JPH0569379A - Error correction device of parallelogramic link mechanism - Google Patents

Abstract

PURPOSE:To correct error in the length automatically by furnishing an eccentric shaft having two journals, whose axes are eccentric from each other, at two link junctions, and supporting the link junctions on the two journals through respective bearings. CONSTITUTION:An eccentric shaft 9 having two journals 91, 92 whose axes are eccentric from each other is installed at the junction of the first link 5 with the second link 6, wherein one of the journals 91 is an borne by a bearing 51. At the junction of the second link 6 with the first link 5, the other journal 92 is supported through a bearing 61. When there is error in the length of the first arm and the length of second link 6, the eccentric shaft 9 rotates in case a first parallelogramic link mechanism 8 is not situated at the dead point and in case of passing the dead point, to correct the error within a range twice as large as the eccentricity amount (e), which allows preventing an excessive force being applied to the first arm, the links, and link junctions.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a parallelogram link mechanism used for driving an arm of an industrial articulated robot or the like, and more particularly to a device for automatically correcting an error in its link dimension.

[0002]

2. Description of the Related Art Conventionally, a mechanism for driving an arm of an industrial articulated robot or the like has one end fixed to a rotary shaft 11 rotatably supported by a base 1 as shown in FIGS. 3 and 4, for example. The first arm 2 is provided, one end of the second arm 3 is fixed to the rotary shaft 21 rotatably connected to the other end of the first arm 2, and the end effector is fixed to the other end of the second arm 3. The wrist portion 4 is connected to be rotatable.
The first arm 2 is a first drive motor 2 fixed to the base unit 1.
It is adapted to be rotated by a rotating shaft 11 by means of 2. Further, one end of the first link 5 is rotatably connected to one side of the rotary shaft 11, and the other end of the first link 5 has a first end.
One end of a second link 6 having the same length as the arm 2 is rotatably connected, and one end of a third link 7 having the same length as the first link 5 is rotatably connected to the other end of the second link 6. The third end of the third link 7 is rotatably connected to the rotary shaft 21. That is, the first arm 2, the first link 5, the second link 6, and the third link 7 constitute a first parallelogram link mechanism 8 that always forms a parallelogram. A second drive motor 31 is coupled to one end of the first link 5 via a timing belt or the like, the first link 5 is rotated coaxially with the rotation shaft 11, and the first parallelogram link mechanism 8 is used to rotate the first link 5 through the first parallelogram link mechanism 8. Two
The arm 3 is adapted to rotate around the rotary shaft 21. Further, on the opposite side of the rotary shaft 11 with the first arm 2 interposed therebetween, a first link 5 ′ and a second link 6 ′ having a phase difference with respect to the first parallelogram link mechanism 8 and having the same size,
Second parallelogram link mechanism 8'consisting of the third link 7 '
Has been placed. The second links 6, 6'are arranged outside the first links 5, 5'and the third links 7, 7 '. Therefore, even when one of the two sets of parallelogram linkages passes through a so-called dead center position where they are aligned on a straight line, there is a phase difference between the two parallelogram linkages, and therefore the other parallelogram linkage. Since the shaped link mechanism is not at the position of the dead center, there is no hindrance to the rotation operation, and the second arm can rotate 180 degrees or more. Further, in order to smoothly operate the parallelogram linkage mechanism, a rolling bearing is provided at a connecting portion between the links (for example, Japanese Patent Laid-Open No. 2-6).
5987 publication).

[0003]

However, in the above structure, when an error occurs in the length of the first arm 2 and the length of the second link 6 due to factors such as machining tolerance, the solid line in FIG. The parallelogram, which is the ideal shape of the parallelogram link mechanism as shown, collapses, and when the parallelogram link mechanism passes through the dead point in that state, the first arm, each link, and each link There is a drawback that excessive force is applied to the connecting portion and the like. According to the present invention, even if the first arm or each link has a difference in length due to machining tolerance or the like, the length error is automatically corrected, and the parallelogram link mechanism can smoothly pass the dead center position. The purpose is to do so.

[0004]

According to the present invention, four links are rotatably connected to each other to always form a parallelogram,
At least one of the links is 180 around the connecting point.
In a parallelogram link mechanism that can rotate more than one degree, an eccentric shaft having two journal parts whose center axes are eccentric to each other is provided at a connecting point of the two links, and the two journal parts are respectively provided with the eccentric shafts. The connection point of the link is supported via a bearing.

[0005]

In the parallelogram linkage, at any connection point between the links, the two eccentric journal portions of the eccentric shaft support the connection points of the two links via bearings. Even when an error occurs in each link, when the parallelogram link mechanism passes the position of the dead center, the eccentric shaft rotates to correct the error, and it is excessive to add to each link and the connecting part of each link. Prevent unnecessary power.

[0006]

Embodiments of the present invention will be described with reference to the drawings.
The basic configuration of the parallelogram link mechanism of the present invention is almost the same as that of the conventional example shown in FIGS. 3 and 4, and the first arm 2 and the first arm 2 are provided.
A first parallelogram link mechanism 8 including a link 5, a second link 6, and a third link 7, and a first arm 2, a first link 5 ', a second link 6', and a third link 7 '. The second parallelogram link mechanism 8'is provided with a phase difference between the first parallelogram link mechanism 8 and the second parallelogram link mechanism 8 '. The difference from the conventional example of the present invention is that the first link 5 and the second link of the first crank mechanism 8 shown in FIG.
A description will be given with reference to a side sectional view of a main part of a connection point with the link 6. An eccentric shaft 9 having journal portions 91 and 92 whose central axes are eccentric to each other is provided at a connecting point of the first link 5 and the second link 6, and a journal portion 91 on one side of the eccentric shaft 9 is provided via a bearing 51. The journal portion 92 on the other side of the eccentric shaft 9 is supported at the coupling point of the second link 6 and the first link 5 via a bearing 61. The amount of eccentricity e of the central axes of the journal portion 91 and the journal portion 92 of the eccentric shaft 9 is set to approximately 1/2 of the maximum length of the assumed machining error. The operation of the parallelogram link mechanism will be described. When an error occurs in the length of the first arm 2 and the length of the second link 6, when the first parallelogram link mechanism 8 is not at the dead point (see FIG. (a) is indicated by a dotted line) and the position of the dead point is passed (shown in FIG. 2 (b)), the eccentric shaft 9 rotates to correct an error within a range of twice the eccentric amount e, and It is possible to prevent an excessive force applied to one arm, each link, a connecting portion of each link, and the like. The same applies to the connection point between the first link 5'and the second link 6'of the second crank mechanism 8 '. Also, an eccentric shaft may be used at a connecting point between other links of the parallelogram link mechanism, and the links may be connected via a bearing. Further, even when a set of parallelogram link mechanisms is used when driving the second arm and a transmission drive system such as a gear or a belt is used to pass the dead point of the parallelogram link mechanism, the present invention is also applicable. The same effect can be obtained by using the error correction device.

[0007]

As described above, according to the present invention, when the parallelogram link mechanism passes through the dead point, the dimensional error of each link constituting the parallelogram link mechanism is automatically corrected. , It is possible to prevent an excessive force from being generated at each link and the connecting point of each link, and there is an effect that a smooth operation becomes possible.

[Brief description of drawings]

FIG. 1 is a side sectional view of an essential part showing an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a parallelogram link mechanism.

FIG. 3 is a side view of an industrial articulated robot using a parallelogram linkage mechanism.

FIG. 4 is a front sectional view of FIG.

[Explanation of symbols]

 1 Base Part 11 Rotating Shaft 2 1st Arm 3 2nd Arm 5 1st Link 51, 61 Bearing 6 2nd Link 7 3rd Link 8 1st Parallelogram Link Mechanism 8'2nd Parallelogram Link Mechanism 9 Eccentric Shaft 91,92 Journal Department

Claims (3)

[Claims] 1. Four links are rotatably connected to each other to always form a parallelogram, and at least one of the links is formed.
In a parallelogram link mechanism in which one can rotate 180 degrees or more around a connecting point as an axis, an eccentric shaft having two journal parts whose central axes are eccentric to each other is provided at the connecting point of the two links, An error compensating device for a parallelogram link mechanism, characterized in that the journals respectively support the connecting points of the two links via bearings. 2. One of the four links is composed of a first arm of an articulated robot, and a second arm rotatably connected to the first arm is connected to any of the other links. The error correction device for a parallelogram link mechanism according to claim 1. 3. The parallelogram link mechanism according to claim 1, wherein the second arm is driven by a winding transmission drive system or a gear transmission drive system to pass a dead point of the parallelogram link mechanism. Error correction device.