Patent Publication Number: US-2021194333-A1

Title: Adapter for motor replacement and motor replacement method

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/165,052, filed Oct. 19, 2018, which claims the benefit of Japanese Patent Application No. 2017-216607, filed Nov. 9, 2017, the contents of which are incorporated herein by reference. 
    
    
     FIELD 
     The present invention relates to an adapter for motor replacement and a motor replacement method. 
     BACKGROUND 
     As a drive mechanism for a joint shaft of a robot, a mechanism may be used to transmit a drive force of a motor to the joint shaft via a pulley and a belt. There is known a robot provided with a plurality of motor units including a motor and a belt as a plurality of joint shafts (e.g., Japanese Unexamined Patent Application, Publication No. 2014-79863). 
     SUMMARY 
     One aspect of the present invention is an adapter for motor replacement including fixing portions. The adapter has a shape of being placeable so as to be bridged between a housing that fixes a motor and a pulley that is fixed to the motor and transmits a rotary drive force via a belt and to avoid a space for removing the motor from the housing. The fixing portions are respectively fixed to the housing, to which the motor is fixed, and the pulley fixed to the motor. 
     Further, another aspect of the present invention provides a motor replacement method including: a fixing step of bridging an adapter for motor replacement between a housing that fixes a motor and a pulley that is fixed to the motor and transmits a rotary drive force via a belt to fix the adapter to each of the housing and the pulley; a pulley removing step of removing the fixation between the pulley and the motor; and a motor removing step of removing the motor from the housing. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a schematic perspective view of a robot in which a motor is replaced using a replacement adapter according to the present embodiment. 
         FIG. 2  is an explanatory view of parts incorporated in a second arm of the robot. 
         FIG. 3  is a perspective view of a replacement adapter for motor replacement according to one embodiment of the present invention. 
         FIG. 4  is an explanatory view in a case where the replacement adapter has been fixed to a housing body. 
         FIG. 5  is a partial front view in the case where the replacement adapter has been fixed to the housing body. 
         FIG. 6  is a partial sectional view in the case where the replacement adapter has been fixed to the housing body. 
         FIG. 7  is a flowchart of a replacement process in the case of replacing a J 5 -axis motor. 
         FIG. 8  is a partial sectional view of a robot to which a replacement adapter according to a second embodiment has been attached. 
         FIG. 9  is an exploded perspective view of the replacement adapter and members therearound. 
         FIG. 10  is a partial front view of a robot to which a replacement adapter has been attached according to a modified example. 
     
    
    
     DETAILED DESCRIPTION 
     A robot  1  in which a motor is replaced using a replacement adapter  10  for motor replacement (adapter for motor replacement) according to an embodiment of the present invention will be described below with reference to the drawings. 
       FIG. 1  is a schematic perspective view of the robot  1  in which the motor is replaced using the replacement adapter  10  according to the present embodiment. The robot  1  of the present embodiment is a robot such as a vertical articulated type robot having six axes J 1  to J 6 . The robot  1  includes: a base  3  fixed to the floor surface; a swinging body  4  rotatably supported around a vertical first axis J 1  with respect to the base  3 ; a first arm  5  rotatably supported around a horizontal second axis J 2  with respect to the swinging body  4 ; a second arm  6  rotatably supported around a horizontal third axis J 3  with respect to the first arm  5 ; a first wrist element  7  rotatably supported around a fourth axis J 4 , which has a twisting positional relation with the third axis J 3 , with respect to the second arm  6 ; a second wrist element  8  rotatably supported around a fifth axis J 5 , which is orthogonal to the fourth axis J 4 , with respect to the first wrist element  7 ; a third wrist element  9  rotatably supported around a sixth axis J 6 , which is orthogonal to the fifth axis J 5 , with respect to the second wrist element  8 ; and a controller  2  that controls rotary drive of each of the six axes J 1  to J 6 . 
     A motor (not shown) for performing rotary drive, and an encoder (not shown) that detects an angle of rotation of the motor are provided for each of the six axes J 1  to J 6 . Using the rotation angle of the motor detected by the encoder for each of the axes J 1  to J 6 , the controller  2  performs feedback control to cause the motor to perform the rotary drive. The controller  2  is made up of a CPU, a ROM, a RAM, and a memory (not shown). 
     The first wrist element  7  includes a housing body  87  in which a J 5 -axis motor for rotating the second wrist element  8  around the fifth axis J 5  and the like are incorporated, and housing covers  88 ,  89  fixed to the housing body  87  to seal the space inside the housing body  87 . 
       FIG. 2  shows an explanatory view for describing the parts incorporated in the first wrist element  7  of the robot  1 . A housing body  87  has a hollow square columnar shape extending in the longitudinal direction of the first wrist element  7 . In the present embodiment, a direction of a longitudinal axis of the first wrist element  7  is defined as an X-axis direction, a direction orthogonal to the planes of the tabular housing covers  88 ,  89  is defined as a Y-axis direction, and a Z-axis orthogonal to the X-axis and the Y-axis is defined. Note that a coordinate system of the defined XYZ-axes is shown in  FIG. 2 , and also in the subsequent drawings, the coordinate system of the XYZ-axes corresponds to the coordinate system of  FIG. 2 . 
     The housing body  87  houses a J 5 -axis motor (motor)  81  that rotates the second wrist element  8  around the fifth axis J 5  and a J 6 -axis motor  91  that rotates the third wrist element  9  around the sixth axis J 6 . As shown in  FIG. 2 , a rotary shaft of the J 5 -axis motor  81  (hereinafter also referred simply as “motor shaft”) extends in the Y-axis positive direction from the J 5 -axis motor  81 , and a first pulley  82  is fixed to the tip of the rotary shaft in the Y-axis positive direction side. On the tip side of the first wrist element  7  on the X-axis positive direction side, the rotary shaft of the fifth axis J 5  is disposed and a second pulley  84  connected to the rotary shaft via a reducer is disposed. A belt  83  is wound on the first pulley  82  and the second pulley  84  therebetween, and a rotary drive force of the J 5 -axis motor  81  is transmitted to the rotary shaft of the fifth axis J 5  via the belt  83 . 
     As shown in  FIG. 2 , when the housing cover  89  is fixed to the housing body  87 , two first threaded holes B 1  and two second threaded holes B 2  for fastening bolts which are inserted from a Y-axis positive direction are formed on a side surface portion  89   a  in the housing body  87  facing the housing cover  89 . 
     As shown in  FIG. 2 , the first threaded hole B 1  is formed on a Z-axis positive direction side and the second threaded hole B 2  is formed on a Z-axis negative direction side with respect to the first pulley  82  fixed to the rotary shaft of the J 5 -axis motor  81  fixed to the housing body  87 . The two first threaded holes B 1  are formed on the same axis parallel to the X-axis, and the two second threaded holes B 2  are also formed on the same axis parallel to the X-axis. The first threaded hole B 1  and the second threaded hole B 2  located on the X-axis negative direction side are formed on the same axis parallel to the Z-axis, and the first threaded hole B 1  and the second threaded hole B 2  located on the X-axis positive direction side are formed on the same axis parallel to the Z-axis. 
     Four third threaded holes B 3  for tightening bolts that are inserted from the Y-axis positive direction are formed in the first pulley  82  fixed to the rotary shaft of the J 5 -axis motor  81  fixed to the housing body  87 . The four third threaded holes B 3  are disposed on the same circumference having the center of the first pulley  82  as the center, at each 90 degrees along a circumferential direction. 
       FIG. 3  shows a perspective view of the adapter  10  for motor replacement (hereinafter referred to as replacement adapter) according to one embodiment of the present invention which is used in the case of replacement of the J 5 -axis motor  81 . The replacement adapter  10  is fixed to the housing body  87  with the bolts by using the first threaded holes B 1  and the second threaded holes B 2  formed in the housing body  87 . Further, in the replacement adapter  10 , the first pulley  82  can be fixed thereto with the bolts by using the third threaded holes B 3  formed in the first pulley  82 . The replacement adapter  10  is, for example, a metal member processed by shaving. 
     The replacement adapter  10  is provided with a tabular pulley fixing plate (fixing portion)  11 , two tabular leg portions (fixing portion)  14 ,  15  along a plane parallel to the pulley fixing plate  11 , and coupling portions  12 ,  13  respectively coupling both ends of the pulley fixing plate  11  and the leg portions. 
     A circular opening C 4  and four second through holes C 3  are formed in the pulley fixing plate  11 . The opening C 4  has a predetermined radius R with a center O as the center and penetrates in a plate-thickness direction. The second through holes C 3  penetrate in the plate-thickness direction radially outside the opening C 4 . 
     The opening C 4  is open with the radius R to such a degree as to be able to avoid the end of the motor shaft, to which the first pulley  82  is fixed, and the bolt fixing the first pulley  82  to the motor shaft and to loosen the bolt by using a tool. 
     The four second through holes C 3  are disposed on the same circumference having the center O as the center at each 90 degrees along a circumferential direction. The radius from the center O to the second through holes C 3  is set so as to be the same as the radius from the center of the first pulley  82  to the third threaded hole B 3  ( FIG. 2 ). Thus, by fastening the bolt, inserted into the second through holes C 3 , into the third threaded hole B 3  in the first pulley  82 , the first pulley  82  can be fixed to the replacement adapter  10 . 
     As shown in  FIG. 3 , each of the leg portions  14 ,  15  is formed with two first through holes C 2  penetrating in the plate-thickness direction. The distance between the two first through holes C 2  formed in each of the leg portions  14 ,  15  is set so as to be the same distance as the distance between the two second threaded holes B 2  formed in the housing body  87 . By fastening the bolts, inserted into the first through holes C 2 , into the first threaded hole B 1  and the second threaded hole B 2  in the housing body  87 , the replacement adapter  10  can be fixed to the housing body  87 . 
     The distance between a fastening surface of the pulley fixing plate  11  with the pulley and a fastening surface  11   d  of each of the leg portions  14 ,  15  with the housing body is set so as to be the same as the distance between the surface of the first pulley  82  on the Y-axis positive direction side, which is fixed to the rotary shaft of the J 5 -axis motor  81  fixed to the housing body  87 , and the surface of the housing body  87  on the Y-axis positive direction side. 
     Each of  FIGS. 4 to 6  shows an explanatory view of a case where the replacement adapter  10  is fixed to the housing body  87  from which the housing cover  89  has been removed. As shown in  FIGS. 4 and 5 , two bolts BT 1  inserted into the first through holes C 2  in the leg portion  14  are fastened into the first threaded holes B 1 , and two bolts BT 2  inserted into the first through holes C 2  in the leg portion  15  are fastened into the second threaded holes B 2 , to thereby fix the replacement adapter  10  to the housing body  87 . 
     As shown in  FIG. 6 , when the replacement adapter  10  is fixed to the housing body  87 , the fastening surface  11   d  of the pulley fixing plate  11  in the replacement adapter  10  comes into contact with the surface of the first pulley  82  on the Y-axis positive direction side. The first pulley  82  is rotated in this state, thereby enabling phase matching between the third threaded holes B 3  formed in the first pulley  82  and the second through holes C 3  formed in the pulley fixing plate  11  of the replacement adapter  10 . In the state of the phases matching each other, four bolts BT 3  are inserted into the second through holes C 3  and fastened into the third threaded holes B 3 , to fix the first pulley  82  to the replacement adapter  10 . 
       FIG. 7  shows a flowchart of a replacement process for the J 5 -axis motor  81  until the J 5 -axis motor  81  fixed to the housing body  87  is removed from the housing body  87 . In the replacement process for the J 5 -axis motor  81 , first, the housing covers  88 ,  89  attached to the housing body  87  are removed (Step S 11 ). Subsequently, as shown in  FIG. 4 , the replacement adapter  10  covering the surface of the first pulley  82  on the Y-axis positive direction side with the pulley fixing plate  11  is disposed, and the replacement adapter  10  is fixed to the housing body  87  with the bolts BT 1 , BT 2  (Step S 12  of  FIG. 7 ). 
     Next, the bolts BT 3  are fastened into the third threaded holes B 3  formed in the first pulley  82  to fix the first pulley  82  to the replacement adapter  10  fixed to the housing body  87  (Step S 13 ). Note that the process in combination of the process of Step S 12  and step S 13  corresponds to the fixing step in the claim. 
     After the fixation of the first pulley  82  to the replacement adapter  10 , a pulley removing step is performed in which a bolt (fastener) BT 4  fastened into the threaded hole formed in the rotary shaft of the J 5 -axis motor  81  shown in  FIG. 5  is removed using a tool, such as a hexagonal wrench, caused to access via the opening C 4  formed in the replacement adapter  10 , to remove the J 5 -axis motor  81  from the first pulley  82  (Step S 14  of  FIG. 7 ). Next, a motor removing step is performed in which the bolts fixing the J 5 -axis motor  81  to the housing body  87  and the like are removed to remove the motor from the housing body  87  (Step S 15 ). 
     Thereafter, the removed J 5 -axis motor  81  is replaced with a new motor, and the new motor is fixed to the housing body  87  (Step S 16 ). The rotary shaft of the fixed new J 5 -axis motor  81  and the first pulley  82  fixed to the replacement adapter  10  are fixed to each other with the bolt BT 4  (Step S 17 ). Next, the bolts BT 3  fastened into the third threaded holes B 3  of the first pulley  82  are released to remove the first pulley  82  from the replacement adapter  10  (Step S 18 ). 
     Thereafter, the bolts BT 1 , BT 2  fastened into the first threaded hole B 1  and the second threaded hole B 2  are released, to remove the replacement adapter  10  from the housing body  87  (Step S 19 ). Next, the housing cover  89  is attached so as to seal the space for housing the first pulley  82  (Step S 20 ), to complete the replacement process for the J 5 -axis motor  81 . 
     The replacement adapter  10  for motor replacement according to the present embodiment as thus configured is fixed so as to be wound on the housing body  87  fixing the J 5 -axis motor  81  and on the first pulley  82  fixed to the rotary shaft of the J 5 -axis motor  81 . Therefore, in a state where the position of the first pulley  82  is fixed with respect to the housing body  87 , the J 5 -axis motor  81  can be removed from the first pulley  82  and replaced with a new J 5 -axis motor  81 . 
     That is, although the belt  83  is wound on the first pulley  82  fixed by the replacement adapter  10  and on the second pulley  84  in the state of being applied with a tension, even when the J 5 -axis motor  81  is removed, the tension of the belt  83  is kept the same as the tension when the J 5 -axis motor  81  performs rotary drive. Hence the present embodiment has an advantage that the J 5 -axis motor  81  can be replaced without loosening the tension of the belt  83 , thus improving the maintainability of the J 5 -axis motor  81  in the robot  1 . 
     Further, the replacement adapter  10  for motor replacement of the present embodiment is provided with the pulley fixing plate  11  formed with the circular opening C 4  having the predetermined radius R. When the replacement adapter  10  is fixed to the housing body  87  in a state where the J 5 -axis motor  81  is fixed to the housing body  87  and the first pulley  82  is fixed to the rotary shaft of the J 5 -axis motor  81 , the opening C 4  formed in the pulley fixing plate  11  is disposed at a position that faces the bolt BT 4  fastening the rotary shaft of the J 5 -axis motor  81  and the first pulley  82 . Thus, even when the first pulley  82  is fixed to the replacement adapter  10 , the tool such as the hexagonal wrench for removing the bolt BT 4  is caused to access the bolt BT 4  via the opening C 4  formed in the replacement adapter  10 , thereby preventing the replacement adapter  10  from hindering removal of the first pulley  82  and the J 5 -axis motor  81  to improve the maintainability of the J 5 -axis motor  81 . 
       FIG. 8  shows a replacement adapter  10   a  according to a second embodiment including a housing cover  85  and a sleeve  21  for fixing the first pulley  82  in the case of replacing the J 5 -axis motor  81 . In the second embodiment, the housing cover  85  which remains fixed to the housing body  87  and the sleeve  21  inserted into a third through hole  85   b  formed in the housing cover  85  function as the replacement adapter  10   a . For this reason, in the second embodiment, a configuration different from that in the first embodiment will be described, and descriptions of the same configuration as in the first embodiment will be omitted. 
     As shown in  FIG. 8 , the housing cover  85  is fixed to the housing body  87  to seal a space in which the first pulley  82  is housed. The housing cover  85  is formed with an opening C 4   a  through which the bolt BT 4  that fixes the first pulley  82  to the rotary shaft of the J 5 -axis motor  81  is accessible, four third through holes  85   b  into which the sleeves  21  are inserted, and a plurality of fifth threaded holes B 5  capable of fastening bolts. The four third through holes  85   b  are formed at positions with different phases for each 90 degrees around the opening C 4   a . As shown in the exploded perspective view of  FIG. 9 , the fifth threaded holes B 5  are formed at positions with different phases for each 90 degrees around the third through hole  85   b.    
     As shown in  FIG. 9 , the sleeve  21  is provided with a disc-shaped small diameter portion  21   b  having the same outer diameter as the diameter of the third through hole  85   b , and a flange-shaped large diameter portion  21   a  coaxial to the small diameter portion  21   b  and having an outer diameter larger than that of the small diameter portion  21   b . The sleeve  21  is formed with a fourth through hole  21   c  for insertion of the bolt BT 3  penetrating the centers of the small diameter portion  21   b  and the large diameter portion  21   a  in the thickness direction, and four fifth through holes  21   d  which penetrate a flange-shaped portion in the large diameter portion  21   a  in the thickness direction. The fifth through holes  21   d  are formed at positions with different phases for each 90 degrees with a central axis OL 2  of the sleeve at the center. A bolt BT 5  which is fastened into the third through hole  85   b  of the housing cover  85  is inserted into each fifth through hole  21   d.    
     As shown in  FIG. 8 , the length of the small diameter portion  21   b  in the sleeve  21  in the thickness direction is set to be such a length that a first abutting surface  23  in the small diameter portion  21   b  comes into contact with the side surface of the first pulley  82  when the sleeve  21  is inserted into the third through hole  85   b  and a second abutting surface  22  in the large diameter portion  21   a  comes into contact. That is, when the sleeve  21  is inserted into the third through hole  85   b , the first abutting surface  23  comes into contact with the side surface of the first pulley  82  while the second abutting surface  22  comes into contact with the surface of the housing cover  85 . 
     In the state shown in  FIG. 8 , after insertion of the sleeve  21  into the third through hole  85   b  of the housing cover  85 , the sleeve  21  is fixed to the housing cover  85  by using the bolt BT 5  inserted in a state where the phases of the fifth threaded hole B 5  of the housing cover  85  and the fifth through hole  21   d  match. Further, the first pulley  82  is fixed to the sleeve  21  by using the bolt BT 3  inserted into the fourth through hole  21   c  of the sleeve  21  inserted into the third through hole  85   b.    
     After the fixation of the first pulley  82 , the hexagonal wrench or the like is caused to access the bolt BT 4  fastening the rotary shaft of the J 5 -axis motor  81  via the opening C 4   a  of the housing cover  85 , to remove the J 5 -axis motor  81  from the first pulley  82 . Thereafter, the housing cover  88  fixed to the Y-axis negative direction side in the housing body  87  is removed, and the J 5 -axis motor  81  can thus be removed from the housing body  87 . 
     The replacement adapter  10   a  according to the second embodiment as thus configured is provided with the housing cover  85  formed with the third through hole  85   b , into which the sleeve  21  is inserted, and the sleeve  21  fixed to the housing cover  85  and fixes the first pulley  82 . The first abutting surface  23  in the sleeve  21  inserted into the third through hole  85   b  comes into contact with the side surface of the first pulley  82 , and the first pulley  82  is fixed using the bolt BT 3  via the sleeve  21 . 
     In this manner, even when the housing cover  85  sealing the space in which the first pulley  82  is housed is not removed as in the first embodiment, the J 5 -axis motor  81  can be replaced without loosening the tension of the belt  83  by fixing the sleeve  21  to the third through hole  85   b , thus leading to improvement in maintainability of the J 5 -axis motor  81 . 
       FIG. 10  shows a robot  1   b  as a modified example of the case where a motor adapter  30  capable of adjusting the tension of the belt  83  wound on the first pulley  82  is disposed between the housing body  87  and a replacement adapter  10   b . The motor adapter  30  has a tabular shape, and as shown in  FIG. 10 , the motor adapter  30  includes: long holes B 1   b , B 2   b  at four corners, with the X-axis direction taken as long axes; a second opening  31  formed in an adapter  10   b  and fitted with a spigot fit portion of the motor; a threaded hole (not shown) for fixing a J 5 -axis motor by bolt fastening; and a threaded hole (not shown) for fixing the replacement adapter  10   b  by bolt fastening. The J 5 -axis motor is attached to the motor adapter  30  through a through hole (not shown) provided in the housing body  87 . 
     Bolts BT 6  are inserted into each the respective four long holes B 1   b , B 2   b , and by fastening the bolts BT 6  into the first threaded holes B 1  (not shown in  FIG. 10 ) formed in the housing body  87 , the motor adapter  30  is fixed to the housing body  87 . The bolts BT 1 , BT 2 , inserted into the first through holes C 2  of the replacement adapter  10   b , are fastened into the threaded holes (not shown) formed in the motor adapter  30 , thereby fixing the replacement adapter  10   b  to the motor adapter  30 . 
     By fastening of the bolt BT 3  into a third bolt hole B 3  (not shown in  FIG. 10 ) formed on the side surface of the first pulley  82 , the first pulley  82  is fixed to the replacement adapter  10   b . In the replacement adapter  10   b  of the modified example, as compared to the replacement adapter  10  of the first embodiment, the lengths of coupling portions  12   b ,  13   b  along the Y-axis are short by the thickness of the motor adapter  30  along the Y-axis. Therefore, in the modified example, even when the motor adapter  30  is placed between the housing body  87  and the replacement adapter  10   b , the fastening surface of a pulley fixing plate  11   b  in the replacement adapter  10   b  comes into contact with the side surface of the first pulley  82 . 
     In this modified example, the replacement adapter  10   b  that fixes the first pulley  82  is fixed to the housing body  87  via the motor adapter  30 . The motor adapter  30  is fixed to the housing body  87  by using the bolts BT 6  inserted into the long holes B 1   b , B 2   b . The motor adapter  30  can change its position with respect to the first threaded holes B 1  where the bolts BT 6  are fastened along the longitudinal axes of the long holes B 1   b , B 2   b . That is, the motor adapter  30  changes its position with respect to the housing body  87  along the X-axis to change the interval between the first pulley  82  and the second pulley  84 , thus enabling adjustment of the tension that is applied to the belt. 
     In the modified example shown in  FIG. 10 , one form of placement of the motor adapter  30  between the housing body  87  and the replacement adapter  10   b  has been described, but a motor adapter  30   a  may be disposed between the housing body  87  and an attachment portion of the J 5 -axis motor  81 . In this case, the motor adapter  30   a  is disposed on the opposite side to the replacement adapter  10   b  with respect to the housing body  87 , the J 5 -axis motor  81  and the motor adapter  30   a  are fixed to each other, and the motor adapter  30   a  and the housing body  87  are fixed to each other. Therefore, when the fastening between the motor adapter  30   a  and the housing body  87  is released after the first pulley  82  is fixed to the housing body  87  by the replacement adapter  10   b  and the fixation between the first pulley  82  and the rotary shaft of the J 5 -axis motor  81  is released, the motor adapter  30   a  can also be replaced in the state of being unified with the J 5 -axis motor  81 . Meanwhile, when the J 5 -axis motor  81  is removed from the motor adapter  30   a  fixed to the housing body  87  after the first pulley  82  and the rotary shaft of the J 5 -axis motor  81  are removed, only the J 5 -axis motor  81  can be replaced while the motor adapter  30   a  remains fixed to the housing body  87 . 
     In the embodiment, the robot  1  including the J 5 -axis motor  81  housed in the housing body  87  has been described as one example, but various modifications can be made on the replacement adapter  10  of the first embodiment and the replacement adapter  10   a  of the second embodiment. For example, a replacement adapter  10 ,  10   a  may be used for replacement of a motor to be used in a robot other than the vertical articulated type robot. As the replacement adapter  10 ,  10   a , the shape thereof is not limited to that in the first embodiment, but the replacement adapter  10 ,  10   a  may only be a member capable of fixing the housing body  87  without loosening the tension of the belt  83  wound on the first pulley  82 . Similarly, as the housing cover  85  and the sleeve  21  of the second embodiment, the shapes and members thereof are not limited to those in the second embodiment but may only be shapes or members capable of fixing the housing body  87  without loosening the tension of the belt  83  wound on the first pulley  82 . 
     In the replacement adapter  10  of the first embodiment, the third threaded holes B 3  and the like for insertion of the bolts BT 3  and the like have been formed as perfect circular through holes, but various modification can be made on the shape of the threaded hole into which the bolt is inserted. For example, in the replacement adapter  10  of the first embodiment, one of the first through holes C 2  may be a long hole having a long axis extending along the X-axis as in the second embodiment, or a long hole having a long axis extending along the Z-axis. 
     From the above-described embodiment, the following invention is derived. 
     One aspect of the present invention is an adapter for motor replacement including fixing portions. The adapter has a shape of being placeable so as to be bridged between a housing that fixes a motor and a pulley that is fixed to the motor and transmits a rotary drive force via a belt and to avoid a space for removing the motor from the housing. The fixing portions are respectively fixed to the housing, to which the motor is fixed, and the pulley fixed to the motor. 
     According to the present aspect, when the adapter for motor replacement is disposed so as to be bridged between the housing to which the motor is attached and the pulley fixed to the motor, the adapter for motor replacement is disposed so as to avoid the space for removing the motor from the housing. In this state, while the adapter for motor replacement is fixed to each of the housing and the pulley with the fixing portions, the pulley is separated from the motor and the motor is removed from the housing, so that the pulley is kept at a position where the pulley has been attached to the motor. That is, at the time of replacing an aged motor in accordance with the usage conditions of the robot, there is no need to move the position of the pulley, thereby enabling replacement of the motor without loosening the tension of the belt wound on the pulley. This leads to improvement in maintainability of the motor in the robot. 
     In the above aspect, the fixing portions may include a first through hole allowing passage of a bolt that is fastened into a threaded hole provided in the housing, and a second hole that allows passage of a bolt that is fastened into a threaded hole provided in the pulley. 
     In such a manner, when the adapter for motor replacement is displaced so as to be bridged between the housing and the pulley, the adapter for motor replacement is displaced while the first through hole of the fixing portion of the adapter is aligned with the threaded hole of the housing and the second through hole is aligned with the threaded hole of the pulley, and the bolts allowed to pass through the first through hole and the second through hole are respectively fastened into the threaded holes to facilitate fixation of the pulley to the housing by using the adapter for motor replacement. 
     In the above aspect, the adapter for motor replacement may include an opening that enables to access a fastener fixing the pulley to the motor in a state where the adapter is bridged and fixed between the housing and the pulley. 
     By accessing the fastener via the opening, the pulley can be removed from the motor while the position of the pulley with respect to the housing is fixed by the adapter for motor replacement. 
     In the above aspect, the adapter for motor replacement may include: a housing cover having a shape of being placeable so as to be fixed to the housing such that a space for housing the pulley is sealed and to avoid a space for removing the motor from the housing; and a sleeve that is inserted into a third through hole provided in the housing cover and includes a first abutting surface that abuts on a surface of the pulley and a second abutting surface that abuts on a surface of the housing cover, and the sleeve may include a fourth through hole that opens on the first abutting surface and allows passage of a bolt which is fastened into a threaded hole provided in the pulley, and a fifth through hole that opens on the second abutting surface and allows passage of a bolt which is fastened into a threaded hole provided in the housing cover. 
     In this manner, when the sleeve is inserted into the third through hole formed in the housing cover, the first abutting surface of the sleeve abuts on the surface of the pulley and the second abutting surface of the sleeve abuts on the surface of the housing cover. In this state, the position of the sleeve with respect to the housing cover is fixed by the bolt inserted into the fifth through hole, and the position of the pulley with respect to the sleeve is fixed by the bolt inserted into the fourth through hole. Since the position of the pulley is thereby fixed with respect to the housing fixing the housing cover, even when the motor fixed to the pulley is removed, the tension of the belt wound on the pulley remains unchanged. This enables replacement of the motor without loosening the tension of the belt wound on the pulley before and after the motor replacement, thus further improving the maintainability of the motor in the robot. 
     Further, another aspect of the present invention provides a motor replacement method including: a fixing step of bridging an adapter for motor replacement between a housing that fixes a motor and a pulley that is fixed to the motor and transmits a rotary drive force via a belt to fix the adapter to each of the housing and the pulley; a pulley removing step of removing the fixation between the pulley and the motor; and a motor removing step of removing the motor from the housing. 
     According to the present aspect, when the adapter for motor replacement is fixed to the housing and the pulley in the fixing step, the position of the pulley attached to the motor is fixed. With the position of the pulley in the fixed state, by removal of the motor from the pulley and removal of the motor from the housing, the pulley is kept at the position where the pulley has been attached to the motor. That is, at the time of replacing an aged motor in accordance with usage conditions of the robot, there is no need to move the position of the pulley, thereby enabling replacement of the motor without loosening the tension of the belt wound on the pulley, to improve the maintainability of the motor in the robot. 
     REFERENCE SIGNS LIST 
     
         
           10 ,  10   a ,  10   b  replacement adapter (adapter for motor replacement) 
           11  pulley fixing plate (fixing portion) 
           14 ,  15  leg portion (fixing portion) 
           21  sleeve 
           21   c  fourth through hole 
           21   d  fifth through hole 
           22  second abutting surface 
           23  first abutting surface 
           81  J 5 -axis motor (motor) 
           82  first pulley (pulley) 
           83  belt 
           85  housing cover 
           85   b  third through hole 
           87  housing body (housing) 
         C 2  first through hole 
         C 3  second through hole 
         C 4 , C 4   a  opening 
         BT 4  bolt (fastener) 
         S 12 , S 13  fixing step 
         S 14  pulley removing step 
         S 15  motor removing step