Abstract:
An object is to transmit an operation of a first parallel link to a second parallel link through a plurality of rotatably supported arms, to prevent the second parallel link from meandering or rolling so that a wafer can be transported smoothly. 
     Arms ( 61  to  63 ) of a transmission arm unit ( 6 ) are provided for transmitting an operation of a first parallel link ( 4 ) to a second parallel link ( 5 ). An operation of the first parallel link ( 4 ) is transmitted to the second parallel link ( 5 ) so that an angle between an arm ( 53 ) and an arm ( 52 ) in the second parallel link( 5 ) always coincides with an angle between an arm ( 41 ) and an arm ( 42 ) in the first parallel arm unit ( 4 ).

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a horizontal articulated wafer transport robot applied to a semiconductor manufacturing apparatus for transporting a wafer. 
       BACKGROUND ART 
       [0002]    As a horizontal articulated wafer transport robot used for transporting a wafer in semiconductor manufacturing, a robot having first and second parallel links is known. In a conventional wafer transport robot, a double link mechanism is configured by sharing one of four arms constituting a first parallel link as a common arm with a second parallel link to transmit an operation of the first parallel link to the second parallel link symmetrically. The transmission of an operation from the first parallel link to the second parallel link is performed by meshing a gear fixed to an end of a drive arm in the first parallel link with a gear fixed to an end of a driven arm in the second parallel link. 
         [0003]    In another conventional wafer transport robot, an operation of the first parallel link is transmitted to the second parallel link by rotation of a belt extending between a pulley fixed to an end of a drive arm in the first parallel link and a pulley fixed to an end of a driven arm in the second parallel link. 
       CITATION LIST 
     Patent Literature 
       [0004]    [Patent Literature 1] 
         [0005]    Japanese Patent Unexamined Publication No. 6-042602 
       SUMMARY OF INVENTION 
     Technical Problem 
       [0006]    However, in the configuration performing the transmission of an operation from the first parallel link to the second parallel link by meshing a gear fixed to an end of the drive arm with a gear fixed to an end of the driven arm, the second parallel link causes a meandering or a rolling due to the backlash in the gear train. Also, in case of using the belt, the second parallel link causes a meandering or a rolling due to slips between the belt and the pulleys. As a result, in the convention horizontal articulated wafer transport robot, there is such a problem that a misalignment of the wafer or an interference of the wafer at its side surface is caused during wafer loading to or unloading from a cassette or a stage. 
         [0007]    An object of the present invention is to provide a wafer transport robot that can smoothly transport a wafer without causing any meandering or rolling of the second parallel link by transmitting an operation of the first parallel link to the second parallel link through a plurality of arms which are supported in a rotatable manner. 
       Solution to Problem 
       [0008]    A wafer transport robot according to the present invention includes a multi-shaft drive unit, a first parallel link, a second parallel link, a handling arm, and a plurality of transmission arms. The multi-shaft drive unit includes at least an inner shaft and an outer shaft which are disposed coaxially. The first parallel link is configured by first and second arms which have first ends fixed to the inner shaft and the outer shaft, respectively, and third and fourth arms which are arranged in parallel to the first and second arms, respectively. The second parallel link is configured by either one of the third and fourth arms shared as a common arm, a fifth arm parallel to the common arm, a sixth arm has both ends pivotally supported on respective first ends of the common arm and the fifth arm, and a seventh arm has both ends pivotally supported on respective second ends of the common arm and the fifth arm. The handling arm is fixed to the fifth arm to be in parallel to the common arm. The plurality of transmission arms are rotationally connected to each other. The plurality of transmission arms transmits an operation of the first arm or the second arm to a driven arm so that an angle between the driven arm and the common arm coincides with an angle between the first arm and the second arm, where the driven arm is one of the sixth arm and the seventh arm and pivotally supported on the first end of the common arm together with the first arm or the second arm. 
         [0009]    According to this configuration, an operation of the first parallel link is transmitted to the second parallel link by rotations of the plurality of transmission arms. None of backlash and slip is caused during the transmission of an operation from the first parallel link to the second parallel link. 
         [0010]    In this configuration, it is preferable to form the handling arm and the fifth arm integrally. In this manner, the number of components can be reduced, so that the configuration can be simplified. 
         [0011]    Also, it is preferable that a drive arm is provided with an extended part extending outside the first parallel link from the first end of the common arm, and that the plurality of transmission arms are configured by first through third transmission arms, where the drive arm is one of the first arm and the second arm and is pivotally supported on the first end of the common arm together with the driven arm. The first transmission arm has a first end pivotally supported on an open end of the extended part, and has a second end pivotally supported on a first end of the second transmission arm. The second transmission arm has a second end pivotally supported on an intermediate portion of the common arm. The third transmission arm has a first end pivotally supported on an intermediate portion of the first transmission arm, and has a second end pivotally supported on an intermediate portion of the driven arm. A length of each of the first transmission arm and the third transmission arm is made equal to a length from the first end of the common arm to the position at which the second transmission arm is pivotally supported. A length of the second transmission arm is made equal to a length of the extended part. 
         [0012]    An operation of the first parallel link can be smoothly transmitted to the second parallel link by the three transmission arms. 
         [0013]    Further, the multi-shaft drive unit may include a middle shaft coaxial with the inner shaft and the outer shaft, and the wafer transport robot may include two sets of the first parallel link, the second parallel link, the handling arm and the plurality of transmission arms. 
       Advantageous Effects of Invention 
       [0014]    According to the present invention, an operation of the first parallel link is transmitted to the second parallel link without causing any meandering or rolling in the second parallel link, so that a wafer can be transported smoothly. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0015]      FIG. 1  is a schematic diagram showing a wafer transport robot according to a first embodiment of the present invention. 
           [0016]      FIG. 2  is a schematic diagram for explaining an operation of a double-link structure provided in the wafer transport robot. 
           [0017]      FIG. 3  is a schematic diagram showing a wafer transport robot according to a second embodiment of the present invention. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0018]    Hereinafter, embodiments of wafer transport robot according to the present invention will be described with reference to the drawings. 
         [0019]    As shown in  FIG. 1 , a wafer transport robot  10  according to a first embodiment of the present invention places a wafer  100  on a handling arm  1 , and transports the wafer  100  in a direction of an arrow X. The wafer transport robot  10  includes an inner shaft  2 , an outer shaft  3 , a first parallel link  4 , a second parallel link  5 , and a transmission arm unit  6 . 
         [0020]    The inner shaft  2  and the outer shaft  3 , which are disposed coaxially to configure a multi-shaft drive unit of the present invention, are individually driven to rotate by motors not shown in the figure. 
         [0021]    The first parallel link  4  is configured by first to fourth arms  41  to  44  which are pivotally supported at their ends by each other. One end of the first arm  41  is fixed to the inner shaft  2 , and one end of the second arm  42  is fixed to the outer shaft  3 . The third arm.  43  has the same inter-shaft length as that of the first arm  41 , and is arranged in parallel to the first arm.  41 . The fourth arm.  44  has the same inter-shaft length as that of the second arm  42 , and is arranged in parallel to the second arm  42 . 
         [0022]    The second parallel link  5  is configured by fifth to seventh arms  51  to  53  and the fourth arm  44  which are pivotally supported at their ends by each other. The fourth arm  44  is a common arm shared by the first link  4  and the second link  5 . The fifth arm  51  has the same inter-shaft length as that of the fourth arm  44 , and is arranged in parallel to the fourth arm  44 . The sixth arm  52  and the seventh arm  53  are the same in inter-shaft length, and arranged in parallel to each other. 
         [0023]    The first arm  41 , the third arm  43 , the sixth arm  52  and the seventh arm  53  are the same in inter-shaft length. The second arm  42 , the fourth arm  44  and the fifth arm  51  are the same in inter-shaft length. The second arm  42  and the seventh arm  53  are located on a straight line passing through the center of the inner shaft  2  and the outer shaft  3 . In this arrangement, a horizontal articulated wafer transport robot is configured in a double-link structure with the first parallel link  4  and the second parallel link  5 . 
         [0024]    Incidentally, the fifth arm  51  is a part of the handling arm  1 , and formed integrally with the handling arm  1 . This makes it possible to reduce the number of components, and simplify the structure. The handling arm  1  may be formed separately from the fifth arm  51 , and mounted to the fifth arm  51 . 
         [0025]    To move the wafer  100  placed on the handling arm  1  on the straight line X passing through the center of the inner shaft  2  and the outer shaft  3 , it is necessary to move the second parallel link  5  in conjunction with the first parallel link  4 . For this reason, the wafer transport robot  10  is provided with the transmission arm unit  6 . The transmission arm unit  6  transmits an operation of the first parallel link  4  to the second parallel link  5 . 
         [0026]    The transmission arm unit  6 , which corresponds to a plurality of transmission arms of the present invention, is configured by first to third transmission arms  61  to  63 . A first end of the first transmission arm  61  is pivotally supported on an extended part  411  extending from the first arm  41 . A second end of the first transmission arm  61  is pivotally supported on a first end of the second transmission arm  62 . A second end of the second transmission arm  62  is pivotally supported on an intermediate portion of the fourth arm  44 . Both ends of the third transmission arm  63  is pivotally supported on an intermediate portion of the second transmission arm  62  and an intermediate portion of the sixth arm  52 , respectively. 
         [0027]    Assume, as shown in  FIG. 2 , that the first arm  41  be a side CD, the second arm  42  be a side CJ, the third arm  43  be a side JK, the fourth arm  44  be a side DK, the fifth arm  51  be a side ML, the sixth arm  52  be a side DL, the seventh arm  53  be a side KM, and the center of the inner shaft  2  and the outer shaft  3  be a point C. Assume also that the first transmission arm  61  be a side EF, the second transmission arm  62  be a side FH, and the third transmission arm  63  be a side GI. 
         [0028]    Rotation of the inner shaft  2  causes a change in the angle ∠JCD of the first parallel link  4  to change. Such a linkage operation that the angle ∠LMK of the second parallel link  5  is always equal to the angle ∠JCD allows the handling arm  1  to move on the line X. 
         [0029]    Assume the length of each side be as 
         [0000]      DH=EF=GI  Formula 1
 
         [0000]      DE=FH  Formula 2
 
         [0000]        HG=DI=DH   2   /FH   Formula 3.
 
         [0030]    Since HG:DH=DH:FH from Formula 3, ΔHFD ∞ ΔHDG holds. 
         [0031]    Therefore, following formulae are obtained. 
         [0000]      ∠HFD=∠HDG  Formula 4
 
         [0000]      ∠FDH=∠DGH  Formula 5
 
         [0032]    From Formula 1 and Formula 2, ΔHFD≡ΔDF holds as all three corresponding sides are equal in length. Therefore, a following formula is obtained. 
         [0000]      ∠HFD=∠EDF  Formula 6
 
         [0033]    From Formula 1 and Formula 3, ΔHDG=ΔIGD holds as all three corresponding sides are equal in length. Therefore, a following formula is obtained 
         [0000]      ∠IGD=∠HDG  Formula 7
 
         [0034]    From Formula 6 and Formula 7, a following formula is obtained. 
         [0000]      ∠EDF=∠IGD  Formula 8
 
         [0035]    Here, the following relations hold: 
         [0000]      ∠ HDE=∠FDH−∠EDF   Formula 9
 
         [0000]      ∠ IGH=∠DGH−∠IGD   Formula 10.
 
         [0000]    Therefore, from Formula 5, Formula 8, Formula 9 and Formula 10, a following formula is obtained. 
         [0000]      ∠HDE=∠IGH  Formula 11.
 
         [0036]    Also, from Formula 1 and Formula 3, ΔIHD≡ΔHIG holds as all three corresponding sides are equal in length. Therefore, a following formula is obtained. 
         [0000]      ∠IGH=∠HDI  Formula 12
 
         [0037]    From Formula 11 and Formula 12, a following formula is obtained. 
         [0000]      ∠HDE=∠HDI  Formula 13
 
         [0038]    Here, the following relations hold: 
         [0000]      ∠HDE=∠JCD  Formula 14
 
         [0000]      ∠HDI=∠LMK  Formula 15.
 
         [0000]    Therefore, from Formula 13, Formula 14 and Formula 15, a following formula is obtained. 
         [0000]      ∠JCD=∠LMK  Formula 16
 
         [0000]    This means that the handling arm  1  moves on the line X. 
         [0039]    If the inner shaft  2  and the outer shaft  3  are simultaneously rotated in the same direction at a same angular velocity, the first parallel link  4  and the second parallel link  5  rotate integrally. If the outer shaft  3  is stopped and the inner shaft  2  is rotated, the angle ∠JCD of the first parallel link  4  changes, and, at the same time, the angle ∠LMK of the second parallel link  5  changes in the same manner, so that the handling arm  1  moves linearly. By combining these rotational operation and linear operation, it is possible to transport the wafer  100  placed on the handling arm  1  to a target position. 
         [0040]    As shown in  FIG. 3 , a wafer transport robot  20  according to a second embodiment of the present invention is configured by adding a middle shaft  8 , a handling arm  11 , a third parallel link  14 , a fourth parallel link  15 , and a transmission arm unit  16  to the wafer transport robot  10 . The middle shaft  8  is coaxially disposed between the inner shaft  2  and the outer shaft  3 . 
         [0041]    The third parallel link  14  is configured by pivotally supporting the second arm  42  and the eighth to tenth arms  141  to  143  by each other at their ends. One end of the eighth arm  141  is fixed to the middle shaft  8 . The ninth arm  142  has the same inter-shaft length as that of the eighth arm  141 , and is arranged in parallel to the eighth arm  141 . The tenth arm  143  has the same inter-shaft length as that of the second arm  42 , and is arranged in parallel to the second arm  42 . 
         [0042]    The fourth parallel link  15  is configured by pivotally supporting the eleventh to thirteenth arms  151  to  153  and the tenth arm  143  by each other at their ends. The tenth arm  143  is a common arm shared by the third parallel link  14  and the fourth parallel link  15 . The eleventh arm  151  has the same inter-shaft length as that of the tenth arm  143 , and is arranged in parallel to the tenth arm  143 . The twelfth arm  152  and the thirteenth arm  153  are the same in inter-shaft length, and arranged in parallel to each other. 
         [0043]    The eighth arm  141 , the ninth arm  142 , the twelfth arm  152  and the thirteenth arm  153  are made to be the same in inter-shaft length. The second arm  42 , the tenth arm  143  and the eleventh arm  151  are made to be the same in inter-shaft length. The second arm  42  and the eleventh arm  151  are located on the line X passing through the center of the inner shaft  2 , the outer shaft  3  and the middle shaft  8 . In this arrangement, a horizontal articulated wafer transport robot is configured to have also a double-link structure with the third parallel link  14  and the fourth parallel link  151 . 
         [0044]    Incidentally, the eleventh arm  151  is a part of the handling arm  11 , and formed integrally with the handling arm  11 . This makes it possible to reduce the number of components, and simplify the structure. The handling arm  11  may be formed separately from the eleventh arm  151 , and mounted on the eleventh arm  51 . 
         [0045]    The transmission arm unit  16  is configured by fourth to sixth transmission arms  161  to  163 . A first end of the fourth transmission arm  161  is pivotally supported on an extended part  1411  extending from the eighth arm  141 . A second end of the fourth transmission arm  161  is pivotally supported on a first end of the fifth transmission arm  162 . A second end of the fifth transmission arm  162  is pivotally supported on an intermediate portion of the tenth arm  143 . Both ends of the sixth transmission arm  163  are pivotally supported on an intermediate portion of the fifth transmission arm  162  and an intermediate portion of the thirteenth arm  153 , respectively. 
         [0046]    If the inner shaft  2 , the outer shaft  3  and the middle shaft  8  are simultaneously rotated in a same direction at a same angular velocity, the first to fourth parallel links  4 ,  5 ,  14  and  15  rotate integrally. If the outer shaft  3  and the middle shaft  8  are stopped and the inner shaft  2  is rotated, the first parallel link  4  and the second parallel link  5  move linearly. If the outer shaft  3  and the inner shaft  2  are stopped and the middle shaft  8  is rotated, the third parallel link  14  and the fourth parallel link  15  move linearly. By combining these rotational operation and linear operations, it is possible to transport two wafers  100  placed on the handling arm  1  and the handling arm  11 , respectively, to respective target positions. Since the wafer transport robot  20  simultaneously holds two wafers  100  in total on the handling arm  1  and the handling arm  11 , processing efficiency of wafer transport is improved. 
         [0047]    It should be understood that the embodiments described above are exemplifications in all respects, and are not limitative. Scope of the present invention is defined, not in the above-described embodiments, but in the accompanying claims. Further, it is intended that the scope of the present invention includes any modifications within the meaning and scope of the claims and equivalents thereof. 
       REFERENCE SIGNS LIST 
       [0048]      1 ,  11  handling arm 
         [0049]      2  inner shaft 
         [0050]      3  outer shaft 
         [0051]      4  first parallel link 
         [0052]      5  second parallel link 
         [0053]      6  transmission arm unit 
         [0054]      8  middle shaft 
         [0055]      10 ,  20  wafer transport robot 
         [0056]      100  wafer