Patent Publication Number: US-10315314-B2

Title: End effector, industrial robot, and operation method thereof

Description:
TECHNICAL FIELD 
     The present invention relates to an end effector, particularly an end effector used for assembling components, to an industrial robot comprising the end effector, and to an operation method of the industrial robot. 
     BACKGROUND ART 
     In an industrial robot, a suitable end effector (hand) corresponding to its work contents is mounted to a distal end of a robot arm, and an object to be handled which is held by the end effector is transferred by driving the robot arm. In a production line for completing a product by assembling various kinds of objects to be handled (components) with different forms and dimensions, an industrial robot capable of dealing with multiple kinds of objects to be handled is needed. 
     If dedicated robots are arranged for each kind of object to be handled, space needed to install the robots increases and cost for manufacturing the robots also increases. Therefore, there is a request that a single robot can deal with different work contents and objects to be handled. 
     Thus, industrial robots are proposed, wherein a hand mounted to a distal end of a robot arm can be automatically exchanged as a whole according to work contents, or wherein the configuration of the hand mounted to the distal end of the robot arm can be partially changed according to forms and dimensions of objects to be handled (Patent Documents 1, 2). 
     CITATION LIST 
     Patent Documents 
     [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-192365 
     [Patent Document 2] Japanese Patent Application Laid-Open No. 2011-177862 
     SUMMARY OF INVENTION 
     Objects to be Achieved by the Invention 
     However, the industrial robot wherein the configuration of the hand mounted to the distal end of the robot arm can be changed according to kinds and sizes of objects to be handled requires a complicated configuration since the configuration of the hand is changed, thus increasing space for installing hands to be exchanged, declining credibility due to the complicated configuration, and also increasing the cost. 
     This problem becomes serious particularly when automating a work for fitting a O ring into a O ring mounting groove of an assembly component by a robot. Specifically, in order to fit an O ring into an O ring mounting groove of an assembly component, it is needed to first make the O ring in its slightly-stretched state from its natural state and to fit the O ring into the O ring mounting groove utilizing a contraction force of the O ring from this extended state. Therefore, the configuration of the hand needed for the work becomes complicated and the work contents also becomes complicated. 
     This becomes a problem when fitting not only the O ring but also an annular or C-shaped component having elasticity such as an oil seal and a snap ring by a robot. 
     Additionally, the complication of a fitting work of an elastic component such as the O ring is not necessarily limited to the fitting work by a robot having an exchangeable hand and a configuration changeable hand. 
     The present invention is made considering the above-mentioned problems of the conventional technologies, and its object is to provide an end effector capable of simplifying the fitting work of an elastic component such as the O ring by a robot, an industrial robot comprising the end effector, and an operation method of the industrial robot. 
     Means for Achieving the Objects 
     In order to achieve the objects above, a first aspect of the present invention is an end effector mounted to a robot arm, comprising: an end effector base portion connected to the robot arm; and an elastic component holding unit provided to the end effector base portion so as to hold an elastic component, wherein the elastic component holding unit has a plurality of elastic component gripping members which releasably grip the elastic component; and a biasing unit for repulsively biasing each distal end portion of the plurality of elastic component gripping members from a releasing position for releasing the elastic component toward a gripping position for gripping the elastic component. 
     A second aspect of the present invention is that, in the first aspect, an object holding unit provided to the end effector base portion so as to hold an object to be handled; and a holding mechanism provided to the end effector base portion so as to releasably hold the elastic component holding unit are further provided. 
     A third aspect of the present invention is that, in the second aspect, the elastic component holding unit held by the holding mechanism is driven by the object holding unit. 
     A fourth aspect of the present invention is that, in the third aspect, the object holding unit has an object gripping member for gripping the object to be handled, and the elastic component holding unit held by the holding mechanism is driven by the object gripping member. 
     A fifth aspect of the present invention is that, in the fourth aspect, the elastic component gripping member of the elastic component holding unit held by the holding mechanism is driven by the object gripping member. 
     A sixth aspect of the present invention is that, in the fifth aspect, the elastic component gripping member is driven by the object gripping member against a biasing force of the biasing unit in a direction that the elastic component is released. 
     A seventh aspect of the present invention is that, in any one of the first to sixth aspects, the holding mechanism is provided in a center portion of the end effector base portion, and the object holding unit is provided in a periphery of the holding mechanism. 
     An eighth aspect of the present invention is that, in any one of the first to seventh aspects, distal end portions of the plurality of elastic component gripping members lower along an outer surface of a tapered part of an object to which the elastic component is fitted while being displaced from the gripping position toward the releasing position against a repulsive force of the biasing unit. 
     A ninth aspect of the present invention is that, in any one of the first to eighth aspects, the elastic component gripping member has an elongated swinging member which is swingably provided to the end effector base portion, and distal end portions of the plurality of elongated swinging members grip the elastic component. 
     A tenth aspect of the present invention is that, in any one of the first to ninth aspects, the each distal end portion of the plurality of elastic component gripping members in the gripping position has a part positioned inner side than an outer peripheral edge of the elastic component which is gripped. 
     An eleventh aspect of the present invention is that, in any one of the first to tenth aspects, the elastic component is an annular or C-shaped component having elasticity. 
     An industrial robot according to a twelfth aspect of the present invention comprises the end effector according to any one of the first to eleventh aspects; and a robot arm to which the end effector is mounted. 
     A thirteenth aspect of the present invention is an operation method of the industrial robot according to the twelfth aspect, comprising: a transfer step in which the robot arm is driven so as to transfer the elastic component which is held by the elastic component holding unit; a fitting step in which the elastic component holding unit is driven so that the elastic component which has been held by the elastic component holding unit is released and fitted to a guide jig; and a pressing down step in which the elastic component is pressed down along an outer surface of the guide jig by distal end portions of the plurality of elastic component gripping members of the elastic component holding unit. 
     A fourteenth aspect of the present invention is that, in the thirteenth aspect, in the fitting step, the elastic component is fitted to a tapered part of the guide jig, and, in the pressing down step, the distal end portions of the plurality of elastic component gripping members lower along an outer surface of the tapered part of the guide jig while being displaced from the gripping position toward the releasing position against a repulsive force of the biasing unit. 
     A fifteenth aspect of the present invention is that, in the thirteenth or fourteenth aspect, the elastic component is an annular or c-shaped component having elasticity. 
     Effect of the Invention 
     According to the present invention, a fitting work of an elastic component such as the O ring using a robot can be simplified. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view illustrating a schematic configuration of an industrial robot to which an end effector according to one embodiment of the present invention is mounted (in a state that a second object holding unit is removed). 
         FIG. 2  is a perspective view from diagonally below illustrating the end effector of the industrial robot in  FIG. 1  in a state that the second object holding unit is removed. 
         FIG. 3  is a front view of the end effector in  FIG. 2 . 
         FIG. 4  is a bottom view of the end effector in  FIG. 2 . 
         FIG. 5  is a longitudinal section view illustrating the end effector in  FIG. 2  together with a first type of object to be handled (O ring guide jig). 
         FIG. 6  is a longitudinal section view illustrating a state that the first type of object to be handled (O ring guide jig) is fitted to an assembly component to which the O ring is to be mounted. 
         FIG. 7  is a perspective view illustrating a state that a second object holding unit is mounted to the end effector in  FIG. 2  in a state that a second type of object to be handled (O ring) is held. 
         FIG. 8  is a longitudinal section view illustrating the end effector in  FIG. 7  in a state that the second type of object to be handled (O ring) is held. 
         FIG. 9  is a perspective view illustrating a state that the second object holding unit of the end effector in  FIG. 7  is driven and the second type of object to be handled (O ring) is released. 
         FIG. 10  is a front view illustrating a state that the O ring is fitted to an upper end portion of the O ring guide jig. 
         FIG. 11  is a view taken in the direction of an arrow XI-XI in  FIG. 10 . 
         FIG. 12A  is a front view illustrating a work process when fitting the O ring into the O ring mounting groove of the assembly component by a second gripping member of the second object holding unit. 
         FIG. 12B  is another front view illustrating the work process when fitting the O ring into the O ring mounting groove of the assembly component by the second gripping member of the second object holding unit. 
         FIG. 12C  is another front view illustrating the work process when fitting the O ring into the O ring mounting groove of the assembly component by the second gripping member of the second object holding unit. 
         FIG. 12D  is another front view illustrating the work process when fitting the O ring into the O ring mounting groove of the assembly component by the second gripping member of the second object holding unit. 
     
    
    
     EMBODIMENT OF THE INVENTION 
     Hereunder, an end effector  4  of an industrial robot  1  according to one embodiment of the present invention will be described referring to the drawings. 
     As illustrated in  FIG. 1 , the industrial robot  1  of this embodiment has an articulated robot arm  2  and the end effector (hand)  4  mounted to a wrist shaft  3  on a distal end of the robot arm. 
     Note that kinds of industrial robots to which the present invention is applied are not particularly limited and the present invention can be applied to various kinds of industrial robots such as a vertical articulated robot, a horizontal articulated robot, or the like. 
     As illustrated in  FIGS. 2 to 4 , the end effector  4  in this embodiment comprises an end effector base portion  5  connected to the robot arm  2  ( FIG. 1 ). The end effector base portion  5  is provided with a first object holding mechanism  6  for holding a first type of object to be handled. 
     The first object holding mechanism  6  has a plurality of first gripping members (object griping members)  7  for gripping the first type of object to be handled, and a gripping member drive unit  8  for driving these first gripping members  7 . 
     In this embodiment, three first gripping members  7  are arranged at equal angular intervals (120°) around a center axis L 0  of the end effector  4 . Each of the first gripping members  7  is driven back and forth in a radial direction with respect to the center axis L 0  of the end effector  4  by the gripping member drive unit  8 . 
     A type of the gripping member drive unit  8  is not particularly limited, and various drive sources such as a fluid pressure cylinder such as an air cylinder or an electric drive source such as a servo motor can be used. 
     As illustrated in  FIG. 5 , when holding a first type of object to be handled O 1  by the first object holding mechanism  6 , each of the first gripping members  7  is positioned outside in the radial direction by the gripping member drive unit  8  and the robot arm  2  is driven so as to position the three first gripping members  7  around a side peripheral surface of the first type of object to be handled O 1 . 
     In the state, each of the first gripping members  7  is moved inside in the radial direction so that the side peripheral surface of the first type of object to be handled O 1  is gripped by each of the first gripping members  7  from three directions. Subsequently, the robot arm  2  is driven so as to transfer the first type of object to be handled O 1  to a predetermined transfer destination and each of the first gripping members  7  is moved outside in the radial direction by the gripping member drive unit  8  so as to release the grip of the first type of object to be handled O 1 . 
     At the transfer destination of the first type of object to be handled O 1 , an assembly component  16  to which an O ring (second type of object to be handled) should be mounted is placed on a work table, as illustrated in  FIG. 6 . By the above-mentioned operation of the robot arm  2  and the end effector  4 , the first type of object to be handled O 1  is fitted to the assembly component  16  from above. Namely, the first type of object to be handled O 1  is formed of a cylindrical member having a tapered upper end portion, and it is fitted to the assembly component  16  via its lower end opening from above. An O ring mounting groove  17  is formed in a side peripheral surface of the assembly component  16 . 
     In this example, the first type of object to be handled O 1  functions as an O ring guide jig for guiding the O ring up to the O ring mounting groove  17  when fitting the O ring to the O ring mounting groove  17  of the assembly component  16 . 
     As illustrated in  FIG. 7  and  FIG. 8 , a unit holding mechanism  10  for releasably holding a second object holding unit (elastic member holding unit)  9  is provided at the center portion of the end effector base portion  5 . The second object holding unit  9  is a unit for holding the second type of object to be handled O 2 . In this example, the unit holding mechanism  10  holds the second object holding unit  9  by adsorption. 
     Note that a mechanism for the unit holding mechanism  10  to hold the second object holding unit  9  is not limited to adsorption and may be grip by a gripping member. That is, any mechanism may be employed as long as it can releasably fix the second object holding unit  9  to the end effector base portion  5 . 
     Note that, in this embodiment, the second type of object to be handled O 2  is smaller in diameter in its part to be held than the first type of object to be handled O 1 , and therefore the second type of object to be handled O 2  cannot be held by the first gripping member  7  of the first object holding mechanism  6 . 
     Namely, in the end effector of this embodiment, even an object to be handled having a too small diameter to be held by the first object holding mechanism  6  can be held by the second object holding unit  9  which is held by the unit holding mechanism  10 . 
     Note that the second type of object to be held O 2  in this embodiment is an O ring. 
     The second object holding unit  9  has a unit body  11  which is adsorbed and held by the unit holding mechanism  10  and a plurality of second gripping members (elastic component gripping members)  12  for gripping the second type of object to be handled O 2 . In this embodiment, three second gripping members  12  are arranged at equal angular intervals (120°) around a center axis L 0  of the end effector  5 . A recessed portion  12 A into which the O ring as the second type of object to be held O 2  is fitted is formed at a lower end portion (distal end portion) of each of the second gripping members  12 . 
     As illustrated in  FIG. 8 , each of the second gripping members  12  is swingably supported by a pivot pin  13  relative to the unit body  11  and also energized in a direction of gripping the second type of object to be handled O 2  (object gripping direction) by a compression spring (biasing unit)  14 . Swinging motion of the second gripping member  12  in the object gripping direction is restricted by each stopper member  15  provided inside in the radial direction with respect to each of the second gripping members  12 . 
     The end effector  5  according to this embodiment is configured so that the second object holding unit  9  held by the unit holding mechanism  10  is driven by the first object holding mechanism  6 . More specifically, it is configured so that the second gripping member  12  of the second object holding unit  9  held by the unit holding mechanism  10  is driven by the first gripping member  7  of the first object holding mechanism  6 . 
     Specifically, when the first gripping member  7  of the first object holding mechanism  6  is moved inside in the radial direction from the state illustrated in  FIG. 7  and  FIG. 8 , the upper end portion of the second gripping member  12  of the second object holding unit  9  is pushed in by a claw portion of the distal end of the first gripping member  6  against the biasing force of the compression spring  14 , as illustrated in  FIG. 9 . Thereby, a lower end portion of each of the second gripping members  12  is driven in a direction that the second type of object to be handled O 2  is released. 
     When holding the second type of object to be handled O 2  by the second object holding unit  9  held by the unit holding mechanism  10 , each of the second gripping members  12  is driven by each of the first gripping members  7  against the biasing force of each compression spring  14  so as to move each of the second gripping members  12  to a releasing position. In this state, the robot arm  2  is driven so as to position the three second gripping members  12  around the second type of object to be handled O 2 . 
     In this state, each of the first gripping members  7  is moved outside in the radial direction so as to move each of the second gripping members  12  in the object gripping direction by the biasing force of each compression spring  14 . Thereby, the second type of object to be handled O 2  is gripped by each of the second gripping members  12  from three directions. 
     Subsequently, the robot arm  2  is driven so as to transfer the second type of object to be handled (O ring) O 2  to above the O ring guide jig as the first type of object to be handled O 1  (transfer step). Subsequently, each of the first gripping members  7  is moved inside in the radial direction so as to move each of the second gripping members  12  in the object releasing direction, thereby releasing the grip of the second type of object to be handled O 2 . 
     Since an upper end diameter of the tapered upper end portion of the O ring guide jig O 1  is set smaller than an inner diameter of the O ring O 2 , the O ring O 2  released from the second gripping member  12  fits to the tapered upper end portion of the O ring guide jig O 1  (fitting step). 
     Next, a work for fitting the O ring O 2  which is fitted to the tapered upper end portion of the O ring guide jig O 1  into the O ring mounting groove  17  of the assembly component  16  will be described. 
     The first gripping member  7  moved inside in the radial direction for releasing the O ring O 2  from the second gripping member  12  is moved outside in the radial direction again so as to release the pressing force from the first gripping member  7  against the upper end of the second gripping member  12 . Then, the upper end portion of the second gripping member  12  is pressed outside in the radial direction by the biasing force of the compression spring  14  and the lower end portion of the second gripping member  12  is moved inside in the radial direction (refer to  FIG. 8 ). 
     As illustrated in  FIG. 10  and  FIG. 11 , the lower end portion of the second gripping member  12  moved inside in the radial direction is positioned outer side than an upper end peripheral edge of the tapered upper end portion of the O ring guide jig O 1 . 
     From the state illustrated in  FIG. 10  and  FIG. 11 , the robot arm  2  is driven so as to move the end effector  4  downward. Consequently, as illustrated in  FIG. 12A , the lower end portion of the second gripping member  12  abuts on the outer surface of the tapered upper end portion of the O ring guide jig O 1  and slides on the tapered surface while pressed and displaced outside in the radial direction. Namely, the lower end portion of the second gripping member  12  lowers along the outer surface of the tapered upper end portion of the O ring guide jig O 1  while displaced from a gripping position toward a releasing position against the repulsive force of the compression spring  14 . Here, the gripping position unit a position of the lower end portion of the second gripping member  12  in the state of gripping the O ring O 2  and the releasing position unit a position of the lower end portion of the second gripping member  12  in the state of releasing the O ring O 2 . 
     Since the O ring O 2  is previously fitted to the tapered upper end portion of the O ring guide jig O 1  using the robot arm  2  and the end effector  4 , the lower end portion of the second gripping member  12  which lowers while sliding on the tapered surface abuts on the O ring O 2 , as illustrated in  FIG. 12B . Accordingly, the O ring O 2  is pressed down along the tapered surface of the O ring guide jig O 1  by the lower end portion of the lowering second gripping member  12  (pressing down step). Namely, the O ring O 2  lowers sliding on the tapered surface of the upper end portion of the O ring guide jig O 1  while enlarging its diameter due to its elasticity. 
     The O ring O 2  which lowers together with the second gripping member  12  passes the tapered upper end portion of the O ring guide jig O 1  and lowers sliding on the straight part of the O ring guide jig O 1 , as illustrated in  FIG. 12C . 
     Then, as illustrated in  FIG. 12D , the O ring O 2  passed the lower end portion of the straight part of the O ring guide jig O 1  contracts its diameter which has been enlarged by the O ring guide jig O 1  by its elasticity. The O ring groove  17  which is formed on the side peripheral surface of the assembly component  16  is located in a position corresponding to the lower end portion of the straight part of the O ring guide jig O 1 . Accordingly, the O ring O 2  which is released from the O ring guide jig O 1  and contracts its diameter fits into the O ring groove  17  formed on the side peripheral surface of the assembly component  16 . 
     After finishing the fitting work of the O ring O 2  into the O ring groove of the assembly component  16 , the first gripping member  7  is moved inside in the radial direction again so as to press in the upper end portion of the second gripping member  12 , thereby displacing its lower end portion outside in the radial direction. In this state, the robot arm  2  is driven so as to raise the end effector  4  and move the end effector  4  to a predetermined location. 
     Then, the first gripping member  7  is moved outside in the radial direction again so that it retreats from the upper end portion of the second gripping member  12  and also the unit holding mechanism  10  is operated so as to release the holding state of the second object holding unit  9 , thereby removing the second object holding unit  9  from the end effector  4 . 
     In the state that the second object holding unit  9  is removed from the end effector  4 , the robot arm  2  is driven so as to move the end effector  4  above the O ring guide jig O 1 . Subsequently, the O ring guide jig O 1  is gripped by the first gripping member  7  and pulled upward so as to be removed from the assembly component  16  and transferred to and placed in a predetermined location. 
     According to the above-mentioned series of steps, the fitting work of the O ring O 2  into the O ring mounting groove  17  of the assembly component  16  is finished. 
     Note that, although the unit holding mechanism  10  is used for holding the second object holding unit  9  as mentioned above, it also can be used for holding a third type of object to be handled. The robot arm  2  is driven in a state that the third type of object to be handled is held by the unit holding mechanism  10  so as to transfer the third type of object to be handled to a predetermined location. 
     As stated above, according to this embodiment, the second object holding unit  9  can be used when holding the O ring O 2  and transferring it up to the O ring guide jig O 1  and also it can be used when pressing down the O ring O 2  along the outer surface of the O ring guide jig O 1  so as to move it up to the guide groove  17  of the assembly component  16 . Therefore, the fitting work of the O ring O 2  into the O ring mounding groove  17  can be performed in a short time in a few work processes by a simple configuration. 
     Additionally, according to this embodiment, the first object holding mechanism  6  and the unit holding mechanism  10  are provided to the end effector base portion  5 , and also the second gripping member  12  of the second object holding unit  9  held by the unit holding mechanism  10  is driven by the first gripping member  7  of the first object holding mechanism  6 . Therefore, it can considerably enlarge a range of kinds and sizes of objects which can be handled while suppressing increase of manufacturing cost of the industrial robot  1 , decline in credibility accompanying complication of the configuration, and increase in space for installing exchanged hands. 
     Additionally, the unit holding mechanism  10  for holding the second object holding unit  9  can be used for holding an object to be handled, and therefore the range of kinds and sizes of objects which can be handled can be further enlarged. 
     Note that, although the case when the second type of object to be handled is the O ring was described in the above-stated example, the second type of object to be handled in the present invention is not limited to the O ring, and annular or c-shaped components having elasticity such as an oil seal and a snap ring will be handled widely. 
     Additionally, although the second object holding unit (elastic component holding unit)  9  is detachable relative to the end effector base portion  5  in the above-stated example, this is not necessarily essential in the present invention and the elastic component holding unit also can be fixedly provided to the end effector base portion. 
     Additionally, although the case when the O ring O 2  is fitted into the O ring mounting groove of the assembly component  16  via the O ring guide jig O 1  was described in the above-stated example, this is not necessarily essential in the present invention and also an elastic component such as the O ring can be fitted using a tapered shape of the assembly component itself, for example. 
     DESCRIPTION OF REFERENCE NUMERALS 
     
         
           1  . . . industrial robot 
           2  . . . robot arm 
           3  . . . wrist shaft 
           4  . . . end effector (hand) 
           5  . . . end effector base portion 
           6  . . . first object holding mechanism (object holding unit) 
           7  . . . first gripping member (object gripping member) 
           8  . . . gripping member drive unit 
           9  . . . second object holding unit (elastic component holding unit) 
           10  . . . unit holding mechanism 
           11  . . . unit body 
           12  . . . second gripping member (elastic component gripping member) 
           12 A . . . recessed portion of second gripping member 
           13  . . . pivot support pin 
           14  . . . compression spring (biasing unit) 
           15  . . . stopper member 
           16  . . . assembly component 
           17  . . . O ring mounting groove of assembly component 
         O 1  . . . first type of object to be handled (O ring guide jig) 
         O 2  . . . second type of object to be handled (O ring)