Patent Publication Number: US-2016221185-A1

Title: Robot

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application claims priority under 35 U.S.C. §119 to Japanese Patent Application No. 2015-015706, filed Jan. 29, 2015. The contents of this application are incorporated herein by reference in their entirety. 
     BACKGROUND 
     1. Field of the Invention 
     The embodiments disclosed herein relate to a robot. 
     2. Discussion of the Background 
     Japanese Unexamined Patent Application Publication No. 2003-200376 discloses an industrial robot that includes a base, a turnable base, a lower arm, and an upper arm. The turnable base turns about an S axis relative to the base. The lower arm swings about an L axis relative to the turnable base. The upper arm swings about a U axis relative to the lower arm. The lower arm operates by a motor that is coaxial with the L axis, and the upper arm operates by a motor that is coaxial with the U axis. The turnable base operates by a motor that is coaxial with the S axis. The lower arm operates by a motor that is coaxial with the L axis. The upper arm operates by a motor that is coaxial with the U axis. 
     SUMMARY 
     According to one aspect of the present disclosure, a robot includes a base, a turnable portion, an arm, a first motor, and a second motor. The turnable portion is mounted on the base and turnable about a first axis approximately perpendicular to an installation surface on which the base is disposed. The arm is mounted on the turnable portion and swingable about a second axis parallel to the installation surface. The first motor is accommodated in the turnable portion and configured to move the turnable portion about the first axis relative to the base. The first motor includes a body and a protrusion. The body includes an axial dimension in a direction along an output shaft of the first motor and a perpendicular dimension in a direction approximately perpendicular to the output shaft of the first motor. The axial dimension is smaller than the perpendicular dimension. The protrusion protrudes from a first surface of the body in a direction along the output shaft of the first motor and is disposed at a position displaced from the output shaft of the first motor. The second motor is configured to move the arm about the second axis relative to the turnable portion. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the present disclosure and many of the attendant advantages thereof will be readily obtained as the same becomes better understood by reference to the following detailed description when considered in connection with the accompanying drawings, wherein: 
         FIG. 1  is a perspective view of a robot according to an embodiment; 
         FIG. 2  is a side view of the robot illustrated in  FIG. 1 ; 
         FIG. 3  is a rear view of the robot illustrated in  FIG. 1 ; 
         FIG. 4  is a perspective view of a motor illustrating an external appearance of the motor; 
         FIG. 5  is a cross-sectional view of the motor; 
         FIG. 6  illustrates an internal configuration of a base and a turnable portion; and 
         FIG. 7  illustrates where the motor is arranged. 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     The embodiments will now be described with reference to the accompanying drawings, wherein like reference numerals designate corresponding or identical elements throughout the various drawings. 
     Configuration of Robot 
       FIG. 1  is a perspective view of a robot according to this embodiment.  FIG. 2  is a side view of the robot illustrated in  FIG. 1 .  FIG. 3  is a rear view of the robot illustrated in  FIG. 1 . The robot,  1 , illustrated in the drawings is an industrial robot that works on workpieces, not illustrated. 
     As illustrated in  FIGS. 1 to 3 , the robot  1  includes a base  3 , a turnable portion  5 , a first arm  7 , a second arm  9 , and an end base  11 . The base  3 , the turnable portion  5 , the first arm  7 , the second arm  9 , and the end base  11  are coupled to each other in this order from the base end of the robot  1  to the distal end of the robot  1 . 
     The base  3  is fixed to an installation surface and supports the entire robot  1 . 
     The turnable portion  5  is disposed on the base  3 . The turnable portion  5  is turnable about a turning axis, namely, a first axis Ax 1 , which extends in the vertical direction, relative to the base  3 . The turnable portion  5  is driven into turning operation about the first axis Axl by a power source, namely, a first motor, which is accommodated in the turnable portion  5 . The first axis Ax 1  will be occasionally referred to as “S axis”. 
     The first arm  7  is swingable about a swing axis, namely, a second axis Ax 2  relative to the turnable portion  5 . The second axis Ax 2  passes through a connection portion  6  (the end of the first arm  7  on the side of the turnable portion  5 ), at which the turnable portion  5  and the first arm  7  are coupled to each other. The connection portion  6 , at which the turnable portion  5  and the first arm  7  are coupled to each other, is equipped with a second motor. 
     The first arm  7  is driven by a power source, namely, the second motor, which is parallel to the installation surface, into swing operation about the second axis Ax 2 . Specifically, as illustrated in  FIG. 6 , the first arm  7  is swingable in a first direction D 1  (frontward) up to a first swing angle θ 1  relative to a reference line LS. The reference line LS is in a direction approximately perpendicular to the installation surface and passes through the second axis Ax 2 . The first arm  7  is also swingable relative to the reference line LS in a second direction D 2  (rearward), which is opposite to the first direction D 1 , up to a second swing angle θ 2 . The second swing angle θ 2  is smaller than the first swing angle θ 1  (θ 1 &gt;θ 2 ). In a view from a direction along the second axis Ax 2 , the first axis Ax 1  is disposed at a position that is further in the second direction D 2  than the reference line LS. The second axis Ax 2  will be occasionally referred to as “L axis”. 
     The second arm  9  includes a base end  9   a  and a distal end  9   b.  The base end  9   a  is on the side of the first arm  7 , and the distal end  9   b  is on the side of the end base  11 . The base end  9   a  is swingable about a swing axis, namely, a third axis Ax 3  relative to the first arm  7 . The third axis Ax 3  passes through a connection portion  10  (the end of the first arm  7  on the side of the base end  9   a ), at which the first arm  7  and the second arm  9  are coupled to each other. This configuration makes the second arm  9  as a whole swingable about the third axis Ax 3  relative to the first arm  7 . The connection portion  10 , at which the first arm  7  and the second arm  9  are coupled to each other, is equipped with a third motor. The second arm  9  (base end  9   a ) is driven by a power source, namely, the third motor, into swing operation about the third axis Ax 3 . The third axis Ax 3  extends in parallel to the second axis Ax 2 . The third axis Ax 3  will be occasionally referred to as “U axis”. 
     The distal end  9   b  is turnable about a turning axis, namely, a fourth axis Ax 4 , relative to the base end  9   a.  The fourth axis Ax 4  passes through the center of the second arm  9 . The distal end  9   b  is driven by a power source, namely, a fourth motor, into turning operation about the fourth axis Ax 4 . The fourth axis Ax 4  will be occasionally referred to as “R axis”. 
     The end base  11  includes a base end  11   a  and a distal end  11   b.  The base end  11   a  is on the side of the second arm  9 , and the distal end  11   b  is on the side of the distal end of the robot  1 . The base end  11  a is swingable about a swing axis, namely, a fifth axis Ax 5  relative to the distal end  9   b.  The fifth axis Ax 5  passes through a connection portion at which the second arm  9  (distal end  9   b ) and the end base  11  (base end  11   a ) are coupled to each other. The base end  11   a  is driven by a power source, namely, a fifth motor, into swing movement about the fifth axis Ax 5 . The fifth axis Ax 5  will be occasionally referred to as “B axis”. 
     The distal end  11   b  is mounted on the base end  11   a  in a rotatable manner about a rotation axis, namely, a sixth axis Ax 6 , relative to the base end  11   a . The sixth axis Ax 6  passes through the center of the end base  11 . The distal end  11   b  is driven by a power source, namely, a sixth motor, into rotational movement about the sixth axis Ax 6 . The sixth axis Ax 6  will be occasionally referred to as “T axis”. An end effector is attachable to the end base  11 . A non-limiting example of the end effector is a welding torch. 
     Configurations of Motors 
     Next, the first to sixth motors provided in the robot  1  will be described in detail. The first to sixth motors have similar configurations and may hereinafter occasionally be referred to as “motor  20 ” collectively.  FIG. 4  is a perspective view of the motor illustrating an external appearance of the motor  20 .  FIG. 5  is a cross-sectional view of the motor  20 . As illustrated in  FIGS. 4 and 5 , the motor  20  includes a casing (body)  30 , a rotor  40 , a stator  50 , an encoder  60 , and a brake (protrusion)  70 . 
     The casing  30  holds elements such as the rotor  40 , the stator  50 , and the encoder  60 . In this embodiment, the casing  30  has a circular outer shape. The casing  30  includes a first surface  30   a  (second surface), a second surface (first surface)  30   b,  and a third surface  30   c . The first surface  30   a  and the second surface  30   b  are orthogonal to the output shaft, Ax, of the motor  20 . The third surface  30   c  has a circular shape extending along the output shaft Ax. The casing  30  has an axial dimension in a direction along the output shaft Ax of the motor  20  and a perpendicular dimension in direction approximately perpendicular to the output shaft Ax. The axial dimension is smaller than the perpendicular dimension. Specifically, the casing  30  has such a flat shape that dimension L 1 , which is between the first surface  30   a  and the second surface  30   b,  is smaller than dimension L 2 , which is the diameter of the third surface  30   c  (L 1 &lt;L 2 ). In this embodiment, the dimension L 1  is equal to or less than half the dimension L 2 . 
     The rotor  40  includes a rotator  42  and a brake pad  44 . The rotator  42  is a member that can be driven into rotation about the output shaft Ax. The rotator  42  is rotatable by ring-shaped bearings  46   a  and  46   b,  which are fixed to the casing  30 . The bearings  46   a  and  46   b  are aligned in a direction along the output shaft Ax with a predetermined distance between the bearings  46   a  and  46   b.  On the outer surface of the rotor  40 , magnets  48  are aligned in the circumferential direction. The rotator  42  includes a shaft member  43 . The shaft member  43  protrudes from the first surface  30   a  of the casing  30 . 
     The brake pad  44  is a member that performs braking operation as controlled by the brake  70 . The brake pad  44  is disposed over the circumference of the rotator  42 . The brake pad  44  has a ring shape. The brake pad  44  is coaxial with the output shaft Ax. The outer edge of the brake pad  44  is further outward than the outer edge of the rotator  42 . That is, the outer diameter of the brake pad  44  is larger than the outer diameter of the rotator  42 . In this embodiment, the brake pad  44  is made of metal. 
     The stator  50  is a member that imparts rotational force to the rotor  40 . The stator  50  includes a core  52  and a coil  54 . In this embodiment, the core  52  has a ring shape. The core  52  faces the outer surface of the rotator  42 . The coil  54  is disposed on the core  52 . 
     The encoder  60  is a rotation detector that detects the rotation of the rotor  40 . A non-limiting example of the encoder  60  is a rotary encoder capable of detecting amounts by which the motor  20  is driven, such as the number of rotations of the rotor  40 , the rotational angle of the rotor  40 , and/or the rotational speed of the rotor  40 . The encoder  60  is partially disposed in a depression  42   a  of the rotator  42 . 
     The brake  70  is a braking device that causes the rotating rotor  40  to brake. The brake  70  protrudes outward from the second surface  30   b  of the casing  30  along the output shaft Ax. The brake  70  is decentered from the output shaft Ax. The brake  70  includes a case  72 , a friction material  74 , a holding member  76 , a biasing member  78 , and a coil  79 . 
     The case  72  accommodates the holding member  76 , the biasing member  78 , and the coil  79 . In this embodiment, the case  72  is fixed to the casing  30  with a screw. In the embodiment illustrated in  FIG. 4 , the case  72  has a solid cylindrical outer shape. The case  72  may be designed into any convenient shape. 
     The friction material  74  comes into sliding contact with the brake pad  44  of the rotor  40  to impart frictional force to the brake pad  44 . The friction material  74  is disposed on the holding member  76 . Examples of the material of the friction material  74  include, but are not limited to, resin mold, semi-metallic material, and sintered alloy (of iron and/or copper). 
     The holding member  76  holds the friction material  74 . In this embodiment, the holding member  76  is made of metal. The holding member  76  has an approximately T shape. The holding member  76  includes a body  76   a  and a holder  76   b.    
     In this embodiment, the body  76   a  has a solid cylindrical shape. The body  76   a  extends in the direction along the output shaft Ax. In this embodiment, the holder  76   b  has a disc shape. The holder  76   b  is disposed on one end (the end closer to the brake pad  44 ) of the body  76   a.  The outer diameter of the holder  76   b  is larger than the outer diameter of the body  76   a.  The holder  76   b  faces the brake pad  44  of the rotor  40 . That is, the friction material  74  faces the brake pad  44 . 
     The holding member  76  is movable (sliding-movable) in the direction along the output shaft Ax. Specifically, the holding member  76  is movable between a first position (initial position) and a second position. At the first position, the holder  76   b  contacts the coil  79 . At the second position, the friction material  74  sliding-contacts the brake pad  44 . 
     The biasing member  78  biases the holding member  76 . In this embodiment, the biasing member  78  is a coil spring. The biasing member  78  is disposed on the other end of the body  76   a  of the holding member  76 . When the holding member  76  is at the first position, the biasing member  78  biases the holding member  76  toward the rotor  40 . 
     The coil  79  regulates the movement of the holding member  76 . The coil  79  surrounds the body  76   a  of the holding member  76 . When current is supplied through the coil  79 , the coil  79  effects electromagnetic force against the biasing force of the biasing member  78  to pull the holder  76   b  and holds the holding member  76  at the first position. When no current is supplied through the coil  79 , the coil  79  releases the holding member  76 . 
     When supply of current through the coil  79  is discontinued, the brake  70  with the above-described configuration causes the coil  79  to release the holding member  76 , and allows the biasing force of the biasing member  78  to move the holding member  76  toward the rotor  40 . That is, the brake  70  positions the holding member  76  at the second position. Then, the brake  70  causes the friction material  74  to sliding-contact the brake pad  44  to impart frictional force to the brake pad  44 . This configuration causes the rotating rotor  40  to decelerate or stop and prevents the stationary rotor  40  from rotating. 
     When current is supplied through the coil  79 , the brake  70  causes the coil  79  to pull the holding member  76  to separate the friction material  74  and the brake pad  44  from each other. That is, the brake  70  positions the holding member  76  at the first position. This configuration makes the rotor  40  rotatable. 
     Motor Arrangement 
     Next, arrangement of the motor  20  (first motor) with the above-described configuration will be described.  FIG. 6  illustrates an internal configuration of the base  3  and the turnable portion  5 .  FIG. 7  illustrates where the motor  20  is arranged. 
     As illustrated in  FIG. 6 , the first motor  20  is accommodated in the turnable portion  5  and is fixed to the turnable portion  5 . Specifically, the first motor  20  is arranged with the first surface  30   a  of the casing  30  facing the installation surface. Specifically, the motor  20  is disposed in the turnable portion  5  with the brake  70  facing upward. The first motor  20  is fixed to the tamable portion  5  with the output shaft Ax of the first motor  20  coaxial with the first axis Axl. This configuration makes the first motor  20  rotatable together with the turnable portion  5 . The brake  70  of the first motor  20  is disposed on the casing  30  and between the first axis Ax 1  and the reference line LS. More specifically, the brake  70  is on a line that connects the first axis Ax 1  and the reference line LS to each other. 
     The first motor  20  is coupled to a reducer  15 . The reducer  15  is disposed in the base  3  and is fixed to the base  3 . The input shaft of the reducer  15  is coaxial with the output shaft Ax of the first motor  20 . Specifically, the output shaft Ax of the first motor  20  and the input shaft of the reducer  15  are coaxial with the first axis Ax 1 . 
     Advantageous Effects 
     As has been described hereinbefore, in the robot  1  according to this embodiment, the casing  30  of the motor  20  has a smaller axial dimension, which is in the direction along the output shaft Ax, than the perpendicular dimension of the casing  30  in the direction approximately perpendicular to the output shaft Ax. That is, the casing  30  has a flat shape. The brake  70  is disposed at a position displaced from the output shaft Ax. Thus, the motor  20  has a flat casing  30  and a brake  70  offset from the output shaft Ax, and the motor  20  is disposed with its output shaft Ax parallel to the first axis Ax 1 . This configuration decreases the dimension of the motor  20  motor  20  in the direction along the first axis Ax 1  of the turnable portion  5 , which accommodates the motor  20  (that is, the height dimension of the motor  20 ). This configuration avoids contact between the first arm  7  and the turnable portion  5  and increases the second swing angle θ 2  of the first arm  7 . This, as a result, widens the movable range of the robot while preventing an increase in size of the apparatus. 
     In this embodiment, the first motor  20  is fixed to the turnable portion  5  and is rotatable together with the turnable portion  5 . This configuration keeps the position relationship between the first motor  20  and the turnable portion  5  unchanged even while the turnable portion  5  is turning. This eliminates or minimizes complications in the turnable portion  5 , such as wiring of the cables. 
     In this embodiment, the output shaft Ax of the first motor  20  is coaxial with the first axis Ax 1 , and the second surface  30   b  of the casing  30 , which is opposite to the first surface  30   a,  faces the installation surface. The first arm  7  is swingable in the first direction D 1  up to the first swing angle θ 1  relative to the reference line LS, which is in the direction approximately perpendicular to the installation surface and which passes through the second axis Ax 2 . The first arm  7  is also swingable relative to the reference line LS in the second direction D 2 , which is opposite to the first direction D 1 , up to the second swing angle θ 2 . In a view from the direction along the second axis Ax 2 , the first axis Ax 1  is disposed at a position that is further in the second direction D 2  than the reference line LS. The brake  70  of the first motor  20  is disposed on the casing  30  and between the first axis Ax 1  and the reference line LS. Thus, the brake  70  is disposed on the side of the first arm  7 . This configuration involves increasing the height dimension of the turnable portion  5 , which accommodates the first motor  20 , only at a portion that is on the side of the first aim  7  in accordance with the brake  70 . That is, it is not necessary to increase the height dimensions of portions of the turnable portion  5  that are further away from the first arm  7 . This configuration avoids contact between the first arm  7  and the turnable portion  5  while the first arm  7  is swinging in the second direction D 2 , and thus increases the second swing angle θ 2 . This, as a result, widens the movable range of the robot. 
     In this embodiment, the robot  1  includes the reducer  15 . The reducer  15  is coupled to the first motor  20  and has an input shaft coaxial with the output shaft Ax. The reducer  15  is fixed to the base  3 . This configuration eliminates or minimizes an increase in size of the turnable portion  5  and the base  3  in the width direction. This, as a result, minimizes the interference radius of the turnable portion  5  while the turnable portion  5  is turning. 
     The above-described embodiment should not be construed in a limiting sense. For example, while the above-described embodiment has been described as including the first arm  7  and the second arm  9 , an additional arm may be coupled to the second arm  9 . 
     While in the above-described embodiment the motor  20  has been described as having the configuration illustrated in  FIG. 5 , this configuration of the motor  20  should not be construed in a limiting sense. 
     Obviously, numerous modifications and variations of the present disclosure are possible in light of the above teachings. It is therefore to be understood that within the scope of the appended claims, the invention may be practiced otherwise than as specifically described herein.