality of shafts <NUM> are inserted into the plurality of fixing holes <NUM> of the planetary gear fixing portion <NUM> of the recursive rotation bracket <NUM>, the shaft holes 23a of the plurality of planet gears <NUM>, and the plurality of through holes <NUM> of the carrier <NUM> and the plurality of snap rings 29c are disposed in the ring grooves 29b of the tips of the plurality of shafts <NUM> protruding outward of the carrier <NUM>, the recursive rotation bracket <NUM>, the plurality of planet gears <NUM>, and the carrier <NUM> are integrally fixed.

Accordingly, when the plurality of planet gears <NUM> are rotated by the sun gear <NUM>, the carrier <NUM> and the recursive rotation bracket <NUM> are rotated integrally. In addition, the plurality of planet gears <NUM> may rotate with respect to the plurality of shafts <NUM>, respectively.

The motor fixing portion <NUM> may be provided with a plurality of motor fixing holes <NUM> for fixing the motor <NUM>. One side surface of the motor <NUM> may be provided with a plurality of female screws corresponding to the plurality of motor fixing holes <NUM>.

Therefore, when the plurality of bolts <NUM> are fastened to the plurality of female screws of the motor <NUM> through the plurality of motor fixing holes <NUM> of the motor fixing portion <NUM> of the recursive rotation bracket <NUM>, the motor <NUM> is fixed to the recursive rotation bracket <NUM>.

In addition, a plurality of sub-motor fixing portions <NUM> may be provided in the planetary gear fixing portion <NUM>. The plurality of sub-motor fixing portions <NUM> may be provided with sub fixing holes 58a. A plurality of front female screws corresponding to the plurality of sub fixing holes 58a may be provided on the front surface of the motor <NUM>.

Therefore, when a plurality of bolts <NUM> are fastened to the plurality of front female screws of the motor <NUM> through the sub fixing holes 58a of the plurality of sub-motor fixing portions <NUM> of the recursive rotation bracket <NUM>, the motor <NUM> is fixed to the recursive rotation bracket <NUM>.

As described above, when the recursive rotation bracket <NUM> is disposed on the motor <NUM> with the motor fixing portion <NUM> and the plurality of sub-motor fixing portions <NUM>, the recursive rotation bracket <NUM> and the motor <NUM> may be firmly coupled to each other.

In the above description, the motor <NUM> and the recursive rotation bracket <NUM> are coupled to each other using the plurality of bolts, but the method of coupling the motor <NUM> and the recursive rotation bracket <NUM> is not limited thereto. Although not illustrated, various coupling methods may be used as long as the motor <NUM> and the recursive rotation bracket <NUM> can be coupled to each other.

When the motor <NUM> is fixed to the recursive rotation bracket <NUM>, the adapter <NUM> disposed at the front end of the motor shaft <NUM> may protrude through the adapter hole <NUM> of the recursive rotation bracket <NUM>. The shaft portion <NUM> of the adapter <NUM> may be coupled to the sun gear <NUM> disposed at the center of the plurality of planet gears <NUM>. Accordingly, when the motor shaft <NUM> rotates, the sun gear <NUM> is rotated integrally with the motor shaft <NUM> by the connecting plate <NUM> and the adapter <NUM>.

When the sun gear <NUM> rotates, the plurality of planet gears <NUM> meshed with the sun gear <NUM> are rotated. When the plurality of planet gears <NUM> rotate, the carrier <NUM> and the recursive rotation bracket <NUM> are rotated based on the rotation axis of the sun gear <NUM>, that is, the central axis of the motor shaft <NUM>. In other words, when the sun gear <NUM> rotates, the plurality of planet gears <NUM> meshed with the sun gear <NUM> are rotated based on the shafts <NUM>, respectively, and are revolved along the ring gear <NUM>.

The revolving rotation of the plurality of planet gears <NUM> causes the carrier <NUM> and the recursive rotation bracket <NUM> to rotate based on the central axis of the sun gear <NUM>.

An output member may be fixed to the recursive rotation bracket <NUM>. For example, when the planetary gear transmission device <NUM> according to an embodiment is applied to a head joint of a robot (see <FIG>), the recursive rotation bracket <NUM> may be fixed to the head of the robot. In this case, when the recursive rotation bracket <NUM> rotates, the head of the robot may be rotated at a predetermined angle with respect to the main body.

On the other hand, in the planetary gear transmission device <NUM> according to an embodiment, when the recursive rotation bracket <NUM> rotates, the motor <NUM> fixed to the recursive rotation bracket <NUM> also rotates integrally with the recursive rotation bracket <NUM>. Accordingly, rotation of the recursive rotation bracket <NUM> further rotates the motor shaft <NUM>. As a result, the gear ratio of the planetary gear transmission device <NUM> according to an embodiment may be different from that of the planetary gear device of the related art.

As in the above-described embodiment, when the ring gear <NUM> is fixed, the sun gear <NUM> is used as an input part, and the carrier <NUM> is used as an output part, the gear ratio of the planetary gear device <NUM> of the related art is S/(S + R). Here, S is the number of teeth of the sun gear, and R is the number of teeth of the ring gear.

Therefore, when the motor <NUM> rotates the sun gear <NUM> by N, the carrier <NUM> rotates {S/(S+R)}N = aN (a=S/(S+R)).

At this time, because the recursive rotation bracket <NUM> is fixed to the carrier <NUM> and the motor <NUM> is fixed to the recursive rotation bracket <NUM>, the rotation of the carrier <NUM> rotates the motor <NUM> by a predetermined angle. Accordingly, the sun gear <NUM> is also rotated by an additional predetermined angle. When the sun gear <NUM> is further rotated by the predetermined angle, the carrier <NUM> is also rotated further. This process may be repeated infinitely and converge. This result may be expressed as a formula as follows:.

In other words, in the planetary gear transmission device <NUM> according to an embodiment, when the sun gear <NUM> is rotated N by the motor <NUM>, the carrier <NUM> is rotated bN. Because the carrier <NUM> is provided with the recursive rotation bracket <NUM>, when the carrier <NUM> rotates, the recursive rotation bracket <NUM> integrally rotates. Accordingly, the output member fixed to the recursive rotation bracket <NUM> is rotated bN. As a result, the torque by the planetary gear transmission device <NUM> according to an embodiment may be increased by <NUM>/b times by the gear ratio.

As described above, in the planetary gear transmission device <NUM> according to an embodiment, because the motor <NUM> for inputting power and the output member for outputting power are both disposed in the recursive rotation bracket <NUM> provided on one side of the planetary gear device <NUM>, the gear ratio is different from that of the planetary gear device <NUM> of the related art.

In the above description, the recursive rotation bracket <NUM> is disposed on the opposite side of the carrier <NUM> based on the plurality of planet gears <NUM>. However, the installation of the recursive rotation bracket <NUM> is not limited thereto. As another example, although not illustrated, the recursive rotation bracket <NUM> may be directly fixed to the carrier <NUM>.

In addition, in the above description, the motor shaft <NUM> and the sun gear <NUM> are connected to each other using the adapter <NUM> and the connecting plate <NUM>, but the connection of the motor shaft <NUM> and the sun gear <NUM> is not limited thereto. As another example, as illustrated in <FIG>, the sun gear <NUM> may be directly disposed at the front end of the motor shaft <NUM>'.

<FIG> is a cross-sectional view illustrating a planetary gear transmission device according to an embodiment.

Referring to <FIG>, when the motor <NUM>' is fixed to the recursive rotation bracket <NUM>, the motor shaft <NUM>' protrudes through the adaptor hole <NUM> of the recursive rotation bracket <NUM>. The motor shaft <NUM><NUM>' is coupled to the sun gear <NUM> disposed at the center of the plurality of planet gears <NUM>. Accordingly, when the motor shaft <NUM>' rotates, the sun gear <NUM> rotates integrally with the motor shaft <NUM>'.

The planetary gear transmission device <NUM>' shown in <FIG> is different from the planetary gear transmission device <NUM> according to the above-described embodiment only in the connection structure between the motor shaft <NUM>' and the sun gear <NUM>, so a detailed description thereof is omitted.

In the above description, the planetary gear transmission device <NUM> uses the planetary gear device <NUM> including the plurality of protrusions <NUM> provided on the outer circumferential surface of the ring gear <NUM> as illustrated in <FIG>. However, as another embodiment, the planetary gear transmission device <NUM> according to an embodiment may be implemented using the planetary gear device <NUM> without the protrusions on the outer circumferential surface of the ring gear as illustrated in <FIG>.

Next, a planetary gear transmission device <NUM> in which a carrier <NUM> of a planetary gear device <NUM> is fixed, a sun gear <NUM> is used as an input part, and a ring gear <NUM> is uses as an output part will be described in detail with reference to <FIG>, <FIG>, <FIG>, and <FIG>.

<FIG> is a perspective view illustrating a planetary gear transmission device according to an embodiment. <FIG> is a cross-sectional view illustrating a planetary gear transmission device according to an embodiment. <FIG> is a cross-sectional view illustrating the planetary gear transmission device of <FIG> taken along line ±-± according to an embodiment. <FIG> is an exploded perspective view illustrating the planetary gear transmission device of <FIG> according to an embodiment.

Referring to <FIG>, a fixing bracket <NUM> may be formed to fix a carrier <NUM> of a planetary gear device <NUM>. Therefore, when the motor shaft <NUM> rotates, the carrier <NUM> disposed on the fixing bracket <NUM> is not rotated.

The fixing bracket <NUM> may include a fixing portion <NUM> and an extension portion <NUM>.

The fixing portion <NUM> may be formed in a cylindrical shape to fix the carrier <NUM> of the planetary gear device <NUM>. Therefore, the carrier <NUM> may be fixed to one end of the fixing portion <NUM>. In the case of the embodiment shown in <FIG>, and <FIG>, the carrier <NUM> may be formed integrally with the top surface of the fixing portion <NUM>. In other words, the top surface of the fixing portion <NUM> may be formed to serve as the carrier <NUM>.

A plurality of holes <NUM> corresponding to a plurality of through holes <NUM> and a center hole <NUM> of the carrier <NUM> may be formed inside the fixing portion <NUM> having the cylindrical shape.

The carrier <NUM> may be formed in a disk shape and provided with the plurality of through holes <NUM> corresponding to a plurality of planet gears <NUM>. For example, when the planetary gear device <NUM> includes four planet gears <NUM>, four through holes <NUM> are formed in the carrier <NUM>.

The center hole <NUM> through which an adapter <NUM> disposed on the motor shaft <NUM> passes may be formed in the center of the carrier <NUM>. The plurality of through holes <NUM> may be formed around the center hole <NUM> of the carrier <NUM> at predetermined intervals.

A shaft hole 123a may be formed in the center of each of the plurality of planet gears <NUM>.

The plurality of planet gears <NUM> may be fixed to the carrier <NUM> by the plurality of shafts <NUM>. To this end, each of the plurality of shafts <NUM> may include a head portion 129a formed at one end of the shaft <NUM> and a ring groove 129b formed at the other end thereof.

The head portion 129a may be formed to have a diameter larger than the diameter of the shaft <NUM>. The ring groove 129b may be formed as a groove having a predetermined depth along the outer circumferential surface of the shaft <NUM> so that a snap ring 129c is inserted into the ring groove 129b.

Accordingly, when the plurality of shafts <NUM> are inserted into the plurality of shaft holes 123a of the plurality of planet gears <NUM> and the plurality of through holes <NUM> of the carrier <NUM>, and the plurality of snap rings 129c are disposed in the ring grooves 129b of the tips of the plurality of shafts <NUM> protruding downward of the carrier <NUM>, the plurality of planet gears <NUM> are fixed to the carrier <NUM>.

Accordingly, each of the plurality of planet gears <NUM> may rotate with respect to each of the plurality of shafts <NUM> while being disposed on the carrier <NUM>.

The extension portion <NUM> may extend from the other end of the fixing portion <NUM> and may be formed to be fixed to another component on which the fixing bracket <NUM> is disposed. For example, when the planetary gear transmission device <NUM> according to an embodiment is applied to a head joint of a robot (see <FIG>), the extension portion <NUM> of the fixing bracket <NUM> may be fixed to the main body of the robot.

A recursive rotation bracket <NUM> may be disposed to rotate integrally with the ring gear <NUM>. In this embodiment, the ring gear <NUM> is fixed to the recursive rotation bracket <NUM>, so that when the ring gear <NUM> rotates, the recursive rotation bracket <NUM> is rotated integrally with the ring gear <NUM>.

The recursive rotation bracket <NUM> may include a ring gear fixing portion <NUM> and a motor fixing portion <NUM>. The ring gear fixing portion <NUM> and the motor fixing portion <NUM> may be formed to form a substantially right angle. Accordingly, the recursive rotation bracket <NUM> may be formed in an approximately L-shape.

The ring gear fixing portion <NUM> may be formed integrally with the ring gear <NUM>. For example, the ring gear <NUM> may be formed in the ring gear fixing portion <NUM>. Then, when the ring gear <NUM> rotates, the recursive rotation bracket <NUM> rotates integrally with the ring gear <NUM>.

As another example, although not illustrated, the ring gear fixing portion <NUM> and the ring gear <NUM> may be separately formed. In this case, a ring gear hole into which the ring gear <NUM> of the planetary gear device <NUM> as illustrated in <FIG> is inserted may be formed in the ring gear fixing portion <NUM>, and the ring gear <NUM> may be connected to the ring gear hole. In this case, a plurality of grooves corresponding to the plurality of protrusions <NUM> of the planetary gear device <NUM> may be provided around the ring gear hole.

The motor fixing portion <NUM> may be provided with a plurality of motor fixing holes <NUM> for fixing the motor <NUM>. A plurality of female screws corresponding to the plurality of motor fixing holes <NUM> may be provided on one side surface of the motor <NUM>.

In addition, the recursive rotation bracket <NUM> may include a sub-motor fixing portion <NUM>. The sub-motor fixing portion <NUM> may be provided on the ring gear fixing portion <NUM> and may be formed to be fixed to the front surface of the motor <NUM>.

In the case of the embodiment shown in <FIG>, the recursive rotation bracket <NUM> includes two sub-motor fixing portions <NUM>. A sub fixing hole 158a may be provided at the front end of the sub-motor fixing portion <NUM>.

In addition, a front female screw corresponding to the sub fixing hole 158a of the sub-motor fixing portion <NUM> may be provided on the front surface of the motor <NUM>. Therefore, when a bolt <NUM> is fastened to the front female screw of the motor <NUM> through the sub fixing hole 158a of the sub-motor fixing portion <NUM>, the recursive rotation bracket <NUM> may be fixed to the front surface of the motor <NUM>.

The motor shaft <NUM> of the motor <NUM> and the sun gear <NUM> of the planetary gear device <NUM> may be connected by an adapter <NUM> and a connecting plate <NUM>. Accordingly, when the motor shaft <NUM> rotates, the sun gear <NUM> is rotated integrally with the motor shaft <NUM>.

The structure of the adapter <NUM> and the connecting plate <NUM> is the same as or similar to the adapter <NUM> and the connecting plate <NUM> of the planetary gear transmission device <NUM> according to the above-described embodiment; therefore, a detailed description thereof is omitted.

When the motor shaft <NUM> rotates, the connecting plate <NUM> is rotated, and when the connecting plate <NUM> rotates, the adapter <NUM> is rotated integrally with the connecting plate <NUM>. When the adapter <NUM> rotates, the sun gear <NUM> fixed to the shaft portion <NUM> of the adapter <NUM> is rotated integrally with the adapter <NUM>.

When the sun gear <NUM> rotates, each of the plurality of planet gears <NUM> meshed with the sun gear <NUM> rotates about the shaft <NUM>.

When the plurality of planet gears <NUM> rotate, the ring gear <NUM> meshed with the plurality of planet gears <NUM> is rotated about the central axis of the sun gear <NUM>, that is, the central axis of the motor shaft <NUM>.

At this time, because the carrier <NUM> is integrally formed with the fixing bracket <NUM>, when the sun gear <NUM> rotates, the carrier <NUM> is not rotated and the plurality of planet gears <NUM> meshed with the sun gear <NUM> are rotated based on the plurality of shafts <NUM>, respectively. Then, the ring gear <NUM> is rotated based on the central axis of the sun gear <NUM> by the rotation of the plurality of planet gears <NUM>.

In this case, because the ring gear <NUM> is fixed to the recursive rotation bracket <NUM>, when the ring gear <NUM> rotates, the recursive rotation bracket <NUM> is rotated integrally with the ring gear <NUM>.

On the other hand, in the planetary gear transmission device <NUM> according to an embodiment, when the recursive rotation bracket <NUM> rotates, the motor <NUM> fixed to the recursive rotation bracket <NUM> also rotates integrally with the recursive rotation bracket <NUM>.

Accordingly, the rotation of the recursive rotation bracket <NUM> further rotates the motor shaft <NUM> by a predetermined angle. As a result, the gear ratio of the planetary gear transmission device <NUM> according to an embodiment may be different from that of the planetary gear device <NUM> of the related art.

As in the above-described embodiment, when the carrier <NUM> is fixed, the sun gear <NUM> is used as an input part, and the ring gear <NUM> is used as an output part, the gear ratio of the planetary gear device <NUM> of the related art is -S/R. Here, S is the number of teeth of the sun gear, and R is the number of teeth of the ring gear.

Therefore, when the motor <NUM> rotates the sun gear <NUM> by N, the ring gear <NUM> rotates (-S/R)N = -bN (b=S/R).

At this time, because the ring gear <NUM> is disposed in the recursive rotation bracket <NUM> and the motor <NUM> is fixed to the recursive rotation bracket <NUM>, the rotation of the ring gear <NUM> causes the motor <NUM> to rotate by a predetermined angle. Accordingly, the sun gear <NUM> is also rotated at the same angle as the motor <NUM>.

When the sun gear <NUM> is further rotated, the ring gear <NUM> is also rotated further. This process may be repeated infinitely and converge. This result may be expressed as a formula as follows:.

In other words, in the planetary gear transmission device <NUM> according to an embodiment, when the sun gear <NUM> is rotated N by the motor <NUM>, the ring gear <NUM> is rotated -aN. Because the ring gear <NUM> is disposed in the recursive rotation bracket <NUM>, when the ring gear <NUM> rotates, the recursive rotation bracket <NUM> integrally rotates. Accordingly, the output member fixed to the recursive rotation bracket <NUM> rotates -aN. As a result, the torque by the planetary gear transmission device <NUM> according to an embodiment may be increased by <NUM>/a times due to the gear ratio.

Finally, a planetary gear transmission device <NUM> in which a sun gear <NUM> of a planetary gear device <NUM> is fixed, a ring gear <NUM> is used as an input part, and a carrier <NUM> is used as an output part will be described in detail with reference to <FIG>, <FIG>, <FIG>, and <FIG>.

<FIG> is a perspective view illustrating a planetary gear transmission device according to an embodiment. <FIG> is a cross-sectional view illustrating a planetary gear transmission device according to an embodiment. <FIG> is a cross-sectional view illustrating the planetary gear transmission device of <FIG> taken along line 2_2 according to an embodiment of the disclosure. <FIG> is an exploded perspective view illustrating the planetary gear transmission device of <FIG> according to an embodiment.

Referring to <FIG>, a fixing bracket <NUM> may be formed to fix a sun gear <NUM> of a planetary gear device <NUM>. Therefore, when the motor shaft <NUM> rotates, the sun gear <NUM> disposed on the fixing bracket <NUM> is not rotated.

The fixing portion <NUM> may be formed in a cylindrical shape to fix the sun gear <NUM> of the planetary gear device <NUM>.

For example, a bearing support portion <NUM> may be formed at the front end of the fixing portion <NUM>, and a sun gear fixing portion <NUM> may be formed at the leading end of the bearing support portion <NUM>. The diameter of the bearing support portion <NUM> may be formed smaller than the diameter of the fixing portion <NUM>. Accordingly, a step capable of supporting a bearing <NUM> may be formed between the fixing portion <NUM> and the bearing support portion <NUM>.

The diameter of the sun gear fixing portion <NUM> may be formed smaller than the diameter of the bearing support portion <NUM>. Accordingly, a step capable of supporting the sun gear <NUM> may be formed between the bearing support portion <NUM> and the sun gear fixing portion <NUM>.

A sun gear hole 222a into which the sun gear fixing portion <NUM> is inserted may be formed in the center of the sun gear <NUM>. The sun gear fixing portion <NUM> is inserted into the sun gear hole 222a, and the sun gear <NUM> is fixed so as not to rotate with respect to the sun gear fixing portion <NUM>.

A recursive rotation bracket <NUM> may be disposed to rotate integrally with the carrier <NUM>. In the case of this embodiment, the recursive rotation bracket <NUM> may be formed to be fixed to the carrier <NUM>. Accordingly, when the carrier <NUM> rotates, the recursive rotation bracket <NUM> may be rotated integrally with the carrier <NUM>.

The motor <NUM> may be disposed on the recursive rotation bracket <NUM> to transmit power to the ring gear <NUM>.

The recursive rotation bracket <NUM> may include a carrier fixing portion <NUM> and a motor fixing portion <NUM>. The carrier fixing portion <NUM> and the motor fixing portion <NUM> may be formed to form a substantially right angle. In the case of this embodiment, as illustrated in <FIG>, the recursive rotation bracket <NUM> may be formed in an approximately U-shape with a flat bottom.

The carrier <NUM> may be disposed on one surface of the carrier fixing portion <NUM>. The carrier <NUM> may be formed integrally with the carrier fixing portion <NUM> or may be formed separately from the carrier fixing portion <NUM>. When the carrier <NUM> is formed separately from the carrier fixing portion <NUM>, the carrier <NUM> may be fixed to the carrier fixing portion <NUM> with fastening elements such as bolts. In the case of this embodiment, the carrier <NUM> is integrally formed on the upper surface of the carrier fixing portion <NUM>.

The carrier <NUM> may be formed in a disk shape, and may be provided with a plurality of through holes <NUM> corresponding to a plurality of planet gears <NUM>. For example, when the planetary gear device <NUM> includes four planet gears <NUM>, four through holes <NUM> are formed in the carrier <NUM>. In addition, the carrier fixing portion <NUM> may be provided with four fixing holes <NUM> corresponding to the four through holes <NUM> of the carrier <NUM>.

In the case of this embodiment, because the carrier <NUM> and the carrier fixing portion <NUM> are integrally formed, the four through holes <NUM> of the carrier <NUM> and the four fixing holes <NUM> of the carrier fixing portion <NUM> may be formed integrally, respectively.

A center hole <NUM> through which the sun gear fixing portion <NUM> of the fixing portion <NUM> passes may be formed in the center of the carrier <NUM>. The plurality of through holes <NUM> may be formed around the center hole <NUM> of the carrier <NUM> at predetermined intervals.

A bearing hole <NUM> that corresponds to the center hole <NUM> of the carrier <NUM> and through which the fixing portion <NUM> of the fixing bracket <NUM> passes may be formed in the center of the carrier fixing portion <NUM>. The plurality of fixing holes <NUM> may be formed at predetermined intervals around the bearing hole <NUM> of the carrier fixing portion <NUM>.

In the case of this embodiment, because the carrier <NUM> and the carrier fixing portion <NUM> are integrally formed, the center hole <NUM> of the carrier <NUM> and the bearing hole <NUM> of the carrier fixing portion <NUM> may be formed integrally.

A bearing <NUM> may be disposed in the bearing hole <NUM> of the carrier fixing portion <NUM> and may support the carrier fixing portion <NUM> to rotate smoothly with respect to the fixing portion <NUM>. Accordingly, the recursive rotation bracket <NUM> may rotate based on the fixing portion <NUM> of the fixing bracket <NUM>.

A shaft hole 223a may be formed in the center of each of the plurality of planet gears <NUM>.

The plurality of planet gears <NUM>, the carrier <NUM>, and the carrier fixing portion <NUM> may be integrally fixed by the plurality of shafts <NUM>. To this end, each of the plurality of shafts <NUM> may include a head portion 229a formed at one end of the shaft <NUM> and a ring groove 229b formed at the other end thereof.

The head portion 229a may be formed to have a diameter larger than the diameter of the shaft <NUM>. The ring groove 229b may be formed as a groove having a predetermined depth along the outer circumferential surface of the shaft <NUM> so that a snap ring 229c is inserted into the ring groove 229b.

Accordingly, when the plurality of shafts <NUM> are inserted into the plurality of shaft holes 223a of the plurality of planet gears <NUM> and the plurality of through holes <NUM> of the carrier <NUM>, and the plurality of snap rings 229c are disposed in the ring grooves 229b of the tips of the plurality of shafts <NUM> protruding outward of the carrier <NUM>, the plurality of planet gears <NUM>, the carrier <NUM>, and the carrier fixing portion <NUM> of the recursive rotation bracket <NUM> are integrally fixed.

Accordingly, when the plurality of planet gears <NUM> rotate, the carrier <NUM> and the recursive rotation bracket <NUM> are rotated integrally. In addition, each of the plurality of planet gears <NUM> may rotate with respect to each of the plurality of shafts <NUM>.

The motor fixing portion <NUM> may be provided with a plurality of motor fixing holes <NUM> for fixing the motor <NUM>. The motor fixing portion <NUM> may be formed in two flat plates extending vertically from both ends of the carrier fixing portion <NUM>.

Both side surfaces of the motor <NUM> may be provided with a plurality of female screws <NUM> corresponding to the plurality of motor fixing holes <NUM> formed in the motor fixing portion <NUM>.

Therefore, when a plurality of bolts <NUM> are fastened to the plurality of female screws <NUM> of the motor <NUM> through the plurality of motor fixing holes <NUM> of the motor fixing portion <NUM> of the recursive rotation bracket <NUM>, the motor <NUM> is fixed to the recursive rotation bracket <NUM>.

An adapter <NUM> may be formed to connect the ring gear <NUM> and the motor shaft <NUM> so that the power of the motor shaft <NUM> is transmitted to the ring gear <NUM>.

A connecting plate <NUM> may be disposed at the front end of the motor shaft <NUM>. The connecting plate <NUM> may be formed to rotate integrally with the motor shaft <NUM> at the front end of the motor shaft <NUM>.

The connecting plate <NUM> may be formed in a substantially disk shape, and may be provided with a plurality of fastening holes <NUM> formed around the motor shaft <NUM>. A female screw may be formed in each of the plurality of fastening holes <NUM>.

The adapter <NUM> may be coupled to the ring gear <NUM>, and may be fixed to the connecting plate <NUM> connected to the motor shaft <NUM>. The adapter <NUM> may be formed integrally with the ring gear <NUM>.

The adapter <NUM> may include a base portion <NUM>, a connecting portion <NUM>, and a ring gear plate <NUM>.

The base portion <NUM> may be formed in a disk corresponding to the connecting plate <NUM> of the motor <NUM>, and may be provided with a plurality of fixing holes <NUM> that are formed around the connecting portion <NUM> at predetermined intervals. Accordingly, when the plurality of bolts <NUM> are fastened to the plurality of fastening holes <NUM> of the connecting plate <NUM> through the plurality of fixing holes <NUM>, the adapter <NUM> is fixed to the connecting plate <NUM>.

The connecting portion <NUM> may be extend vertically from the center of the base portion <NUM>, and may be connected to the ring gear plate <NUM>. The connecting portion <NUM> may be integrally formed with the base portion <NUM> and the ring gear plate <NUM>.

The ring gear plate <NUM> may be formed in a disk corresponding to the ring gear <NUM>, may be spaced apart from the plurality of planet gears <NUM> and the sun gear <NUM>, and may be formed to be connected to the ring gear <NUM>.

In the case of this embodiment, the ring gear plate <NUM> may be formed integrally with the ring gear <NUM>. Although not illustrated, as another example, the ring gear plate <NUM> may be formed separately from the ring gear <NUM>, and may be coupled to the ring gear <NUM> by fastening elements such as bolts.

When the motor <NUM> is fixed to the recursive rotation bracket <NUM>, the connecting plate <NUM> disposed at the front end of the motor shaft <NUM> is connected to the adapter <NUM> coupled to the ring gear <NUM>. Accordingly, when the motor shaft <NUM> rotates, the connecting plate <NUM> is rotated. When the connecting plate <NUM> rotates, the adapter <NUM> is rotated integrally with the connecting plate <NUM>.

When the adapter <NUM> rotates, the ring gear <NUM> fixed to the ring gear plate <NUM> of the adapter <NUM> may rotate integrally with the motor shaft <NUM>.

When the ring gear <NUM> rotates, the plurality of planet gears <NUM> meshed with the ring gear <NUM> are rotated. When the plurality of planet gears <NUM> rotate, the carrier <NUM> and the recursive rotation bracket <NUM> are rotated based on the central axis of the sun gear <NUM>, that is, the central axis of the motor shaft <NUM>.

In other words, when the ring gear <NUM> rotates, the plurality of planet gears <NUM> meshed with the ring gear <NUM> are rotated about the plurality of shafts <NUM>, respectively, and are revolved around the sun gear <NUM> along the ring gear <NUM>. The carrier <NUM> and the recursive rotation bracket <NUM> are rotated based on the sun gear <NUM> by the revolution of the plurality of planet gears <NUM>.

Accordingly, the rotation of the recursive rotation bracket <NUM> further rotates the motor shaft <NUM> by a predetermined angle. As a result, the gear ratio of the planetary gear transmission device <NUM> according to an embodiment may be different from that of the planetary gear device of the related art.

As in the above-described embodiment, when the sun gear <NUM> is fixed, the ring gear <NUM> is used as an input part, and the carrier <NUM> is used as an output part, the gear ratio of the planetary gear device <NUM> of the related art is R/(S+R). Here, S is the number of teeth of the sun gear, and R is the number of teeth of the ring gear.

Therefore, when the motor <NUM> rotates the ring gear <NUM> by N, the carrier <NUM> rotates (R/(S+R))N= cN (c=R/(S+R)).

At this time, because the carrier <NUM> is disposed in the recursive rotation bracket <NUM> and the motor <NUM> is fixed to the recursive rotation bracket <NUM>, the rotation of the carrier <NUM> causes the motor <NUM> to rotate by a predetermined angle. Accordingly, the ring gear <NUM> is also rotated at the same angle as the motor <NUM>.

When the ring gear <NUM> is further rotated, the carrier <NUM> is also rotated further. This process may be repeated infinitely and converge. This result may be expressed as a formula as follows:.

In other words, in the planetary gear transmission device <NUM> according to an embodiment, when the ring gear <NUM> is rotated N by the motor <NUM>, the carrier <NUM> is rotated (<NUM>/b)N. Because the carrier <NUM> is disposed in the recursive rotation bracket <NUM>, when the carrier <NUM> rotates, the recursive rotation bracket <NUM> integrally rotates. Accordingly, the output member fixed to the recursive rotation bracket <NUM> rotates (<NUM>/b)N. As a result, the torque by the planetary gear transmission device <NUM> according to an embodiment may be increased by b times due to the gear ratio.

When both the input part and the output part are disposed one side of the planetary gear devices <NUM>, <NUM>, and <NUM>, like the planetary gear transmission device <NUM>, <NUM>, and <NUM> according to an embodiment having the above-described structure, the size of the planetary gear transmission device may be reduced compared to the planetary gear transmission device of the related art in which the input part and the output part are disposed on opposite sides of the planetary gear device interposed therebetween.

Hereinafter, a robot including a planetary gear transmission device according to an embodiment as described above will be described.

<FIG> is a perspective view illustrating a robot using a planetary gear transmission device according to an embodiment. For reference, a robot <NUM> shown in <FIG> represents a robot that is capable of autonomous movement to transport items that may be used in stores, etc. and has a head <NUM> to be rotated at a predetermined angle.

Referring to <FIG>, a robot <NUM> according to an embodiment may include a main body <NUM> and a head <NUM>.

The main body <NUM> is provided with a plurality of wheels (not illustrated) at the lower part of the main body <NUM>, so that the main body <NUM> may be driven autonomously. Shelves <NUM> capable of receiving items may be provided at the rear of the main body <NUM>. The shelves <NUM> may be formed in an appropriate shape according to the type of the item carried by the robot <NUM>.

The head <NUM> is disposed on the upper end of the main body <NUM> and may be formed to rotate at a predetermined angle in a vertical direction and a horizontal direction with the main body <NUM>. The planetary gear transmission device <NUM>, <NUM>, and <NUM> according to an embodiment may be used as a joint <NUM> connecting the head <NUM> and the main body <NUM>.

Hereinafter, the structure of the joint <NUM> connecting the main body <NUM> and the head <NUM> of the robot <NUM> of <FIG> will be described in detail with reference to <FIG>.

<FIG> is a perspective view illustrating a structure of a joint connecting a main body and a head of the robot of <FIG> according to an embodiment. For reference, <FIG> shows a state in which covers covering the main body <NUM> and the head <NUM> are removed from the robot <NUM> of <FIG>.

Referring to <FIG>, the joint <NUM> connecting the main body <NUM> and the head <NUM> of the robot <NUM> according to an embodiment may include a main body frame <NUM>, a head frame <NUM>, and a planetary gear transmission device <NUM>.

The main body frame <NUM> may be disposed on the upper end of the main body <NUM>, and the planetary gear transmission device <NUM> may be disposed in the main body frame <NUM>.

A horizontal rotation part <NUM> that allows the head frame <NUM> to rotate in the left-and-right direction (arrow A) with respect to the main body frame <NUM> around a vertical axis <NUM> perpendicular to the main body frame <NUM> may be disposed on the upper surface of the main body frame <NUM>.

A pair of fixing parts <NUM> for supporting the head frame <NUM> may be provided on the upper surface of the horizontal rotation part <NUM>. The pair of fixing parts <NUM> may be disposed at a predetermined distance apart from each other on the upper surface of the horizontal rotation part <NUM>. The fixing bracket <NUM> and a support bracket <NUM> connected to the planetary gear transmission device <NUM> may be disposed at the pair of fixing parts <NUM>, respectively.

The head frame <NUM> may be disposed to rotate at a predetermined angle with respect to the main body <NUM>, that is, the main body frame <NUM>. For example, the head frame <NUM> may be disposed to rotate at a predetermined angle in the vertical direction (arrow B) around a horizontal axis <NUM> parallel to the upper surface of the main body frame <NUM>. Accordingly, the head frame <NUM> may be referred to as a moving member capable of rotating at a predetermined angle with respect to the main body <NUM>.

The planetary gear transmission device <NUM> may be disposed between the main body <NUM> and the head <NUM>, and may allow the head <NUM> to rotate at a predetermined angle in the vertical direction with respect to the main body <NUM>. For example, the planetary gear transmission device <NUM> is disposed between the main body frame <NUM> and the head frame <NUM>, and allows the head frame <NUM> to rotate at a predetermined angle in the vertical direction with respect to the main body frame <NUM>.

In detail, the head frame <NUM> is fixed to the output part of the planetary gear transmission device <NUM>, so that the head frame <NUM> may be rotated at a predetermined angle by the output of the planetary gear device <NUM>. In this case, the motor <NUM> for inputting power to the planetary gear device <NUM> is disposed at the output part of the planetary gear device <NUM>.

As described above, the planetary gear transmission device <NUM> according to an embodiment may be formed to output power of the motor <NUM> through any one of the carrier <NUM>, the ring gear <NUM>, and the sun gear <NUM> of the planetary gear device <NUM>.

Accordingly, between the main body frame <NUM> and the head frame <NUM>, any one of the above-described various planetary gear transmission devices <NUM>, <NUM>, <NUM> may be disposed.

<FIG> illustrates the structure of the joint <NUM> connecting the main body <NUM> and the head <NUM> of the robot <NUM>, and the planetary gear transmission device <NUM>, in which the rotational force of the motor <NUM> is input to the sun gear <NUM>, and then is output through the carrier <NUM> as illustrated in <FIG>, <FIG>, <FIG>, and <FIG>, is applied to the joint <NUM>.

Referring to <FIG>, the planetary gear transmission device <NUM> may include the planetary gear device <NUM>, the fixing bracket <NUM>, the recursive rotation bracket <NUM>, and the motor <NUM>.

The planetary gear device <NUM> may include a sun gear <NUM>, a ring gear <NUM>, a plurality of planet gears <NUM>, and a carrier <NUM> supporting the plurality of planet gears <NUM>, and the ring gear <NUM> may be fixed to the main body <NUM>.

In detail, the ring gear <NUM> is fixed to the fixing bracket <NUM>, and the fixing bracket <NUM> is disposed on the main body frame <NUM>. In other words, the fixing bracket <NUM> is disposed on one of the pair of fixing parts <NUM> disposed on the horizontal rotation part <NUM> of the main body frame <NUM>.

The support bracket <NUM> is disposed on the other one of the pair of fixing parts <NUM> of the horizontal rotation part <NUM> to face the fixing bracket <NUM>. The support bracket <NUM> may be disposed to rotatably support the other end of the motor <NUM>.

Accordingly, the motor <NUM> may rotate with respect to the fixing bracket <NUM> and the support bracket <NUM> based on a straight line passing through the motor shaft <NUM> (see <FIG>), that is, the horizontal axis <NUM>.

Because the motor <NUM> is fixed to the head frame <NUM>, when the motor <NUM> rotates, the head frame <NUM> also rotates.

In addition, the motor <NUM> is disposed in the recursive rotation bracket <NUM>, and the motor shaft <NUM> of the motor <NUM> is connected to the sun gear <NUM> of the planetary gear device <NUM>. Further, the recursive rotation bracket <NUM> is fixed to the carrier <NUM> of the planetary gear device <NUM>.

Therefore, when the sun gear <NUM> of the planetary gear device <NUM> is rotated by the motor shaft <NUM>, the motor <NUM> is rotated by the recursive rotation bracket <NUM>, and the head frame <NUM> is also rotated. In other words, the motor <NUM> and the head frame <NUM> are rotated at the same time by the recursive rotation bracket <NUM>.

In detail, when the motor <NUM> is turned on and the motor shaft <NUM> rotates, the sun gear <NUM> of the planetary gear device <NUM> is rotated. Because the ring gear <NUM> is fixed by the fixing bracket <NUM> disposed on the main body frame <NUM>, when the sun gear <NUM> of the planetary gear device <NUM> rotates, the carrier <NUM> is rotated. In other words, the rotation of the motor <NUM> input to the sun gear <NUM> is output as the rotation of the carrier <NUM>.

Because the recursive rotation bracket <NUM> is fixed to the carrier <NUM>, when the carrier <NUM> rotates, the recursive rotation bracket <NUM> rotates integrally. Because the motor <NUM> is fixed to the recursive rotation bracket <NUM>, when the recursive rotation bracket <NUM> rotates, the motor <NUM> rotates integrally with the recursive rotation bracket <NUM>.

Because the motor <NUM> is fixed to the head frame <NUM>, when the motor <NUM> rotates, the head frame <NUM> is rotated integrally with the motor <NUM>. In other words, when the motor shaft <NUM> rotates, the recursive rotation bracket <NUM> is rotated through the sun gear <NUM> and the carrier <NUM> of the planetary gear device <NUM> so that the head frame <NUM> is rotated.

Hereinafter, a case where the planetary gear transmission device <NUM> according to an embodiment is used in a robot arm manipulator <NUM> will be described with reference to <FIG> and <FIG>.

<FIG> is a perspective view illustrating a robot arm manipulator using a planetary gear transmission device according to an embodiment. <FIG> is an exploded perspective view illustrating a pitch rotation axis of the robot arm manipulator of <FIG> according to an embodiment.

Referring to <FIG>, the robot arm manipulator <NUM> may include a plurality of arm parts <NUM>, <NUM>, <NUM>, and <NUM>, two pitch rotation axes <NUM> and <NUM>, and one roll rotation axis <NUM>.

A first pitch rotation axis <NUM> may be disposed between a first arm part <NUM> and a second arm part <NUM>, and may be formed to allow the second arm part <NUM> to rotate at a predetermined angle in a direction perpendicular to the first arm part <NUM> (arrow C). Although not illustrated, the first arm part <NUM> may be disposed on a main body. The first arm part <NUM> may be disposed to rotate with respect to the main body.

A second pitch rotation axis <NUM> may be disposed between a third arm part <NUM> and a fourth arm part <NUM>, and may be formed to allow the fourth arm part <NUM> to rotate at a predetermined angle in a direction perpendicular to the third arm part <NUM> (arrow D). Although not illustrated, a hand capable of holding an object may be disposed at the tip of the fourth arm part <NUM>.

The roll rotation axis <NUM> may be disposed between the second arm part <NUM> and the third arm part <NUM>, and may be formed to allow the third arm part <NUM> to rotate in both directions (arrow E) around the central axis of the second arm part <NUM>.

The first pitch rotation axis <NUM>, the second pitch rotation axis <NUM>, and the roll rotation axis <NUM> may use the planetary gear transmission device <NUM> according to an embodiment as described above.

Hereinafter, an example in which the planetary gear transmission device <NUM> according to an embodiment is used in the first pitch rotation axis <NUM> will be described with reference to <FIG>.

<FIG> illustrates the first pitch rotation axis <NUM> of the robot arm manipulator <NUM> to which the planetary gear transmission device <NUM>, in which the power of the motor <NUM> is input to the sun gear <NUM>, and then is output through the carrier <NUM> as illustrated in <FIG>, <FIG>, <FIG>, and <FIG>, is applied.

One end of the second arm part <NUM> may be coupled to one end of the first arm part <NUM> to rotate at a predetermined angle in the vertical direction with respect to the first arm part <NUM>.

The planetary gear transmission device <NUM> may be disposed between one end of the first arm part <NUM> and one end of the second arm part <NUM>, and may allow the second arm part <NUM> to rotate at a predetermined angle with respect to one end of the first arm part <NUM>.

Referring to <FIG>, the planetary gear transmission device <NUM> may include the planetary gear device <NUM>, the recursive rotation bracket <NUM>, and the motor <NUM>.

The planetary gear device <NUM> may include a sun gear <NUM>, a ring gear <NUM>, a plurality of planet gears <NUM>, and a carrier <NUM> supporting the plurality of planet gears <NUM>, and the ring gear <NUM> may be fixed to one end of the first arm part <NUM>.

In detail, the ring gear <NUM> is fixed to the fixing bracket <NUM>, and the fixing bracket <NUM> is disposed at one end of the first arm part <NUM>. Because the other end of the first arm part <NUM> is disposed in the main body (not illustrated), the fixing bracket <NUM> is disposed in the main body.

The motor <NUM> is disposed at one end of the second arm part <NUM>. In detail, a motor bracket <NUM> is disposed at one end of the second arm part <NUM>, and the motor <NUM> is fixed to the motor bracket <NUM>. Accordingly, when the motor <NUM> rotates, the second arm part <NUM> rotates integrally with the motor <NUM>.

In addition, the motor <NUM> is disposed in the recursive rotation bracket <NUM>, and the motor shaft <NUM> of the motor <NUM> is connected to the sun gear <NUM> of the planetary gear device <NUM> through an adapter <NUM>. Further, the recursive rotation bracket <NUM> is fixed to the carrier <NUM> of the planetary gear device <NUM>.

Therefore, when the sun gear <NUM> of the planetary gear device <NUM> is rotated by the motor shaft <NUM>, the motor <NUM> is rotated by the recursive rotation bracket <NUM>, and the second arm part <NUM> is also rotated. In other words, the motor <NUM> and the second arm part <NUM> are rotated at the same time by the recursive rotation bracket <NUM>.

In detail, when the motor shaft <NUM> of the motor <NUM> rotates, the sun gear <NUM> of the planetary gear device <NUM> is rotated. Because the ring gear <NUM> is fixed by the fixing bracket <NUM> disposed at one end of the first arm part <NUM>, when the sun gear <NUM> of the planetary gear device <NUM> rotates, the carrier <NUM> is rotated. In other words, the rotation of the motor <NUM> input to the sun gear <NUM> is output as the rotation of the carrier <NUM>.

Because the motor <NUM> is fixed to the motor bracket <NUM> of the second arm part <NUM>, when the motor <NUM> rotates, the second arm part <NUM> rotates integrally with the motor <NUM>. In other words, when the motor shaft <NUM> rotates, the recursive rotation bracket <NUM> is rotated through the sun gear <NUM> and the carrier <NUM> of the planetary gear device <NUM> so that the second arm part <NUM> is rotated.

Therefore, in the embodiment of the robot arm manipulator <NUM> shown in <FIG>, the first arm part <NUM> functions as a main body fixing the planetary gear transmission device <NUM>, and the second arm part <NUM> functions as a moving member that is rotated by the planetary gear transmission device <NUM>.

In the above description, the second arm part <NUM> is fixed to the motor <NUM>. However, in another embodiment, the second arm part <NUM> may be directly fixed to the recursive rotation bracket <NUM>, not the motor <NUM>. Even in this case, when the recursive rotation bracket <NUM> rotates, the second arm part <NUM> is rotated.

On the other hand, in <FIG>, the planetary gear transmission device <NUM>, in which the power of the motor <NUM> is input to the sun gear <NUM>, and then is output through the carrier <NUM>, is applied to the robot arm manipulator <NUM>. However, the planetary gear transmission device applied to the robot arm manipulator <NUM> is not limited thereto. The planetary gear transmission devices <NUM> and <NUM> according to the other embodiments described above may be applied to the robot arm manipulator <NUM>.

Hereinafter, a case where a planetary gear transmission device according to an embodiment is used in a robot waist joint <NUM> will be described with reference to <FIG>.

<FIG> is a perspective view illustrating a robot waist joint using a planetary gear transmission device according to an embodiment.

Referring to <FIG>, a robot waist joint <NUM> may be disposed between a lower body <NUM> and an upper body <NUM>. The robot waist joint <NUM> may be provided so that the upper body <NUM> rotates at a predetermined angle in the front and rear direction (arrow F) with respect to the lower body <NUM>.

The robot waist joint <NUM> may include a fixed plate <NUM>, a moving plate <NUM>, and a planetary gear transmission device <NUM> disposed between the fixed plate <NUM> and the moving plate <NUM>.

The fixed plate <NUM> is fixed to the upper end of the lower body <NUM>, and the moving plate <NUM> that is fixed to the lower end of the upper body <NUM> and provided to rotate at a predetermined angle with respect to the fixed plate <NUM>.

The planetary gear transmission device <NUM> allows the moving plate <NUM> to rotate with respect to the fixed plate <NUM> at a predetermined angle.

The planetary gear device <NUM> may include a sun gear <NUM>, a ring gear <NUM>, a plurality of planet gears <NUM>, and a carrier <NUM> supporting the plurality of planet gears <NUM>, and the ring gear <NUM> may be fixed to the fixed plate <NUM>.

In detail, the ring gear <NUM> is fixed to the fixing bracket <NUM>, and the fixing bracket <NUM> is disposed on the upper surface of the fixed plate <NUM>. Because the fixed plate <NUM> is disposed on the upper end of the lower body <NUM>, the fixing bracket <NUM> is disposed on the lower body <NUM>.

The motor <NUM> is disposed in the lower surface of the moving plate <NUM>. Accordingly, when the motor <NUM> rotates, the moving plate <NUM> rotates integrally with the motor <NUM>. The other end of the motor <NUM> may be supported by a support bracket <NUM> so that the moving plate <NUM> may stably rotate. In other words, the support bracket <NUM> may be disposed to rotatably support the motor <NUM> on the opposite side of the fixing bracket <NUM>.

Therefore, when the sun gear <NUM> of the planetary gear device <NUM> is rotated by the motor shaft <NUM>, the motor <NUM> is rotated by the recursive rotation bracket <NUM>, and the moving plate <NUM> is also rotated. In other words, the motor <NUM> and the moving plate <NUM> are rotated at the same time by the recursive rotation bracket <NUM>.

In detail, when the motor shaft <NUM> of the motor <NUM> rotates, the sun gear <NUM> of the planetary gear device <NUM> is rotated. Because the ring gear <NUM> is fixed by the fixing bracket <NUM> disposed on the fixed plate <NUM>, when the sun gear <NUM> of the planetary gear device <NUM> rotates, the carrier <NUM> is rotated. In other words, the rotation of the motor <NUM> input to the sun gear <NUM> is output as the rotation of the carrier <NUM>.

Because the motor <NUM> is fixed to the lower surface of the moving plate <NUM>, when the motor <NUM> rotates, the moving plate <NUM> rotates integrally with the motor <NUM>. In other words, when the motor shaft <NUM> rotates, the recursive rotation bracket <NUM> is rotated through the sun gear <NUM> and the carrier <NUM> of the planetary gear device <NUM> so that the moving plate <NUM> is rotated.

Because the fixed plate <NUM> is disposed on the upper end of the lower body <NUM> and the moving plate <NUM> is disposed on the lower end of the upper body <NUM>, when the moving plate <NUM> is rotated with respect to the fixed plate <NUM>, the upper body <NUM> is rotated at a predetermined angle with respect to the lower body <NUM>.

Therefore, in the embodiment of the robot waist joint <NUM> shown in <FIG>, the lower body <NUM> functions as a main body fixing the planetary gear transmission device <NUM>, and the upper body <NUM> functions as a moving member that is rotated by the planetary gear transmission device <NUM>.

In the above description, the moving plate <NUM> is fixed to the motor <NUM>. However, as another embodiment, the moving plate <NUM> may be directly fixed to the recursive rotation bracket <NUM> instead of the motor <NUM>. Even in this case, when the recursive rotation bracket <NUM> rotates, the moving plate <NUM> is rotated.

Claim 1:
A planetary gear transmission device (<NUM>, <NUM>', <NUM>, <NUM>) comprising:
a planetary gear device (<NUM>, <NUM>, <NUM>) including a sun gear (<NUM>, <NUM>, <NUM>), a ring gear (<NUM>, <NUM>, <NUM>), a plurality of planet gears (<NUM>, <NUM>, <NUM>), and a carrier (<NUM>, <NUM>, <NUM>) supporting the plurality of planet gears (<NUM>, <NUM>, <NUM>); and
a motor (<NUM>) configured to generate a rotational force input to the planetary gear device (<NUM>, <NUM>, <NUM>), the motor (<NUM>, <NUM>') including a motor shaft (<NUM>, <NUM>') and a motor body (<NUM>) supporting the motor shaft (<NUM>, <NUM>');
characterized in that the planetary gear transmission device (<NUM>, <NUM>', <NUM>, <NUM>) comprises:
a fixing bracket (<NUM>, <NUM>, <NUM>) formed to fix any one of the sun gear (<NUM>, <NUM>, <NUM>), the ring gear (<NUM>, <NUM>, <NUM>), or the carrier (<NUM>, <NUM>, <NUM>) of the planetary gear device (<NUM>, <NUM>, <NUM>) to prevent rotation; and
a recursive rotation bracket (<NUM>, <NUM>, <NUM>) provided with the motor (<NUM>, <NUM>') and fixed to any one of the sun gear (<NUM>, <NUM>, <NUM>), the ring gear (<NUM>, <NUM>, <NUM>), or the carrier (<NUM>, <NUM>, <NUM>) of the planetary gear device (<NUM>, <NUM>, <NUM>), which is not fixed by the fixing bracket (<NUM>, <NUM>, <NUM>),
wherein the recursive rotation bracket (<NUM>, <NUM>, <NUM>) is formed so that the motor shaft (<NUM>, <NUM>') of the motor (<NUM>, <NUM>') is connected to any one of the sun gear (<NUM>, <NUM>, <NUM>), the ring gear (<NUM>, <NUM>, <NUM>), or the carrier (<NUM>, <NUM>, <NUM>) of the planetary gear device (<NUM>, <NUM>, <NUM>), to which the fixing bracket (<NUM>, <NUM>, <NUM>) and the recursive rotation bracket (<NUM>, <NUM>, <NUM>) are not fixed, and
wherein, when any one of the sun gear (<NUM>, <NUM>, <NUM>), the ring gear (<NUM>, <NUM>, <NUM>), or the carrier (<NUM>, <NUM>, <NUM>) of the planetary gear device (<NUM>, <NUM>, <NUM>) connected to the motor shaft (<NUM>, <NUM>') is rotated by the motor shaft (<NUM>, <NUM>'), the motor body (<NUM>) is rotated by the recursive rotation bracket (<NUM>, <NUM>, <NUM>) and the rotational force of the motor shaft (<NUM>, <NUM>') is output through the recursive rotation bracket (<NUM>, <NUM>, <NUM>).