Patent Description:
Production sites such as factories employ industrial robots (hereinafter, referred to as "articulated robots") such as robot arms (also referred to as "manipulators"). Among various articulated robots, particularly articulated robots for use in processing workpieces have an arm that is fixed to a base, or a plurality of arms coupled to each other at a joint (movable part), and such articulated robots move their arm or arms to perform processing such as picking and working on the workpieces.

For example, <CIT> discloses "a robot stop device including a stopper member that is provided at least one of a pair of relative movement parts, which move relative to each other, and is configured to be interposed between the pair of relative movement parts to stop the relative movement in case of a collision thereof'. Specifically, the stopper member of the robot stop device according to <CIT> is a "combined member that is obtained by bonding at least two types of members having different degrees of hardness to each other, and is combined in such a manner that two end faces of the member having the higher degree of hardness are in direct contact with the pair of relative movement parts, and receive a compressive load in case of a collision of the pair of relative movement parts, substantially perpendicularly".

<CIT> discloses multi-stage stop devices for robotic arms. During a first stage, rotational motion of a link of a robotic arm compresses a compressible member of the multi-stage stop device to absorb and dissipate at least some of the force generated by the collision. A second stage provides a hard stop the stops any further rotation. The multi-stage stop devices described herein can include a collapsing pin configured to compress a compressible member during the first stage. After the pin has collapsed a rigid sidewall provides a hard stop preventing further rotation during the second stage.

<CIT> discloses a stop device for a robot for stopping the relative motion of a pair of mutually movable parts, having a stopper member provided at least one of the pair of mutually movable parts, the stopper member being sandwiched between the pair of mutually movable parts when the pair of mutually movable parts collide with the stopper member, wherein the stopper member is a combination member composed of at least two members of different hardness adhered to each other, such that opposite end faces of one member of highest hardness of at least two members, are adapted respectively to come into direct contact with the pair of mutually movable parts and to receive a compression load exerted between the pair of mutually movable parts at a time of collision in a generally perpendicular direction to the end faces.

In recent years, an increase in speed of operation of articulated robots has led to an increase in impact energy (load) that is generated when an arm comes into contact with a base, or when arms come into contact with each other. Even if a user tries to use a rubber stopper made of an elastic body such as urethane to absorb the energy, it is difficult to ensure a space with a thickness and a width required in the direction of a compressive load at, for example, an axis of an articulated robot such as a J1 axis at which the arm has a large operation range, namely, an operating angle exceeding <NUM> degrees. Also, even if such an elastic body is arranged in a limited space, the elastic body alone cannot receive shear loads due to dynamic loads, and does not function as a stopper.

That is to say, for an axis such as a J1 axis at which the arm has a large operation range, it was difficult to realize a stopper structure that takes advantage of the absorption impact of an elastic body. Also, when the robot is in an orientation such as a forward tilting orientation in which it has a large inertia and a motion energy is increased, the robot needs to decelerate to protect structural members such as a stopper member or an arm.

Also, although the stopper member disclosed in <CIT> can absorb compressive loads, it cannot absorb other loads such as shear loads. According to <CIT>, the stopper member is provided on each of two sides of the base. However, if there is no sufficient space for arranging such stopper members at an axis at which the arm has a large operation range, it may be difficult to arrange the stopper members adjacent to the base in a manner as described in <CIT>.

In view of the above-described problems, it is an object of the present invention to provide a stopper structure that can be arranged even at a position where no sufficient space can be ensured, such as at an axis at which an arm has a large operation range, and can appropriately absorb a shear load, and an articulated robot including such a stopper structure.

In order to solve the foregoing problems, a representative configuration of a stopper structure according to the present invention relates to a stopper structure having the features of claim <NUM>.

Preferably, the block may be a polygonal prism. Also, the mechanical element may preferably be a base or another arm of an articulated robot.

The stopper structure includes a retaining plate that biases the stopper to prevent the stopper from being removed from the hole.

In order to solve the foregoing problems, a representative configuration of an articulated robot according to the present invention relates to an articulated robot including the above-described stopper structure.

According to the present invention, it is possible to provide a stopper structure that can be arranged even at a position where no sufficient space can be ensured, such as at an axis at which an arm has a large operation range, and can appropriately absorb a shear load, and an articulated robot including such a stopper structure.

Referring to the accompanying drawings, the following is a detailed explanation of preferred embodiments of the present invention. All dimensions, materials and further specific numbers shown in the embodiment are merely given as examples in order to aid the understanding of the invention, and are not meant to limit the present invention, unless otherwise stated. It should be further noted that throughout this specification and in the drawings, elements that have substantially the same functionality and/or structure are denoted by the same reference numerals and are not described redundantly. Furthermore, elements that are not directly related to the present invention may not necessarily be shown in the figures.

The present embodiment will describe an example in which the stopper structure according to the present invention is applied to a J1 axis of an articulated robot. That is to say, the stopper structure shown in <FIG> is a stopper structure for restricting relative rotation between an arm (mechanical element) and a base (mechanical element) by a predetermined angle or more at a J1 axis of an articulated robot. The stopper structure includes: a protrusion provided on the arm; a hole formed in the base; and a stopper inserted into the hole while being partially exposed from the hole. The stopper includes: a block made of an elastic resin; and a metal surface plate that has a bent cross-section, and is provided on a surface of the block along a front side on which the stopper comes into contact with the protrusion.

<FIG> is a perspective view illustrating a J1 axis of an articulated robot (hereinafter, referred to as "robot <NUM>") with a stopper structure 100a according to the present embodiment. <FIG> is a diagram illustrating the stopper structure 100a of <FIG> in an exploded state. The robot <NUM> is an articulated robot such as a <NUM>-axis or <NUM>-axis articulated robot, but descriptions of the J2 axis onwards are not essential for the description of the invention and thus are omitted. In the following embodiment, a description of the stopper structure 100a of the present embodiment will be given together with a detailed description of the robot <NUM> with reference to the drawings at the same time.

Note that in the present embodiment, a base <NUM> is exemplified as a mechanical element, but the present invention is not limited to this, and the stopper structure according to the present invention may also be applied to another joint of the articulated robot such as the J2,. , J5, or J6 axis. In this case, preferably, a stopper may be provided on one of the arms at the corresponding joint, and a hole into which the stopper is inserted may be formed in the other arm (mechanical element). Also in the present embodiment, an example is given in which a protrusion is provided on an arm <NUM>, and a stopper is provided on the base <NUM>, but by contraries, a protrusion may be provided on the base <NUM> and the stopper may be provided on the arm <NUM>.

As shown in <FIG> and <FIG>, the robot of the present embodiment includes the base <NUM> (mechanical element) and the arm <NUM>. The base <NUM> is a member for fixing the robot <NUM> of the present embodiment to a seating or the like (not shown). The arm <NUM> is pivotally supported on the base <NUM> and rotates with respect to the base <NUM>.

<FIG> illustrates the robot <NUM> of <FIG> in a top view and a side view. <FIG> is a top view of the robot <NUM> shown in <FIG>. <FIG> is a side view of the robot <NUM> shown in <FIG>. <FIG> is a cross-sectional view taken along the line A-A in <FIG>.

As shown in <FIG> and <FIG>, the robot <NUM> of the present embodiment includes the stopper structure 100a for restricting the arm <NUM> from "rotating by a predetermined angle (e.g., <NUM> degrees, see <FIG>) or more" with respect to the base <NUM>. The stopper structure 100a of the present embodiment includes a protrusion <NUM> formed on the arm <NUM>, a hole <NUM> formed in the base <NUM>, which is a mechanical element, and a stopper <NUM> that is inserted into the hole <NUM> while being partially exposed from the hole <NUM>.

The protrusion <NUM> protrudes from an outer circumference 120a of the arm <NUM> outward in a radial direction. <FIG> show a state in which the protrusion <NUM> is in a default position (located opposite to the stopper <NUM>).

The base <NUM> includes a body portion <NUM>, and an attaching portion <NUM> that protrudes upward from the body portion <NUM> (in a direction toward the protrusion <NUM>). Note that in the present embodiment, a case is exemplified where the attaching portion <NUM> is part of the base <NUM>, but the present invention is not limited to this, and a configuration is also possible in which the attaching portion <NUM> is a member separate from the base <NUM> and is bolted thereto.

The attaching portion <NUM> is a backrest that supports the back side (facing away from the arm <NUM>) of a block <NUM>. The base <NUM> has a vertical hole <NUM> (extending in the direction orthogonal to the rotation direction of the protrusion <NUM>) and the stopper <NUM> is inserted into the hole <NUM>. The hole <NUM> is located on the arm <NUM> side of the attaching portion <NUM>, and about a half of the hole <NUM> forms a bore in the attaching portion <NUM>, and the remaining part of the hole <NUM> juts out from the attaching portion <NUM> toward the arm <NUM>.

The stopper <NUM> is constituted by a block <NUM> made of an elastic resin, and a metal surface plate <NUM> having a bent cross section. The metal surface plate <NUM> is arranged on the surface of the block <NUM> along the front side (that is, the arm <NUM> side) on which the stopper <NUM> comes into contact with the protrusion <NUM>. The metal surface plate <NUM> does not cover the back surface of the block <NUM>, and is not interposed between the block <NUM> and the attaching portion <NUM>.

The block <NUM> is, for example, polygonal and columnar in the shape of a substantially triangular prism. The front side of the block <NUM> protrudes when viewed in a plan view in the direction in which the block <NUM> is inserted into the hole <NUM>, and the entire stopper <NUM> including the block <NUM> and the metal surface plate <NUM> attached thereto is also polygonal and columnar. Also, the outer shape of the hole <NUM> conforms to the shape of the stopper <NUM>. With this, even if the protrusion <NUM> comes into contact with the stopper <NUM>, and the stopper <NUM> is subjected to a moment force in the rotational direction generated when a shear load is applied from the protrusion <NUM>, it is possible to appropriately prevent rotation of the stopper <NUM> that is caused by a moment force generated by deformation of the metal surface plate <NUM> and the block <NUM>. Note that the present embodiment describes an example in which the block <NUM> has the shape of a substantially triangular prism (hexagonal prism obtained by chamfering the corners of a triangular prism, when observed in detail). However, the present invention is not limited to this, and the block <NUM> may also be a polygonal prism other than a triangular prism.

Also, as shown in <FIG>, according to the present embodiment, the stopper structure 100a includes a retaining plate <NUM> that biases (e.g. applies a spring force to) the stopper <NUM> to prevent the stopper <NUM> from being removed from the hole <NUM>. The retaining plate <NUM> is attached to the attaching portion <NUM> by screws <NUM> after the insertion of the stopper <NUM> into the hole <NUM> of the robot <NUM> as shown in <FIG>.

<FIG> shows cross-sectional views taken along the line B-B in <FIG>. <FIG> shows a case where the protrusion <NUM> shown in <FIG> is located at a position (default position) opposite to the stopper <NUM>. <FIG> shows a case where the protrusion <NUM> shown in <FIG> is located at a position (restriction position) on the stopper <NUM> side. In the robot <NUM> of the present embodiment, the arm <NUM> is rotatable by up to a predetermined angle shown in <FIG>, and is restricted from rotating by more than the predetermined angle by the protrusion <NUM> coming into contact with the stopper <NUM> as shown in <FIG>.

Specifically, when the arm <NUM> is about to rotate by more than the predetermined angle, and the protrusion <NUM> comes into contact with the stopper <NUM>, the protrusion <NUM> applies, upon contact, a load in a tangential direction of the circle of rotation (the outer circumference 120a of the arm <NUM>). Accordingly, the load in a shear direction (a force in a direction of shifting an object in a parallel fashion, hereinafter, referred to as "shear load") acts on the stopper <NUM> with which the protrusion <NUM> has come into contact.

Here, according to the present embodiment, due to the configuration of the stopper <NUM> in which the metal surface plate <NUM> is arranged on the front side of the block <NUM> on which the stopper <NUM> comes into contact with the protrusion <NUM>, when the shear load is applied to the stopper <NUM>, the metal surface plate <NUM> elastically or plastically deforms, and thus the stopper <NUM> can absorb the impact. Also, due to being arranged inside the metal surface plate <NUM>, the block <NUM> also deforms together with the plastic deformation of the metal surface plate <NUM>, and thus it is possible to more efficiently absorb the shear load applied upon the contact. That is to say, the motion energy of the arm <NUM> is absorbed by the energy of the plastic deformation of the metal surface plate <NUM> and the energy of the elastic deformation of the block <NUM>.

If the stopper <NUM> is constituted only by the elastic resin block <NUM> without any metal surface plate <NUM>, the block <NUM> will be broken and damaged by the shear load, and the stopper <NUM> cannot absorb the impact of the contact. Also, if a stopper made only of an elastic resin is used, the stopper needs to have an increased thickness and an increased width in order to achieve high impact-absorbing performance. In contrast, according to the robot <NUM> of the present embodiment, the stopper <NUM> constituted by the block <NUM> and the metal surface plate <NUM> has high load-absorbing performance, and it is thus possible to realize the stopper <NUM> having a volume smaller than that of a stopper made only of an elastic resin. Accordingly, it is possible to arrange the stopper <NUM> even at an axis at which the arm <NUM> has a large operation range, without any space restrictions.

Also, since, with the above-described configuration, high impact-absorbing performance is realized, it is possible to sufficiently absorb impact at an axis such as a J1 axis at which the arm has a large operation range, namely, an operating angle exceeding <NUM> degrees. Therefore, an articulated robot no longer needs to decelerate to protect the stopper member, and can realize highspeed operation.

While preferred embodiments of the present invention have been described with reference to the attached drawings, it goes without saying that the present invention is not limited to the examples according to the present invention. A person skilled in the art will appreciate that various modifications and alterations can be made within the scope of the claims, and that all such modifications and alterations are also naturally encompassed in the technical scope of the present invention.

Claim 1:
A stopper structure (100a) for restricting relative rotation between an arm (<NUM>) of an articulated robot and a mechanical element (<NUM>) by a predetermined angle or more, the stopper structure (100a) comprising:
a protrusion suitable to be provided on one of the arm (<NUM>) and the mechanical element (<NUM>);
a stopper (<NUM>) suitable to be inserted into a hole (<NUM>) formed in the other one of the arm (<NUM>) and the mechanical element (<NUM>), while being suitable to be partially exposed from the hole (<NUM>); and
a retaining plate (<NUM>) that biases the stopper (<NUM>) to prevent the stopper (<NUM>) from being removed from the hole (<NUM>),
wherein the stopper (<NUM>) includes:
a block (<NUM>) made of an elastic resin; and
a metal surface plate (<NUM>) that has a bent cross-section, and is provided on a surface of the block (<NUM>) along a front side on which the stopper (<NUM>) comes into contact with the protrusion (<NUM>).