Patent Publication Number: US-2022238788-A1

Title: Robot and end effector

Description:
The present application is based on, and claims priority from JP Application Serial Number 2021-009360, filed Jan. 25, 2021, the disclosure of which is hereby incorporated by reference herein in its entirety. 
     BACKGROUND 
     1. Technical Field 
     The present disclosure relates to a robot and an end effector. 
     2. Related Art 
     For example, a robot disclosed in JP-A-2015-71214 includes an end effector having a gripping function at the distal end of a robot arm and uses an ultrasonic motor as a rotary drive source. When work of feeding, removing, transport, assembly, etc. of precision apparatuses and components forming the apparatuses is performed, downsizing of the end effector and the robot arm is required with downsizing of the precision apparatuses and the components forming the apparatuses. 
     However, in the robot disclosed in JP-A-2015-71214, there is a problem that downsizing of the end effector and the robot arm is difficult in view of the structure. 
     SUMMARY 
     A robot including a manipulator having a plurality of joints and a base supporting the manipulator, includes a first piezoelectric motor and a second piezoelectric motor respectively having vibrators that transmit drive forces to a driven portion and performing rotary driving, wherein a distance between a rotation axis and the vibrator is smaller in the second piezoelectric motor than in the first piezoelectric motor, a plurality of the vibrators are placed along rotation axis directions in the second piezoelectric motor, and the second piezoelectric motor is placed closer to a distal end side opposite to the base than the first piezoelectric motor. 
     An end effector is attached to a distal end of a manipulator, and includes a first piezoelectric motor and a second piezoelectric motor respectively having vibrators that transmit drive forces to a driven portion and performing rotary driving, wherein a distance between a rotation axis and the vibrator is smaller in the second piezoelectric motor than in the first piezoelectric motor, a plurality of the vibrators are placed along rotation axis directions in the second piezoelectric motor, and the second piezoelectric motor is placed closer to a distal end side opposite to the manipulator than the first piezoelectric motor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing a robot according to a first embodiment. 
         FIG. 2  is a plan view showing an end effector of the robot. 
         FIG. 3  is a sectional view showing a first piezoelectric motor of the end effector in  FIG. 2 . 
         FIG. 4  is a plan view showing a vibrator of the first piezoelectric motor in  FIG. 3 . 
         FIG. 5  is a sectional view showing a second piezoelectric motor of the end effector in  FIG. 2 . 
         FIG. 6  a sectional view showing a second piezoelectric motor of a robot according to a second embodiment. 
     
    
    
     DESCRIPTION OF EXEMPLARY EMBODIMENTS 
     1. First Embodiment 
     First, a robot  1  according to a first embodiment will be explained with reference to  FIGS. 1 to 5 . 
     For convenience of explanation, in the following drawings, an X-axis, a Y-axis, and a Z-axis are shown as three axes orthogonal to one another. Further, directions along the X-axis are referred to as “X directions”, directions along the Y-axis are referred to as “Y directions”, and directions along the Z-axis are referred to as “Z directions”. Furthermore, the arrow-head sides of the individual axes are also referred to as “plus sides”, and the opposite sides to the arrow-heads are also referred to as “minus sides”. 
     The robot  1  shown in  FIG. 1  may perform work of e.g. feeding, removing, transport, assembly, etc. of precision apparatuses and components forming the apparatuses. The application of the robot  1  is not limited to that. The robot  1  is a vertical articulated robot having a plurality of joints and includes a base  2  and a manipulator  3 . The manipulator  3  has a first arm  31 , a second arm  32 , a third arm  33 , a fourth arm  34 , a fifth arm  35 , a sixth arm  36 , and an end effector  4 . In the following explanation, the base  2  side of the manipulator  3  is also referred to as “proximal end” or “proximal end side” and the opposite side to the base  2 , i.e., a side away from the base  2  is also referred to as “distal end” or “distal end side”. 
     The base  2  is fixed to a floor, a wall, a ceiling, or the like. The first arm  31  is coupled to the base  2  pivotably around a first arm pivot axis O 1  at the proximal end side of the first arm. The second arm  32  is coupled to the first arm  31  pivotably around a second arm pivot axis O 2  orthogonal to the first arm pivot axis O 1  at the proximal end side of the second arm. The third arm  33  is coupled to the second arm  32  pivotably around a third arm pivot axis O 3  parallel to the second arm pivot axis O 2  at the proximal end side of the third arm. The fourth arm  34  is coupled to the third arm  33  pivotably around a fourth arm pivot axis O 4  orthogonal to the third arm pivot axis O 3  at the proximal end side of the fourth arm. The fifth arm  35  is coupled to the fourth arm  34  pivotably around a fifth arm pivot axis O 5  orthogonal to the fourth arm pivot axis O 4  at the proximal end side of the fifth arm. The sixth arm  36  is coupled to the fifth arm  35  pivotably around a sixth arm pivot axis O 6  orthogonal to the fifth arm pivot axis O 5  at the proximal end side of the sixth arm. The end effector  4  is detachably attached to the distal end side of the sixth arm  36 . 
     Note that, regarding the first arm pivot axis O 1  to sixth arm pivot axis O 6  and a first axis O 7  and a second axis O 8 , which will be described later, “orthogonal” includes a case where an angle between two axes is different within a range of ±5° from 90°, and “parallel” includes a case where one of two axes is inclined within a range of ±5° relative to the other. 
     The robot  1  has a first arm drive unit  51  provided in the coupling portion between the base  2  and the first arm  31  and pivoting the first arm  31  relative to the base  2 , a second arm drive unit  52  provided in the coupling portion between the first arm  31  and the second arm  32  and pivoting the second arm  32  relative to the first arm  31 , a third arm drive unit  53  provided in the coupling portion between the second arm  32  and the third arm  33  and pivoting the third arm  33  relative to the second arm  32 , a fourth arm drive unit  54  provided in the coupling portion between the third arm  33  and the fourth arm  34  and pivoting the fourth arm  34  relative to the third arm  33 , a fifth arm drive unit  55  provided in the coupling portion between the fourth arm  34  and the fifth arm  35  and pivoting the fifth arm  35  relative to the fourth arm  34 , and a sixth arm drive unit  56  provided in the coupling portion between the fifth arm  35  and the sixth arm  36  and pivoting the sixth arm  36  relative to the fifth arm  35 . The individual arm drive units  51  to  56  correspond to the joints of the robot  1 . 
     Each of the first arm drive unit  51  to sixth arm drive unit  56  includes e.g. a motor M as a drive source of the arm, a controller that controls driving of the motor M, a reducer, an encoder, etc. The motor M is not particularly limited, but a piezoelectric motor using expansion and contraction of a piezoelectric element by energization is preferably used. Thereby, for example, compared to a case where an electromagnetic motor or the like is used as the motor M, downsizing of the motor M may be realized. Further, for example, the piezoelectric motor has an advantage in driving at a lower speed and lower torque over an electromagnetic motor and is suitable for driving of the robot  1  because of the advantage. The configuration of the piezoelectric motor is not particularly limited, but may be e.g. the same configuration as a first piezoelectric motor  7  and a second piezoelectric motor  8 , which will be described later. 
     As shown in  FIG. 2 , the end effector  4  has a gripping unit  9  that grips a workpiece, a first holding unit  71  that holds the first piezoelectric motor  7  pivoting the gripping unit  9  around the first axis O 7 , and a second holding unit  81  that holds the second piezoelectric motor  8  pivoting the gripping unit  9  around the second axis O 8  orthogonal to the first axis O 7 . The second piezoelectric motor  8  is placed closer to the distal end side opposite to the manipulator  3  than the first piezoelectric motor  7 . 
     The end effector  4  is attached to the distal end side of the sixth arm  36  via the first holding unit  71  having the first piezoelectric motor  7 . 
     The first holding unit  71  has an L-shape bending at a right angle in the middle, and has a first coupling portion  711  coupling to the distal end side of the sixth arm  36  and a second coupling portion  712  holding the first piezoelectric motor  7  and coupling to the second holding unit  81  having the second piezoelectric motor  8 . Further, the first coupling portion  711  extends in directions orthogonal to the sixth arm pivot axis O 6  of the sixth arm  36  and couples to the second coupling portion  712 , and the second coupling portion  712  extends along the sixth arm pivot axis O 6  of the sixth arm  36  from the coupling part to the first coupling portion  711 . 
     The second holding unit  81  has a first coupling portion  811  coupling to the first piezoelectric motor  7  of the first holding unit  71 , a second coupling portion  812  coupling to a motor holding portion  813 , the motor holding portion  813  holding the second piezoelectric motor  8  inside, and an attachment portion  814  attaching the gripping unit  9 . The first coupling portion  811  extends in directions orthogonal to the first axis O 7  of the first piezoelectric motor  7  and couples to the second coupling portion  812 , and the second coupling portion  812  extends along the first axis O 7  of the first piezoelectric motor  7  from the coupling part to the first coupling portion  811 . The second holding unit  81  has the attachment portion  814  that can detachably attach the gripping unit  9  in the distal end portion of the second holding unit. As described above, the gripping unit  9  is detachably provided for the second holding unit  81 , and thereby, the gripping unit  9  may be easily replaced according to the details of work. Further, the maintenance of the gripping unit  9  is easier. Note that the attachment method of the attachment portion  814  to the gripping unit  9  is not particularly limited, but may be any method including concavo-convex fitting, screwing, fastening by screws, and magnetic attraction. A gap  66  having a size to prevent contact between the second holding unit  81  and the gripping unit  9  when these units pivot around the first axis O 7  is provided between the first coupling portion  711  of the first holding unit  71  and the second coupling portion  812  of the second holding unit  81 . 
     The gripping unit  9  is placed along the second axis O 8  of the second piezoelectric motor  8  and coupled pivotably around the second axis O 8 . The gripping unit  9  has a base portion  91  detachably attached to the attachment portion  814  of the second holding unit  81  and a pair of finger portions  92 ,  93  sliding in directions orthogonal to the second axis O 8 . Further, a driver sliding the finger portions  92 ,  93  is provided within the base portion  91 . Note that the gripping unit  9  of the embodiment grips an object with the pair of finger portions  92 ,  93 , however, the configuration is not limited to that. The number of finger portions may be e.g. three or more. Or, a suction portion that suctions an object by negative pressure may be employed. 
     As shown in  FIG. 3 , the first piezoelectric motor  7  has a housing  72 , a rotor  73  rotatable relative to the housing  72 , and a plurality of vibrators  74  having convex portions  744  in contact with a contact surface  731  as a side surface of the rotor  73 . The housing  72  is fixed to the first holding unit  71 . The rotor  73  is supported by the housing  72  via a bearing  75  and rotatable around the first axis O 7  relative to the housing  72 . The vibrator  74  that transmits a drive force to the rotor  73  as a driven portion is fixed to the housing  72  with the convex portion  744  pressed against the contact surface  731  of the rotor  73  by an urging member (not shown). Note that the plurality of vibrators  74  are placed at a fixed distance L 1  from the first axis O 7 . More specifically, the vibrators are respectively placed at the plus side in the Y direction and the minus side in the Y direction with respect to the first axis O 7 . 
     As shown in  FIG. 4 , the vibrator  74  has a vibrating body  741 , a supporting portion  742  supporting the vibrating body  741 , a coupling portion  743  coupling the vibrating body  741  and the supporting portion  742 , and the convex portion  744  provided on the vibrating body  741  and transmitting vibration of the vibrating body  741  to the rotor  73 . In the vibrating body  741 , five piezoelectric elements  745 A to  745 E are placed. These five piezoelectric elements  745 A to  745 E are each configured to expand and contract in longitudinal directions of the vibrating body  741 . When the piezoelectric elements  745 A to  745 E are expanded and contracted at predetermined timings, the vibrator  74  flexurally vibrates in S shapes and the flexural vibration is transmitted to the rotor  73 , and thereby, the rotor  73  rotates around the first axis O 7  relative to the housing  72 . Accordingly, the first piezoelectric motor  7  may pivot the gripping unit  9  around the first axis O 7 . Note that the vibrator  74  of the first piezoelectric motor  7  performs flexural vibration as in-plane vibration in the YZ-plane, and the plane containing the vibration surface is orthogonal to the first axis O 7  as the rotation axis of the first piezoelectric motor  7 . Therefore, the thickness as the length of the first piezoelectric motor  7  in the X directions may be reduced and the width dimension of the end effector  4  along the first axis O 7  may be reduced. 
     As shown in  FIG. 5 , the second piezoelectric motor  8  is formed by stacking of two piezoelectric motors  8 A,  8 B. Each of the two piezoelectric motors  8 A,  8 B has a plurality of vibrators  84  that transmit drive forces to a rotor  83  as a driven portion. Note that the vibrators  84  have the same configurations as the above described vibrators  74  of the first piezoelectric motor  7 . 
     Each of the two piezoelectric motors  8 A,  8 B has a housing  82 , the rotor  83  rotatable relative to the housing  82 , and the plurality of vibrators  84  having convex portions  844  in contact with a contact surface  832  of the rotor  83 . The housing  82  is fixed to the second coupling portion  812 . The rotor  83  is supported by the housing  82  via a bearing  85  and rotatable around the second axis O 8  relative to the housing  82 . The rotor  83  has a projecting portion  831  projecting in the outer circumferential direction and the contact surface  832  in contact with the convex portion  844  of the vibrator  84  is provided on the projecting portion  831 . The attachment portion  814  is coupled to one portion of the rotor  83  of the piezoelectric motor  8 A and the rotor  83  of the piezoelectric motor  8 B is coupled to the other portion of the rotor  83  of the piezoelectric motor  8 A. The vibrator  84  is fixed to the housing  82  with the convex portion  844  pressed against the contact surface  832  of the rotor  83  by an urging member (not shown). 
     Note that the plurality of vibrators  84  are placed at a fixed distance L 2  from the second axis O 8  along the second axis O 8  directions as the rotation axis directions of the second piezoelectric motor  8 . More specifically, the vibrators are respectively placed at the plus side in the X direction and the minus side in the X direction with respect to the second axis O 8 . The second piezoelectric motor  8  has lower torque because the distance L 2  between the second axis O 8  as the rotation axis of the second piezoelectric motor  8  and the vibrator  84  is smaller than the distance L 1  between the first axis O 7  as the rotation axis of the first piezoelectric motor  7  and the vibrator  74 , in other words, the diameter of the rotor  83  of the second piezoelectric motor  8  is smaller than the diameter of the rotor  73  of the first piezoelectric motor  7 . Accordingly, to provide equal torque to that of the first piezoelectric motor  7 , the second piezoelectric motor  8  is formed using the two piezoelectric motors  8 A,  8 B. The two piezoelectric motors  8 A,  8 B having the rotors  83  with the smaller diameters are stacked, and thereby, the width dimension as the length of the second piezoelectric motor  8  in the X directions may be reduced and the width dimension of the end effector  4  along the first axis O 7  may be reduced. 
     When the vibrator  84  is flexurally vibrated in S shapes, the vibration is transmitted to the rotor  83  and the rotor  83  rotates around the second axis O 8 . Accordingly, the second piezoelectric motor  8  may pivot the gripping unit  9  around the second axis O 8  orthogonal to the first axis O 7 . Note that the vibrator  84  of the second piezoelectric motor  8  performs flexural vibration as in-plane vibration in the YZ-plane, and the plane containing the vibration surface is along the second axis O 8  as the rotation axis of the second piezoelectric motor  8 . 
     The first piezoelectric motor  7  of the end effector  4  of the embodiment corresponds to a seventh joint as the second joint from the distal end of the manipulator  3 , and the second piezoelectric motor  8  corresponds to an eighth joint at the most distal end of the manipulator  3 . Accordingly, the robot  1  of the embodiment is an articulated robot having eight joints. 
     In the embodiment, the first piezoelectric motor  7  and the second piezoelectric motor  8  are placed in the end effector  4  having the gripping unit  9 , however, the first piezoelectric motor  7  may be placed in the fifth arm drive unit  55  near the base  2  and the second piezoelectric motor  8  may be placed in the sixth arm drive unit  56  placed at the distal end side opposite to the base  2 . In other words, the piezoelectric motor  7  may be placed in the fifth arm drive unit  55  as the second joint from the distal end of the manipulator  3 , and the second piezoelectric motor  8  may be placed in the sixth arm drive unit  56  as the joint at the most distal end. Therefore, the gripping unit  9  is attached to the second piezoelectric motor  8 , and thereby, the same function as the end effector  4  may be fulfilled without the end effector  4 . 
     As described above, in the end effector  4  of the robot  1  of the embodiment, the first piezoelectric motor  7  having the rotor  73  with the larger diameter and having the smaller thickness is placed at the base  2  side and the second piezoelectric motor  8  having the rotor  83  with the smaller diameter and having the smaller width dimension is placed at the distal end side opposite to the base  2 , and thereby, downsizing of the end effector  4  may be realized. Therefore, the robot  1  easily performing work in a narrow area is obtained. 
     2. Second Embodiment 
     Next, a robot  1   a  according to a second embodiment will be explained with reference to  FIG. 6 . 
     The robot  1   a  of the embodiment is the same as the robot  1  of the first embodiment except that the configuration of a second piezoelectric motor  8   a  of an end effector  4   a  is different. The embodiment will be explained with a focus on the differences from the above described first embodiment and the explanation of the same items will be omitted. 
     As shown in  FIG. 6 , the end effector  4   a  of the robot  1   a  has the second piezoelectric motor  8   a  in which three piezoelectric motors  8 A,  8 B,  8 C are stacked. 
     Each of the three piezoelectric motors  8 A,  8 B,  8 C has the housing  82 , the rotor  83  rotatable relative to the housing  82 , and the plurality of vibrators  84  having convex portions  844  in contact with the contact surface  832  of the rotor  83 . The housing  82  is fixed to the second coupling portion  812 . The rotor  83  is supported by the housing  82  via the bearing  85  and rotatable around the second axis O 8  relative to the housing  82 . The rotor  83  has the projecting portion  831  projecting in the outer circumferential direction and the contact surface  832  in contact with the convex portion  844  of the vibrator  84  is provided on the projecting portion  831 . The attachment portion  814  is coupled to one portion of the rotor  83  of the piezoelectric motor  8 A, the rotor  83  of the piezoelectric motor  8 B is coupled to the other portion of the rotor  83  of the piezoelectric motor  8 A, and the rotor  83  of the piezoelectric motor  8 C is coupled to the rotor  83  of the piezoelectric motor  8 B at the opposite side to the piezoelectric motor  8 A. The vibrator  84  is fixed to the housing  82  with the convex portion  844  pressed against the contact surface  832  of the rotor  83  by an urging member (not shown). Note that the plurality of vibrators  84  are respectively placed at the plus side in the X direction and the minus side in the X direction with respect to the second axis O 8  along the second axis O 8  directions as the rotation axis directions of the second piezoelectric motor  8 . 
     The second piezoelectric motor  8   a  is formed by stacking of the three piezoelectric motors  8 A,  8 B,  8 C, and thereby, the torque of the second piezoelectric motor  8   a  may be increased with the width dimension of the end effector  4   a  along the first axis O 7  kept. 
     According to the configuration, the second piezoelectric motor  8   a  with the higher torque may be placed and the same effects as those of the robot  1  of the first embodiment may be obtained.