Abstract:
A robot includes a body, a first arm, and a second arm. The first arm includes one joint, an adjacent joint that is adjacent to the one joint, and another adjacent joint that is adjacent to the adjacent joint. When the first arm is extended in a vertical orientation relative to the body, the one joint of the first arm has a rotation axis that is offset by a first distance in a first horizontal direction from a rotation axis of the adjacent joint of the first arm, and the another adjacent joint of the first arm has a rotation axis that is offset by a second distance in a second horizontal direction from the rotation axis of the adjacent joint of the first arm. The first horizontal direction is opposite to the second horizontal direction.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a continuation application of the U.S. patent application Ser. No. 12/912,750 filed Oct. 27, 2010, which claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2009-257212, filed Nov. 10, 2009. The contents of these applications are incorporated herein by reference in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a robot. 
     2. Description of the Related Art 
     In most typical vertical articulated robots, an arm mounted on a base includes six or seven rotary joints, and portions provided on distal-end sides (robot-hand sides) of the joints are rotated or turned. 
     The moving range of the hand of such a robot can be widened by increasing the length of the arm. Meanwhile, if the arm is folded so that the hand of the robot is placed in an area near the base, it is necessary to prevent the hand from interfering with the arm. For this reason, the moving range of the hand of the robot is set such as not to include the area near the base. 
     In recent years, there has been a demand for a robot that can perform more complicated operation and moving range. Hence, the robot is required to operate in a manner such that the hand can be placed both at positions sufficiently distant from the base and positions closer to the base. 
     As a technique for solving this problem, Japanese Patent Laid-Open Publication No. 2008-272883 discloses a structure for offsetting the rotation axis of an arm in a middle portion of the arm. According to this disclosed technique, even in a state in which the arm is folded, a wide moving range can be ensured while avoiding interference between the arm portions. 
     SUMMARY OF THE INVENTION 
     According to one aspect of the present invention, a robot includes a body, a first arm, and a second arm. The first arm includes a plurality of members connected by a plurality of joints. The second arm includes a plurality of members connected by a plurality of joints. The first arm includes one joint, an adjacent joint that is adjacent to the one joint, and another adjacent joint that is adjacent to the adjacent joint. When the first arm is extended in a vertical orientation relative to the body, the one joint of the first arm has a rotation axis that is offset by a first distance in a first horizontal direction from a rotation axis of the adjacent joint of the first arm, and the another adjacent joint of the first arm has a rotation axis that is offset by a second distance in a second horizontal direction from the rotation axis of the adjacent joint of the first arm. The first horizontal direction is opposite to the second horizontal direction. The second arm includes one joint, an adjacent joint that is adjacent to the one joint of the second arm, and another adjacent joint that is adjacent to the adjacent joint of the second arm. When the second arm is extended in a vertical orientation relative to the body, the one joint of the second arm has a rotation axis that is offset by a third distance in a third horizontal direction from a rotation axis of the adjacent joint of the second arm, and the another adjacent joint of the second arm has a rotation axis that is offset by a fourth distance in a fourth horizontal direction from the rotation axis of the adjacent joint of the second arm. The third horizontal direction is opposite to the fourth horizontal direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The embodiments of the present invention will be described in further detail with reference to the accompanying drawings wherein: 
         FIG. 1  is a side view illustrating a configuration of a robot according to a first embodiment; 
         FIG. 2  is a side view illustrating the configuration of the robot of the first embodiment; 
         FIG. 3  is a side view illustrating a configuration of a robot according to a second embodiment; 
         FIG. 4  is a side view illustrating a configuration of a robot according to a third embodiment; and 
         FIG. 5  is a top view illustrating the configuration and a moving range of the robot of the third embodiment. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     First Embodiment 
     Overall Configuration 
     A first embodiment will be described below with reference to the drawings. 
     As illustrated in  FIG. 1 , a robot system  100  according to the first embodiment includes a seven-axis vertical articulated robot  1 , a robot controller  2 , and a cable  3  that connects the robot  1  and the robot controller  2 . 
     The robot controller  2  is formed by a computer including a memory, an electronic processor, and an input (all of them not illustrated), and is connected to below-described actuators in the robot  1  by the cable  3 . The cable  3  is formed by bundling and sheathing signal communication lines between the robot controller  2  and the actuators and power feeding lines for supplying power from a power supply (not shown) to the actuators. 
     The robot  1  includes a base  10  fixed to a mounting surface (e.g., floor or ceiling)  101 , and an arm. In the arm, an arm member (first member)  11 , an arm member (second member)  12 , an arm member (third member)  13 , an arm member (fourth member)  14 , an arm member (fifth member)  15 , an arm member (sixth member)  16 , and a flange (seventh member  17 ) are connected by rotary joints (first to seventh joints) in order from the base  10  to a leading end of the robot  1 . That is, the arm is constituted by the arm members  11  to  17  and the rotary joints. 
     More specifically, the base  10  and the arm member  11  are connected by a first actuator (first joint)  11 A, and the arm member  11  is rotated by driving of the first actuator  11 A. The arm member  11  and the arm member  12  are connected by a second actuator (second joint)  12 A, and the arm member  12  is pivoted by driving of the second actuator  12 A. 
     The arm member  12  and the arm member  13  are connected by a third actuator (third joint)  13 A, and the arm member  13  is rotated by driving of the third actuator  13 A. The arm member  13  and the arm member  14  are connected by a fourth actuator (fourth joint)  14 A, and the arm member  14  is pivoted by driving of the fourth actuator  14 A. 
     The arm member  14  and the arm member  15  are connected by a fifth actuator (fifth joint)  15 A, and the arm member  15  is rotated by driving of the fifth actuator  15 A. The arm member  15  and the arm member  16  are connected by a sixth actuator (sixth joint)  16 A, and the arm member  16  is pivoted by driving of the sixth actuator  16 A. 
     The arm member  16  and the flange  17  are connected by a seventh actuator (seventh joint)  17 A, and the flange  17  and an end effecter (not shown), such as a hand, which is attached to the flange  17  are pivoted by driving of the seventh actuator  17 A. 
     As illustrated in  FIG. 1 , the arm member  13  includes a receiving portion (receiving portion A)  20 A that receives the third actuator  13 A, a connecting portion (connecting portion A)  20 B obliquely extending from the receiving portion  20 A to the upper right side of the figure (in the R-direction and a direction towards the leading end), and a receiving portion (receiving portion B)  20 C that receives the fourth actuator  14 A. The receiving portion  20 A, the receiving portion  20 C, and the connecting portion  20 B form a continuous internal space, where the cable  3  is stored. 
     The arm member  14  includes a receiving portion (receiving portion A)  21 A that receives the fourth actuator  14 A, a connecting portion (connecting portion B)  21 B obliquely extending from the receiving portion  21 A to the upper left side of the figure (in the L-direction and a direction towards the leading end), and a receiving portion (receiving portion D)  21 C that receives the fifth actuator  15 A. The receiving portion  21 A, the receiving portion  21 C, and the connecting portion  21 B form a continuous internal space. 
     That is, the receiving portion  20 A, the receiving portion  20 C, the connecting portion  20 B, the receiving portion  21 A, the receiving portion  21 C, and the connecting portion  21 B correspond to the offset portion. 
     Each of the first to seventh actuators  11 A to  17 A is formed by a servo motor with built-in reduction gears. The servo motor has a hole through which the cable  3  can extend. The first to seventh actuators  11 A to  17 A are connected to the robot controller  2  by the cable  3 . 
     When the robot  1  takes an attitude such that rotation axes A1, A3, and A5 (referred to as rotation axes in the rotating direction) are perpendicular to the mounting surface  101  (a state illustrated in  FIG. 1 ), rotation axes A2, A4, A6, and A7 (rotation axes in the pivot direction) are at an angle of 90 degrees to the rotation axes in the rotating direction. Further, the rotation axis A6 is at an angle of 90 degrees to the rotation axis A7. 
     The rotation axis A1 of the first actuator  11 A and the rotation axis A3 of the third actuator  13 A are substantially aligned with each other. Also, the rotation axis A1 and the rotation axis A3 are orthogonal to the rotation axis A2 of the second actuator  12 A. 
     The rotation axes A1 and A3 do not intersect the rotation axis A4 of the fourth actuator  14 A, and are offset from the rotation axis A4 by a length d1 in a direction horizontal to the mounting surface  101  (in a R-direction with reference to the rotation axis A3). 
     In other words, the offset refers to a state in which a rotation axis different from a rotation axis at a base end is shifted from the rotation axis at the base end in the orthogonal direction when the robot or the arm takes an attitude such that the projection area thereof on the mounting surface is the smallest. 
     Further, the rotation axis A4 does not intersect the rotation axis A5 of the fifth actuator  15 A, and is offset from the rotation axis A5 by a length d2 in the direction horizontal to the mounting surface  101  (in the rightward direction of the figure with reference to the rotation axis A4). 
     Therefore, the rotation axis A3 and the rotation axis A5 are offset by a length |d1−d2| in the direction horizontal to the mounting surface  101  (in the rightward direction of the figure with reference to the rotation axis A3). 
     In the first embodiment, the length d1 is set to be larger than the length d2 (that is, d1&gt;d2). The width of the arm member  13  is larger than the width of the arm member  15 . 
     The base  10  has a cable insertion hole (not shown). As illustrated in  FIG. 2 , the cable  3  passes, in order, through the interior of the base  10 , the hole of the first actuator  11 A, the arm member  11 , the hole of the second actuator  12 A, the arm member  12 , the hole of the third actuator  13 A, the receiving portion  20 A, the connecting portion  20 B, the receiving portion  20 C, the hole of the fourth actuator  14 A, the receiving portion  21 A, the connecting portion  21 B, the receiving portion  21 C, the hole of the fifth actuator  15 A, the arm member  15 , the hole of the sixth actuator  16 A, the arm member  16 , and the hole of the seventh actuator  17 A. Further, the cable  3  is connected to the end effecter (not shown) via a hole of the flange  17 . 
     Since the robot system  100  of the first embodiment has the above-described configuration, when the robot system  100  operates with the flange  17  being placed near the base  10  or the arm member  11 , in a state in which the fourth actuator  14 A is greatly rotated, as illustrated in  FIG. 2 , the rotation axis A3 and the rotation axis A5 are offset from each other by the sum of the length d1 and the length d2 (that is, d1+d2), which increases the offset amount between the rotation axis A3 and the rotation axis A5. For this reason, even when the fourth actuator  14 A is bent to obtain an attitude such that the rotation axis A3 and the rotation axis A5 become substantially parallel to each other, it is possible to prevent the arm member  13  and the arm member  15  from touching and interfering each other and to allow the flange  17  to reach a lower position near the arm member  11 . 
     In contrast, during a standby state of the robot system  100 , the robot  1  is operated so that the rotation axis A1, the rotation axis A3, and the rotation axis A5 become perpendicular to the mounting surface  101 . This can minimize the amount of protrusion of the robot  1  in the direction horizontal to the mounting surface  101 . In this case, the offset amount of the rotation axes A1 and A3 from the rotation axis A4 is limited to the length d1. 
     In other words, the offset amount corresponding to d1+d2 can be obtained in the state where the fourth actuator  14 A is bent, and the offset amount can be limited to d1 (d1&lt;d1+d2) in the standby state. Thus, a wide moving range of the flange  17  can be ensured by the offset, and moreover space saving can be achieved. 
     The cable  3  passes through the hole of the third actuator  13 A, is gently bent in the connecting portion  20 B, passes through the hole of the fourth actuator  14 A, is gently bent in the connecting portion  21 B, and is then guided to the hole of the fifth actuator  15 A. Therefore, even if the angle between the arm member  13  and the arm member  14  is made more acute by greatly rotating the fourth actuator  14 A, the curvature of the cable  3  can be limited to a relatively small value. Hence, it is possible to reduce damage to the cable  3  due to the increase in curvature of the cable  3 . 
     In the first embodiment, the fifth actuator  15 A rotates the arm member  15 , the sixth actuator  16 A pivots the arm member  16 , and the seventh actuator  17 A rocks the flange  17  at an angle of 90 degrees to the pivot direction of the arm member  16 . Hence, unlike the case in which the seventh actuator  17 A rotates the flange  17 , it is possible to prevent an out-of-control point (singular point) from being caused by overlapping of the rotation axis A5 and the rotation axis A7. For this reason, it is unnecessary to perform an operation for avoiding the singular point in the attitude such that the fourth actuator  14 A is bent (state of  FIG. 2 ). This increases the degree of flexibility in operation of the robot  1 . 
     Second Embodiment 
     Next, a second embodiment will be described. As illustrated in  FIG. 3 , a robot system  200  of the second embodiment is different from the robot  1  of the first embodiment only in an attachment direction of a seventh actuator  27 A (seventh joint) and a flange  27 . Therefore, in the following description, for convenience of explanation, redundant descriptions are appropriately omitted, and like components are denoted by like reference numerals. 
     In the second embodiment, an arm member  16  is connected to the flange  27  by the seventh actuator  27 A, and the flange  27  and an end effecter (not shown), such as a hand, attached to the flange  27  are rotated by driving of the seventh actuator  27 A. 
     Since the robot system  200  of the second embodiment has the above-described configuration, in contrast to the robot  1  of the first embodiment, it is necessary to avoid a singular point caused when a fourth actuator  14 A is bent, but it is possible to easily rotate the end effecter attached to the flange  27  by simply driving the seventh actuator  27 A. Thus, the second embodiment is suitable for an application in which the end effecter is rotated. 
     Third Embodiment 
     Next, a third embodiment will be described. As illustrated in  FIGS. 4 and 5 , the third embodiment is different from the first embodiment in that the base adopted in the first embodiment is removed and the body is provided with a pair of (two) arms  400  having a structure similar to that of the arm of the robot  1 . Therefore, descriptions overlapping with the first embodiment are appropriately omitted, and like components are denoted by like reference numerals. 
     In a robot system  300  of the third embodiment, two arms  400  are attached to a body  301  (corresponding to the base) fixed to a mounting surface  101 . 
     The body  301  includes a base portion  301 A fixed to the mounting surface  101 , and a turning body portion (main body)  301 B that turns relative to the base portion  301 A via an actuator  301 C. 
     The turning body portion  301 B obliquely extends upward (to the upper right of  FIG. 4 ) from the actuator  301 C, and has an opening where the pair of arms  400  can be attached. 
     A rotation axis Ab of the actuator  301 C is offset from rotation axes A1 of first actuators  11 A in the arms  400  by a length d3 in a direction horizontal to the mounting surface  101  (R-direction with reference to the rotation axis Ab). 
     In the third embodiment, the arms  400  are attached to the turning body portion  301 B in a manner such that the rotation axes A1 of the respective first actuators  11 A are arranged on the same straight line (the orientations of the arms  400  can be changed appropriately). That is, the turning body portion  301 B also functions as a bases for both of the arms  400 . A robot controller  302  is connected to the arms  400  by a cable  303  so that the actuators of the arms  400  operate according to commands from the robot controller  302 . 
     Since the robot system  300  of the third embodiment has the above-described configuration, it is possible to enlarge the moving range where the pair of arms  400  cooperate near the body, for example, during assembly of mechanical products. This achieves further space saving. 
     Further, the turning body portion  301 B obliquely extends upward and the pair of arms  400  are attached thereto. Thus, the offset between the rotation axis Ab and the rotation axis A1 allows the flanges  17  of the arms  400  to be moved to farther positions by rotating the actuator  301 C. 
     In addition, ends of the arms  400  can reach even a space formed near the base portion  301 A and below the turning body portion  301 B. Therefore, operation can be performed utilizing the space below the turning body portion  301 B, and this achieves further space saving. 
     While the embodiments of the present invention have been described above, the robot system of the present invention is not limited to the above embodiments, and appropriate modifications can be made without departing from the scope of the present invention. 
     For example, while the robot of the first embodiment is attached to the body in the third embodiment, the arm attached to the body may be similar to the arm adopted in the robot system  200  of the second embodiment. 
     While the robot has seven joints in the above embodiments, it may have three joints. For example, the structures other than the third to fifth actuators  13 A,  14 A, and  15 A and the arm members  13  to  15  in the first embodiment may be removed from the robot.