Abstract:
Provided is a motor enabling more simple and efficient cleaning of the inside of an air path. The motor includes a stator, a housing which holds the stator, a fan arranged outside the stator, a fan cover which houses the fan and is mounted on the housing, an air path including an inlet and an outlet for a cooling gas, and a first cleaning hole extending from a first opening that faces and opens to the air path at a position closer to the outlet than the inlet to a second opening which opens to the outside.

Description:
BACKGROUND ART 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to a motor having an air path of a stator, or a fan cleanable, and a cleaning system of the motor. 
         [0003]    2. Description of the Related Art 
         [0004]    To cool a stator and a rotor during operation of a motor, the motor including a fan, and an air path arranged around the stator and in the rotor in such a manner as to communicate with the fan and allowing an airflow generated by the fan to pass through the interior is known. Conventionally, in such a motor, various elements for cleaning the inside of the air path have been proposed (for example, Japanese Laid-open Patent Publication No. 2007-20258). 
         [0005]    A technique which enables more simple and efficient cleaning of the inside of the air path has been demanded. 
       SUMMARY OF THE INVENTION 
       [0006]    In an aspect of the invention, a motor comprises a stator, a housing which holds the stator, a fan arranged outside the stator, and a fan cover mounted on the housing and housing the fan. 
         [0007]    Further, the motor comprises an air path provided at the stator or the housing and including an inlet and an outlet for a cooling gas; and a first cleaning hole formed at the stator, the housing, or the fan cover, and extending from a first opening which opens to face the air path at a position closer to the outlet than the inlet to a second opening which opens to an outside. 
         [0008]    The motor may comprise a plurality of air paths, and a plurality of first cleaning holes arranged to face the respective air paths. The first opening may be arranged at a position separated from the outlet so as to face the outlet. 
         [0009]    The first opening may be arranged between the inlet and the outlet. An inner wall of the first cleaning hole may be threaded. The motor may further comprise a second cleaning hole formed at the stator, the housing, or the fan cover, and extending from a third opening which opens to face the fan to a fourth opening which opens to the outside. 
         [0010]    The second opening and the fourth opening may be the same one opening. The second cleaning hole may extend from the third opening so as to be connected to the first cleaning hole. The housing may include a hollow part extending between the stator and the fan cover, and having an inner space which is in fluid communication with the air path and the inside of the fan cover. The first cleaning hole may be formed at the hollow part. 
         [0011]    In another aspect of the invention, a cleaning system for cleaning the inside of the stator as described above comprises a fluid supply device for supplying a compressed fluid into the first cleaning hole, and a controller for controlling the fluid supply device. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0012]    The above and other objects, features, and advantages of the invention will be clarified by the following description of embodiments with reference to the accompanying drawings, in which: 
           [0013]      FIG. 1  is a side view of a motor according to an embodiment of the invention, in which a part of the motor is shown cross-sectionally; 
           [0014]      FIG. 2  is a view of the motor shown in  FIG. 1  when seen from axially front side, i.e., from an arrow II in  FIG. 1 , in which a part of the front housing of the motor is omitted; 
           [0015]      FIG. 3  is a view of the motor shown in  FIG. 1  when seen from axially rear side, i.e., from an arrow III in  FIG. 1 ; 
           [0016]      FIG. 4  is an enlarged view of a section in  FIG. 1 , in which the plug in  FIG. 1  is omitted; 
           [0017]      FIG. 5  is a diagram for describing airflow when cleaning the air path of the stator or the fan of the motor shown in  FIG. 1 ; 
           [0018]      FIG. 6  is a view of a motor according to another embodiment of the invention when seen from axially rear side, in which a part of a rear housing of the motor is omitted; 
           [0019]      FIG. 7  is a side view of a motor according to still another embodiment of the invention, in which a part of the motor is shown cross-sectionally; 
           [0020]      FIG. 8  is an enlarged view of the cleaning hole shown in  FIG. 7 ; 
           [0021]      FIG. 9  is a side view of a motor according to still another embodiment of the invention, in which a part of the motor is shown cross-sectionally; 
           [0022]      FIG. 10  is a side view of a motor according to still another embodiment of the invention that cross-sectionally illustrates a part of the motor; 
           [0023]      FIG. 11  is an enlarged view of a section in  FIG. 10 ; 
           [0024]      FIG. 12  is a side view of a motor according to still another embodiment of the invention, in which a part of the motor is shown cross-sectionally; 
           [0025]      FIG. 13  is an enlarged view of a section in  FIG. 12 ; 
           [0026]      FIG. 14  is a side view of a motor according to still another embodiment of the invention, in which a part of the motor is shown cross-sectionally; 
           [0027]      FIG. 15  is an enlarged view of a section in  FIG. 14 ; 
           [0028]      FIG. 16  is a side view of a motor according to still another embodiment of the invention, in which a part of the motor is shown cross-sectionally; 
           [0029]      FIG. 17  is an enlarged view of a section in  FIG. 16 ; 
           [0030]      FIG. 18  is a diagram illustrating a state where a bolt is inserted into the cleaning hole shown in  FIG. 16 ; and 
           [0031]      FIG. 19  is a diagram of a cleaning system according to an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0032]    Hereinafter, embodiments of the invention will be described with reference to the accompanying drawings. First, a motor  10  according to an embodiment of the invention will be described with reference to  FIGS. 1-4 . Note that, in the below description, an axial direction refers to a direction along a rotation axis O of a shaft  12  shown in  FIG. 1 , a radial direction refers to a direction of radius of a circle centered about the axis O, and a circumferential direction refers to a circumferential direction of a circle centered about the axis O. Meanwhile, axial frontward refers to a leftward direction as viewed in  FIG. 1 . 
         [0033]    The motor  10  includes a shaft  12 , a stator  14 , a housing  16 , a fan  18 , and a fan cover  20 . The shaft  12  is provided as to be rotatable relative to the stator  14 . A rotor (not shown) is fixed to the radially outside of the shaft  12 . The stator  14  is comprised of e.g. a plurality of magnetic steel plates stacked in the axial direction, and is fixed to be separated radially outward of the shaft  12 . 
         [0034]    The housing  16  supports the stator  14 . In this embodiment, the housing  16  includes a front housing  16   a  arranged at an axially front (second direction) end  14   a  of the stator  14  and a rear housing  16   b  arranged at an axially rear (first direction) end  14   b  of the stator  14 . 
         [0035]    The fan  18  is e.g. a centrifugal fan which generates an airflow in the axial direction by rotating a rotational body having a plurality of banes. The fan  18  is arranged to be separated axially rearward of the stator  14 . The fan cover  20  is fixed to the rear housing  16   b,  and houses the fan  18  in an inner space S 1  thereof. As shown in  FIG. 3 , the fan cover  20  is formed with a plurality of fan holes  20   a  which allow an outside air to flow into the inner space S 1  and an air in the inner space S 1  to flow out thereof. 
         [0036]    The motor  10  further includes an air path  22  for cooling the stator  14  during operation. In this embodiment, the air path  22  is defined by a through hole formed at a radially outer part of the stator so as to penetrate the stator  14  in the axial direction. 
         [0037]    Specifically, the air path  22  extends in the axial direction from an opening  22   a  (inlet) at axially frontward to an opening  22   b  (outlet) at axially rearward. The opening  22   a  is arranged at the front housing  16   a  in the vicinity of the axially front end  14   a  of the stator  14 , and opens to outside of the motor  10 . 
         [0038]    On the other hand, the opening  22   b  is arranged at the rear housing  16   b  in the vicinity of the axially front end  14   b  of the stator  14 , and opens to an inner space S 2  defined inside of the rear housing  16   b.  The inner space S 2  is in fluid communication with the inner space S 1  of the fan cover  20 . Therefore, the opening  22   b  is in fluid communication with the inner space S 1  of the fan cover  20  through the inner space S 2 . 
         [0039]    In this embodiment, as shown in  FIG. 2 , the stator  14  is formed with a plurality of air paths  22  arranged in the circumferential direction. Note that, instead of the plurality of air paths  22 , only one air path  22  may be provided. 
         [0040]    The motor  10  further includes a first cleaning hole  24  for supplying a compressed fluid from outside into the air path  22 . In this embodiment, the first cleaning hole  24  is constituted by a through hole formed at the fan cover  20  so as to extend in the axial direction. The first cleaning hole  24  is arranged to face one of the plurality of air paths  22 . 
         [0041]    Specifically, as shown in  FIG. 4 , the first cleaning hole  24  extends in the axial direction from an opening  24   a  (first opening) to an opening  24   b  (second opening). The opening  24   a  is arranged axially rearward of the opening  22   b  of the air path  22  so as to face the opening  22   b.  Thus, the opening  24   a  is arranged closer to the opening  22   b  than the opening  22   a  of the air path  22 . 
         [0042]    More specifically, the opening  24   a  is arranged relative to the opening  22   b  so that at least a part of a projection region of the opening  24   a  (for example, 30% or more) overlaps with the opening  22   b  when the opening  24   a  is projected axially frontward so as to overlap with the opening  22   b  of the air path  22 . On the other hand, the opening  24   b  opens to the outside on an outer surface  20   b  of the fan cover  20 . 
         [0043]    The motor  10  further includes a second cleaning hole  26  for supplying the compressed fluid from the outside to the fan  18 . In this embodiment, the second cleaning hole  26  is constituted by a through hole formed at the fan cover  20  so as to extend in the radial direction. 
         [0044]    Specifically, the second cleaning hole  26  extends from an opening  26   a  (third opening) which opens to the inner space S 1  so as to face the fan  18  to an opening  26   b  (fourth opening) which opens to the outside on the outer surface  20   b  of the fan cover  20 . The opening  26   a  is arranged adjacent to the fan  18  at radially outside of the fan  18 . 
         [0045]    As shown in  FIGS. 1 and 3 , the first cleaning hole  24  and the second cleaning hole  26  are ordinarily plugged with plugs  28  and  30 , respectively. The plugs  28  and  30  are removed from the first cleaning hole  24  and the second cleaning hole  26 , respectively, when cleaning the inside of the motor  10 , and a compressed fluid is introduced into each of the first cleaning hole  24  and the second cleaning hole  26  from a fluid supply device or the like (not shown) provided outside. Note that, a cleaning operation on the motor  10  will be described later. 
         [0046]    Next, the function of the motor  10  according to this embodiment will be described with reference to  FIGS. 1-4 . When the motor  10  is operated, heat is generated in the stator  14 , so it is necessary to cool the stator  14 . For this, the fan  18  is driven to generate an airflow which flows axially rearward. 
         [0047]    Then, an outside air (cooling gas) flows into the air path  22  through the opening  22   a,  flows through the air path  22  axially rearward, and flows out from the opening  22   b  of the air path  22  into the inner space S 2  through. The airflow flowing out from the opening  22   b  passes the inner space S 2 , then reaches the fan  18 , and then is discharged from the fan holes  20   a  of the fan cover  20  to the outside. By the airflow flowing through the air path  22  in such a manner, the heat generated in the stator  14  is removed, whereby the stator  14  is cooled. 
         [0048]    As the outside air is introduced into the air path  22  to cool the stator  14 , dusts or the like contained in the outside air may gradually adhere to the inside of the air path  22 . Further, dusts which have entered the air path  22  may be carried by the airflow to reach the fan  18 , and adhere to the fan  18 . 
         [0049]    In this regard, in the motor  10  according to this embodiment, a compressed fluid is fed into the first cleaning hole  24  and the second cleaning hole  26  to sweep out the dusts adhering to the air path  22  and the fan  18 , whereby the air path  22  and the fan  18  of the motor  10  can be cleaned. 
         [0050]    Hereinafter, the flows of the compressed fluid during cleaning of the air path  22  and the fan  18  of the motor  10  will be described with reference to  FIG. 5 . The compressed fluid introduced into the first cleaning hole  24  via the opening  24   b  flows axially frontward and is discharged axially frontward from the opening  24   a.    
         [0051]    As described above, the opening  24   a  is arranged to face the opening  22   b  of the air path  22 . Accordingly, the compressed fluid discharged from the opening  24   a  of the first cleaning hole  24  is effectively introduced into the air path  22  through the opening  22   b.    
         [0052]    Further, according to this embodiment, the first cleaning hole  24  is formed so as to axially extend. Accordingly, the compressed fluid introduced into the first cleaning hole  24  is oriented to be discharged axially frontward, i.e., toward the opening  22   b  of the air path  22 . Due to this, the compressed fluid can be introduced into the air path  22  more effectively. 
         [0053]    The compressed fluid flown into the air path  22  via the opening  22   b  flows through the air path  22  axially frontward, and is discharged from the opening  22   a  to the outside. As the compressed fluid passes through the air path  22 , the dusts adhering into the air path  22  are gradually swept away, and are discharged from the opening  22   a  to the outside together with the compressed fluid. 
         [0054]    Thus, according to this embodiment, it is possible to sweep out the dusts adhering into the air path  22  only by introducing the compressed fluid into the first cleaning hole  24 . Therefore, it is not necessary to disassemble the motor  10  for cleaning the inside of the air path  22 , so the air path  22  can be cleaned in an easy and cost-effective manner. 
         [0055]    On the other hand, a compressed fluid introduced into the second cleaning hole  26  is discharged from the opening  26   a  radially inward. As described above, the opening  26   a  of the second cleaning hole  26  is arranged to face the fan  18 . Accordingly, the compressed fluid discharged from the opening  24   a  of the first cleaning hole  24  is effectively blown to the fan  18 . 
         [0056]    The dusts adhering to the fan  18  are blown off due to the compressed fluid blown to the fan  18 , pass the inner space S 2  together with the compressed fluid, and flow into the air path  22 . Then, the dusts join a compressed gas flown from the first cleaning hole  24 , and are swept away from the opening  22   a  of the air path  22  to the outside. Whereby, the dusts adhering to the fan  18  can be swept away to the outside. 
         [0057]    Thus, according to this embodiment, it is possible to sweep out the dusts adhering to the fan  18  only by introducing the compressed fluid into the second cleaning hole  26 . Accordingly, it is possible to clean the fan  18  in an easy and cost-effective manner, without disassembling the motor  10 . 
         [0058]    Next, a motor  40  according to another embodiment of the invention will be described with reference to  FIG. 6 . Note that, in various embodiments described below, elements similar to those in the already-mentioned embodiments are assigned the same reference numerals, and the detailed description thereof will be omitted. The motor  40  according to this embodiment differs from the above-mentioned motor  10  in a fan cover  42 . 
         [0059]    Specifically, the motor  40  includes a fan cover  42  which houses a fan (not shown) inside thereof, and the fan cover  42  is formed with a plurality of first cleaning holes  24  arranged to face the respective air paths  22  (see  FIG. 2 ). According to this embodiment, when a compressed fluid is introduced into the first cleaning holes  24 , it is possible to effectively introduce the compressed fluid into the respective air paths  22 . 
         [0060]    Next, a motor  50  according to still another embodiment of the invention will be described with reference to  FIGS. 7 and 8 . The motor  50  includes the shaft  12 , the stator  14 , a housing  52 , the fan  18 , and a fan cover  54 . 
         [0061]    The housing  52  according to this embodiment includes the front housing  16   a  similar to that in the above-mentioned embodiments; and a rear housing  52   b  arranged at the axially rear end  14   b  of the stator  14 . The fan cover  54  is fixed to the rear housing  52   b,  and houses the fan  18  in the inner space S 1  thereof. The fan cover  54  according to this embodiment has a configuration similar to that of the above-mentioned fan cover  20 , except that the second cleaning hole  26  is not formed in the fan cover  54 . 
         [0062]    The motor  50  further includes a (first) cleaning hole  56  formed at the rear housing  52   b.  As shown in  FIG. 8 , the cleaning hole  56  extends from an opening  56   a  (first opening), which opens so as to face the opening  22   b  of the air path  22 , to an opening  56   b  (second opening), which opens to the outside on an outer surface  52   c  of the rear housing  52   b.    
         [0063]    The cleaning hole  56  includes a first hole part  56   c  extending from the opening  56   a  axially rearward; and a second hole part  56   d  extending in the radial direction from the axially rear end of the first hole part  56   c  to the opening  56   b.    
         [0064]    When cleaning the air path  22  of the motor  50 , a compressed fluid is fed into the cleaning hole  56 . The compressed fluid introduced into the cleaning hole  56  passes through the second hole part  56   d  and the first hole part  56   c,  and is discharged from the opening  56   a  axially frontward. 
         [0065]    Since the opening  56   a  is arranged to face the opening  22   b  of the air path  22 , the compressed fluid discharged from the opening  56   a  of the cleaning hole  56  is effectively introduced into the air path  22  from the opening  22   b.    
         [0066]    Further, the first hole part  56   c  of the cleaning hole  56  is formed so as to extend in the axial direction. Accordingly, the compressed fluid introduced into the cleaning hole  56  is oriented so as to be discharged axially frontward, i.e., toward the opening  22   b  of the air path  22 . Thereby, it is possible to introduce the compressed fluid into the air path  22  more effectively. 
         [0067]    Next, a motor  60  according to still another embodiment of the invention will be described with reference to  FIG. 9 . The motor  60  includes the shaft  12 , a stator  62 , the housing  16 , the fan  18 , and the fan cover  54 . 
         [0068]    The stator  62  is formed with the air path  22  axially extending from the opening  22   a  arranged at an axially front end  62   a  of the stator  62  to the opening  22   b  arranged in the vicinity of an axially rear end  62   b  of the stator  62 . The motor  60  according to this embodiment includes a (first) cleaning hole  64  formed at the stator  62 . 
         [0069]    Specifically, the cleaning hole  64  extends from an opening  64   a  (first opening), which opens to the air path  22  to an opening  64   b  (second opening) which opens to the outside on an outer surface  62   c  of the stator  62 . The opening  64   a  is arranged between the opening  22   a  and the opening  22   b  of the air path  22  so as to be closer to the opening  22   b  than the opening  22   a  of the air path  22 , and opens so as to face the air path  22 . 
         [0070]    When cleaning the air path  22  and the fan  18  of the motor  60 , a compressed fluid is fed into the cleaning hole  64 . The compressed fluid introduced into the cleaning hole  64  is discharged from the opening  64   a  into the air path  22 . The compressed fluid flowing into the air path  22  is diverged into a flow toward axially frontward from the opening  64   a  through the air path  22  and a flow toward axially rearward from the opening  64   a  through the air path  22 . 
         [0071]    The compressed fluid flowing axially frontward from the opening  64   a  sweeps away dusts adhering to the passage  22  and is discharged from the opening  22   a  to the outside. On the other hand, the compressed fluid flowing axially rearward from the opening  64   a  sweeps away dusts adhering to the passage  22  and is discharged from the opening  22   b  to the inner space S 2 . 
         [0072]    The compressed fluid discharged from the opening  22   b  passes the inner space S 2  together with the dusts, and flows into the inner space S 1  of the fan cover  54 , and a part thereof is blown to the fan  18 . Thereby, dusts adhering to the fan  18  can be swept away as well. Then, the compressed fluid is discharged to the outside through the fan holes  20   a  ( FIG. 3 ) formed at the fan cover  54 , together with the dusts carried by the compressed fluid. 
         [0073]    According to this embodiment, it is possible to sweep out the dusts adhering to the air path  22  and the fan  18  only by introducing the compressed fluid into the cleaning hole  64 . Therefore, it is not necessary for the user to disassemble the motor  10  for cleaning the air path  22 , so the air path  18  and the fan  18  of the motor  60  can be cleaned in an easy and cost-effective manner. 
         [0074]    Next, a motor  70  according to still another embodiment of the invention will be described with reference to  FIGS. 10 and 11 . The motor  70  includes the shaft  12 , the stator  14 , the housing  16 , the fan  18 , and a fan cover  72 . 
         [0075]    The fan cover  72  is fixed to the rear housing  16   b  of the housing  16 , and houses the fan  18  in the inner space S 1  thereof. Similar to the fan cover  20  shown in  FIG. 3 , the fan cover  72  is formed with a plurality of fan holes (not shown) which allow an outside air to flow into the inner space S 1  and a fluid to flow out of the inner space S 1 . 
         [0076]    The motor  70  further includes a cleaning hole  74  formed at the fan cover  72 . As shown in  FIG. 11 , the cleaning hole  74  includes a first cleaning hole  74   c  axially extending from an opening  74   a  (first opening) to an opening  74   b  (second opening, fourth opening); and a second cleaning hole  74   e  extending from an opening  74   d  (third opening) to the opening  74   b.    
         [0077]    The opening  74   a  is arranged so as to face the opening  22   b  at axially rearward of the opening  22   b.  The opening  74   b  opens to the outside on an outer surface  72   a  of the fan cover  72 . The opening  74   d  opens so as to face the fan  18  at axially frontward of the fan  18 . 
         [0078]    The second cleaning hole  74   e  includes a first hole part  74   f  extending axially frontward from the opening  74   d;  a second hole part  74   g  extending radially outward from the axially front end of the first hole part  74   f  so as to be connected to the first cleaning hole  74   c;  and a third hole part  74   h  axially extending from a connection part of the second hole part  74   g  and the first cleaning hole  74   c  to the opening  74   b.  The third hole part  74   h  constitutes a part of the first cleaning hole  74   c.    
         [0079]    When cleaning the air path  22  and the fan  18  of the motor  70 , a compressed fluid is fed into the cleaning hole  74 . The compressed fluid introduced into the cleaning hole  74  passes through the first cleaning hole  74   c,  and a part thereof is discharged from the opening  74   a  axially frontward. 
         [0080]    Since the opening  74   a  is arranged to face the opening  22   b  of the air path  22 , the compressed fluid discharged from the opening  74   a  of the first cleaning hole  74   c  is effectively introduced into the air path  22  from the opening  22   b.    
         [0081]    Further, the first cleaning hole  74   c  is formed to extend in the axial direction. Therefore, the compressed fluid passing through the first cleaning hole  74   c  is oriented so as to be discharged axially frontward, i.e., toward the opening  22   b  of the air path  22 . 
         [0082]    Thereby, the discharged compressed fluid can be more effectively introduced into the air path  22 . The compressed fluid flowing into the air path  22  from the opening  22   b  flows axially frontward through the air path  22  while sweeping away dusts adhering to the air path  22 , and is discharged from the opening  22   a  to the outside. 
         [0083]    On the other hand, a part of the compressed fluid introduced into the cleaning hole  74  diverges at the connection part of the second hole part  74   g  and the first cleaning hole  74   c,  and flows into the second hole part  74   g.  The compressed fluid flowing into the second hole part  74   g  passes through the second hole part  74   g  and the first hole part  74   f,  and is discharged from the opening  74   d  axially rearward. 
         [0084]    As described above, the opening  74   d  is arranged to face the fan  18 , so the compressed fluid discharged from the opening  74   d  is effectively blown to the fan  18 . Further, the first hole part  74   f  is formed to extend in the axial direction. Therefore, the compressed fluid passing through the first hole part  74   f  is oriented so as to be discharged axially rearward, i.e., toward the fan  18 . 
         [0085]    Thus, according to this embodiment, the first cleaning hole  74   c  and the second cleaning hole  74   e  have the common opening  74   b  from which a compressed fluid is introduced, and the compressed fluid introduced from the opening  74   b  is led to the air path  22  and the fan  18  by the first cleaning hole  74   c  and the second cleaning hole  74   e,  respectively. Thereby, dusts adhering to the air path  22  and the fan  18  can be efficiently swept away by the compressed fluid. 
         [0086]    Next, a motor  80  according to still another embodiment of the invention will be described with reference to  FIGS. 12 and 13 . The motor  80  includes the shaft  12 , the stator  14 , a housing  82 , the fan  18 , and the fan cover  54 . 
         [0087]    In this embodiment, the housing  82  includes the front housing  16   a  similar to that in the above-mentioned embodiments; and a rear housing  82   b  arranged at the axially rear end  14   b  of the stator  14 . The motor  80  further includes a cleaning hole  84  formed at the rear housing  82   b.    
         [0088]    As shown in  FIG. 13 , the cleaning hole  84  includes a first cleaning hole  84   c  extending from an opening  84   a  (first opening) to an opening  84   b  (second opening, fourth opening); and a second cleaning hole  84   e  extending from an opening  84   d  (third opening) to the opening  84   b.    
         [0089]    The opening  84   a  is arranged at axially rear side of the opening  22   b  of the passage  22  so as to adjoin the opening  22   b.  In other words, the opening  84   a  is arranged so that the whole region thereof overlaps with the opening  22   b  of the air path  22 . The opening  84   b  opens to the outside on an outer surface  82   c  of the rear housing  82   b.  The opening  84   d  opens so as to face the fan  18  at axially frontward of the fan  18 . 
         [0090]    The second cleaning hole  84   e  includes a first hole part  84   f  extending axially frontward from the opening  84   d;  and a second hole part  84   g  radially extending from the axially front end of the first hole part  84   f  to the opening  84   b.    
         [0091]    On the other hand, the first cleaning hole  84   c  includes a third hole part  84   h  extending axially rearward from the opening  84   a  so as to be connected to the second hole part  84   g;  and a fourth hole part  84   i  radially extending from the connection part of the second hole part  84   g  and the third hole part  84   h  to the opening  84   b.  The fourth hole part  84   i  constitutes a part of the second hole part  84   g.    
         [0092]    When cleaning the air path  22  and the fan  18  of the motor  80 , a compressed fluid is fed into the cleaning hole  84 . A part of the compressed fluid introduced into the cleaning hole  84  passes through the first cleaning hole  84   c,  and is discharged from the opening  84   a.  Since the opening  84   a  is arranged to adjoin the opening  22   b  of the air path  22 , the compressed fluid passing through the first cleaning hole  84   c  is reliably introduced into the air path  22 . 
         [0093]    On the other hand, a part of the compressed fluid introduced into the cleaning hole  84  passes through the second cleaning hole  84   e  and is discharged from the opening  84   d.  Since the opening  84   d  is arranged to face the fan  18 , the compressed fluid discharged from the opening  84   d  is effectively blown to the fan  18 . 
         [0094]    Thus, according to this embodiment, the first cleaning hole  84   c  and the second cleaning hole  84   e  have the common opening  84   b  from which the compressed fluid is introduced, and the compressed fluid introduced from the opening  84   b  is led to the air path  22  the fan  18  by the first cleaning hole  84   c  and the second cleaning hole  84   e,  respectively. Thereby, it is possible to effectively sweep out the dusts adhering to the air path  22  and the fan  18 . 
         [0095]    Next, a motor  90  according to still another embodiment of the invention will be described with reference to  FIGS. 14 and 15 . The motor  90  includes a shaft  92 , the stator  14 , a housing  94 , the fan  18 , and the fan cover  54 . 
         [0096]    The shaft  92  is provided so as to be rotatable relative to the stator  14 , and the rotor having a magnet (not shown) is fixed to the radially outside of the shaft  92 . In this embodiment, the shaft  92  includes a through hole  92   a  axially penetrating the shaft  92 . 
         [0097]    The housing  94  includes the front housing  16   a  and the rear housing  16   b  similar to those in the embodiments as described above, and a hollow part  94   c.  The hollow part  94   c  is fixed to the axially rear end of the rear housing  16   b  so as to extend between the rear housing  16   b  and the fan cover  54 . 
         [0098]    The hollow part  94   c  defines an inner space S 3  which is in fluid communication with the air path  22  and the inner space S 1  of the fan cover  54 . A rotary joint  96  is provided in the inner space S 3 . The rotary joint  96  receives the shaft  92  in a rotatable manner, and includes an inner space (not shown) which is in fluid communication with the through hole  92   a  of the shaft  92 . 
         [0099]    A fluid supply tube  98  extending from an external fluid supply device (not shown) is connected to the rotary joint  96 , and a fluid supplied from the fluid supply device is fed into the through hole  92   a  via the rotary joint  96 . 
         [0100]    The motor  90  according to this embodiment includes a cleaning hole  100  formed at the hollow part  94   c.  As shown in  FIG. 15 , the cleaning hole  100  includes a first cleaning hole  100   c  extending from an opening  100   a  (first opening) to an opening  100   b  (second opening, fourth opening); and a second cleaning hole  100   e  extending from an opening  100   d  (third opening) to the opening  100   b.    
         [0101]    The opening  100   a  is arranged so as to face the opening  22   b  of the passage  22  at axially rearward of the opening  22   b.  The opening  100   b  opens to the outside on an outer surface  94   d  of the hollow part  94   c.  The opening  100   d  opens so as to face the fan  18  at axially frontward of the fan  18 . 
         [0102]    The second cleaning hole  100   e  includes a first hole part  100   f  extending from the opening  100   d  axially frontward and radially outward so as to be slanted relative to the axial direction; and a second hole part  100   g  radially extending from the axially front end of the first hole part  100   f  to the opening  100   b.    
         [0103]    On the other hand, the first cleaning hole  100   c  includes a third hole part  100   h  extending from the opening  100   a  axially rearward so as to be connected to the second hole part  100   g;  and a fourth hole part  100   i  radially extending from the connection part of the second hole part  100   g  and the third hole part  100   h  to the opening  100   b.  The fourth hole part  100   i  constitutes a part of the second hole part  100   g.    
         [0104]    When cleaning the air path  22  and the fan  18  of the motor  90 , a compressed fluid is fed into the cleaning hole  100 . A part of the compressed fluid introduced into the cleaning hole  100  passes through the first cleaning hole  100   c,  and is discharged from the opening  100   a.  Since the opening  100   a  is arranged to face the opening  22   b  of the air path  22 , the compressed fluid discharged from the opening  100   a  is effectively introduced into the air path  22 . 
         [0105]    On the other hand, a part of the compressed fluid introduced into the cleaning hole  100  passes through the second cleaning hole  100   e,  and is discharged from the opening  100   d.  Since the opening  100   d  is arranged to face the fan  18 , the compressed fluid discharged from the opening  100   d  is effectively blown to the fan  18 . 
         [0106]    Thus, according to this embodiment, the first cleaning hole  100   c  and the second cleaning hole  100   e  have the common opening  100   b  from which the compressed fluid is introduced, and the compressed fluid introduced from the opening  100   b  is led to the air path  22  and the fan  18  by the first cleaning hole  100   c  and the second cleaning hole  100   e,  respectively. Thereby, it is possible to effectively sweep out dusts adhering to the air path  22  and the fan  18  by the compressed fluid. 
         [0107]    Further, in this embodiment, the first hole part  100   f  constituting the second cleaning hole  100   e  is formed to extend so as to be slanted relative to the axial direction. The inclination angle of the first hole part  100   f  relative to the axial direction is determined so that the extension direction of the first hole part  100   f  intersects an element of the fan  18  (for example, the center of the rotation body of the fan). 
         [0108]    According to this configuration, the flow of the compressed fluid discharged from the opening  100   d  can be oriented in a direction toward the fan  18 , more effectively. As a result, it is possible to more effectively sweep out dusts adhering to the fan  18  by the compressed fluid discharged from the opening  100   d.    
         [0109]    Next, a motor  110  according to still another embodiment of the invention will be described with reference to  FIGS. 16 and 17 . The motor  110  includes the shaft  12 , the stator  14 , a housing  112 , the fan  18 , and a fan cover  114 . 
         [0110]    The housing  112  includes the front housing  16   a  similar to that in the above-mentioned embodiments; and a rear housing  112   b  arranged at the axially rear end  14   b  of the stator  14 . The fan cover  114  is fixed to the rear housing  112   b,  and houses the fan  18  in the inner space S 1  thereof. 
         [0111]    The motor  110  according to this embodiment includes a (first) cleaning hole  116  formed at the rear housing  112   b  and the fan cover  114 . As shown in  FIG. 17 , the cleaning hole  116  includes a first hole part  116   c  formed at the rear housing  112   b;  and a second hole part  116   d  formed at the fan cover  114  so as to be in fluid communication with the first hole part  116   c.    
         [0112]    The first hole part  116   c  extends axially rearward from an opening  116   a  (first opening) formed on the inner surface  112   c  of the rear housing  112   b  so as to axially penetrate the rear housing  112   b.  The opening  116   a  is arranged at axially rearward of the opening  22   b  of the air path  22  to face the opening  22   b.    
         [0113]    On the other hand, the second hole part  116   d  extends axially frontward from an opening  116   b  (second opening) formed on the outer surface  114   a  of the fan cover  114  so as to open to the outside, and axially penetrates the fan cover  114 . 
         [0114]    The first hole part  116   c  and the second hole part  116   d  are arranged so as to straightly align in the axial direction. The inner wall of the first hole part  116   c  is threaded. 
         [0115]    The cleaning hole  116  according to this embodiment ordinarily functions as a bolt hole for fixing the rear housing  112   b  and the fan cover  114  to each other. Specifically, as shown in  FIG. 18 , a bolt  118  is inserted into the cleaning hole  116  to as to be screwed into the threaded part formed at the inner wall of the first hole part  116   c.  Thereby, the rear housing  112   b  and the fan cover  114  can be bolted with each other. 
         [0116]    On the other hand, when cleaning the motor  110 , the bolt  118  is removed from the cleaning hole  116 , and a compressed fluid is fed into the cleaning hole  116 . The compressed fluid introduced into the cleaning hole  116  is discharged from the opening  116   a  axially frontward. 
         [0117]    Since the opening  116   a  is arranged to face the opening  22   b  of the air path  22 , the compressed fluid discharged from the opening  116   a  is effectively introduced into the air path  22  from the opening  22   b.  Thereby, dusts adhering to the air path  22  can be swept away. 
         [0118]    Thus, according to this embodiment, the inner wall of the cleaning hole  116  is threaded, and the cleaning hole  116  functions as a bolt hole and also as, a hole for introducing the compressed fluid. Due to this configuration, it is possible to easily clean the inside of the motor  110 , while the number of holes to be formed and the number of components can be reduced. 
         [0119]    Next, a cleaning system  120  according to an embodiment of the invention will be described with reference to  FIG. 19 . The cleaning system  120  is for cleaning the air path  22  and the fan  18  of the motor  10  described above. 
         [0120]    The cleaning system  120  includes a fluid supply device  122  for supplying a compressed fluid into the first cleaning hole  24  and the second cleaning hole  26 ; and a controller  124  which controls the fluid supply device  122 . A plurality of fluid supply tubes  126  are connected to the fluid supply device  122 , and each of the fluid supply tubes  126  is connected to each of the first holes  24  and second hole  26 . 
         [0121]    The fluid supply device  122  generates a compressed fluid inside thereof, and supplies it to each of the first cleaning holes  24  and the second cleaning hole  26  via the fluid supply tubes  126 . When a compressed gas is supplied as the compressed fluid, the fluid supply device  122  is comprised of e.g. a compressor. 
         [0122]    The controller  124  controls a flow rate, a pressure, a timing, or supply time of the compressed fluid supplied by the fluid supply device  122 . Note that, when the motor  10  is installed in a machine tool, the controller  124  may be incorporated in a machine tool controller for controlling the machine tool. In this case, the machine tool controller functions as the controller  124  so as to control the operation of the fluid supply device  122 . 
         [0123]    Note that, in this embodiment, the cleaning system  120  is used to clean the motor  10 . However, it would be easily understood that the cleaning system  120  can also clean the motor  40 ,  50 ,  60 ,  70 ,  80 ,  90 , or  110 . 
         [0124]    In this case, each fluid supply tube  126  is connected to each cleaning hole  56 ,  64 ,  74 ,  84 ,  100 , or  116  of the motor  40 ,  50 ,  60 ,  70 ,  80 ,  90 , or  110 , and a compressed fluid is supplied from the fluid supply device  122  through the fluid supply tube  126 . 
         [0125]    Note that, in the above-mentioned embodiments, a case is described where the air path  22  is formed at the stator  14 . However, the air path may be provided as a member other than the stator, and arranged adjacent to the stator. For example, a housing, such as a cooling jacket, may be provided at an outer periphery of the stator, wherein the air path may be provided at the housing. 
         [0126]    Further, at least two of the cleaning holes  24 ,  26 ,  56 ,  64 ,  74 ,  84 ,  100 , and  116  may be provided in one motor. Further, at least two features included in the various embodiments described above may be combined. For example, the inner wall of each of the cleaning holes  24 ,  26 ,  56 ,  64 ,  74 ,  84 , and  100  may be threaded, as in the cleaning hole  116 . 
         [0127]    The invention has been described through the embodiments of invention, but the embodiments as described above are not intended to limit the invention as in the appended claims. In addition, embodiments in which the features described in the embodiments of the invention are combined can be included in the technical scope of the invention, but not all the combinations of these features are essential for solution of the invention. Further, it is also apparent to a person skilled in the art that various modifications and improvements can be added to the embodiments as described above.