Abstract:
An apparatus holds plural cables arranged in a robot. A first fixing member secures ones of both ends of the cables on a first shaft portion in a flat form, the ones of the end portions being directed in a rotation direction of the second shaft portion. A second fixing member secures the others of both end portions of the cables on a second shaft portion in the flat form, the other end portions being directed in the rotation direction. The remaining portions of the cables are bent and suspended along the first and second shaft portions in a U-shaped and flat form when being viewed in the rotation direction. A first cable guide, fixed to the first shaft portion, accommodates part of the cables therein in the plat form. A second cable guide, fixed to the second shaft portion, accommodates part of the cables therein in the flat form.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application is based on and claims the benefit of priority from earlier Japanese Patent Application No. 2009-142306 filed Jun. 15, 2009, the description of which is incorporated herein by reference. 
       BACKGROUND OF THE INVENTION 
       [0002]    1. Technical Field of the Invention 
         [0003]    The present invention relates to an apparatus for holding cables in arms of an articulated type of robot, and in particular, to the apparatus that holds the cables bridging a fixed part and a rotary part in the arms. 
         [0004]    2. Related Art 
         [0005]    A robot having an articulated arm includes motors and joints. The motors are located at the axes of the respective joints to actuate the joints. Such a robot is controlled by a controller with the supply of electric power to the motors. Therefore, the controller and the robot are connected via cables. Generally, such cables are bundled up. Also, such cables are usually accommodated inside the robot and connected to respective parts from the inside, in order to save space or avoid the cables per se from becoming a hindrance. 
         [0006]    However, under the conditions as described above, rotation of the robot arm may cause the cables to be in contact with the members producing the rotation (rotating members), and may create friction between the rotating members and the cables. In particular, the friction created between the rotating members and the cables is liable to increase when the overall structure of the robot is made compact, because in such a compact structure the cables are pressed against the rotating members. The increase of friction may disable smooth rotational movement of the arm. As a result, the movement of the arm may become sluggish, or rotation per se of the rotating members may be disabled. For example, JP-A-2006-187841 discloses that rotating members of a robot are prevented from contacting with cables by arranging the cables outside the robot and providing members that restrict the movement of the cables. 
         [0007]    The configuration disclosed in JP-A-2006-187841 is able to prevent the Interference between the shaft located on a tip end side of the arm and the cables to effectively reduce friction. In return, however, this configuration necessitates external routing of the cables, i.e. routing of the cables outside the robot. Therefore, the space occupied by the robot is increased by an amount corresponding to the space required for the external routing of the cables. For this reason, the external routing of cables cannot be applied to those robots which are required to be contributory to space saving. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention has been made in light of the circumstances set forth above, and has as its object to provide a cable holding structure for a rotary shaft of a robot, which structure is able to save space in arranging cables and prevent, as much as possible, friction between each of the cables and each of the members that produce rotation. 
         [0009]    According to a cable holding structure for a rotary shaft of a robot based on one aspect of the present invention, a plurality of cables are arranged flat along an outer peripheral portion of a rotary shaft. Therefore, when a rotary part starts rotational movement, one tip end of each group of cables (hereinafter referred to as “cable group”) starts moving with the rotational movement. Meanwhile, other portion of the cable group, which is in a state of being bent into a U-shape, follows the rotational movement along the outer peripheral portion. At this moment, the U-shaped bent portion (hereinafter referred to as are “R portion”) of the cable group takes a movement in relation to the direction of the rotation, while straight portions of the cable group rotate integrally with the rotary part and rotary cable guides. 
         [0010]    In other words, when the rotary shaft starts rotational movement, friction is caused only at the R portion of each cable group. Accordingly, friction can be significantly reduced and thus smooth rotational movement can be ensured. In this way, each cable group can be compactly arranged along the outer peripheral portion of the rotary shaft, saving space and without becoming a hindrance to the rotational movement. In addition, since the load that would be imposed on the cables is reduced, the cables are unlikely to be damaged and thus reliability can be enhanced. 
         [0011]    According to a cable holding structure for a rotary shaft of a robot based on another aspect of the present invention, each cable guide has a U-shaped cross section with a predetermined gap and is formed, in its entirety, of a cylindrical member. Specifically, each cable guide has a U-shaped portion by which each flat cable group can be held. Accordingly, similar to the foregoing, when the rotary part starts rotational movement, friction is caused only at the R portion of each cable group. Thus, the same advantages as the foregoing can be obtained. 
         [0012]    According to the cable holding structure for a rotary shaft of a robot based on another aspect of the present invention, when the controller and the robot are connected using two cable groups, the two cable groups are fixed such that tip end portions of one cable group are opposed to tip end portions of the other cable group, displaying a bilaterally symmetrical arrangement as a result. With this configuration, in whichever direction the rotary part may rotate, the cable groups can move along the outer peripheral portion without becoming a hindrance to each other&#39;s movement In this way, if the number of cables connecting between the controller and the robot is increased, space can be saved without permitting the cables to prevent the rotational movement. 
         [0013]    According to the cable holding structure for a rotary shaft of a robot based on another aspect of the present invention, the width of the gap formed by the cable guides is set to be larger than the diameter of each cable by a factor of 1.7 or less. In the event a portion of each cable gravitationally hangs down, the above setting, coupled with the comparatively low flexibility of the cable, can permit the cable at an upper position to stay in a state of its center being deviated outward by 45 degrees or less from the center of the cable at a lower position. In this way, smooth rotational movement can be maintained. 
         [0014]    Specifically, let us assume that two cables are vertically in contact with each other and that these cables stay in a state where the center of the upper cable is deviated outward from the center of the lower cable by 45 degrees. The width of the gap suitable for this state can be expressed by: 
         [0000]      (1+1/2 1/2 )D≈1.7D, 
         [0000]    where D is a diameter of the cable. As a matter of course, the lower limit of the width of the gap should exceed the diameter of each cable. 
         [0015]    Still another aspect of the present invention, there is provided an articulated type of robot, comprising: a plurality of articulated arms respectively provided with electric motors to drive the arms, the motors receiving drive signals from a controller, the arms having rotary shaft portions which allow the arms to rotate on axes given thereto, each of the rotary shaft portions being divided into two shaft portions a first of which is fixed and a second of which is rotatable; a plurality of cables electrically connecting the controller and the motors for transmitting the drive signals to the motors; a first fixing member that secures ones of both ends of the cables on and along the first shaft portion in a flat form in which the cables are arranged in parallel with each other, the ones of both end portions of the cables being directed in a rotation direction along which the second shaft portion rotates; a second fixing member that secures the others of both end portions of the cables on and along the second shaft portion in the flat form, the others of both end portions of the cables being directed in the rotation direction so that remaining portions of the cables are bent and suspended along the first and second shaft portions in a U-shaped and flat form when being viewed in the rotation direction; a first cable guide that is fixedly arranged along the first shaft portion and has a circular tube-shaped space therealong in which the cables are partly accommodated in the flat form; and a second cable guide that is arranged along the second shaft portion so as to rotate together with the second shaft portion and has a circular tube-shaped space therealong in which the cables are partly accommodated in the flat form. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0016]    In the accompanying drawings: 
           [0017]      FIG. 1  is a perspective view illustrating the configuration of a vertical articulated robot, according to a first embodiment of the present invention; 
           [0018]      FIG. 2A  is a perspective view illustrating the inside of a base of the robot; 
           [0019]      FIG. 2B  is a vertical cross-sectional view illustrating the inside of the base; 
           [0020]      FIG. 3  is a diagram illustrating a principle of restricting the width of a gap defined by cable guides in the base; 
           [0021]      FIGS. 4A to 4D  are diagrams each illustrating the movement of individual cables when a rotary part of the base starts rotation; 
           [0022]      FIG. 5  is a diagram illustrating a cable-routing structure of the conventional art, in a manner analogous to  FIG. 2B ; and 
           [0023]      FIG. 6  is a cross-sectional view illustrating the inside of the base so of a robot, according to a second embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]    With reference to the accompanying drawings, hereinafter are described some embodiments of the present invention. 
       First Embodiment 
       [0025]    With reference to  FIGS. 1 to 5 , hereinafter is described a first embodiment of the present invention.  FIG. 1  is a perspective view illustrating the configuration of a vertical articulated (six-axis) robot  1  according to the first embodiment. The robot  1  includes a base (functioning as one of rotary shaft portions)  2  on which an arm, a six-axis arm in this case, is provided. The base  2  includes a housing  2 H and a substantially rectangular bottom plate  11 . The arm has a tip end to which a tool, such as a hand, not shown, is attached. Specifically, the arm includes first, second, third, fourth, fifth and sixth joints J 1 , J 2 , J 3 , J 4 , J 5  and J 6 , and first, second, third, fourth, fifth and sixth arms  3 ,  4 ,  5 ,  6 ,  7  and  8 , as well as servomotors M 1  to M 6 . The is first arm  3  is rotatably connected onto the base  2  via the first joint J 1 . The second arm  4  extending upward has a lower end portion which is rotatably connected to the first arm  3  via the second joint J 2 . The second arm  4  has a tip end portion to which the third arm  5  is rotatably connected via the third joint J 3 . 
         [0026]    The third arm  5  has a tip end to which the fourth arm  6  is rotatably connected via the fourth joint J 4 . The fourth arm  6  has a tip end to which the fifth arm  7  is rotatably connected via the fifth joint J 5 . The sixth arm  8  is rotatably connected to the fifth arm  7  via the sixth joint J 6 . The arms  3  to  8  are adapted to be rotated and actuated by the servomotors M 1  to M 6  located in the respective joints J 1  to J 6 . 
         [0027]    The present invention is characterized in the structure with which the cables can be arranged inside the base  2  (inside the housing  2 H), the cables connecting the servomotors M 1  to M 6  in the robot  1  to a controller (control unit) CT. The controller CT sends out drive signal to the motors M 1  to M 6  to drive rotation of those motors. 
         [0028]      FIG. 2A  is a perspective view illustrating the inside of the base  2  of the robot  1 , with the housing  2 H being removed.  FIG. 2B  is a vertical cross-sectional view illustrating the inside of the base  2 , with the housing  2 H being removed. The base  2  includes therein the servomotor M 1 , a rotary shaft  12 , a cylindrical motor cover  13  having an opening  13   a , a disc-shaped attachment member  14 , a substantially disc-shaped top plate  15 , bolts  16 , stationary cable guides  17  and  18 , bolts  19 , cables  20  forming each group  21  ( 21 A or  21 B) of cables (hereinafter represented as a “cable group  21 ”), rotary cable guides  22  and  23 , and bolts  24 . 
         [0029]    The servomotor M 1  is disposed at the center of the substantially rectangular bottom plate  11  such that the rotary shaft  12  of the servomotor M 1  is directed upward. The motor cover  13  is disposed enclosing the outer peripheral portion of the body of the servomotor M 1  with a predetermined space therebetween. The opening  13   a  is provided at an upper part of the motor cover  13 . The rotary shaft  12  has a tip end to which the disc-like attachment member  14  is fixed. The diameter of the attachment member  14  is set to be smaller than that of the opening  13   a . The substantially disc-like top plate  15  is attached to the attachment member  14 , being screwed therein via the bolts  16 . The arm  3  is fixedly mounted on the top plate  15 , for rotation around the joint J 1 . 
         [0030]    The motor cover  13  has a lower half portion which is covered by the stationary cable guides  17  and  18  each having a cylindrical shape. In covering the motor cover  13 , the stationary cable guides  17  and  18  are coaxially and doubly arranged, being screwed from the side of the bottom plate  11  using the bolts  19 . The stationary cable guides  17  and  18  are arranged with a predetermined gap therebetween. In the gap, a plurality of cables  20  are flatly juxtaposed forming one of the cable groups  21 . Specifically, the gap between the stationary cable guides  17  and  18  is set to be slightly larger than the diameter of each cable  20  (see  FIG. 3  described later). 
         [0031]    The motor cover  13  has an upper half portion which is covered by the rotary cable guides  22  and  23  each having a cylindrical shape. In covering the motor cover  13 , the rotary cable guides  22  and  23  are coaxially and doubly arranged being screwed from the side of the top plate  15  using the bolts  24 . The cable guides  22  and  23  are positioned so as to be symmetrical to the stationary cable guides  17  and  18 . The rotary cable guides  22  and  23  are ensured to face the stationary cable guides  17  and  18  through a predetermined space. As shown in  FIG. 1 , these cable guides  17 ,  18 ,  22  and  23  are externally covered by the housing  2 H of the base  2 . 
         [0032]    As shown in  FIG. 1 , the stationary cable guide  18  arranged outside has a front portion in which a cut-off portion is provided. In the cut-off portion, cable-lower-end fixing members  25 , each made up, for example, of a U-shaped steel member, are fixedly screwed, at upper ends of the respective members  25 , into the stationary cable guide  17  via bolts  26 . Each cable group  21  has a portion at a lower end (one tip end), which portion is adapted to extend from the cable-lower-end fixing members  25  to the outside of the base  2  and be connected to a connector  27  and then, via the connector  27 , to the controller CT. 
         [0033]    As shown in  FIG. 2A , each cable group  21 , with its lower end being maintained flat, and in a state of being fixed by the cable-lower-end fixing members  25 , is extended straight along the stationary cable guide  17 . Then, this cable group  21  is turned back, drawing a shape of U (i.e. providing a U-shaped bent portion), in the direction in which the cables  20  are juxtaposed, and directed to the gap between the rotary cable guides  22  and  23 . Each cable group  21  is then extended straight again in a direction reverse to the direction in which the cable group  21  has been extended between the stationary cable guides  17  and  18 . Thus, an upper end (the other tip end) of each cable group  21  arrives at a position above the cable-lower-end fixing members  25 . 
         [0034]    Each cable group  21 , with its upper end also being maintained flat, is fixed at the above arrival position by cable-upper-end fixing members  28  each having a configuration similar to the cable-lower-end fixing member  25 . The cable-upper-end fixing members  28  are screwed in and fixed to the rotary cable guide  22  located inside, using respective bolts  29  (see  FIG. 1 ). From there, the upper end of each cable group  21  is extended upward and inserted into the respective arms  3  to  7  of the robot  1 , so that tip ends of the cables  20  are connected to the respective servomotors M 1  to M 6  and the like. 
         [0035]    In the configuration of the present embodiment, as shown in  FIGS. 1 and 2A , two cable groups  21  (i.e.,  21 A and  21 B) are arranged. Specifically, the two cable groups  21  are arranged so that the upper ends as well as the lower ends of the cable groups  21  are opposed to each other, displaying a bilaterally symmetrical arrangement. In other words, as can be seen from  FIG. 2A , outer portions of the U-shaped bent portions (hereinafter each referred to as an “R portion”) of the respective cable groups  21  are opposed to each other. 
         [0036]    It should be appreciated that the cables  20  are not necessarily restrictively used for electric wiring. The cables  20  may include, for example, those which convey compressed air or those which suck air, liquid or materials for performing vacuum adsorption. 
         [0037]    In the base  2  described above, the housing  211 , the bottom plate  11 , the motor cover  13 , and the stationary cable guides  17  and  18  configure a stationary part  30 . Meanwhile, the top plate  15 , and the rotary cable guides  22  and  23  configure a rotary part  31 . 
         [0038]      FIG. 3  is a diagram illustrating a principle of restricting the width of the gap between the stationary cable guides  17  and  18 , and between the rotary cable guides  22  and  23 . Specifically,  FIG. 3  schematically illustrates the rotary cable guides  22  and  23  and cross sections of two cables  20 A and  20 B located therebetween.  FIG. 3  shows a state where the center of the cable  20 A at an upper position is deviated outward by 45 degrees from the center of the cable  20 B at a lower position. 
         [0039]    More specifically, as shown in  FIG. 3 , when the width of the gap between the rotary cable guides  22  and  23  is set larger than a diameter D of the cable  20 , the cable  20 A at the upper position is expected to be deviated outward. As will be described later, it is desirable that the flatness of the cable groups  21  is maintained when the arm  3  is rotated relative to the base  2 . Appropriate setting of an upper limit in the width of the gap can prevent excessive derailing (deviation) of the cable  20 A at the upper position. In  FIG. 3 , the outward deviation of the center of the cable  20 A at the upper position is ensured to be restricted to less than 45 degrees. The angle of 45 degrees is a limit that allows the cables to move. When the deviation is exactly 45 degrees, the width of the gap between the rotary cable guides  22  and  23  is expressed by; 
         [0000]      ( D/ 2)×2+ D/ 2 1/2 =(1+/2 1/2 ) D 1.7 D,    
         [0000]    where D is a diameter of the cable  20 . Accordingly, it may be appropriate to set the width of the gap to be larger than the diameter of the cable  20  by a factor of 1.7 or less (e.g., by a factor of 1.5). 
         [0040]    Referring now to  FIGS. 4A to 4D , advantages of the present embodiment will be explained.  FIGS. 4A to 4D  are diagrams each illustrating the movement of the individual cables  20  when the rotary part  31  of the base  2  is rotated. Specifically,  FIGS. 4A to 4D  each illustrate the movement of each cable group  21  (i.e.,  21 A or  21 B) when the rotary part  31  of the base  2  is rotated from an initial state shown in  FIG. 4A , where the upper and lower ends of each cable group  21  are vertically positioned. The illustrations are given each focusing on the U-shaped R portion of each cable group  21 . In  FIGS. 4A to 4D , the cable guides  17 ,  18 ,  22  and  23  are made experimentally transparent for observation. 
         [0041]    At an initial position indicated by the vertical dashed line in  FIG. 4A , the stationary cable guide  18  and the rotary cable guide  23  are marked with up and down arrows, respectively, such that the tip ends of the arrows coincide. The cables  20  inside forming each cable group  21  are marked with straight lines. The rotary cable guide  23  is also marked with a right arrow such that the tip end of the right arrow coincides with a horizontal line marked at the R portion of the cable group  21 , the horizontal line being one of the straight lines marked on the cable group  21 . 
         [0042]    From this state, the rotary part  31  on the side of the top plate  15  is rotated clockwise (CW) as viewed from the top. Then, as shown in  FIG. 4B , the down arrow of the rotary cable guide  23  moves leftward in the figure. With this movement, the upper end of the cable group  21  is pulled leftward in the figure, allowing the R portion to entirely move leftward. Further, the horizontal line marked at the R portion moves upward relative to the right arrow marked on the rotary cable guide  23 . 
         [0043]    As shown in  FIG. 4C , with further clockwise rotation of the rotary part  31 , the right arrow of the rotary cable guide  23  moves leftward relative to the vertical dashed line indicating the initial position, while the R portion of each cable group  21  comes closer to the dashed line. In the R portion, an amount of movement appears to be larger in a cable  201  located innermost of the cable group  21  than in a cable  200  located outermost of the cable group  21 . Specifically, the amount of movement appears to be different cable by cable, or more specifically, appears to increase as the cable is located more inside. As a result of the different amount of movement of the individual cables  20 , the horizontal line, which has coincided with the right arrow in the initial state shown in  FIG. 4A , has turned into a staircase pattern. 
         [0044]    As shown in  FIG. 4D , with further clockwise rotation of the rotary part  31 , the above tendency of drawing a staircase pattern becomes more apparent. As can be seen, the rear end of the R portion of another cable group  21  has appeared from behind, i.e. from the right in the figure, with the rotation. It should be appreciated that the range of clockwise and counterclockwise (CCW) rotation of the rotary part  31  is so set, for example, to be about ±170 degrees. 
         [0045]    With this range of rotation, each cable group  21 , when it is bent in the shape of U with the rotation of the rotary part  31 , can follow the movement of the rotary part  31 , maintaining the flatness. 
         [0046]    Far comparison,  FIG. 5  illustrates a cable-routing structure of the conventional art, in a manner analogous to  FIG. 2B . In  FIG. 5 , the components identical with or similar to those of  FIG. 2B  (present embodiment) are given the same reference numerals. As shown in  FIG. 5 , a cable  32  in the conventional art is a thick single cable in which individual lines a bundled together. In a space formed between the motor cover  13  and the housing  2 H of the base  2 , only a cable guide  33  is provided. The cable guide  33  corresponds to the stationary cable guides  17  and  18  of the present embodiment. The cable  32  is bent drawing a sideways U shape, not shown. When a rotary part including the top plate  15  is rotated, permitting the upper end of the cable  32  to follow the rotation, a large amount of friction is caused between the cable  32  and the cable guide  33  in a fixed state. 
         [0047]    In this regard, in the configuration of the present embodiment, the plurality of thin cables  20  are flatly bundled to provide each cable group  21 . Each cable group  21  is arranged along the motor cover  13  of the base  2  to reduce the horizontal space occupied by the cable group  21  in the base  2 . Thus, since the rotary cable guides  22  and  23  are rotated integrally with the rotation of the rotary part  31 , the friction caused when the upper end of the cable group  21  follows the rotation is considerably reduced. 
         [0048]    According to the present embodiment described so far, the plurality of cables  20  are flatly arranged in the base  2  along the stationary cable guide  17  and the rotary cable guide  22  (these correspond to the “outer peripheral portion of the rotary part”). When the rotary part  31  starts rotational movement, the upper end of each cable group  21  is permitted to move along the outer periphery of the rotary cable guide  22  to follow the rotational movement, in a state of so being bent in a shape of U. At this moment, the R portion of the cable group  21  takes a movement in relation to the direction of the rotational movement. In this case, the straight portion of the cable group  21 , i.e. the portion held by the rotary cable guides  22  and  23 , rotates integrally with the rotary part  31  and the rotary cable guides  22  and  23 . 
         [0049]    In other words, the rotational movement of the base  2  causes friction only at the R portions of each cable groups  21 . Therefore, friction can be significantly reduced, whereby smooth rotation of the base  2  can be ensured. Thus, the cable groups  21  can be compactly arranged inside the base  2 , along the outer peripheries of the stationary cable guide  17  and the rotary cable guide  22 , saving space and without becoming a hindrance to the rotational movement. In addition, since the load that would be imposed on the cables  20  can be reduced, the cables are unlikely to be damaged and thus reliability can be enhanced. 
         [0050]    In the present embodiment, when the controller CT and the robot  1  are connected via two cable groups  21 , these two cable groups  21  are fixed such that the tip end portions of one cable group  21  as well as the tip end portions of the other cable group  21  are opposed to each other, displaying a bilaterally symmetrical arrangement as a result. Accordingly, in whichever direction the rotary part  31  may rotate, the cable groups  21  can move along the outer peripheries of the stationary cable guide  17  and the rotary cable guide  22  without becoming a hindrance to each other&#39;s movement. In this way, if the number of the cables  20  connecting between the controller CT and the robot  1  is increased, space can be saved without permitting the cables to prevent the rotational movement. 
         [0051]    According to the present embodiment, the width, of the gap between the stationary cable guides  17  and  18 , and between the rotary cable guides  22  and  23  is set to be larger than the diameter of each cable  20  by a factor 1.7 or less. In the event a portion of each cable  20  gravitationally hangs down, the above setting, coupled with the comparatively low flexibility of the cable  20 , can permit the cable  20  at so an upper position to stay in a state of its center being deviated outward by 45 degrees or less from the center of the cable  20  at a lower position. In this way, smooth rotational movement can be maintained. 
       Second Embodiment 
       [0052]    Referring now to  FIG. 6 , a second embodiment of the present invention is described. In the second embodiment and in the subsequent modifications, the components identical with or similar to those in the first embodiment are given the same reference numerals for the sake of omitting explanation. 
         [0053]      FIG. 6  is a cross-sectional view illustrating the inside of the base of a robot, according to the second embodiment.  FIG. 6  corresponds to  FIG. 2B  of the first embodiment. In the second embodiment, a stationary cable guide  41  and a rotary cable guide  42  are provided, replacing the stationary cable guides  17  and  18  and the rotary cable guides  22  and  23 . Each of the stationary and rotary cable guides  41  and  42  constitutes a single body and has a U-shaped cross section. Similar to the first embodiment, the width of the gap formed in each of the stationary and rotary cable guides  41  and  42  having a U-shaped cross section is set to be larger than the diameter D of each cable  20  by a factor of 1.7 or less. 
         [0054]    According to the second embodiment configured as explained above, the stationary cable guide  41  and the rotary cable guide  42  are each formed of a member having a cylindrical shape in its entirety and having a U-shaped cross section with a predetermined gap. Thus, each cable group  21  can be held by U-shaped portions of the cable guides  41  and  42 . Therefore, similar to the first embodiment, when a rotary part  31 A starts rotational movement, friction is caused only at the R portions of the cable groups  21 , achieving the advantages similar to those in the first embodiment. 
         [0055]    (Modifications) 
         [0056]    The present invention is not intended to be limited to the embodiments described above and illustrated in the drawings, but may be modified or extended as set forth below. 
         [0057]    If cables can be satisfactorily wired with a required number, only one cable group  21  may be arranged. The motor cover  13  may be provided as required. Also, the housing  2 H may be removed, allowing the cable guides  18  and  23  located outside to serve as a housing. 
         [0058]    Alternatively, a member MC corresponding to the motor cover  13  may be horizontally divided into two, i.e. an upper member MC_U and a lower member MC_D. In this case, the upper member MC_U may be connected to the rotary shaft  12  to serve as a rotary part. Also, the stationary cable guide  18  and the rotary cable guide  23  located outside may be removed to arrange the cable groups  21  each between the lower member MC_D and the stationary cable guide  17  and between the upper member MC_U and the rotary cable guide  22 . In this case, the outer periphery of the member MC corresponds to the “outer peripheral portion of the rotary shaft”. 
         [0059]    The width of the gap formed in a U-shaped single cable guide or formed between two cable guides may be appropriately changed. 
         [0060]    Also, the number of axes of the robot is not limited to six. Further, the present invention may be applied not only to a vertical articulated robot but also to a horizontal articulated robot.