Abstract:
Suppression of the effects of electromagnetic waves on the signals which are transmitted by signal lines and manufacturing composite cables more compactly and with higher efficiency have been sought. For this, provision is made of a composite cable  30  comprised of a center member  32  for supplying the fluid or wire material used for the work of the industrial robot, first signal lines  34  which are arranged at the outer circumferential side of the center member  32,  a tubular shield  36  which surrounds the first signal lines  34  and shields them from electromagnetic waves, power lines  40  which are arranged at the outer circumferential side of the shield  36,  and a tubular sheath  42  which surrounds the power lines  40.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to a composite cable mounted in an industrial robot. 
         [0003]    2. Description of the Related Art 
         [0004]    Various composite cables mounted in industrial robots are known (for example, Japanese Patent Publication No. 2003-230963A, Japanese Patent Publication No. 2005-271003A, Japanese Patent Publication No. 2-126513A, Japanese Utility Model Publication No. 6-72119U). 
         [0005]    The above-mentioned composite cables are provided with signal lines and with power lines which transmit power larger than the signal lines. In the past, in such composite cables, suppression of the effects of electromagnetic waves on the signals which are transmitted by signal lines and manufacturing composite cables more compactly and with higher efficiency have been sought. 
       SUMMARY OF INVENTION 
       [0006]    In an aspect of the invention, a composite cable mounted in an industrial robot comprises a center member for feeding a fluid or wire material used for a work of the industrial robot, a first signal line arranged at the outer circumferential side of the center member, a shield which surrounds the first signal line and blocks an electromagnetic wave, a power line arranged at the outer circumferential side of the shield, and a tubular sheath which surrounds the power line. 
         [0007]    The composite cable may further comprise a second signal line arranged between the first signal line and the shield or between the shield and the power line. The center member may be a tubular member. The fluid or wire material may be arranged in the inner space of the center member. A plurality of the first signal lines may be arranged to align in the circumferential direction of the center member. A plurality of the power lines may be arranged to align in the circumferential direction of the shield. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0008]      FIG. 1  is a view of a robot system in which a composite cable according to an embodiment of the invention is mounted. 
           [0009]      FIG. 2  is a cross-sectional view of a composite cable shown in  FIG. 1 . 
           [0010]      FIG. 3  is a cross-sectional view of a composite cable according to another embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0011]    Below, embodiments of the invention will be explained in detail based on the drawings. First, referring to  FIG. 1 , a robot system  10  will be explained. The robot system  10  is an industrial robot system for performing a work such as welding or machining, and includes a robot  12 , a controller  14 , and a composite cable  30 . 
         [0012]    The robot  12  includes a first base  16 , a second base  17 , an upper arm  18 , a forearm  20 , and a wrist  22 . The first base  16  is fixed on a floor of a work cell. The second base  17  is attached to the first base  16  so as to be able to swivel about the vertical axis. The upper arm  18  is attached to the second base  17  so as to be rotatable about the horizontal axis. The forearm  20  is rotatably attached to the distal end of the upper arm  18 . 
         [0013]    The wrist  22  is attached to the distal end of the forearm  20 . An end effecter (not shown), such as a welding torch, is attached to the wrist  22 . The wrist  22  is driven by a servo motor so as to operate the end effecter to rotate the end effecter about three axes. The controller  14  directly or indirectly controls each element of the robot  12 . 
         [0014]    The composite cable  30  is laid so as to extend from a connector  16   a  provided at the first base  16  to a predetermined position at an element of the robot  12 . On the other hand, the controller  14  and connector  16   a  are connected each other via a cable  24 . In this embodiment, the composite cable  30  is laid from the connector  16   a  to a position P at the proximal end of the forearm  20 . 
         [0015]    Next, referring to  FIG. 2 , the configuration of the composite cable  30  will be explained. Note that, in the following explanation, the axial direction corresponds to a direction along the center axis O of the composite cable  30 , while the radial direction corresponds to a direction along an imaginary line radially extending from the center axis O. 
         [0016]    The composite cable  30  includes a center member  32 , motor control-use signal lines (first signal lines)  34 , a shield  36 , general-use signal lines (second signal lines)  38 , power lines  40 , and a sheath  42 . The center member  32  is a cylindrical member extending along the axis O. 
         [0017]    The motor control-use signal lines  34  are arranged at the outer circumferential side of the center member  32 . Specifically, a plurality of the motor control-use signal lines  34  are arranged on the outer circumferential surface  32   a  of the center member  32  so as to align in the circumferential direction of the center member  32 . 
         [0018]    Each of the motor control-use signal lines  34  includes two conductors  34   a  twisted together. Each of the motor control-use signal lines  34  extends in the axial direction. 
         [0019]    The shield  36  is a cylindrical member extending in the axial direction, or a member produced by winding a tape member into a cylindrical shape. The shield  36  is arranged so as to surround the plurality of motor control-use signal lines  34  from radially outside. The shield  36  is made of a material capable of blocking an electromagnetic wave. The inner circumferential surface  36   a  of the shield  36  contacts a drain line  35 . The drain line  35  is grounded at one end thereof so as to make the potential of the shield  36  to be a ground potential. 
         [0020]    The general-use signal lines  38  are arranged at the outer circumferential side of the shield  36 , i.e., arranged between the shield  36  and the power lines  40 . Specifically, a plurality of the general-use signal lines  38  are arranged on the outer circumferential surface  36   b  of the shield  36  so as to align in the circumferential direction of the shield  36  at equal intervals. 
         [0021]    A cylindrical partition member  44  is provided between the general-use signal lines  38  and the power lines  40 . The partition member  44  is made of e.g. a paper material, and covers the general-use signal lines  38  from radially outside. The partition member  44  functions to divide the general-use signal lines  38  and power lines  40  into different radial layers. 
         [0022]    The power lines  40  are arranged at the outer circumferential side of the shield  36 . Specifically, a plurality of the power lines  40  are arranged at radially outside of the general-use signal lines  38  so as to align in the circumferential direction of the shield  36  at equal intervals. 
         [0023]    The sheath  42  is a cylindrical member extending in the axial direction, and arranged so as to surround the power lines  40  from radially outside. The sheath  42  is made of e.g. a plastic. The sheath  42  holds the motor control-use signal lines  34 , the shield  36 , the general-use signal lines  38 , and the power lines  40  between the center member  32  and the sheath  42 , in order to make the composite cable  30  to be an integral structure. 
         [0024]    In this embodiment, a partition member  46  is interposed between the power lines  40  and sheath  42 . This partition member  46  has a configuration similar to the above-mentioned partition member  44 , and surrounds the power lines  40  from outside. 
         [0025]    Next, referring to  FIG. 1  and  FIG. 2 , the functions of the composite cable  30  according to this embodiment will be explained. As explained above, the composite cable  30  is laid from the connector  16   a  to the position P. 
         [0026]    The motor control-use signal lines  34  of the composite cable  30  are electrically connected to the controller  14  via the cable  24  at first ends thereof, while connected to e.g. encoders (not shown) built in the servo motors  48  and  50  shown in  FIG. 1  at second ends thereof. The servo motors  48  and  50  are mounted in the forearm  20  in order to drive the wrist  22 . 
         [0027]    The motor control-use signal lines  34  are wired so as to further extend from the position P to the inside of the forearm  20 , pass through the inside of the forearm  20 , and be connected to the above-mentioned encoders. The motor control-use signal lines  34  transmit signals from the encoders to the controller  14 . 
         [0028]    The general-use signal lines  38  are electrically connected to the controller  14  via the cable  24  at first ends thereof, while connected to the end effecter attached to the wrist  22  at second ends thereof. For example, the general-use signal lines  38  transmit various command signals from the controller  14  to the end effecter. 
         [0029]    The power lines  40  are connected to the controller  14  via the cable  24  at first ends thereof, while connected to the servo motors  48  and  50  at second ends thereof. The power lines  40  transmit power for driving these servo motors  48  and  50 . Note that, the power lines  40  may transmit power for driving brakes built in the servo motors  48  and  50 . 
         [0030]    The power for driving the servo motors  48  and  50  (or the power for driving the brakes) is greater than the power of the signal transmitted from the encoder to the controller  14  and the power of the command signal transmitted to the end effecter. Therefore, the power lines  40  are configured to be able to transmit signals having power larger than the signals transmitted by the motor control-use signal lines  34  and the general-use signal lines  38 . 
         [0031]    The center member  32  feeds the fluid or wire material to be used for the work of the robot  12 . As an example, when a welding torch is attached to the wrist  22  and the robot  12  performs welding work on the workpiece, the center member  32  feeds an assist gas to the welding torch. Alternatively, the center member  32  accommodates e.g. a liner of a welding wire in the inner space thereof, and feeds it to the welding torch. 
         [0032]    As another example, when a tool is attached to the wrist  22  and the robot  12  performs machining work on a workpiece, the center member  32  carries a compressed air in the inner space thereof, and feeds it to the tool. 
         [0033]    As explained with  FIG. 2 , in this embodiment, the motor control-use signal lines  34 , general-use signal lines  38 , and power lines  40  are stacked in the radial direction so as to be substantially concentric with each other, and are held between the center member  32  and the sheath  42  to form an integral structure. 
         [0034]    According to this configuration, since the dead space between the center member  32  and the sheath  42  can be reduced and the motor control-use signal lines  34 , general-use signal lines  38 , and power lines  40  can be densely held, it is possible to reduce the cross-sectional area of the composite cable  30 . 
         [0035]    Further, in this embodiment, the center member  32 , motor control-use signal lines  34 , general-use signal lines  38 , and power lines  40  are made to be integral, so it is possible to reduce the number of cables to be dealt with, compared with the prior art where these lines are configured by separate cables for each type. Therefore, it is possible to simplify the work of installing the composite cable  30  to the robot  12 . 
         [0036]    Further, according to this embodiment, when forming the layers of the motor control-use signal lines  34 , general-use signal lines  38 , and power lines  40 , the same type of wire material is used for the assembly work for each layer. Due to this, the manufacturing process of the composite cable  30  can be simplified. 
         [0037]    Further, in this embodiment, the motor control-use signal lines  34  are arranged at radially inside of the shield  36 , while the power lines  40  are arranged at radially outside of the shield  36 . According to this configuration, the shield  36  can block both the electromagnetic wave propagated from the outside of the composite cable  30  toward radially inside of the composite cable  30  and the electromagnetic waves transmitted from the power lines  40  toward radially inside of the composite cable  30 . 
         [0038]    Due to this, the motor control-use signal lines  34  are shielded from not only the electromagnetic wave from the outside, but also the electromagnetic wave from the power lines  40 . Therefore, it is possible to prevent noise, which propagate from the outside and the power lines  40 , from interfering in the signals transmitted by the motor control-use signal lines  34 . 
         [0039]    Further, in this embodiment, the center member  32  is arranged at the center of the composite cable  30 , and the motor control-use signal lines  34 , the general-use signal lines  38 , and power lines  40  are arranged at radially outside of center member  32 . According to this configuration, the motor control-use signal lines  34 , the general-use signal lines  38 , and power lines  40  are arranged away from the center of the composite cable  30  which is susceptible to damage during the operation of the robot  12 , so longer service life of the composite cable  30  can be realized. 
         [0040]    Further, in this embodiment, the center member  32  for feeding the fluid or wire material used in the work of the robot  12  is built in the center of the composite cable  30 . According to this configuration, the composite cable  30  can be configured more compactly. Further, a protective member for protecting the center member  32  from weld spatter or cutting dust becomes unnecessary, so the cost of the composite cable  30  can be cut. 
         [0041]    In the above-mentioned embodiment, one shield  36  is provided between the motor control-use signal lines  34  and the general-use signal lines  38 . However, the composite cable may be provided with a plurality of shields. 
         [0042]    Such an embodiment will be explained with reference to  FIG. 3 . Note that, elements similar to the above-mentioned embodiments are assigned the same reference numerals, and detailed explanations thereof will be omitted. The composite cable  60  according to this embodiment is different from the above-mentioned composite cable  30  in the following matters. 
         [0043]    The composite cable  60  includes a second shield  62 , instead of the above-mentioned partition member  44 . Specifically, the second shield  62  is arranged between the general-use signal lines  38  and the power lines  40 , and surrounds the motor control-use signal lines  34  from outside. The second shield  62  is a cylindrical member which can block an electromagnetic wave, similar as the shield  36 . 
         [0044]    According to this embodiment, the second shield  62  can shield not only the motor control-use signal lines  34 , but also the general-use signal lines  38  from electromagnetic waves from the outside and the power lines  40 , so the motor control-use signal lines  34  and the general-use signal lines  38  can be kept from being influenced by the electromagnetic waves. 
         [0045]    Note that, in the composite cable  60  shown in  FIG. 3 , a tubular partition member may be applied, instead of the shield  36 . In this case, the motor control-use signal lines  34  and the general-use signal lines  38  can be shielded from electromagnetic waves from outside of the composite cable and from the power lines. 
         [0046]    Further, in the above-mentioned embodiments, the power lines  40  are connected to the servo motors  48  and  50  for driving the wrist  22 . However, the power line may be connected to a servo motor for driving the upper arm  18 , the forearm  20 , or any other element of the robot  12 . 
         [0047]    Similarly, the motor control-use signal line  34  may be connected to an encoder built into any servo motor. Further, the motor control-use signal line  34  may be connected to e.g. a Hall element other than the encoder, or any other sensor (element) necessary for the operation of a servo motor. 
         [0048]    Further, in the above-mentioned embodiment, the center member  32 , the shields  36  and  62 , and the sheath  42  are cylindrical. However, at least one of the center member  32 , the shields  36  and  62 , and the sheath  42  may be a polygonal or elliptical hollow member. 
         [0049]    Further, the center member  32  may be a solid member. In this case, a wire material such as e.g. a liner of a welding wire may be embedded in the center member  32 , and the wire material may be guided to a welding torch by the center member  32 . 
         [0050]    Above, embodiments of the invention were used to explain the invention, but the above embodiments do not limit the inventions according to the claims. Further, combinations of the features which are explained in the embodiments of the invention may also be included in the technical scope of the invention. However, not all of the combinations of these features are necessarily essential for the solution of the invention. Further, the fact that the above embodiments can be changed or improved in various ways would be clear to a person skilled in the art. 
         [0051]    Further, it should be noted that the operations, routines, steps, stages, and other processing in the cable in the claims, specification, and drawings, unless particularly clearly indicated by “before”, “in advance of”, etc. or the output of prior processing being used for later processing, can be realized in any order. In the flow of operations in the claims, specification, and drawings, even if explained using “first”, “next”, etc. for convenience, this does not mean the execution in this order is essential.