Abstract:
An industrial robot may include a main body section, a first arm, a second arm, a third arm, a first speed reducer which connects the main body section and the first arm, a second speed reducer which connects the first arm and the second arm, and a connecting mechanism which connects the input shaft of the first speed reducer and the input shaft of the second speed reducer, and a second drive motor which drives the third arm. The speed reduction ratio of the first and second speed reducer are set such that the movement loci of a third articulation section which connects the second and third arm are rectilinear. The connecting mechanism connects the input shafts at a predetermined speed ratio. The second drive motor is mounted on the second arm closer to the tip than where a third articulation section is located.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This is a U.S. national stage of International Application No. PCT/JP2011/058674, filed on Apr. 6, 2011. Priority under 35 U.S.C. §119(a) and 35 U.S.C. §365(b) is claimed from Japanese Application No. 2010-104066, filed Apr. 28, 2010, the disclosures of which are also incorporated herein by reference. 
     TECHNICAL FIELD 
     The present invention relates to an articulated type industrial robot provided with a plurality of joint parts. 
     BACKGROUND 
     Conventionally, an industrial robot for carrying a work-piece such as a semiconductor wafer has been known which is structured of a base, a link mechanism, an arm part and a hand part (see, for example, Patent Literature 1). In the industrial robot described in Patent Literature 1, the link mechanism is provided with a base side link part which is turnably attached to the base and an arm side link part which is turnably attached to the base side link part. 
     The base side link part is turnably held by a link mechanism motor which is incorporated into the base. Further, the base side link part is incorporated with a base side pulley which is fixed to the base, an arm part side pulley which is fixed to the arm side link part, and a belt which is stretched over the base side pulley and the arm part side pulley. The base side pulley and the arm part side pulley of the industrial robot are formed so that the ratio of their diameters is set to be 2:1 and, when the link mechanism motor is rotated, a tip end side of the arm side link part performs a linear operation. 
     Further, in the industrial robot, the arm part is turnably attached to a tip end side of the arm side link part. The arm part is connected with an arm part motor which is incorporated into the arm side link part. The arm part motor is incorporated into the arm side link part with an upper and lower direction as a direction of its turning shaft. 
     [PTL 1] Japanese Patent Laid-Open No. 2007-152490 
     In the industrial robot described in Patent Literature 1, the ratio of the diameter of the base side pulley to the diameter of the arm part side pulley is set to be 2:1. Further, loads of the arm side link part, the arm part and the hand part are applied to the belt which is stretched over the base side pulley and the arm part side pulley. Therefore, the sizes of the base side pulley, the arm part side pulley and the belt which are disposed in the inside of the base side link part tend to be increased. Accordingly, in the industrial robot, the size of the base side link part tends to be increased and, as a result, the industrial robot tends to be enlarged. 
     Further, in the industrial robot, the arm part motor is incorporated into the arm side link part with the upper and lower direction as a direction of its turning shaft and thus the thickness of the arm side link part is increased. Therefore, in the industrial robot, the height of the hand part tends to be increased and the minimum height (pass line) that the robot is accessible may be increased. 
     SUMMARY 
     In view of the problem described above, at least an embodiment of the present invention provides an industrial robot whose size is capable of being reduced and whose pass line is capable of being lowered. 
     In order to attain the above, at least an embodiment of the present invention provides an industrial robot including a main body part, a first arm whose base end side is turnably attached to the main body part, a second arm whose base end side is turnably attached to a tip end side of the first arm, a tip end side operation part whose base end side is turnably attached to a tip end side of the second arm, a first speed reducer structuring a first joint part which connects the main body part with the first arm, a second speed reducer structuring a second joint part which connects the first arm with the second arm, a third joint part which connects the second arm with the tip end side operation part, a connecting mechanism which connects a first input shaft that is an input shaft of the first speed reducer with a second input shaft that is an input shaft of the second speed reducer, the connecting mechanism being disposed in an inside of the first arm, a first drive motor which is connected with the first input shaft, and a second drive motor which drives to turn the tip end side operation part. A reduction ratio of the first speed reducer and a reduction ratio of the second speed reducer are set so that a moving trace of the third joint part is formed in a straight line shape, and the connecting mechanism connects the first input shaft with the second input shaft in a predetermined speed ratio, and the second drive motor is attached to the second arm on a tip end side with respect to the third joint part so as to protrude to the first arm side. 
     In the industrial robot in accordance with at least an embodiment of the present invention, the second drive motor is attached to the second arm on a tip end side with respect to the third joint part so as to protrude to the first arm side. Therefore, in comparison with a case that the second drive motor is incorporated in the second arm between the second joint part and the third joint part, the thickness of the second arm can be reduced. Therefore, according to at least an embodiment of the present invention, the pass line of the industrial robot can be lowered. 
     Further, in at least an embodiment of the present invention, the connecting mechanism connects the first input shaft which is an input shaft of the first speed reducer with the second input shaft which is an input shaft of the second speed reducer. Therefore, a load applied to the connecting mechanism can be reduced. Accordingly, the size of the connecting mechanism which is disposed in the inside of the first arm is reduced and the size of the first arm can be reduced. Further, since the size of the first arm can be reduced, even when the second drive motor is attached to the second arm so as to protrude to the first arm side, interference of the first arm with the second drive motor is prevented without enlarging the size of the second arm. In other words, in at least an embodiment of the present invention, even when the second drive motor is attached to the second arm so as to protrude to the first arm side, the size of the second arm can be reduced while preventing interference of the first arm with the second drive motor. As described above, according to at least an embodiment of the present invention, the sizes of the first arm and the second arm can be reduced. Further, according to the present invention, as described above, the thickness of the second arm can be reduced. Therefore, according to at least an embodiment of the present invention, the size of the industrial robot can be reduced. 
     Further, according to at least an embodiment of the present invention, the first joint part is structured of the first speed reducer and the second joint part is structured of the second speed reducer and thus the rigidities of the first joint part and the second joint part can be increased. 
     In at least an embodiment of the present invention, it is preferable that the industrial robot includes a hollow shaft which is formed in a hollow shape and which is disposed so as to pass through a center of the first speed reducer and/or a center of the second speed reducer, and the first input shaft and/or the second input shaft are turnably disposed on an outer peripheral side of the hollow shaft. According to this structure, even when the first joint part and the second joint part are structured of a speed reducer, wiring lines of the industrial robot can be passed by using the inner peripheral side of the hollow shaft in the first joint part and the second joint part. In other words, even when a space for passing the wiring lines is not provided on an outer peripheral side of the speed reducer in the first joint part and the second joint part, the wiring lines of the industrial robot can be passed. Therefore, the diameters of the first joint part and/or the second joint part can be made small and thus the size of the industrial robot can be reduced. 
     In at least an embodiment of the present invention, it is preferable that the third joint part is structured of a third speed reducer. According to this structure, rigidity of the third joint part can be increased. 
     In at least an embodiment of the present invention, it is preferable that the industrial robot includes a second hollow shaft which is formed in a hollow shape and is disposed so as to pass through a center of the third speed reducer, and a third input shaft which is an input shaft of the third speed reducer is turnably disposed on an outer peripheral side of the second hollow shaft. According to this structure, even when the third joint part is structured of a speed reducer, the wiring lines of the industrial robot can be passed by using an inner peripheral side of the second hollow shaft in the third joint part. In other words, even when a space for passing the wiring lines is not provided on an outer peripheral side of the speed reducer in the third joint part, the wiring lines of the industrial robot can be passed. Therefore, the diameter of the third joint part can be made small and thus the size of the industrial robot can be reduced. 
     In at least an embodiment of the present invention, for example, the connecting mechanism includes a first pulley which is fixed to the first input shaft, a second pulley which is fixed to the second input shaft, and a belt which is stretched over the first pulley and the second pulley. 
     In at least an embodiment of the present invention, it is preferable that the tip end side operation part includes a third arm whose base end side is turnably attached to a tip end side of the second arm, a hand whose base end side is turnably attached to a tip end side of the third arm, and a hand drive mechanism which drives to turn the hand. The hand drive mechanism includes a hand drive motor, a hand speed reducer which is attached to an output shaft of the hand drive motor, and a hand pulley which is attached to the hand speed reducer and, in addition, the hand pulley is formed in a substantially tube-like shape and is attached to the hand speed reducer so as to cover a part of an outer peripheral face of a main body of the hand drive motor. According to this structure, the hand pulley is attached to a hand speed reducer so as to cover a part of an outer peripheral face of the main body of the hand drive motor and thus the height of the hand drive mechanism is lowered and the pass line of the industrial robot can be lowered. 
     In at least an embodiment of the present invention, it is preferable that the hand speed reducer is attached to an output shaft of the hand drive motor so as to cover an outer peripheral face of the output shaft of the hand drive motor. According to this structure, the height of the hand drive mechanism is further lowered and the pass line of the industrial robot can be further lowered. 
     In at least an embodiment of the present invention, it is preferable that the tip end side operation part includes a first hand and a second hand as the hand which are disposed so as to superpose on each other in an upper and lower direction, and a first hand drive mechanism which drives to turn the first hand and a second hand drive mechanism which drives to turn the second hand as the hand drive mechanism. The first hand drive mechanism includes a first hand drive motor as the hand drive motor, a first hand speed reducer as the hand speed reducer, and a first hand pulley as the hand pulley, and the second hand drive mechanism includes a second hand drive motor as the hand drive motor, a second hand speed reducer as the hand speed reducer, and a second hand pulley as the hand pulley. The first hand drive motor and the second hand drive motor are disposed at substantially the same height, the first hand speed reducer and the second hand speed reducer are disposed at substantially the same height, and the first hand pulley and the second hand pulley are disposed at positions which are displaced from each other in the upper and lower direction. According to this structure, even when the tip end side operation part includes two hands, the height of the hand drive mechanism is lowered and the pass line of the industrial robot can be lowered. 
     As described above, in the industrial robot in accordance with at least an embodiment of the present invention, its size is capable of being reduced and its pass line is capable of being lowered. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       Embodiments will now be described, by way of example only, with reference to the accompanying drawings which are meant to be exemplary, not limiting, and wherein like elements are numbered alike in several Figures, in which: 
         FIG. 1  is a schematic side view showing an industrial robot in accordance with an embodiment of the present invention. 
         FIG. 2  is a schematic plan view showing the industrial robot which is viewed in the “E-E” direction in  FIG. 1 . 
         FIG. 3  is a schematic plan view showing a semiconductor manufacturing system in which the industrial robot shown in  FIG. 1  is used. 
         FIG. 4  is a cross-sectional view showing an internal structure of the industrial robot in  FIG. 1 . 
         FIG. 5  is an enlarged cross-sectional view showing a structure of a first speed reducer and its surrounding portion shown in  FIG. 4 . 
         FIG. 6  is an enlarged cross-sectional view showing a structure of a second speed reducer and its surrounding portion shown in  FIG. 4 . 
         FIG. 7  is an enlarged view showing the “F” part in  FIG. 4 . 
         FIG. 8  is an enlarged cross-sectional view showing a structure of a first hand drive motor and its surrounding portion shown in  FIG. 7 . 
         FIG. 9  is an enlarged cross-sectional view showing a structure of a second hand drive motor and its surrounding portion shown in  FIG. 7 . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the present invention will be described below with reference to the accompanying drawings. 
     (Schematic Structure of Industrial Robot) 
       FIG. 1  is a schematic side view showing an industrial robot  1  in accordance with an embodiment of the present invention.  FIG. 2  is a schematic plan view showing the industrial robot  1  which is viewed in the “E-E” direction in  FIG. 1 .  FIG. 3  is a schematic plan view showing a semiconductor manufacturing system  16  in which the industrial robot  1  shown in  FIG. 1  is used. In  FIG. 2 , hands  7  and  8  are not shown. 
     The industrial robot  1  in this embodiment is an articulated type robot for carrying a semiconductor wafer  2  (see  FIG. 3 ). The industrial robot  1  includes, as shown in  FIG. 1 , a main body part  3 , a first arm  4  turnably attached to the main body part  3 , a second arm  5  turnably attached to the first arm  4 , a third arm  6  turnably attached to the second arm  5 , and hands  7  and  8  turnably attached to the third arm  6 . In the following descriptions, the industrial robot  1  is referred to as a “robot  1 ” and the semiconductor wafer  2  is referred to as a “wafer  2 ”. 
     The robot  1  includes an arm part drive mechanism  11  which turns the first arm  4  and the second arm  5  to expand and contract the arm part  9  which is comprised of the first arm  4  and the second arm  5 , a third arm drive mechanism  12  which drives to turn the third arm  6 , a hand drive mechanism  13  which drives to turn the hand  7 , and a hand drive mechanism  14  which drives to turn the hand  8 . 
     As shown in  FIG. 3 , for example, the robot  1  is incorporated and used in a semiconductor manufacturing system  16 . Specifically, the robot  1  is disposed in an inlet port of the semiconductor manufacturing system  16  to take out a wafer  2  accommodated in a cassette  17  and to accommodate the wafer  2  in an inside of the processing device  18 . 
     The main body part  3  is formed in a cylindrical tube shape. An elevating/lowering mechanism (not shown) for elevating and lowering the first arm  4  is accommodated in the inside of the main body part  3 . The first arm  4 , the second arm  5  and the third arm  6  are formed in a hollow shape. A base end side of the first arm  4  is turnably attached to the main body part  3 . A base end side of the second arm  5  is turnably attached to a tip end side of the first arm  4 . A base end side of the third arm  6  is turnably attached to a tip end side of the second arm  5 . In this embodiment, in the upper and lower direction, the main body part  3 , the first arm  4 , the second arm  5  and the third arm  6  are disposed in this order from the lower side. 
     The hand  7  is, as shown in  FIG. 3 , formed in a roughly “Y” shape when viewed in the upper and lower direction and a wafer  2  is mounted on a tip end part of the hand  7  formed in a two-forked shape. The hand  8  is formed in a similar shape to the hand  7  and a wafer  2  is mounted on a tip end part of the hand  8  formed in a two-forked shape. 
     Base end sides of the hands  7  and  8  are turnably attached to a tip end side of the third arm  6 . The hands  7  and  8  are disposed so as to superpose on each other in the upper and lower direction. Specifically, the hand  7  is disposed on an upper side and the hand  8  is disposed on a lower side. Further, the hands  7  and  8  are disposed on an upper side with respect to the third arm  6 . In this embodiment, for example, the hand  7  is a first hand and the hand  8  is a second hand. Further, in this embodiment, a tip end side operation part whose base end side is turnably attached to a tip end side of the second arm  5  is structured of the third arm  6  and the hands  7  and  8 . 
     In  FIG. 3 , the hand  8  is not shown. Further, at the time of operation of the robot  1  in this embodiment, there may be a case that the hand  7  and the hand  8  are superposed on each other in the upper and lower direction but, in most cases, the hand  7  and the hand  8  are not superposed on each other in the upper and lower direction. For example, as shown by the two-dot chain line in  FIG. 3 , when the hand  7  is entered into the inside of a cassette  17 , the hand  8  is turned to a main body part  3  side and is not entered into the cassette  17 . In this case, a turning angle of the hand  8  with respect to the hand  7  is, for example, set to be 120° through 150°. 
     (Structure of Arm Part Drive Mechanism) 
       FIG. 4  is a cross-sectional view showing an internal structure of the industrial robot  1  in  FIG. 1 .  FIG. 5  is an enlarged cross-sectional view showing a structure of a first speed reducer  21  and its surrounding portion shown in  FIG. 4 .  FIG. 6  is an enlarged cross-sectional view showing a structure of a second speed reducer  22  and its surrounding portion shown in  FIG. 4 . 
     The arm part drive mechanism  11  includes a first drive motor  20  which is a drive source, a first joint part comprising a first speed reducer  21  which decelerates power of the first drive motor  20  to transmit the power to the first arm  4 , a second joint part comprising a second speed reducer  22  which decelerates power of the first drive motor  20  to transmit the power to the second arm  5 , and a connecting mechanism  23  which connects the first speed reducer  21  with the second speed reducer  22 . 
     The first drive motor  20  is disposed in the inside of the main body part  3 . A pulley  24  is fixed to an output shaft of the first drive motor  20 . 
     The first speed reducer  21  connects the main body part  3  with the first arm  4 . The first speed reducer  21  is, for example, a harmonic drive (registered mark) which is a wave motion gear device. As shown in  FIG. 5 , the first speed reducer  21  is structured of a wave generator  25 , a circular spline  26  and a flexspline  27 . The flexspline  27  is fixed to the main body part  3 . The circular spline  26  is fixed to a base end side of the first arm  4 . A pulley  28  is fixed to a lower end of the wave generator  25 . A belt  29  is stretched over the pulley  28  and the pulley  24  fixed to an output shaft of the first drive motor  20 . 
     A base end side of the first arm  4  is fixed with a hollow shaft  30  which is disposed so as to pass through a center of the first speed reducer  21 . The wave generator  25  is turnably disposed on an outer peripheral side of the hollow shaft  30 . In this embodiment, predetermined wiring lines are passed by utilizing an inner peripheral side of the hollow shaft  30 . 
     The second speed reducer  22  connects the first arm  4  with the second arm  5 . The second speed reducer  22  is a harmonic drive (registered mark) having a similar shape to the first speed reducer  21 . As shown in  FIG. 6 , the second speed reducer  22  is structured of a wave generator  32 , a circular spline  33  and a flexspline  34 . The flexspline  34  is fixed to a base end side of the second arm  5 . The circular spline  33  is fixed to a tip end side of the first arm  4 . 
     A tip end side of the first arm  4  is fixed with a hollow shaft  35  which is disposed so as to pass through a center of the second speed reducer  22 . The wave generator  32  is turnably disposed on an outer peripheral side of the hollow shaft  35 . In this embodiment, predetermined wiring lines are passed by utilizing an inner peripheral side of the hollow shaft  35 . 
     The connecting mechanism  23  includes a pulley  36  which is fixed to an upper end of the wave generator  25 , a pulley  37  which is fixed to a lower end of the wave generator  32 , and a belt  38  which is stretched over the pulleys  36  and  37 . The pulleys  36  and  37  and the belt  38  are disposed in the inside of the first arm  4 . 
     The pulley  28  fixed to the lower end of the wave generator  25  is connected with the output shaft of the first drive motor  20  through the belt  29  as described above and thus, the wave generator  25  in this embodiment is a first input shaft which is an input shaft of the first speed reducer  21 . Further, the wave generator  32  is connected with the output shaft of the first drive motor  20  through the wave generator  25 , the belts  29  and  38  and the pulleys  28 ,  36  and  37  and thus, the wave generator  32  in this embodiment is a second input shaft which is an input shaft of the second speed reducer  22 . Further, the pulley  36  is a first pulley fixed to the wave generator  25  which is the first input shaft and the pulley  37  is the second pulley fixed to the wave generator  32  which is the second input shaft. 
     In this embodiment, the first speed reducer  21  and the second speed reducer  22  are a speed reducer having the same shape as each other but their reduction ratios are different from each other. Further, in this embodiment, the reduction ratio of the first speed reducer  21 , the reduction ratio of the second speed reducer  22 , and the ratio of a diameter of the pulley  36  to a diameter of the pulley  37  are set so that a moving trace of the center of a third joint part comprising a third speed reducer  41  described below connecting the second arm  5  with the third arm  6  is formed in a linear shape. In other words, the connecting mechanism  23  connects the wave generators  25  and  32  with each other with a predetermined speed ratio in consideration of the reduction ratios of the first speed reducer  21  and the second speed reducer  22  so that the moving trace of the center of the third speed reducer  41  is formed in a straight line shape. Specifically, a ratio between a diameter of the pulley  36  and a diameter of the pulley  37  is set so that, when viewed in the upper and lower direction, a moving trace of the center of the third speed reducer  41  at the time of expanding and contracting of the arm part  9  is formed in a straight line “L” (see  FIGS. 2 and 3 ) which passes the center of the first speed reducer  21 . 
     (Structure of Third Arm Drive Mechanism) 
       FIG. 7  is an enlarged view showing the “F” part in  FIG. 4 . The third arm part drive mechanism  12  includes a second drive motor  40  which is a drive source and a third speed reducer  41  which decelerates power of the second drive motor  40  to transmit the power to the third arm  6 . 
     The second drive motor  40  is attached to a tip end side of the second arm  5 . Specifically, the second drive motor  40  is fixed on a tip end side with respect to a portion of the second arm  5  at which the third speed reducer  41  is disposed. The second drive motor  40  is fixed to a tip end side of the second arm  5  and, as shown in  FIG. 4 , a main body of the second drive motor  40  is protruded to a first arm  4  side (in other words, lower side) with respect to an under face of the second arm  5 . A pulley  42  is fixed to an output shaft of the second drive motor  40 . A main body portion of the second drive motor  40  protruded to a lower side with respect to the under face of the second arm  5  is covered by a cover. 
     Further, the second drive motor  40  is fixed to the tip end side of the second arm  5  so that, when the arm part  9  is contracted (in a state shown in  FIGS. 2 and 4  and the like), the main body of the second drive motor  40  is disposed on a side with respect to the base end side of the first arm  4  and is not interfered with the first arm  4 . Further, as shown in  FIG. 2 , the second drive motor  40  is fixed to a tip end side of the second arm  5  so that, when the arm part  9  is contracted, the second drive motor  40  is not protruded to an outer side in a radial direction with respect to an outer peripheral face of the main body part  3 . 
     The third speed reducer  41  structures a third joint part which connects the second arm  5  with the third arm  6 . The third speed reducer  41  is a harmonic drive (registered mark) and, as shown in  FIG. 7 , the third speed reducer  41  is structured of a wave generator  45 , a circular spline  46  and a flexspline  47 . The flexspline  47  is fixed to the third arm  6 . The circular spline  46  is fixed to a tip end side of the second arm  5 . A pulley  48  is fixed to a lower end of the wave generator  45 . A belt  49  is stretched over the pulley  48  and a pulley  42  which is fixed to the output shaft of the second drive motor  40 . As described above, the pulley  48  is connected with the output shaft of the second drive motor  40  through the belt  49  and thus the wave generator  45  in this embodiment is a third input shaft which is an input shaft of the third speed reducer  41 . 
     A tip end side of the second arm  5  is fixed with a hollow shaft  50  as a second hollow shaft which is disposed so as to pass through a center of the third speed reducer  41 . The wave generator  45  is turnably disposed on an outer peripheral side of the hollow shaft  50 . In this embodiment, predetermined wiring lines are passed by utilizing an inner peripheral side of the hollow shaft  50 . 
     (Structure of Hand Drive Mechanism) 
       FIG. 8  is an enlarged cross-sectional view showing a structure of a hand drive motor  52  and its surrounding portion shown in  FIG. 7 .  FIG. 9  is an enlarged cross-sectional view showing a structure of a hand drive motor  58  and its surrounding portion shown in  FIG. 7 . 
     The hand drive mechanism  13  includes a hand drive motor  52  which is a drive source, a hand speed reducer  53  which decelerates power of the hand drive motor  52  to transmit the power to the hand  7 , a pulley  54  attached to the hand speed reducer  53 , a pulley  55  attached to the hand  7 , and a belt  56  stretched over the pulleys  54  and  55 . As shown in  FIG. 7 , the hand drive motor  52 , the hand speed reducer  53 , the pulleys  54  and  55  and the belt  56  are disposed in the inside of the third arm  6 . 
     The hand drive mechanism  14  includes, similarly to the hand drive mechanism  13 , a hand drive motor  58  which is a drive source, a hand speed reducer  59  which decelerates power of the hand drive motor  58  to transmit the power to the hand  8 , a pulley  60  attached to the hand speed reducer  59 , a pulley  61  attached to the hand  8 , and a belt  62  which is stretched over the pulleys  60  and  61 . As shown in  FIG. 7 , the hand drive motor  58 , the hand speed reducer  59 , the pulleys  60  and  61  and the belt  62  are disposed in the inside of the third arm  6 . 
     The hand drive motors  52  and  58  are a motor having the same structure. The hand drive motors  52  and  58  are point-symmetrically disposed with respect to the center shaft of the third speed reducer  41  when viewed in the upper and lower direction. In this embodiment, the hand drive motor  52  is fixed to a tip end side of the third arm  6  with respect to the center shaft of the third speed reducer  41  and the hand drive motor  58  is fixed to a base end side of the third arm  6  with respect to the center shaft of the third speed reducer  41 . Further, the hand drive motors  52  and  58  are disposed at substantially the same height. 
     The hand speed reducer  53  is a harmonic drive (registered mark) and, as shown in  FIG. 8 , the hand speed reducer  53  is structured of a wave generator  65 , a circular spline  66  and a flexspline  67 . The flexspline  67  is fixed with the pulley  54 . The circular spline  66  is fixed to the third arm  6 . The wave generator  65  is fixed to an output shaft of the hand drive motor  52 . In this embodiment, a thickness of the hand speed reducer  53  is almost equal to a length of the output shaft of the hand drive motor  52  and the hand speed reducer  53  is disposed so as to cover an outer peripheral face of the output shaft of the hand drive motor  52 . 
     The hand speed reducer  59  is a harmonic drive (registered mark) which is similar (the same shape) to the hand speed reducer  53 . As shown in  FIG. 9 , the hand speed reducer  59  is structured of a wave generator  69 , a circular spline  70  and a flexspline  71 . The flexspline  71  is fixed with the pulley  60 . The circular spline  70  is fixed to the third arm  6 . The wave generator  69  is fixed to an output shaft of the hand drive motor  58 . In this embodiment, a thickness of the hand speed reducer  59  is almost equal to a length of the output shaft of the hand drive motor  58  and the hand speed reducer  59  is disposed so as to cover an outer peripheral face of the output shaft of the hand drive motor  58 . Further, in this embodiment, the hand speed reducers  53  and  59  are disposed at substantially the same height. 
     The pulley  54  is formed in a substantially cylindrical tube shape. As shown in  FIG. 8 , an upper end of the pulley  54  is fixed to a lower end of the flexspline  67  and the pulley  54  covers a part of an outer peripheral face on the upper end side of the main body  52   a  of the hand drive motor  52 . An engagement part  54   a  with which the belt  56  is engaged is formed on a lower end side of the side face of the pulley  54 . 
     The pulley  60  is formed in a substantially cylindrical tube shape whose length in the upper and lower direction is shorter than the pulley  54 . As shown in  FIG. 9 , an upper end of the pulley  60  is fixed to a lower end of the flexspline  71  and the pulley  60  covers a part of an outer peripheral face on the upper end side of the main body  58   a  of the hand drive motor  58 . An engagement part  60   a  with which the belt  62  is engaged is formed on a side face of the pulley  60 . 
     As shown in  FIG. 7 , a pulley  55  is fixed to a lower end side of a hollow shaft  73  which is fixed to a base end side of the hand  7 . In other words, the pulley  55  is fixed to the hand  7  through the hollow shaft  73 . A pulley  61  is fixed to a lower end of a hollow shaft  74  which is fixed to a base end side of the hand  8 . In other words, the pulley  61  is fixed to the hand  8  through the hollow shaft  74 . The hollow shaft  74  is concentrically disposed with the hollow shaft  73  so as to cover an outer peripheral face of the hollow shaft  73  and the pulleys  55  and  61  are disposed so as to superpose on each other in the upper and lower direction. In this embodiment, the pulley  55  is disposed on a lower side and the pulley  61  is disposed on an upper side. Further, since the pulleys  55  and  61  are disposed so as to superpose on each other in the upper and lower direction, the engagement part  54   a  of the pulley  54  and the engagement part  60   a  of the pulley  60  are disposed at positions which are displaced from each other in the upper and lower direction. In this embodiment, the engagement part  54   a  is disposed on a lower side and the engagement part  60   a  is disposed on an upper side. 
     In this embodiment, the pulleys  54  and  60  are hand pulleys which are attached to the hand speed reducers  53  and  59 . Further, the hand drive mechanism  13  is a first hand drive mechanism which drives to turn the hand  7  that is a first hand and the hand drive mechanism  14  is a second hand drive mechanism which drives to turn the hand  8  that is a second hand. In addition, the hand drive motor  52  is a first hand drive motor, the hand drive motor  58  is a second hand drive motor, the hand speed reducer  53  is a first hand speed reducer, the hand speed reducer  59  is a second hand speed reducer, the pulley  54  is a first hand pulley, and the pulley  60  is a second hand pulley. 
     (Schematic Operation of Industrial Robot) 
     In the robot  1  structured as described above, when the first drive motor  20  is driven, as shown in  FIG. 3 , the arm part  9  is expanded and contracted so that the center of the third speed reducer  41  is moved on the straight line “L”. Further, when the second drive motor  40  is driven, the third arm  6  is relatively turned with respect to the arm part  9  with the third speed reducer  41  as a turning center. In addition, when the hand drive motor  52  is driven, the hand  7  is relatively turned with respect to the third arm  6  with the hollow shaft  73  as a turning center and, when the hand drive motor  58  is driven, the hand  8  is relatively turned with respect to the third arm  6  with the hollow shaft  74  as a turning center. 
     The robot  1  takes out a wafer  2  which is accommodated in the cassette  17  to accommodate the wafer  2  in the inside of the processing device  18  by combining the above-mentioned operations. When a wafer  2  is to be carried by the robot  1 , the arm part  9 , the third arm  6  and the hands  7  and  8  are moved up and down by an elevating/lowering mechanism disposed in the inside of the main body part  3  as needed. 
     Principal Effects in this Embodiment 
     As described above, in this embodiment, the second drive motor  40  is attached to the second arm  5  so as to protrude to the first arm  4  side on a tip end side with respect to a portion of the second arm  5  where the third speed reducer  41  is disposed. Therefore, in comparison with a case that the second drive motor  40  is incorporated into the second arm  5  between the second speed reducer  22  and the third speed reducer  41 , the thickness of the second arm  5  can be reduced. 
     Further, in this embodiment, the pulley  54  is fixed to the hand speed reducer  53  so as to cover a part of the outer peripheral face on the upper end side of the main body  52   a  of the hand drive motor  52 , and the pulley  60  is fixed to the hand speed reducer  59  so as to cover a part of the outer peripheral face on the upper end side of the main body  58   a  of the hand drive motor  58 . Further, in this embodiment, the hand speed reducer  53  whose thickness is almost equal to a length of the output shaft of the hand drive motor  52  is disposed so as to cover an outer peripheral face of the output shaft of the hand drive motor  52 , and the hand speed reducer  59  whose thickness is almost equal to a length of the output shaft of the hand drive motor  58  is disposed so as to cover an outer peripheral face of the output shaft of the hand drive motor  58 . Therefore, even when the hand speed reducers  53  and  59  are fixed to the output shafts of the hand drive motors  52  and  58  and, even when the pulleys  54  and  60  are fixed to the hand speed reducers  53  and  59 , the heights of the hand drive mechanisms  13  and  14  are reduced and the thickness of the third arm  6  can be reduced. 
     Especially, in this embodiment, the shape of the pulley  54  and the shape of the pulley  60  are different from each other. Therefore, even when the hand drive motors  52  and  58  are disposed at substantially the same height as each other and the hand speed reducers  53  and  59  are disposed at substantially the same height as each other, the engagement part  54   a  of the pulley  54  and the engagement part  60   a  of the pulley  60  are disposed at positions displaced from each other in the upper and lower direction. Accordingly, even when the robot  1  includes two hands  7  and  8 , the thickness of the third arm  6  can be reduced. 
     As described above, in this embodiment, the thicknesses of the second arm  5  and the third arm  6  can be reduced. Therefore, in this embodiment, the heights to the upper faces of the hands  7  and  8  are lowered and thus the pass line of the robot  1  can be lowered. 
     In this embodiment, the wave generator  25  which is the input shaft of the first speed reducer  21  and the wave generator  32  which is the input shaft of the second speed reducer  22  are connected with each other through the connecting mechanism  23 . Therefore, a load applied to the connecting mechanism  23  can be reduced. Accordingly, the size of the connecting mechanism  23  which is disposed in the inside of the first arm  4  is reduced and the size of the first arm  4  can be reduced. 
     Further, in this embodiment, since the size of the first arm  4  can be reduced, even when the main body of the second drive motor  40  is fixed to a tip end side of the second arm  5  so that the second drive motor  40  is protruded to the first arm  4  side with respect to the under face of the second arm  5 , interference of the main body of the second drive motor  40  with the first arm  4  can be prevented when the arm part  9  is contracted without increasing the size of the second arm  5 . In other words, in this embodiment, even when the second drive motor  40  is attached to the second arm  5  so as to protrude to the first arm  4  side, the size of the second arm  5  can be reduced while preventing interference of the main body of the second drive motor  40  with the first arm  4  when the arm part  9  is contracted. 
     As described above, in this embodiment, the sizes of the first arm  4  and the second arm  5  can be reduced. Further, in this embodiment, as described above, the thicknesses of the second arm  5  and the third arm  6  can be reduced. Therefore, in this embodiment, the size of the robot  1  can be reduced. 
     In this embodiment, the first speed reducer  21  structures a first joint part which connects the main body part  3  with the first arm  4 , the second speed reducer  22  structures a second joint part which connects the first arm  4  with the second arm  5 , and the third speed reducer  41  structures a third joint part which connects the second arm  5  with the third arm  6 . Therefore, the rigidities of the first joint part, the second joint part and the third joint part can be increased. 
     In this embodiment, the wiring lines are passed by utilizing the inner peripheral sides of the hollow shaft  30  disposed so as to pass through the center of the first speed reducer  21 , the hollow shaft  35  disposed so as to pass through the center of the second speed reducer  22 , and the hollow shaft  50  disposed so as to pass through the center of the third speed reducer  41 . Therefore, even when the first joint part, the second joint part and the third joint part are structured of a speed reducer, the wiring lines are not required to be passed on outer peripheral sides of the speed reducers in the first joint part, the second joint part and the third joint part. Accordingly, in this embodiment, the diameters of the first joint part, the second joint part and the third joint part are made small and thus the size of the robot  1  can be reduced. 
     Other Embodiments 
     Although the present invention has been shown and described with reference to a specific embodiment, various changes and modifications will be apparent to those skilled in the art from the teachings herein. 
     In the embodiment described above, the flexspline  27  of the first speed reducer  21  is fixed to the main body part  3  and the circular spline  26  is fixed to the base end side of the first arm  4 . Further, the flexspline  34  of the second speed reducer  22  is fixed to the base end side of the second arm  5  and the circular spline  33  is fixed to the tip end side of the first arm  4 . However, the present invention is not limited to this embodiment. For example, it may be structured that the circular spline  26  is fixed to the main body part  3  and the flexspline  27  is fixed to the base end side of the first arm  4 , and that the circular spline  33  is fixed to the base end side of the second arm  5  and the flexspline  34  is fixed to the tip end side of the first arm  4 . In other words, the first speed reducer  21  and the second speed reducer  22  may be disposed so as to be reversed in the upper and lower direction. In this case, the ratio between the diameter of the pulley  36  and the diameter of the pulley  37  is set so that a moving trace of the center of the third speed reducer  41  is formed in a straight line shape. Further, the third speed reducer  41  may be disposed so as to be reversed in the upper and lower direction. 
     In the embodiment described above, the first speed reducer  21 , the second speed reducer  22  and the third speed reducer  41  are a harmonic drive (registered mark). However, the first speed reducer  21 , the second speed reducer  22  and/or the third speed reducer  41  may be a gear device having a hollow structure other than a harmonic drive (registered mark). For example, the first speed reducer  21 , the second speed reducer  22  and/or the third speed reducer  41  may be a cyclo-speed reducer (registered mark), an RV (Rotor Vector) speed reducer, or a planetary gear speed reducer. Further, the first speed reducer  21 , the second speed reducer  22  and/or the third speed reducer  41  may be a speed reducer which is provided with a first hypoid gear and a second hypoid gear engaged with the first hypoid gear. Further, the first speed reducer  21 , the second speed reducer  22  and/or the third speed reducer  41  may be provided with no hollow structure. 
     In the embodiment described above, the connecting mechanism  23  is structured of the pulleys  36  and  37  and the belt  38 . However, the present invention is not limited to this embodiment. For example, the connecting mechanism  23  may be structured of a gear train. Alternatively, the connecting mechanism  23  may be structured of a sprocket and a chain. 
     In the embodiment described above, the tip end side operation part whose base end side is turnably attached to the tip end side of the second arm  5  is structured of the third arm  6  and the hands  7  and  8 . However, the present invention is not limited to this embodiment. For example, the tip end side operation part may be structured of the hands  7  and  8 . Alternatively, the tip end side operation part may be structured of a predetermined end effector. 
     In the embodiment described above, power of the second drive motor  40  is decelerated by the third speed reducer  41  to be transmitted to the third arm  6 . However, the present invention is not limited to this embodiment. For example, instead of using the third speed reducer  41 , power of the second drive motor  40  is decelerated by using a pulley and a belt or by using a sprocket and a chain to be transmitted to the third arm  6 . 
     In the embodiment described above, two hands  7  and  8  are attached to the tip end side of the third arm  6 . However, one hand may be attached to the tip end side of the third arm  6 . Further, in the embodiment described above, the robot  1  is a robot for carrying a semiconductor wafer  2 . However, the robot  1  may be a carrying robot for carrying another carrying object such as a glass substrate for liquid crystal or may be an industrial robot such as an assembling robot other than a carrying robot. 
     In the embodiment described above, the hands  7  and  8  are formed in a roughly “Y” shape when viewed in the upper and lower direction but the hands  7  and  8  may be formed in other shapes. Further, in the embodiment described above, the hands  7  and  8  are formed in the same shape but the hands  7  and  8  are not required to be formed in the same shape. 
     While the description above refers to particular embodiments of the present invention, it will be understood that many modifications may be made without departing from the spirit thereof. The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of the present invention. 
     The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.