U.S. patent application number 13/553019 was filed with the patent office on 2012-11-08 for horizontal articulated robot.
This patent application is currently assigned to SEIKO EPSON CORPORATION. Invention is credited to Christoph Meyerhoff, Masatoshi ONO.
Application Number | 20120279341 13/553019 |
Document ID | / |
Family ID | 41137862 |
Filed Date | 2012-11-08 |
United States Patent
Application |
20120279341 |
Kind Code |
A1 |
ONO; Masatoshi ; et
al. |
November 8, 2012 |
HORIZONTAL ARTICULATED ROBOT
Abstract
A horizontal articulated robot includes a base, a first arm
provided rotatably around a first rotation axis on the base, a
second arm provided rotatably around a second rotation axis on the
first arm, the second rotation axis being parallel to the first
rotation axis, and a main shaft provided in the second arm to be
extended in a direction parallel to the second rotation axis. A
distance between the second rotation axis and the main shaft is
shorter than a length of a straight line connecting the first and
the second rotation axes. Additionally, the first arm has a
recessed portion formed so as to include a position on a rotation
path where a rotation radius around the second rotation axis is
equivalent to the distance between the second rotation axis and the
main shaft.
Inventors: |
ONO; Masatoshi; (Suwa,
JP) ; Meyerhoff; Christoph; (Krefeld, DE) |
Assignee: |
SEIKO EPSON CORPORATION
Tokyo
JP
|
Family ID: |
41137862 |
Appl. No.: |
13/553019 |
Filed: |
July 19, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12547533 |
Aug 26, 2009 |
|
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13553019 |
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Current U.S.
Class: |
74/490.01 |
Current CPC
Class: |
B25J 9/044 20130101;
Y10T 74/20311 20150115; B25J 18/005 20130101; Y10T 74/20305
20150115 |
Class at
Publication: |
74/490.01 |
International
Class: |
B25J 18/00 20060101
B25J018/00 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 1, 2008 |
JP |
2008-223868 |
Claims
1. A horizontal articulated robot, comprising: a base; a first arm
provided rotatably around a first rotation axis on the base; a
second arm provided rotatably around a second rotation axis on the
first arm, the second rotation axis being parallel to the first
rotation axis; and a main shaft provided in the second arm and
extending in a first direction parallel to the second rotation
axis, wherein a distance between the second rotation axis and the
main shaft is less than a distance between the first rotation axis
and the second rotation axis, the first arm has a recess
selectively accommodating the main shaft therein, and the first arm
is invertibly mountable to the base to dictate a rightward or
leftward facing direction of the recess.
2. The horizontal articulated robot according to claim 1, wherein
the recess comprises a curved portion of the first arm.
3. The horizontal articulated robot according to claim 1, wherein
the recess is located at an intersection of a straight line
extending between the first and second rotation axes and a rotation
path where a rotation radius around the second rotation axis is
equivalent to the distance between the second rotation axis and the
main shaft such that at least a part of the main shaft can be
located at the intersection.
4. The horizontal articulated robot according to claim 1, further
comprising: a first connection shaft protruding from the base, the
first connection shaft rotating around the first rotation axis, and
a second connection shaft protruding from the second arm, the
second connection shaft rotating around the second rotation axis,
the first arm having a base end connection portion connected to the
first connection shaft and an extreme end connection portion
connected to the second connection shaft, the base end connection
portion being connectable to the first connection shaft on both
horizontal surfaces of the first arm, and the extreme end
connection portion being connectable to the second connection shaft
on both horizontal surfaces of the first arm.
5. The horizontal articulated robot according to claim 1 further
comprising: a wiring duct provided on the base to store wiring, the
wiring duct being located in a position to be selectively
accommodated by the recessed portion of the first arm.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/547,533 filed on Aug. 26, 2009, which
claims priority to Japanese Patent Application No. 2008-223868
filed on Sep. 1, 2008, both of which are hereby expressly
incorporated by reference herein in their entireties.
BACKGROUND
[0002] 1. Technical Field
[0003] The present invention relates to an industrial robot, and
more particularly to a horizontal articulated robot having a
plurality of horizontally rotating arms.
[0004] 2. Related Art
[0005] Among industrial robots, there is known a SCARA robot (a
horizontal articulated robot) with a plurality of arms sequentially
connected by means of a horizontal articulation. FIG. 12 shows an
example of a planar structure of a common SCARA robot having two
arms.
[0006] As shown in FIG. 12, the SCARA robot includes a base 51, a
first arm 52 having a base end portion horizontally rotatably
connected to a base 51, and a second arm 53 having a base end
portion connected to an extreme end portion of the first arm 52 by
a horizontal articulation.
[0007] FIG. 13 shows an outline of a movable range in the SCARA
robot thus structured. As in the drawing, the first and the second
arms 52 and 53 work together to move a working portion 53a disposed
at an extreme end portion of the second arm 53 to an arbitrary
position in a movable range WA formed between a maximum radius Rmax
and a minimum radius Rmin. In other words, by using the working
portion 53a at the extreme end portion, the SCARA robot can perform
various operations for a target object (such as an article to be
processed) located in the arbitrary position in the movable range
WA.
[0008] Meanwhile, in the SCARA robot as above, the maximum radius
Rmax defining the movable range WA is determined based on a maximum
rotation radius Dmax obtained by adding an arm length L11
equivalent to a distance between a base rotation axis C11 of the
first arm 52 and a connection rotation axis C12 of the second arm
53 to an arm length L12 equivalent to a distance between the
connection rotation axis C12 and a working shaft C13 of the second
arm 53. Similarly, the minimum radius Rmin defining the movable
range WA is determined based on a minimum rotation radius Dmin
equivalent to a distance between the base rotation axis C11 and a
position Pa or Pb (See FIG. 12) where the working portion 53a can
come closest to the base 51 without interfering with the first arm
52. In the arm structure thus provided, basically, the movable
range WA is made largest when the minimum radius Rmin is set so as
to be equivalent to a difference between the arm lengths L11 and
L12. However, an arm frame of the first arm 52 is required to be
large enough to maintain strength and rigidity for supporting the
second arm 53 and others. Accordingly, miniaturization of the arm
frame is restricted, and it is thus difficult to reduce the minimum
radius Rmin.
[0009] Thus, in order to extend the movable range of such a SCARA
robot, for example, there is proposed a conventional SCARA robot as
in JP-A-2007-168004. The proposed SCARA robot includes a first arm
horizontally rotatably mounted on a base and a second arm connected
to the first arm by a horizontal articulation. The second arm is
formed to be longer than the first arm. In other words, with
respect to a maximum rotation radius of a working portion at an
extreme end portion of the second arm obtained when both arms are
linearly expanded, a minimum rotation radius of the working portion
located in a position closest to the base by collapsing the second
arm is reduced to increase the movable range in the SCARA
robot.
[0010] On the other hand, the SCARA robot as above is generally
expected not only to have as large a movable range as possible but
also to have a more compact size, a high responsiveness, a high
positioning precision, and the like.
[0011] In the SCARA robot proposed as above, however, although the
movable range is surely extended, the second arm longer than the
first arm naturally becomes larger in mass and inertia. This can
deteriorate responsiveness upon movement and positioning
precision.
SUMMARY
[0012] The present invention has been accomplished under the
aforementioned background. An advantage of the invention is to
provide a horizontal articulated robot that achieves a large
mobility range while maintaining a high responsiveness, and a high
positioning precision.
[0013] A horizontal articulated robot according to an aspect of the
invention includes a base, a first arm provided rotatably around a
first rotation axis on the base, a second arm provided rotatably
around a second rotation axis on the first arm, the second rotation
axis being parallel to the first rotation axis, and a main shaft
provided in the second arm to be extended in a direction parallel
to the second rotation axis, a distance between the second rotation
axis and the main shaft being shorter than a length of a straight
line connecting the first and the second rotation axes, and the
first arm having a recessed portion formed so as to include a
position on a rotation path where a rotation radius around the
second rotation axis is equivalent to the distance between the
second rotation axis and the main shaft.
[0014] In the horizontal articulated robot, the main shaft has the
rotation path where the rotation radius around the second rotation
axis is equivalent to the length of the second arm. The main shaft
is movable to be positioned in such a manner that the main shaft
enters into an eccentrically recessed region of the first arm. In
other words, the movable range of the main shaft is extended by an
amount of reduction in a minimum rotation radius with respect to
the first rotation axis of the main shaft.
[0015] In addition, when compared with the conventional horizontal
articulated robot having the first arm without any recessed
portion, there is no change in the lengths of the first and the
second arms in the robot of the aspect. This can minimize an
increase in the mass of the first arm, as well as the second arm as
in the conventional robot can be used without change. As a result,
even when using the eccentric first arm as described above in the
horizontal articulated robot, responsiveness, positioning
precision, and the like can be maintained as in the conventional
robot. Thus, there is no unnecessary increase in robot size.
[0016] Preferably, in the horizontal articulated robot, the
recessed portion is formed by curving the first arm.
[0017] In the structure, the main shaft is movable to be positioned
in such a manner that the main shaft enters into a curved portion
of the first arm. Thereby, the main shaft can be received more
smoothly in the curved portion according to a curving shape of the
first arm.
[0018] Preferably, in the horizontal articulated robot, the first
arm has the recessed portion at an intersection of the straight
line and the rotation path in a rotation direction such that at
least a part of the main shaft can be located on the
intersection.
[0019] In the structure, a distance between the main shaft and the
first rotation axis can be minimized, so that the minimum rotation
radius of the main shaft with respect to the first rotation axis
can be made smaller. In short, the movable range of the main shaft
can be further extended.
[0020] Preferably, the horizontal articulated robot further
includes a first connection shaft provided in the base in a manner
protruding from the base, the first connection shaft rotating
around the first rotation axis, and a second connection shaft
provided in the second arm in a manner protruding from the second
arm, the second connection shaft rotating around the second
rotation axis, the first arm having a base end connection portion
connected to the first connection shaft and an extreme end
connection portion connected to the second connection shaft, the
base end connection portion being formed so as to be connectable to
the first connection shaft on both of horizontal surfaces of the
first arm, and the extreme end connection portion being formed so
as to be connectable to the second connection shaft on both of the
horizontal surfaces of the first arm.
[0021] In the structure, even if the first arm having the recessed
portion is reversed, the first arm can be connected to each of the
first and the second rotation axes. Thus, in the horizontal
articulated robot, configuration (structure) flexibility can be
improved.
[0022] Preferably, the horizontal articulated robot further
includes a wiring duct provided on the base to store wiring, the
wiring duct being located in a position interfering with the
recessed portion of the first arm rotated.
[0023] In the structure, when the second rotation axis of the first
arm is located in a rear direction of the robot while sandwiching
the wiring duct between the first and the second rotation axes, the
movable range of the robot can be extended to a rear side of the
base. Thereby, even in the horizontal articulated robot having the
wiring duct in the position interfering with the first arm on the
base, the movable range of the robot can be suitably extended.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] The invention will be described with reference to the
accompanying drawings, wherein like numbers reference like
elements.
[0025] FIG. 1 is a perspective structural view of a horizontal
articulated robot according to a first embodiment of the
invention.
[0026] FIG. 2 is a plan view of a top-surface structure of the
horizontal articulated robot of the first embodiment.
[0027] FIG. 3A is a plan view of a top-surface structure showing an
arm structure of the horizontal articulated robot of the first
embodiment.
[0028] FIG. 3B is a sectional view showing a sectional structure
taken along line A-A shown in FIG. 3A.
[0029] FIG. 3C is a bottom-surface view showing the arm structure
of the horizontal articulated robot of the first embodiment.
[0030] FIG. 4A is an illustrative view showing a movable range of a
second arm of the horizontal articulated robot of the first
embodiment when the second arm rotates counterclockwise.
[0031] FIG. 4B is an illustrative view showing a movable range of
the second arm of the horizontal articulated robot of the first
embodiment when the second arm rotates clockwise.
[0032] FIG. 5A an illustrative view showing a movable range of a
first arm of the horizontal articulated robot of the first
embodiment when the first arm rotates counterclockwise.
[0033] FIG. 5B is an illustrative view showing a movable range of
the first arm of the horizontal articulated robot of the embodiment
when the first arm rotates clockwise.
[0034] FIG. 6 is a regional view showing a planar path of each axis
and a movable range of a main shaft in the horizontal articulated
robot of the first embodiment.
[0035] FIG. 7 is a layout view showing a layout example of the
horizontal articulated robot of the first embodiment in a
production facility.
[0036] FIG. 8 is a plan view showing a top-surface structure of a
horizontal articulated robot according to a second embodiment.
[0037] FIG. 9A is an illustrative view showing a movable range of a
second arm of the horizontal articulated robot of the second
embodiment when the second arm rotates clockwise.
[0038] FIG. 9B is an illustrative view showing a movable range of
the second arm of the horizontal articulated robot of the second
embodiment when the second arm rotates counterclockwise.
[0039] FIG. 10A an illustrative view showing a movable range of a
first arm of the horizontal articulated robot of the second
embodiment when the first arm rotates clockwise.
[0040] FIG. 10B is an illustrative view showing a movable range of
the first arm of the horizontal articulated robot of the second
embodiment when the first arm rotates counterclockwise.
[0041] FIG. 11 is a regional view showing a planar path of each
axis and a movable range of a main shaft in the horizontal
articulated robot of the second embodiment.
[0042] FIG. 12 is a plan view showing a top-surface structure of a
conventional horizontal articulated robot.
[0043] FIG. 13 is a regional view showing a planar path of each
axis and a movable range of a main shaft in the conventional
horizontal articulated robot.
DESCRIPTION OF EXEMPLARY EMBODIMENTS
[0044] Embodiments of the invention will be described with
reference to the drawings. Hereinafter, a horizontal articulated
robot according to a first embodiment of the invention will be
described in detail.
[0045] FIG. 1 shows a perspective structure of the horizontal
articulated robot (a SCARA robot). FIG. 2 shows a top-surface
structure of the SCARA robot.
[0046] As shown in FIG. 1, the SCARA robot includes a base 11 as a
supporting member disposed on a floor or the like. At an upper end
portion of the base 11 is provided a connection shaft 12 that
rotatably supports a base end portion of a first arm 13, as a
rotating member. The connection shaft 12 is formed in a cylindrical
shape with an axial center C1 and is provided rotatably around the
axial center C1 on the base 11. The connection shaft 12 is rotated
forward or backward by a first motor M1 provided in the base 11.
Thereby, the first arm 13 rotates around the axial center C1 of the
connection shaft 12 rotated by the first motor M1, horizontally
with respect to the base 11.
[0047] At an extreme end portion of the first arm 13, there is
connected a support shaft 14 that rotatably supports a base end
portion of a second arm 15, as a rotating member. The support shaft
14 is provided rotatably around an axial center C2 of the second
arm 15 and drivenly connected to a second motor M2 disposed at the
base end portion of the second arm 15 to be rotated forward or
backward by the second motor M2. Thereby, the second arm 15 is
rotated around the axial center C2 by a reaction force of the
second motor M2, horizontally with respect to the first arm 13.
[0048] In the first embodiment, as shown in FIG. 2, a distance
between the axial center C1 of the base end portion and the axial
center C2 of the extreme end portion in the first arm 13 is set as
an arm length L1, where the axial center C2 is rotated with a
rotation radius of the arm length L1 with respect to the axial
center C1. In addition, the first arm 13 is formed in a shape
eccentric to a center line connecting the axial centers C1 and C2
to each other. In other words, in FIG. 2, the first arm 13 is
formed such that a right side face of the arm 13 near a center part
in a longitudinal direction of the arm 13 bulges rightward and a
left side face thereof near the center part, which is opposite to
the right side face thereof, is recessed rightward to form a
recessed portion 13d so as to be eccentric to the center line. In
short, the first arm 13 has, as it were, a rightward-curved
shape.
[0049] FIGS. 3A, 3B, and 3C, respectively, show a top-surface
structure of the first arm 13, a sectional structure taken along
line A-A of FIG. 3A, and a bottom-surface structure of the first
arm 13, respectively. In FIG. 3A, at the base end portion of the
first arm 13, there is formed a base end connection portion 31, to
which the connection shaft 12 is connectively fixed. The base end
connection portion 31 is formed penetratingly in such a manner that
a center of the base end connection portion 31 coincides with the
axial center C1. Additionally, at the extreme end portion of the
first arm 13, there is formed an extreme end connection portion 35,
to which the support shaft 14 is connectively fixed. The extreme
end connection portion 35 is formed penetratingly in such a manner
that a center of the extreme end connection portion 35 coincides
with the axial center C2.
[0050] In FIG. 3B, at a center of a thickness direction of the base
end connection portion 31 is formed a protruded portion 33
protruding in a direction of the axial center C1. The connection
shaft 12 inserted into the base end connection portion 31 is
received by the protruded portion 33 to be connectively fixed to a
screw hole, which is penetratingly formed on a side surface 32 of
the protruded portion 33, by means of a screw connection or the
like. The base end connection portion 31 thus formed has a same
structure on both of the top and the bottom surfaces of the first
arm 13, as shown in FIGS. 3A and 3C, so that the connection shaft
12 can be connectively fixed to each of the surfaces of the first
arm 13. On an extreme end of the connection shaft 12, a cover is
mounted so as to be flush with the top surface of the first arm in
order to prevent a foreign object or the like from entering into
the base end connection portion 31.
[0051] Additionally, at a center of a thickness direction of the
extreme end connection portion 35 is formed a protruded portion 37
protruding in a direction of the axial center C2. The support shaft
14 inserted into the extreme end connection portion 35 is received
by the protruded portion 37 to be connectively fixed to a screw
hole, which is penetratingly formed on a side surface 36 of the
protruded portion 37, by means of a screw connection or the like.
The extreme end connection portion 35 thus formed has a same
structure on both of the top and the bottom surfaces of the first
arm 13, as shown in FIGS. 3A and 3C, so that the support shaft 14
can be connectively fixed to each of the surfaces of the first arm
13. On a bottom end of the support shaft 14, a cover is mounted so
as to be flush with the bottom surface of the first arm in order to
prevent a foreign object or the like from entering into the extreme
end connection portion 35.
[0052] Thereby, regardless of which one of the top and the bottom
surfaces of the first arm 13 is set as an upper surface, the
connection shaft 12 and the support shaft 14 can be mounted on the
first arm 13. In the present embodiment, the first arm 13 is formed
so as to have the rightward-curved shape. Accordingly, by reversing
a direction of the upper surface of the first arm, a curving
direction of the first arm in a horizontal direction can be shifted
leftward. Thus, using the first arm 13 thus formed allows the
curving direction to be shifted either rightward or leftward by
merely reversing the top and the bottom surfaces of the first arm
13.
[0053] On the extreme end portion of the second arm 15, a main
shaft 16 is supported rotatably as a rotating member and movably in
a vertical direction. The main shaft 16 is rotated forward or
backward around the axial center C3 of the shaft 16 by forward or
backward rotation of a third motor M3 provided in the second arm 15
and is vertically moved up and down by forward or backward rotation
of an elevation motor M4 provided in the second arm 15. On a bottom
end portion 17 of the main shaft 16 is mounted a hand-like tool to
hold a conveyed object, whereby operations for a target object are
performed using the tool moved up and down by elevation of the main
shaft 16.
[0054] In the embodiment, the second arm 15 has an arm length L2
equivalent to a distance between the axial center C2 of the base
end portion and the axial center C3 of the main shaft 16. The arm
length L2 is made shorter than the arm length L1, and the axial
center C3 is rotated with respect to the axial center C2 with a
rotation radius of the arm length L2.
[0055] Thereby, when the first and the second arms 13 and 15 are
linearly expanded, the rotation radius of the axial center C3 of
the main shaft 16 with respect to the axial center C1 of the
connection shaft 12 is equivalent to a maximum rotation radius
D1max as a sum of the arm lengths L1 and L2. Meanwhile, the
rotation radius of the axial center C3 is equivalent to a minimum
rotation radius D1min as a distance between a left limit point PRa
and the axial center C1 when the axial center C3 is located at the
left limit point PRa so as to enter into the recessed portion 13d
of the first arm 13. In this case, when a deepest part of the
recessed portion 13d of the first arm 13 in the horizontal
direction is formed at the arm length L2 from the axial center C2,
the axial center C3 can become closest to a center line, whereby
the minimum rotation radius D1min has a value closer to a possible
shortest length (=L1-L2). In addition, in a bulging direction of
the first arm, the axial center C3 is located at a right limit
point PRb.
[0056] Signal lines for control signals and monitor signals of the
motors M2 to M4 provided in the second arm 15 are gathered in the
base 11 via a flexible wiring duct 19 to be connected to respective
corresponding terminals of a not-shown control device, together
with a signal line of the first motor M1. In FIG. 2, a part of the
wiring duct 19 is omitted for convenience of description.
[0057] The wiring duct 19 includes a base-side duct connecting
portion 20 and an arm-side duct connecting portion 23. The
base-side duct connecting portion 20 is provided in a position
horizontally apart by a length L5 (=L1-L2) from the axial center C1
to a rear side R of the base 11. The arm-side duct connecting
portion 23 is provided around the axial center C2 on a top part of
the second arm 15. The wiring duct 19 is formed so as to connect
the base-side duct connecting portion 20 to the arm-side duct
connecting portion 23. Specifically, the wiring duct 19 includes a
base end portion 21a fixed to the base-side duct connecting portion
20 to be extended upward, a turning portion 21b extended from the
base end portion 21a in a direction of the axial center C1 of the
connection shaft 12, and an extreme end portion 21c having a duct
center line collinear with the axial center C1 of the connection
shaft 12 extended upward from the turning portion 21b. The base end
portion 21a fixed to the base-side duct connecting portion 20 does
not rotate, so that the duct center line of the extreme end portion
21c supported by the base end portion 21a via the turning portion
21b is constantly located collinearly with the axial center C1 of
the connection shaft 12.
[0058] Between the extreme end portion 21c and the arm-side duct
connecting portion 23 is provided a connection portion 22 in a
traversing manner. An end of the connection portion 22 adjacent to
the extreme end portion 21c is rotatably connected to the extreme
end portion 21c around the axial center C1, and an end of the
connection portion 22 adjacent to the arm-side duct connecting
portion 23 is rotatably connected to the arm-side duct connecting
portion 23 around the axial center C2. In other words, even when
the first arm 13 is horizontally rotated with respect to the base
11, a distance between the duct center line of the extreme end
portion 21c collinear with the axial center C1 and the axial center
C2 as a center of the arm-side duct connecting portion 23 is
maintained constant to be the arm length L1. Thereby, the
connection portion 22 transversing between the extreme end portion
21c and the arm-side duct connecting portion 23 is formed such that
a distance between the opposite ends of the connection portion 22
remains the arm length L1, without any change in the length. Due to
no change in the distance between the opposite ends, the connection
portion 22 is maintained to have a constant shape regardless of the
horizontal rotation of the first arm 13. This can reduce fatigue
and abrasion of a member caused by deformation of the shape or the
like, resulting in improvement of durability.
[0059] In the embodiment, the length L5 by which the connecting
portion 20 is located apart from the axial center C1 coincides with
a distance between the axial center C1 and the recessed portion 13d
of the first arm 13. Then, when the recessed portion 13d of the
first arm 13 approaches, the center line of the first arm 13 comes
closest to the base-side duct connecting portion 20. Thereby, even
when the base-side duct connecting portion 20 is located in a
position interfering with a moving plane of the first arm 13, the
first arm 13 allows the axial center C2 of the extreme end portion
and the second arm 15 connected to the axial center C2 to be
located also on the rear side R of the base-side duct connecting
portion 20.
[0060] Next will be described a movable range of the main shaft 16
of the horizontal articulated robot.
[0061] With respect to the axial center C2, the main shaft 16 has,
for example, a movable range from a position of the shaft 16 in a
leftward rotation (FIG. 4A) to a position thereof in a rightward
rotation (FIG. 4B). In addition, with respect to the axial center
C1, the axial center C2 retaining the main shaft 16 has, for
example, a movable range from a position of the center C2 in a
leftward rotation (FIG. 5A) to a position thereof in a rightward
rotation (FIG. 5B). Then, as shown in FIG. 6, the movable range of
the main shaft 16 obtained by combining the above movable ranges is
referred to as a movable range WA1 formed between a maximum radius
Rmax as the maximum rotation radius D1max and a minimum radius Rmin
as a minimum rotation radius D1min. In this case, entry of the main
shaft 16 into the recessed portion 13d allows the minimum rotation
radius D1min to have a value close to a shortest length (=L1-L2).
Thus, the movable range is extended to a position closer to the
axial center C1, as compared to a minimum rotation radius Dmin of
the conventional robot (See FIG. 12). The movable range WA1
includes movable ranges WA1a and WA1b partitioned by a
single-dotted chain line CL. The movable range WA1a shows a region
where the main shaft 16 can reach when located at the center line
or on a left side from the center line, and the movable range WA1b
shows a region where the main shaft 16 can reach when located on a
right side from the center line.
[0062] In general, in order to perform positioning control of the
main shaft 16, the axial center C2 connected to each of the arms 13
and 15 is rotated only in a single direction with respect to the
center line of the first arm 13 (namely, a one-armed system) to
specify only one angle to be made by each of the axial centers C1
and C2 with respect to a locating position of the main shaft 16.
This can make the positioning control thereof easier, that is, can
specify a posture of the SCARA robot with respect to the locating
position of the main shaft 16, thereby facilitating recognition of
interference or the like occurring between the robot and another
device. Meanwhile, when the axial center C2 is rotated in opposite
directions with respect to the center line of the first arm 13,
there occurs a region requiring two postures for the robot with
respect to the locating position of the main shaft 16. This makes
the positioning control complicate and makes it difficult to
recognize interference between the robot and another device.
Accordingly, for the SCARA robot, operation by the one-armed system
is of high utility value in view of controllability. In fact,
movement of the SCARA robot is often controlled so as to work only
in a moving range in accordance with the one-armed system
operation.
[0063] In the embodiment, the movable range WA1a is referred to as
a region of the main shaft 16 operating when the axial center C2 is
rotated only leftward with respect to the center line of the first
arm 13 (namely, a right-armed system). The movable range WA1a in
the right-armed system operation corresponds to a region of a front
side F and a left side with respect to the base 11. In other words,
while a right region with respect to the base 11 is reduced by a
curving amount of the first arm 13, a region including the left
side and the rear side R of the base 11 is increased. The
distribution of the movable range WA1a in the right-armed system is
extremely effective in performing assembly operation using a mode
of single-point supply and single-point incorporation, which is
frequently required of a SCARA robot working on an assembly line.
In the single-point supply and single-point incorporation, a
component obtained from a single point is incorporated into a
single point.
[0064] For example, as shown in FIG. 7, robots RB1 to RB3 as a
plurality of SCARA robots are sequentially placed side by side to
each other, where a product conveyor CV is positioned on the front
side F. In the movable range WA1 of each one of the robots, a
region overlapping with a movable region of an other one of the
robots and a region beyond the overlapping region are reduced as
compared to the conventional robot with the movable range WA (See
FIG. 13). Particularly, in the robots RB1 to RB3, most of the
movable range WA1a of one of the robots in the right-armed system
having a high utility value do not overlap with the movable range
WA1a of an other one of the robots, so that the positioning control
of the respective robots RB1 to RB3 is extremely highly flexible.
When compared with the conventional SCARA robot as shown in FIG.
12, the arm length L11 of the conventional SCARA robot is referred
to as the arm length L1 and the arm length L12 of the robot is
referred to as the arm length L2.
[0065] In addition, as compared to the conventional movable range
WA, a region width of the movable range WA1 (=Rmax-Rmin) is larger.
Thereby, the product conveyor CV can have a larger conveyor width
CVw and thus can convey larger-size products. In addition,
regarding component supply devices PS1 to PS3 supplying a component
to each of the robots RB1 to RB3 from a left side of the each
robot, device widths PS1W to PS3W can be increased. Furthermore,
for example, the number of components supplied each time can be
increased by an amount of extension of the movable range WA to the
rear side R.
[0066] As described above, the horizontal articulated robot of the
embodiment provides advantageous effects as listed below.
[0067] 1. The main shaft 16 has the rotation path in which the
radius of rotation around the axial center C2 is equivalent to the
arm length L2 of the second arm 15. The main shaft 16 is moved up
to a position close to the center axis in such a manner that the
main shaft 16 enters into the eccentric recessed portion 13d of the
first arm. Thereby, the movable range WA1 of the main shaft 16 can
be extended by the amount of reduction in the minimum rotation
radius D1min of the main shaft 16 with respect to the axial center
C1.
[0068] 2. The arm lengths L1 and L2, respectively, of the first and
the second arms, respectively, can be made equal to respective arm
lengths of a SCARA robot having a non-eccentric conventional first
arm. This can minimize an increase in mass of the first arm 13, and
as the second arm 15, the conventional type of arm can be used as
it is. As a result, in the horizontal articulated robot using the
eccentric first arm 13, responsiveness, positioning precision and
the like can be maintained as in the conventional robot. Thus,
there is no unnecessary increase in robot size.
[0069] 3. The main shaft 16 can be moved up to a position close to
the center axis in such a manner that the shaft 16 enters into the
recessed portion 13d as the curved portion of the first arm 13,
thereby allowing the main shaft 16 to be smoothly stored in the
curved shape of the first arm 13.
[0070] 4. The movable range WA1 of the SCARA robot can be extended
up to the rear side R of the base 11 when the axial center C2 of
the first arm 13 is located in a rear direction corresponding to
the rear side R of the SCARA robot while sandwiching the wiring
duct 19 (the base-side duct connecting portion 20) between the
axial centers C2 and C1. This can suitably extend the movable range
of the first arm 13 in the SCARA robot in which the wiring duct 19
(the base-side duct connecting portion 20) is provided in a
position interfering with the first arm 13 on the base 11.
[0071] Furthermore, the embodiment may be modified to be
implemented, as in following examples.
[0072] In the embodiment, the main shaft 16 is located in the most
recessed portion of the first arm 13. However, this is merely an
example and the main shaft 16 may not be located in the most
recessed portion of the first arm. The movable range of the main
shaft 16 can be extended as long as the shaft 16 is located in even
a least recessed portion. This can improve flexibility in the shape
of the first arm.
[0073] In addition, in the embodiment, the base-side duct
connecting portion 20 is also located in the most recessed portion
of the first arm 13, but this may not be necessary. The movable
range of the first arm 13 can be extended as long as the base-side
duct connecting portion 20 is located in even a least recessed
portion, thereby improving flexibility in the shape of the first
arm 13.
[0074] In the embodiment, the connection shaft 12 and the support
shaft 14, respectively, are inserted into the base end connection
portion 31 and the extreme end connection portion 35, respectively,
penetratingly formed on the first arm 13. The shafts 12 and 14 are
connectively fixed to the respective portions by a screw or the
like via a screw hole. However, this is merely an example, and
connective fixation of the connection shaft and the support shaft
to the first arm may be made by other manners. For example, the
connection shaft and the support shaft may be connected to the
first arm by a bolt as vertically penetrating through the first arm
or by inserting the connection shaft and the support shaft,
respectively, into a grooved base end connection portion and a
grooved extreme end connection portion, respectively. This can
improve flexibility in the structure of the first arm.
[0075] In the embodiment, the connection shaft 12 and the support
shaft 14 can be connected to both of the top and the bottom
surfaces of the first arm 13. However, instead of that, each of the
shafts 12 and 14 may be connectable only to one of the top and the
bottom surfaces of the first arm. This facilitates processing of
the first arm.
[0076] In the embodiment, the main shaft 16 cannot be moved to a
position overlapping with the center line, but alternatively, may
be moved thereto. As the main shaft comes closer to the center
line, the minimum rotation radius becomes smaller, whereby the
movable range of the main shaft is extended. As a result, a movable
range for working as the SCARA robot can be extended, so as to
obtain a larger movable range.
[0077] In the embodiment, the first arm 13 has entirely the
rightward-curved shape. This is merely an example of the shape of
the first arm 13. The first arm 13 can have any other shape as long
as the main shaft 16 can be located close to the center line of the
first arm 13 in a position overlapping with the rotation path of
the main shaft 16. For example, only a portion of the first arm 13
overlapping with the rotation path of the main shaft 16 may be
horizontally protruded in a convex form or a horizontal width of
the protruded portion may be made small to form only a horizontally
recessed portion. This can increase flexibility in the shape of the
first arm.
[0078] In the embodiment, the first arm 13 is curved in the
rightward bulging shape. However, alternatively, the first arm 13
may be curved in a leftward bulging shape. For example, as shown in
FIG. 8, the SCARA robot has a maximum rotation radius D2max and a
minimum rotation radius D2mix. However, when the arm length L1 is
equal to the arm length L2, the values become equal to the maximum
rotation radius D1max and the minimum rotation radius D1min of the
embodiment. In this case, due to a difference of the curving
direction in the first arm 13, the main shaft 16 has, for example,
a movable range from a position in a rightward rotation (FIG. 9A)
to a position in a leftward rotation (FIG. 9B), with respect to the
axial center C2. In addition, with respect to the axial center C1,
the axial center C2 retaining the main shaft 16 has, for example, a
movable range from a position when rotated rightward (FIG. 10A) to
a position when rotated leftward (FIG. 10B). Then, the movable
range of the main shaft 16 including the movable ranges is referred
to as a movable range WA2 formed between a maximum radius Rmax as a
maximum rotation radius D2max and a minimum radius Rmin as a
minimum rotation radius D2min, as shown in FIG. 11. In this case,
similarly, the main shaft 16 enters into the recessed portion at a
right limit point PLb to allow the minimum rotation radius D2min to
have a value close to the shortest length (=L1-L2), thereby
extending the movable range of the main shaft 16 in a position
close to the axial center C1. The movable range WA2 includes
movable ranges WA2b and WA2a partitioned by a single-dotted chain
line CL. The movable range WA2b is referred to as a region
reachable when the main shaft is located at a center line or on a
right side from the center line (a left-armed system), and the
movable range WA2a is referred to as a region reachable when the
main shaft 16 is located on a left side from the center line. Thus,
the movable range WA2b of the left-armed system corresponds to a
region of the front side F and the right side with respect to the
base 11. Due to easy positioning control and the like, the utility
value can be improved. In addition, for the SCARA robot,
configuration (structure) flexibility can also be improved.
* * * * *