Patent Publication Number: US-9895815-B2

Title: Multiple joints robot with mechanism for cooling motor

Description:
RELATED APPLICATIONS 
     The present application is a divisional application of U.S. patent application Ser. No. 14/015,810, filed Aug. 30, 2013, which is based on, and claims priority from Japanese Application Number 2012-191342, filed Aug. 31, 2012, and U.S. Provisional Application No. 61/697,914, filed Sep. 7, 2012 the disclosure of which is hereby incorporated by reference herein in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. The Field of the Invention 
     The present invention relates to a multiple joint robot. 
     2. Description of the Related Art 
     A multiple joint robot is often used in a harsh environment that is frequently exposed to splashes or dust, or in a corrosive environment. Thus, components such as a motor for driving an arm are often accommodated in the interior isolated from the exterior in order to prevent malfunction thereof. Such a configuration tends to make it difficult to sufficiently dissipate heat generated from a heat source such as the motor when the robot is in operation. JP-U-62-25193, JP-A-1-274993, and JP-A-9-323286 disclose a structure for enhancing a heat releasing effect by providing a heat conducting member in a gap between a heat generating portion of a motor and a structural member of a robot. 
     There is still a need for a multiple joint robot provided with a cooling structure for cooling a motor accommodated in a closed space. 
     SUMMARY OF THE INVENTION 
     According to a first aspect, a multiple joint robot comprises: a movable body; a motor for generating power to actuate the movable body; a motor housing for accommodating the motor in an interior thereof so as to isolate the motor from an exterior; and a cooling structure for cooling the motor by dissipating heat generated from the motor, wherein the motor has a heat generating surface on which heat is generated, wherein the cooling structure includes a heat conductor situated in the interior of the motor housing, the heat conductor forming a heat conducting path for conducting heat from the motor to the motor housing, and wherein the heat conductor has a first contact surface adapted to be in contact with the heat generating surface of the motor, and a second contact surface adapted to be in contact with an inner surface of the motor housing, so as to form the heat conducting path through an adjustment of a position of the heat conductor by sliding at least one of the first contact surface and the second contact surface on the opposed heat generating surface or inner surface. 
     According to a second aspect, in the multiple joint robot according to the first aspect, the heat generating surface of the motor and the inner surface of the motor housing extend in an inclined manner relative to each other, and the first contact surface and the second contact surface extend in an inclined manner relative to each other, so as to form an angle therebetween, respectively, and the heat conductor is adapted to form the heat conducting path by sliding one of the first contact surface and the second contact surface of the heat conductor on the opposed heat generating surface or inner surface, until the other of the first contact surface and the second contact surface comes in contact with the opposed heat generating surface or inner surface. 
     According to a third aspect, in the multiple joint robot according to the first aspect, the heat generating of the motor and the inner surface of the motor housing extend parallel to each other, and the first contact surface and the second contact surface of the heat conductor extend parallel to each other, respectively, the heat conductor includes a first heat conductor forming the first contact surface and a second heat conductor separate from the first heat conductor, the second heat conductor forming the second contact surface, and the heat conductor is adapted to form the heat conducting path by sliding one of the first contact surface of the first heat conductor and the second contact surface of the second heat conductor on the opposed heat generating surface or inner surface, until the first heat conductor and the second heat conductor comes in contact with each other. 
     These and other objects, features and advantages of the present invention will become more apparent in light of the detailed description of exemplary embodiments thereof as illustrated by the drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a sectional view schematically illustrating a multiple joint robot according to a first embodiment; 
         FIG. 2  is a partially enlarged view illustrating a region II shown in  FIG. 1 ; 
         FIG. 3  is a partially enlarged view illustrating a multiple joint robot according to a second embodiment, corresponding to  FIG. 2 ; 
         FIG. 4  is an enlarged perspective view illustrating the multiple joint robot according to the second embodiment; 
         FIG. 5  is a partially enlarged view illustrating a multiple joint robot according to a third embodiment, corresponding to  FIG. 2 ; 
         FIG. 6  is a partially enlarged view illustrating a multiple joint robot according to a fourth embodiment, corresponding to  FIG. 2 ; 
         FIG. 7  is a partially enlarged view illustrating a multiple joint robot according to a fifth embodiment, corresponding to  FIG. 2 ; and 
         FIG. 8  is an enlarged perspective view illustrating a heat conductor shown in  FIG. 7 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Embodiments of the present invention will be described below with reference to the accompanying drawings. Constituent elements of the illustrated embodiments may be modified in size for better understanding. 
       FIG. 1  is a sectional view schematically illustrating a multiple joint robot  10  according to a first embodiment. The robot  10  includes a base  20  mounted on a mounting surface, a first arm  22  coupled to the base  20  via a joint  30 , a second arm  24  coupled to the first arm  22  via a joint  32 , a third arm  26  coupled to the second arm  24  via a joint  34 , and a wrist part  28  coupled to the third arm  26  via a joint  36 . 
     The respective joints  30 ,  32 ,  34  and  36  are rotatable around axes X 1 , X 2 , X 3  and X 4 , respectively, by motors  40  through reduction gear units  42 . The first arm  22  can rotate relative to the base  20  around the axis X 1  at the joint  30 . The second arm  24  can rotate relative to the first arm  22  around the axis X 2  at the joint  32 . The third arm  26  can rotate relative to the second arm  24  around the axis X 3  at the joint  34 . The wrist part  28  can rotate relative to the third arm  26  around the axis X 4  at the joint  36 . The configuration and operation of such a multiple joint robot  10  is widely known in the art, and therefore a further description of which will be omitted herein. 
       FIG. 2  is a partially enlarged view illustrating a region II shown in  FIG. 1 . The region II represents the joint  32  shown in  FIG. 1  and its surroundings. Although a driving unit of the joint  32  will be described below by way of example, it is self-evident that the present embodiments may also apply to any other joints  30 ,  34  and  36 . 
     A driving unit of the joint  32  includes the second arm  24  as an example of a movable body, a motor  40  for generating power to actuate the second arm  24 , and a motor housing  50  for defining an interior  52  in which the motor  40  is accommodated. The motor  40  is isolated from the exterior by the motor housing  50 , so that the motor  40  is protected from direct exposure to dust and splashes, etc., which may exist in the peripheral environment. The motor  40  includes an output shaft  40   a , through which rotational power generated at the motor  40  is output to the reduction gear unit  42 . The reduction gear unit  42  has an input part and an output part, which are not illustrated. The reduction gear unit  42  is coupled to the output shaft  40   a  of the motor  40  at the input part, while coupled to the second arm  24  at the output part. Rotational power provided by the motor  40  is transmitted to the second arm  24  after decelerated by the reduction gear unit  42  at a predetermined deceleration ratio. On the opposite side of the output shaft  40   a , the motor  40  is provided with an encoder  44 , by which information regarding movement of the motor  40  such as a rotational position or rotational velocity is detected. 
     The motor  40  generates heat during its operation. The heat generated from the motor  40  is released to the peripheral environment through an outer surface of the motor  40 . For example, heat is conducted to other components of the robot  10 , such as the reduction gear unit  42  and the second arm  24 , through an attachment part  40   b  of the motor  40  situated on the axis X 2 . In the present embodiment, since the motor  40  is isolated from the exterior by the motor housing  50 , a heat releasing effect achieved by a gas existent in the surroundings of the motor  40  is not sufficient to cool the motor  40 . Thus, according to the present embodiment, a cooling structure is further provided, in addition to the heat conducting path through the attachment part  40   b  of the motor  40 , in order to dissipate heat from the motor  40  and to cool the motor  40 . 
     The cooling structure in the present embodiment includes a heat conductor  80  situated in the interior  52  of the motor housing  50  and forming a heat conducting path which extends from the motor  40  to the motor housing  50 . The heat conductor  80  is formed from a material with good heat conductivity and rigidity, for example, metal such as aluminum. The heat conductor  80  is a plate having an L-shape in cross section which is formed from a pair of flat plates combined together so as to form an angle therebetween, such as a right angle as shown in  FIG. 2 . Although the heat conductor  80  defines a right angle in the illustrated embodiment, the angle may vary, depending on an angle between the heat generating surface  46  of the motor  40  and the inner surface  54  of the motor housing  50 . The heat conductor  80  has a first contact surface  82  which is in contact with the heat generating surface  46  of the motor  40  through an elastically deformable heat conducting sheet  60 , and a second contact surface  84  which is in contact with the inner surface  54  of the motor housing  50  extending substantially perpendicular to the heat generating surface  46 , likewise through an elastically deformable heat conducting sheet  62 . The heat conducting sheets  60  and  62  exhibit good heat conductivity. As an alternative to the heat conducting sheets  60  and  62 , grease with good heat conductivity may be applied between the first contact surface  82  of the heat conductor  80  and the heat generating surface  46  of the motor  40  and/or between the second contact surface  84  of the heat conductor  80  and the inner surface  54  of motor housing  50 . Alternatively, the heat conductor  80  may also be provided in such a way that the first contact surface  82  and the second contact surface  84  thereof are in direct contact with the heat generating surface  46  and the inner surface  54 , respectively, without any intermediate element such as the heat conducting sheets  60  and  62  and grease interposed therebetween. In this fashion, the term “contact” used herein should be construed to include both cases where the two members are in direct contact with each other and where the two members are in indirect contact with each other via other intermediate elements having good heat conductivity interposed therebetween. 
     The heat conductor  80  is fixed by a fixture  70  in the state where the heat conductor  80  is in contact with the heat generating surface  46  of the motor  40  and with the inner surface  54  of the motor housing  50 , respectively. The fixture  70  may be a string-like, band-like or block-like member to be attached around the motor  40  and the heat conductor  80 . Using the fixture  70 , contact between the heat conductor  80  and the motor  40  and between the heat conductor  80  and the motor housing  50  can be maintained. 
     A process for attaching the heat conductor  80  will now be described. First, the first contact surface  82  of the heat conductor  80  is brought into contact with the heat generating surface  46  of the motor  40 . At this stage, the heat conductor  80  has yet to be secured by the fixture  70 , and thus a position of the heat conductor  80  can be freely changed. Once the first contact surface  82  and the heat generating surface  46  come in contact with each other, the first contact surface  82  of the heat conductor  80  is slid on the heat generating surface  46 , until the second contact surface  84  of the heat conductor  80  comes in contact with the opposed inner surface  54  of the motor housing  50 . After the second contact surface  84  and the inner surface  54  are brought into contact with each other, a position of the first contact surface  82  relative to the heat generating surface  46  may be readjusted. 
     In this way, according to the present embodiment, the second contact surface  84  is brought into contact with the inner surface  54  of the motor housing  50  after the first contact surface  82  of the heat conductor  80  comes in contact with the heat generating surface  46  of the motor  40 , by sliding the heat conductor  80  on the heat generating surface  46 . For example, as in the related art, if a heat conductor is simply provided in a gap between a heat generating surface of the motor and an inner surface of the motor housing, it is difficult to bring the heat conductor into close contact with the motor and the housing, since the size of such gaps could vary from one application to another. In contrast, according to the present embodiment, it is possible to adjust a position of the heat conductor  80  so as to bring the second contact surface  84  into contact with the motor housing  50 , even after the first contact surface  82  of the heat conductor  80  comes in contact with the motor  40 . Therefore, it is ensured that the heat conductor  80  is sufficiently in close contact with both of the motor  40  and the motor housing  50 . Once the heat conductor  80  is positioned in place, the heat conductor  80  can be secured by the fixture  70 . In this way, the contact between the heat conductor  80  and the motor  40  and between the heat conductor  80  and the motor housing  50  can be maintained. 
     It should be noted that a sequence of the process can be altered such that the second contact surface  84  of the heat conductor  80  is first brought into contact with the inner surface  54  of the motor housing  50 , and then, the first contact surface  82  is brought into contact with the heat generating surface  46  of the motor  40 . In this case, the heat conductor  80  is slid on the inner surface  54  of the motor housing  50 . In addition, in the case where an intermediate element such as the heat conducting sheets  60  and  62  is interposed between the heat conductor  80  and the motor  40  and between the heat conductor  80  and the motor housing  50 , it is advantageous in that contact between these members can be easily maintained. 
     Next, other embodiments will be described. In the following, matters which have already been described will be omitted from the explanation as necessary. Like elements are designated with the same referential numerals. 
       FIG. 3  is a partially enlarged view illustrating a multiple joint robot according to a second embodiment, corresponding to  FIG. 2 .  FIG. 4  is an enlarged perspective view illustrating the multiple joint robot according to the second embodiment. In the present embodiment, a position adjustable attachment is provided to the motor housing  50  in order to fix the heat conductor  80  to the motor housing  50  and to adjust a position of the heat conductor  80 . 
     By way of example, a position adjustable attachment is shown in  FIG. 3 , which includes bolts  72  and elongated bores  66  formed in a wall of the motor housing  50 , to which the bolts  72  can be inserted. In the illustrated embodiment, two assemblies of the bolts  72  and the elongated bores  66  are arranged side by side. The elongated bores  66  are formed so as to have an elongated shape in a direction substantially perpendicular to the heat generating surface  46  of the motor  40  (an upper/lower direction in the  FIGS. 3 and 4 ). The heat conductor  80  is provided with threaded holes configured to receive the bolts  72 . The heat conductor  80  can be secured to the motor housing  50  by screwing the bolts  72  into the threaded holes of the heat conductor  80  through the elongated bores  66 . 
     In the present embodiment, prior to the heat conductor  80  being fixed to the motor housing  50  by the bolts  72 , a position of the heat conductor  80  can be freely adjusted within a range in which the elongated bores  66  and the threaded holes of the heat conductor  80  overlap. Thus, even after the heat conductor  80  comes in contact with the heat generating surface  46 , a position of the heat conductor  80  is still adjustable by loosening fastening force by the bolts  72  so as to allow the heat conductor  80  to be slid on the heat generating surface  46  of the motor  40 . In this way, according to the present embodiment, after the first contact surface  82  of the heat conductor  80  comes in contact with the opposed heat generating surface  46  of the motor  40 , it is still possible to adjust a position of the second contact surface  84  relative to the inner surface  54  of the motor housing  50 . 
       FIG. 5  is a partially enlarged view illustrating a multiple joint robot according to a third embodiment, corresponding to  FIG. 2 . In the present embodiment, the heat conductor  80  is the same as those of the first and second embodiments. However, the heat conductor  80  is fixed in the state where the first contact surface  82  thereof is pressed against the heat generating surface  46  of the motor  40  by bolts  74 . The bolts  74  penetrate threaded holes (not shown) extending through an inner surface  56  of the motor housing  50  facing the heat generating surface  46  of the motor  40 , and therefore the bolts  74  protrude into the interior  52 . Accordingly, a position of the first contact surface  82  of the heat conductor  80  can be adjusted in relation to the heat generating surface  46  of the motor  40 , by changing a length of protrusion of the bolts  74  into the interior  52 . 
     According to the present embodiment, after the second contact surface  84  of the heat conductor  80  is brought into contact with the inner surface  54  of the motor housing  50 , the heat conductor  80  can be slid on the inner surface  54  by changing a protruding length of the bolts  74  into the interior  52 . In this way, contact between the heat conductor  80  and the heat generating surface  46  and between the heat conductor  80  and the inner surface  54  can be ensured. 
       FIG. 6  is a partially enlarged view illustrating a multiple joint robot according to a fourth embodiment, corresponding to  FIG. 2 . In the present embodiment, the heat conductor  80  includes a first heat conductor  86  and a second heat conductor  88 . The first heat conductor  86  is a member of L-shape in cross section which includes a parallel portion  86   a  having a first contact surface  82  and extending parallel to the heat generating surface  46  of the motor  40 , and an orthogonal portion  86   b  extending from an end of the parallel portion  86   a  substantially at a right angle toward an inner surface  56  of the motor housing  50  which extends parallel to the heat generating surface  46 . The first heat conductor  86  and the second heat conductor  88  may have the same dimension or different dimensions. 
     The parallel portion  86   a  of the first heat conductor  86  is fixed to the motor  40  by a first fixture  76   a , while its first contact surface  82  is in contact with the heat generating surface  46  of the motor  40 . The orthogonal portion  86   b  of the first heat conductor  86  and the orthogonal portion  88   b  of the second heat conductor  88  are in contact with each other and fixed to each other by a second fixture  76   b . In this way, according to the present embodiment, the first heat conductor  86  and the second heat conductor  88  can remain in contact with the motor  40  and the motor housing  50  by the first fixture  76   a  and the second fixture  76   b , respectively. 
     In the present embodiment, the first heat conductor  86  is first brought into contact with the motor  40 . During this process, the first fixture  76   a  has yet to be secured, and thus a position of the first heat conductor  86  can be freely adjusted. Then, the first heat conductor  86  is fixed to the motor  40  by the first fixture  76   a , while the first contact surface  82  of the first heat conductor  86  is in contact with the heat generating surface  46  of the motor  40 . 
     Subsequently, the second heat conductor  88  is brought into contact with the inner surface  56  of the motor housing  50 . During this process, the second heat conductor  88  has yet to be fixed, and thus a position of the second heat conductor  88  can be freely adjusted. After the second contact surface  84  is brought into contact with the inner surface  56 , the second heat conductor  88  is slid on the inner surface  56 , until the orthogonal portion  88   b  of the second heat conductor  88  comes in contact with the orthogonal portion  86   b  of the first heat conductor  86 . 
     When the orthogonal portion  86   b  of the first heat conductor  86  and the orthogonal portion  88   b  of the second heat conductor  88  are brought into contact with each other so as to allow for sufficient heat conduction therebetween, the first heat conductor  86  and the second heat conductor  88  are fixed to each other by securing the second fixture  76   b  to the orthogonal portions  86   b  and  88   b . In this way, the contacting states can be maintained between the first heat conductor  86  and the motor  40 , between the second heat conductor  88  and the motor housing  50  and between the first heat conductor  86  and the second heat conductor  88 , respectively. According to the present embodiment, it is ensured that a heat conductive path can be established between the heat generating surface  46  of the motor  40  and the inner surface  56  of the motor housing  50  which extends parallel to the heat generating surface  46 . Although the exemplary configuration in which the first heat conductor  86  is fixed first, and the second heat conductor  88  is then slid on the inner surface  56  of the motor housing  50  has been described above, another configuration may be employed, in which the first heat conductor  86  and the second heat conductor  88  are coupled to each other by sliding the first heat conductor  86  on the heat generating surface  46  of the motor  40  after the second heat conductor  88  is fixed to the motor housing  50 . 
       FIG. 7  is a partially enlarged view illustrating a multiple joint robot according to a fifth embodiment, corresponding to  FIG. 2 , and  FIG. 8  is an enlarged perspective view illustrating the heat conductor shown in  FIG. 7 . In the present embodiment, similarly as the fourth embodiment, a heat conductive path is established by the first heat conductor  86  and the second heat conductor  88 . As means for fixing the first heat conductor  86  and the second heat conductor  88 , instead of the first second fixture  76   b , bolts  78  are used in the present embodiment. As shown more clearly in  FIG. 8 , two elongated bores  90  spaced apart from each other are provided in the orthogonal portion  88   b  of the second heat conductor  88 . The respective elongated bores  90  are formed so as to have an elongated shape in a direction substantially perpendicular to the second contact surface  84 . The orthogonal portion  86   b  of the first heat conductor  86  is provided with threaded holes for receiving the bolts  78 . This allows the first heat conductor  86  and the second heat conductor  88  to be fixed to each other by screwing the bolts  78  to the threaded holes of the first heat conductor  86  through the elongated bores  90  of the second heat conductor  88 . 
     In the same way as the fourth embodiment described above, the first heat conductor  86  is fixed by the first fixture  76   a  while contacting with the motor  40 . When positioning the second heat conductor  88 , the second heat conductor  88  has yet to be secured, a position of the second heat conductor  88  relative to the inner surface  56  of the motor housing  50  can be adjusted by changing a fastened position of the bolts  78  in the elongated bores  90 . While the second contact surface  84  of the second heat conductor  88  is in contact with the inner surface  56 , the second heat conductor  88  is fastened with the first heat conductor  86  by the bolts  78 . In this way, the contacting states can be maintained between the first heat conductor  86  and the motor  40 , between the second heat conductor  88  and the motor housing  50 , and between the first heat conductor  86  and the second heat conductor  88 , respectively. Although the elongated bores  90  are provided in the second heat conductor  88 , the first heat conductor  86  may be instead provided with similar elongated bores. 
     Although various embodiments of the present invention have been described above, it is evident to a person skilled in the art that the present invention can also be implemented by any combination of features of the embodiments either explicitly or implicitly disclosed herein. An arm is illustrated by way of example as a movable object, but a swing table may be used as a movable object. Although the embodiments in which the motor has a flat heat generating surface have been described for simplification, a scope of the present invention also extends to the case where the heat generating surface is not flat, but may be curved, for example. 
     Effect of the Invention 
     According to the first aspect, a position of the heat conductor can be adjusted by sliding at least one of the first contact surface and the second contact surface of the heat conductor on the opposed heat generating surface or inner surface. Thus, even after one of the first contact surface and the second contact surface is brought into contact with the motor or the motor housing, a position of the other contact surface can be still adjusted. Therefore, for example, even in the case where the heat conductor has varied thicknesses, where the motor housing has a rough inner surface or an inclined inner surface, or where a gap between the motor and the motor housing is not constant, the heat conductor can be still brought into close contact with both of the motor and the motor housing. 
     According to the second aspect, one of the contact surfaces is brought into contact with the opposed heat generating surface or inner surface by sliding the other of the contact surfaces on the opposed heat generating surface or inner surface. Accordingly, even in the case where the heat generating surface of the motor and the inner surface of the motor housing incline relative to each other, the heat conductor can be still brought into close contact with both of the motor and the motor housing. 
     According to the third aspect, the first heat conductor and the second heat conductor are brought into contact with each other by sliding one of the first heat conductor and the second heat conductor on the opposed heat generating surface or inner surface. Therefore, even in the case where the heat generating surface of the motor and the inner surface of the motor housing extend parallel to each other, close contact can be realized between the first heat conductor and the motor, between the second heat conductor and the motor housing, and between the first heat conductor and the second heat conductor, respectively. 
     Although the invention has been shown and described with exemplary embodiments thereof, it should be understood by a person skilled in the art that the foregoing and various other changes, omissions and additions may be made therein and thereto without departing from the spirit and scope of the invention.