Patent Description:
A joint structure used in a robot may be manufactured in such a manner that a plurality of rotation shafts are sequentially combined. Specifically, a joint for a robot has a series structure in which a motor is directly connected to each rotation shaft, a link structure in which a heavy motor is concentrated to a lower end of a mechanism using a wire or a link, or an interference drive structure in which a plurality of degrees of freedom are connected in parallel.

The interference drive structure is widely used as a joint structure for a robot because a weight can be efficiently distributed by disposing a drive source near an upper shaft, a structure is simple, and modularization can be made in units of shafts.

In the related art, interference drive structures mainly use bevel gears or wires. However, in a case where a bevel gear is used, there are problems in that the gear needs to be machined with high precision, the production cost is very high, and it is difficult to support a load in an axial direction. In addition, when a wire is used, there are problems in that a degree of difficulty is high in terms of assembly and maintenance, and the volume of the entire structure increases because the wire needs to have a radius of curvature having a specific value or more.

<CIT> proposes a robotic joint configured as a <NUM>-axis joint. The joint includes an input roll assembly and a pitch-output roll assembly. The pitch-output roll assembly includes: a housing; a differential mechanism including left and right input gears, an output gear, a cross element interconnecting the gears, and a clevis supporting the gears and the cross element; a left four-bar linkage coupled to the left input gear; a right four-bar linkage coupled to the right input gear; and first and second linear actuators connected to the left and right four-bar linkages. The first and second linear actuators selectively drive the left and right input gears to rotate the output gear about an output roll axis and to rotate the cross element about a pitch axis passing through the cross element and input gears. A linear actuator in the input roll assembly rotates the pitch-output roll housing about an input roll axis.

<CIT> relates to various robotic and/or in vivo medical devices having compact joint configurations and at least three degrees of freedom. Other embodiments relate to various medical device components, including forearms having grasper or cautery end effectors, that can be incorporated into certain robotic and/or in vivo medical devices.

<CIT> relates to a robot wrist structure and a robot. The robot wrist structure comprises a shell, a first motor, a second motor, a first transmission mechanism, a second transmission mechanism, a first driving conical gear, a second driving conical gear, a driven conical gear, a holder, and an output connecting part; the first motor and the second motor are arranged on the shell, the first driving conical gear, the second driving conical gear, and the driven conical gear are rotatably mounted on the holder, the axis of the first driving conical gear is colinear with the axis of the second driving conical gear and is perpendicularly crossed with the driven conical gear, the first driving conical gear, and the second driving conical gear are engaged with the driven conical gear, the first motor is connected with the first driving conical gear through the first transmission mechanism, the second motor is connected with the second driving conical gear through the second transmission mechanism, and the output connecting part is fixedly connected with the driven conical gear. The robot wrist structure is diverse in motion mode, high in flexibility and wide in work range.

The disclosure provides a joint device for a robot having two-directional degrees of freedom of rotation using friction wheels.

According to an aspect of the disclosure, there is provided a joint device according to claim <NUM>.

More specific features are specified in the dependent claims.

It should be understood that embodiments to be described below are exemplarily provided to help the understanding of the disclosure, and the disclosure may be modified in various ways, unlike the embodiments described herein. However, in the following description of the disclosure, if it is determined that a detail description of a related known function or component may unnecessarily obscure the gist of the disclosure, the detailed description and concrete illustration thereof will be omitted. Further, the accompanying drawings are not necessarily illustrated to scale but dimensions of some components may be exaggerated to help the understanding of the disclosure.

The terms used in the specification and the claims are general terms selected in consideration of functions in the disclosure. However, these terms may vary depending on intentions of those skilled in the art, legal or technical interpretation, emergence of new technologies, and the like. Also, some terms may be arbitrarily selected by the applicant. These terms may be construed as meanings defined in the specification, and may be construed based on the entire text of the specification and the common technical knowledge in the art unless specifically defined.

In the specification, the expressions "have", "may have", "include", "may include", and the like indicate the presence of stated features (e.g., numbers, functions, operations, or components such as parts), but do not preclude the presence or additional features.

In addition, in the specification, components required for describing each embodiment of the disclosure are described, and the components are not necessarily limited thereto. Therefore, some components may be changed or omitted and other components may be added. In addition, components may be arranged in different independent devices in a distributed manner.

Furthermore, embodiments of the disclosure will hereinafter be described in detail with reference to the accompanying drawings and contents described in the accompanying drawings, but the disclosure is not limited or restricted by the embodiments.

Hereinafter, the disclosure will be described in more detail with reference to the accompanying drawings.

<FIG> is a perspective view of a joint device for a robot according to an embodiment of the disclosure. <FIG> is an exploded perspective view of the joint device for the robot of <FIG>. <FIG> is an exploded perspective view of components fitted on a first shaft. <FIG> is a cross-sectional view taken along line A-A of the joint device for the robot of <FIG>.

Referring to <FIG>, a joint device <NUM> for a robot according to an embodiment of the disclosure may include a first shaft <NUM>, a second shaft <NUM>, a first friction wheel <NUM>, a second friction wheel <NUM>, a third friction wheel <NUM>, and a driving device <NUM>.

The first shaft <NUM> may rotatably support the first friction wheel <NUM> and the second friction wheel <NUM> at opposite ends of the first shaft <NUM>, respectively. Accordingly, the first and second friction wheels <NUM> and <NUM> may rotate around the first shaft <NUM> with the same rotation axis.

The first shaft <NUM> may be disposed parallel to a Y axis. That is, the rotation axis of the first and second friction wheels <NUM> and <NUM> may be parallel to the Y axis. The first shaft <NUM> may have a cylindrical shape.

The second shaft <NUM> may rotatably support the third friction wheel <NUM> at one end of the second shaft <NUM>. Accordingly, the third friction wheel <NUM> may rotate around the second shaft <NUM>.

The second shaft <NUM> may be disposed perpendicular to the first shaft <NUM>. For example, the second shaft <NUM> may be disposed parallel to an X axis. That is, a rotation axis of the third friction wheel <NUM> may be parallel to the X axis. Like the first shaft <NUM>, the second shaft <NUM> may have a cylindrical shape.

The second shaft <NUM> may be integrally formed with the first shaft <NUM>. Specifically, the first and second shafts <NUM> and <NUM> may together form an integral shaft having a "T" or "X" shape to rotatably support the first, second, and third friction wheels <NUM>, <NUM>, and <NUM>. However, the first and second shafts <NUM> and <NUM> may be formed separately, rather than integrally formed.

The first friction wheel <NUM> and the second friction wheel <NUM> may rotate in a state where they are fitted on the first shaft <NUM>. The first and second friction wheels <NUM> and <NUM> may have a truncated cone shape.

The first and second friction wheels <NUM> and <NUM> may be arranged to be symmetric with respect to the second shaft <NUM>. Specifically, the first and second friction wheels <NUM> and <NUM> may be disposed to have a cross section that becomes smaller as being closer to the second shaft <NUM>.

The third friction wheel <NUM> may rotate in a state where they are fitted on the second shaft <NUM>. The third friction wheel <NUM> may have a truncated cone shape. Specifically, the third friction wheel <NUM> may be disposed to have a cross section that becomes smaller as being closer to the first shaft <NUM>.

The third friction wheel <NUM> may contact the first and second friction wheels <NUM> and <NUM> simultaneously at different positions. Accordingly, the third friction wheel <NUM> may be passively rotated by a rotational force transferred from the first and second friction wheels <NUM> and <NUM> due to a frictional force generated in portions contacting the first and second friction wheels <NUM> and <NUM>.

The first, second, and third friction wheels <NUM>, <NUM>, and <NUM> may be formed of aluminum, but their material is not limited thereto. Accordingly, it is possible to reduce the weight of the joint device <NUM> for the robot and lower the overall specifications of the joint device <NUM> for the robot.

In addition, the first, second, and third friction wheels <NUM>, <NUM>, and <NUM> may smoothly rotate without noise because they continuously contact each other without teeth formed on their surfaces, which does not cause backlash. In addition, the first, second, and third friction wheels <NUM>, <NUM>, and <NUM> may be produced at a lower cost than gears, and may require fewer parts than wires, thereby reducing maintenance costs.

Specifically, a side surface of the third friction wheel <NUM> may simultaneously contact respective side surfaces of the first and second friction wheels <NUM> and <NUM>. Specifically, the third friction wheel <NUM> may contact the first friction wheel <NUM> along a first line L1, and contact the second friction wheel <NUM> along a second line L2. Also, the first and second lines L1 and L2 may intersect at an intersection between central axes C1 and C2 of the first and second shafts <NUM> and <NUM>.

When the first and second friction wheels <NUM> and <NUM> rotate in the same direction, the third friction wheel <NUM> may rotate in a pitch direction because the third friction wheel <NUM> receives a frictional force from the first and second friction wheels <NUM> and <NUM> in the same direction. The pitch direction may be a direction of rotation with respect to a rotation axis parallel to the Y axis.

When the first and second friction wheels <NUM> and <NUM> rotate in opposite directions, the third friction wheel <NUM> may rotate in a roll direction because the third friction wheel <NUM> receives a frictional force from the first and second friction wheels <NUM> and <NUM> in different directions. The roll direction may be a direction of rotation with respect to a rotation axis parallel to the X axis.

That is, the third friction wheel <NUM> may be passively rotated by a rotational force transferred from the first and second friction wheels <NUM> and <NUM>, and may have two degrees of freedom of rotation depending on the rotation directions of the first and second friction wheels <NUM> and <NUM>. A process in which the third friction wheel <NUM> rotates based on the two degrees of freedom of rotation will be described in detail with reference to <FIG> and <FIG>.

A connection plate <NUM> may be disposed on a front surface of the third friction wheel <NUM>. The connection plate <NUM> may have a disk shape and may be coupled to the third friction wheel <NUM> to rotate integrally with the third friction wheel <NUM>.

Any one of various robot structures may be coupled to the connection plate <NUM>. For example, any one of various parts of the robot, such as an arm, a hand, a foot, a leg, and a head, may be coupled to the connection plate <NUM> to rotate together with the third friction wheel <NUM>.

Bearings <NUM> and <NUM> may be disposed between the third friction wheel <NUM> and the second shaft <NUM>. Although the two bearings <NUM> and <NUM> are illustrated, the number of bearings is not limited thereto.

The bearings <NUM> and <NUM> may be angular ball bearings, but the bearing type is not limited thereto. The bearings <NUM> and <NUM> enables the third friction wheel <NUM> to easily rotate relative to the second shaft <NUM>, which is stationary.

The driving device <NUM> may rotate each of the first and second friction wheels <NUM> and <NUM>. For example, the driving device <NUM> may include a first motor <NUM> and a second motor <NUM>. The first motor <NUM> may rotate the first friction wheel <NUM>, and the second motor <NUM> may rotate the second friction wheel <NUM>.

The first and second motors <NUM> and <NUM> may be supported by a frame <NUM>, and may be positioned behind the first, second, and third friction wheels <NUM>, <NUM>, and <NUM>.

For example, the driving device <NUM> may further include a first pulley <NUM>, a second pulley <NUM>, a first timing belt <NUM>, and a second timing belt <NUM>.

The first and second pulleys <NUM> and <NUM> may be fitted on the first shaft <NUM> to rotate around the first shaft <NUM>. The first pulley <NUM> may be disposed on a rear surface of the first friction wheel <NUM>, and the second pulley <NUM> may be disposed at a rear surface of the second friction wheel <NUM>.

The first timing belt <NUM> may partially surround a circumference of the first pulley <NUM> to provide a driving force of the first motor <NUM> to the first pulley <NUM>. In addition, the first pulley <NUM> may be coupled to the first friction wheel <NUM> to rotate integrally with the first friction wheel <NUM>.

Similarly, the second timing belt <NUM> may partially surround a circumference of the second pulley <NUM> to provide a driving force of the second motor <NUM> to the second pulley <NUM>, and the second pulley <NUM> may be coupled to the second friction wheel <NUM> to rotate integrally with the second friction wheel <NUM>.

However, the above-described structure of the driving device <NUM> is an example, and the structure of the driving device <NUM> is not limited thereto. The driving device <NUM> may be implemented in any structure as long as it is capable of rotating the first and second friction wheels <NUM> and <NUM>.

The joint device <NUM> for the robot may further include a first pressing member <NUM> and a second pressing member <NUM>. The first pressing member <NUM> may press the first friction wheel <NUM> toward the third friction wheel <NUM>. The second pressing member <NUM> may press the second friction wheel <NUM> toward the third friction wheel <NUM>.

As a result, the first and second pressing members <NUM> and <NUM> provide a pre-load to the first and second friction wheels <NUM> and <NUM>, thereby providing a sufficient frictional force to the third friction wheel <NUM>. Accordingly, a rotational force of the first and second friction wheels <NUM> and <NUM> may be easily transferred to the third friction wheel <NUM>.

For example, the first and second pressing members <NUM> and <NUM> may be disk springs fitted on the first shaft <NUM>. The disc springs are capable of pressurize the first and second friction wheels <NUM> and <NUM>, respectively, with a large elastic force even with a small displacement. Accordingly, the rotational force of the first and second friction wheels <NUM> and <NUM> can be more effectively transferred to the third friction wheel <NUM>, so that the joint device <NUM> for the robot can be manufactured in a small size.

The joint device <NUM> for the robot may further include a first nut <NUM> and a second nut <NUM>. The first nut <NUM> may be fitted at one end of the first shaft <NUM> to support one end of the first pressing member <NUM>. The second nut <NUM> may be fitted at the other end of the first shaft <NUM> to support one end of the second pressing member <NUM>.

For example, the first and second nuts <NUM> and <NUM> may be fixed by screw threads formed on side surfaces of the first shaft <NUM>. The pre-load of the first and second pressing members <NUM> and <NUM> may be adjusted depending on how much the first and second nuts <NUM> and <NUM> are tightened on the first shaft <NUM>.

The joint device <NUM> for the robot may further include a first bearing <NUM> and a second bearing <NUM>. The first bearing <NUM> may be disposed between the first shaft <NUM> and the first friction wheel <NUM>. The second bearing <NUM> may be disposed between the first shaft <NUM> and the second friction wheel <NUM>.

The first and second bearings <NUM> and <NUM> enable the first and second friction wheels <NUM> and <NUM> to easily rotate relative to the first shaft <NUM>, which is stationary.

The first and second bearings <NUM> and <NUM> may be angular ball bearings, each being capable of transferring an axial-directional load in an easier way. The angular ball bearing is capable of transferring a load in an axial direction as well as in a radial direction in an easy way because a straight line connecting contact points between a ball and inner and outer rings forms a predetermined angle with respect to the radial direction.

Accordingly, the first bearing <NUM> makes it possible to more easily transfer an elastic force transferred from the first pressing member <NUM> to the first friction wheel <NUM>. Similarly, the second bearing <NUM> makes it possible to more easily transfer an elastic force from the second pressing member <NUM> to the second friction wheel <NUM>.

Specifically, the inner ring <NUM> and the outer ring <NUM> of the first bearing <NUM> may contact the first pressing member <NUM> and the first friction wheel <NUM>, respectively. Accordingly, an elastic force of the first pressing member <NUM> may be transferred sequentially through the inner ring <NUM>, the ball <NUM>, and the outer ring <NUM> of the first bearing <NUM>, and finally transferred to the first friction wheel <NUM>.

Similarly, the inner ring <NUM> and the outer ring <NUM> of the second bearing <NUM> may contact the second pressing member <NUM> and the second friction wheel <NUM>, respectively. Accordingly, an elastic force of the second pressing member <NUM> may be transferred sequentially through the inner ring <NUM>, the ball <NUM>, and the outer ring <NUM> of the second bearing <NUM>, and finally transferred to the second friction wheel <NUM>.

That is, the first and second pressing members <NUM> and <NUM> may press the inner rings <NUM> and <NUM> of the first and second bearings <NUM> and <NUM>, which are stationary together with the first shaft <NUM>. Accordingly, since the objects pressed by the first and second pressing members <NUM> and <NUM> are stationary, it is possible to minimize wear resulting from friction.

In addition, the first and second pressing members <NUM> and <NUM> may have a convex shape toward the inner rings <NUM> and <NUM> of the first and second bearings <NUM> and <NUM>. For example, the first and second pressing members <NUM> and <NUM> may be cone-shaped disk springs each having an opening in a central portion.

Accordingly, the above-described shape of the first and second pressing members <NUM> and <NUM> makes it possible to press only the inner rings <NUM> and <NUM>, which are stationary, not the outer rings <NUM> and <NUM>, which are rotating, respectively.

The frame <NUM> may be disposed on a rear side of the joint device <NUM> for the robot to support the first shaft <NUM> and the driving device <NUM>. However, this is an example, and the shape and the arrangement of the frame <NUM> are not limited thereto.

In addition, the joint device <NUM> for the robot may further include a fourth friction wheel <NUM>. The fourth friction wheel <NUM> may be rotatably supported at the other end of the second shaft <NUM> intersecting the first shaft <NUM>.

The fourth friction wheel <NUM> may contact each of the first and second friction wheels <NUM> and <NUM>. For example, the fourth friction wheel <NUM> may have a truncated cone shape, and a side surface of the fourth friction wheel <NUM> may contact the side surfaces of the first and second friction wheels <NUM> and <NUM> simultaneously at different positions.

The fourth friction wheel <NUM> may have a shape to be symmetric to the third friction wheel <NUM> with respect to the first shaft <NUM>. Specifically, the fourth friction wheel <NUM> may have a truncated cone shape with a cross section gradually decreasing toward the first shaft <NUM>.

The fourth friction wheel <NUM> may face the third friction wheel <NUM>, and may rotate in the opposite direction to the third friction wheel <NUM>.

In addition, the fourth friction wheel <NUM> may support an area of each of the first and second pressing members <NUM> and <NUM> on the rear side thereof. Accordingly, the fourth friction wheel <NUM> may prevent the first and second friction wheels <NUM> and <NUM> from being deformed or the rotational axis of the first and second friction wheels <NUM> and <NUM> from being misaligned due to the elastic force of the first and second pressing members <NUM> and <NUM>.

<FIG> is a view illustrating a state in which the third friction wheel rotates in the roll direction. Referring to <FIG>, the first and second friction wheels <NUM> and <NUM> may rotate in different directions.

For example, when the first friction wheel <NUM> rotates in an R1 direction and the second friction wheel <NUM> rotates in an R2 direction, the third friction wheel <NUM> rotates around the second shaft <NUM> in an R4 direction. At this time, the fourth friction wheel <NUM> may rotate around the second shaft <NUM> in an R3 direction as opposed to the third friction wheel <NUM>.

Conversely, when the first friction wheel <NUM> rotates in the R2 direction and the second friction wheel <NUM> rotates in the R1 direction, the third friction wheel <NUM> may rotate around the second shaft <NUM> in the R3 direction. At this time, the fourth friction wheel <NUM> may rotate around the second shaft <NUM> in the R4 direction as opposed to the third friction wheel <NUM>.

That is, when the first and second friction wheels <NUM> and <NUM> rotate in different directions, the third friction wheel <NUM> may rotate around the second shaft <NUM> in the roll direction.

<FIG> is a view illustrating a state in which the third friction wheel rotates in a pitch direction. Referring to <FIG>, the first and second friction wheels <NUM> and <NUM> may rotate in the same direction.

For example, when both the first and second friction wheels <NUM> and <NUM> rotate in the R1 direction, the third friction wheel <NUM> may rotate around the first shaft <NUM> in the R1 direction. At this time, the fourth friction wheel <NUM> may rotate around the first shaft <NUM> in the R2 direction as opposed to the third friction wheel <NUM>.

Conversely, when both the first and second friction wheels <NUM> and <NUM> rotate in the R2 direction, the third friction wheel <NUM> may also rotate around the first shaft <NUM> in the R2 direction. At this time, the fourth friction wheel <NUM> may rotate around the first shaft <NUM> in the R1 direction as opposed to the third friction wheel <NUM>.

Specifically, the frame <NUM> may rotatably support both ends of the first shaft <NUM>, and the first and second shafts <NUM> and <NUM> may be integrally formed. In this case, when the first and second friction wheels <NUM> and <NUM> rotate in the same direction, the first shaft <NUM>, the second shaft <NUM>, and the third friction wheel <NUM> may rotate around the first shaft <NUM> in the R1 or R2 direction.

That is, when the first and second friction wheels <NUM> and <NUM> rotate in the same direction, the third friction wheel <NUM> may rotate around the first shaft <NUM> in the pitch direction.

Accordingly, the third friction wheel <NUM> may be passively rotated with two degrees of freedom of rotation depending on the rotation directions of the first and second friction wheels <NUM> and <NUM>.

Claim 1:
A joint device (<NUM>) for a robot, the joint device (<NUM>) comprising:
a first shaft (<NUM>);
a second shaft (<NUM>) disposed perpendicular to the first shaft (<NUM>);
a first friction wheel (<NUM>) rotatably supported by a first end of the first shaft (<NUM>);
a second friction wheel (<NUM>) rotatably supported by a second end of the first shaft (<NUM>);
a driving device (<NUM>) configured to rotate each of the first friction wheel (<NUM>) and the second friction wheel (<NUM>);
a third friction wheel (<NUM>) rotatably supported by a first end of the second shaft (<NUM>), and contacting the first friction wheel (<NUM>) and the second friction wheels (<NUM>),
wherein when the first friction wheel (<NUM>) and the second friction wheel (<NUM>) rotate in the same direction, the third friction wheel rotates in a pitch direction, and
wherein when the first friction wheel (<NUM>) and the second friction wheel (<NUM>) rotate in different directions, the third friction wheel (<NUM>) rotates in a roll direction,
characterized in that:
the joint device (<NUM>) comprises:
a first pressing member (<NUM>) configured to press the first friction wheel (<NUM>) toward the third friction wheel (<NUM>);
a second pressing member (<NUM>) configured to press the second friction wheel (<NUM>) toward the third friction wheel (<NUM>);
a first angular ball bearing (<NUM>) interposed between the first shaft (<NUM>) and the first friction wheel (<NUM>); and
a second angular ball bearing (<NUM>) interposed between the first shaft (<NUM>) and the second friction wheel (<NUM>),
wherein:
the first angular ball bearing (<NUM>) comprises an inner ring (<NUM>) that contacts the first pressing member (<NUM>), and an outer ring (<NUM>) that contacts the first friction wheel (<NUM>), and
the second angular ball bearing (<NUM>) comprises an inner ring (<NUM>) that contacts the second pressing member (<NUM>), and an outer ring (<NUM>) that contacts the second friction wheel (<NUM>).