Abstract:
A rotating electrical machine includes a rotor and a stator positioned circumferentially around the rotor. The stator includes multiple core elements arrayed in a circumferential direction of the rotor such that the core elements form multiple slots arrayed in the circumferential direction, and a unitary cylindrical coil resin structure including molded resin and lap wound air-core coils resin-molded in the molded resin, each of the air-core coils having an air-core, a first side portion and a second side portion extending on the opposite sides of the air-core such that the first side portion extends through a first one of the slots and the second side portion extends through a second one of the slots.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     The present application is a continuation of and claims the benefit of priority to International Application No. PCT/JP2012/083161, filed Dec. 20, 2012, which is based upon and claims the benefit of priority to Japanese Application No. 2012-131072, filed Jun. 8, 2012. The entire contents of these applications are incorporated herein by reference. 
    
    
     BACKGROUND 
     Technical Field 
     The disclosed embodiment relates to a rotating electrical machine, and a method for manufacturing a rotating electrical machine. 
     Description of Background Art 
     A three-phase AC rotating electrical machine has a stator with a Y-connected winding serving as the winding of each phase of a distributed winding and a lap winding. 
     SUMMARY 
     According to one aspect of the present disclosure, a rotating electrical machine includes a rotor and a stator positioned circumferentially around the rotor. The stator includes multiple core elements arrayed in a circumferential direction of the rotor such that the core elements form multiple slots arrayed in the circumferential direction, and a unitary cylindrical coil resin structure including molded resin and lap wound air-core coils resin-molded in the molded resin, each of the air-core coils having an air-core, a first side portion and a second side portion extending on the opposite sides of the air-core such that the first side portion extends through a first one of the slots and the second side portion extends through a second one of the slots. 
     According to another aspect of the present disclosure, a unitary cylindrical coil resin structure for a rotating electrical machine includes molded resin, and lap wound air-core coils resin-molded in the molded resin, each of the air-core coils having an air-core, a first side portion and a second side portion extending on opposite sides of the air-core. When assembled with core elements of a stator of the rotating electrical machine, the core elements are arrayed in a circumferential direction of a rotor such that the core elements form slots arrayed in the circumferential direction, the first side portion of each of the air-core coils extends through a first one of the slots, and the second side portion of each of the air-core coils extends through a second one of the slots. 
     According to yet another aspect of the present disclosure, a method for manufacturing a rotating electrical machine includes lap-winding air-core coils such that lap wound air-core coils form a substantially cylindrical reel shape, resin-molding the lap wound air-core coils such that a unitary cylindrical coil resin structure including molded resin and the lap wound air-core coils resin-molded in the molded resin is formed, and assembling core elements of a stator to the unitary cylindrical coil resin structure such that the core elements are arrayed in a circumferential direction of a rotor and form slots arrayed in the circumferential direction, each of the air-core coils having an air-core, a first side portion and a second side portion extending on opposite sides of the air-core such that the first side portion extends through a first one of the slots and the second side portion extends through a second one of the slots. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A more complete appreciation of the 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 longitudinal cross-sectional view showing the overall structure of a rotating electrical machine according to embodiment 1; 
         FIG. 2  is a transverse cross-sectional view of the II-II cross-section in  FIG. 1 ; 
         FIG. 3  is a conceptual view showing the outer appearance of the coil resin structure; 
         FIG. 4  is a conceptual view showing the outer appearance of the coil; 
         FIG. 5  is an explanatory view for explaining the lap-winding state of the coil; 
         FIG. 6  is a longitudinal cross-sectional view showing the overall structure of a rotating electrical machine according to embodiment 2; 
         FIG. 7  is a conceptual view showing the outer appearance of the coil resin structure; 
         FIG. 8  is a perspective view showing the overall outer appearance of the coil resin structure; 
         FIG. 9  is a perspective view showing a portion of the outer appearance of the primary molding; 
         FIG. 10A  is an arrow view from the arrow T direction in  FIG. 9 , showing the details of the main parts of the primary molding; 
         FIG. 10B  is an arrow view from the arrow S direction in  FIG. 10A ; 
         FIG. 10C  is a transverse cross-sectional view of the R-R′ cross-section in  FIG. 10A ; 
         FIG. 11A  is an arrow view corresponding to  FIG. 10A  showing the details of the main parts with the coil assembled prior to forming the primary covering layer of the primary molding; 
         FIG. 11B  is an arrow view from the arrow W direction in  FIG. 11A ; 
         FIG. 11C  is a transverse cross-sectional view of the V-V′ cross-section in  FIG. 11A ; 
         FIG. 12A  is an arrow view from the arrow U direction in  FIG. 8 , showing the details of the main parts of the coil resin structure; 
         FIG. 12B  is an arrow view from the arrow Q direction in  FIG. 12A ; 
         FIG. 12C  is a transverse cross-sectional view of the P-P′ cross-section in  FIG. 12A ; and 
         FIG. 13  is a transverse cross-sectional view showing the overall structure of a rotating electrical machine according to embodiment 3. 
     
    
    
     DETAILED 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. 
     Embodiment 1 
     Rotating Electrical Machine 
     First, the structure of the rotating electrical machine in embodiment 1 will be described using  FIG. 1  and  FIG. 2 . 
     As shown in  FIG. 1  and  FIG. 2 , a rotating electrical machine  10  in this embodiment is a magnet-embedded synchronous motor having a rotor  20  inside a stator  30 . That is, the rotating electrical machine  10  has the rotor  20  rotatably supported, and the substantially cylindrical stator  30  disposed so as to enclose a radial-direction outer circumference side of the rotor  20  with a magnetic air gap therebetween. Further, the rotating electrical machine  10  has a cylindrical frame  11  disposed on an outer circumference side of the stator  30 , a load-side bracket  12  disposed on a load side (the right side in  FIG. 1 ) of the frame  11 , a load-side bearing  13  whereby an outer ring is fitted to the load-side bracket  12 , a counter-load side bracket  14  disposed on a counter-load side (the left side in  FIG. 1 ) of the frame  11 , a counter-load side bearing  15  whereby an outer ring is fitted to the counter-load side bracket  14 , a shaft  16  (rotating shaft) rotatably supported by the load-side bearing  13  and the counter-load side bearing  15 , and an encoder  17  that detects a rotating position of the rotor  20 , disposed on a counter-load side (the left side in  FIG. 1 ) end part of the shaft  16 . 
     The load-side bracket  12  and the counter-load side bracket  14  are connected to the frame  11  by bolts (not shown). On the load-side bracket  12 , a dust seal  18  is disposed on the outside of the bearing  13  to prevent entry of foreign matter into the interior of the rotor  20 . A connecting part  44  of a coil  41  of the stator  30  is disposed on a counter-load side end surface of a stator core  32  of the stator  30 . An external power source is connected to the connecting part  44  via a lead wire (not shown), and power is supplied from the external power source to the coil  41  via the connecting part  44 . 
     The rotor  20  has a substantially annular rotor core  22  having an axial-direction hole  21  that fits the shaft  16 , and an axial-direction permanent magnet  23  embedded in the rotor core  22  in a V-shape per pole. With this arrangement, the rotor  20  is structured as a field system part with an embedded magnet type structure of multiple poles (8 in this example). A load-side lateral plate  8  and a counter-load side lateral plate  9  that respectively hold and prevent the load-side end surface and counter-load side end surface of the rotor  20  from moving outward in the load-side direction and outward in the counter-load side direction of the rotor  20  are attached to the shaft  16 . A positioning lateral plate  7  of the rotor  20  is attached between the load-side lateral plate  8  and the above described load-side bearing  13  of the shaft  16 . 
     Structure of Stator 
     The stator  30  has the substantially annular above described stator core  32  having multiple slots  31  (48 slots in this example), and the coils  41  (48 coils in this example) respectively housed in the above described slots  31 . With this arrangement, the stator  30  is structured as an armature part. The stator core  32  is structured by arranging divided core elements  33  (48 core elements in this example) with a substantially fan-shaped transverse cross-section across the entire circumference, along the inner circumferential surface of the frame  11 . Each of the divided core elements  33  has a tooth  34  with a rectangular transverse cross-sectional shape, on the radial-direction inside. At this time, the slot  31  is formed between the teeth ( 34 ,  34 ) respectively included in adjacent divided core elements ( 33 ,  33 ). With this arrangement, the slots  31  are disposed across the entire circumferential-direction circumference so as to extend along the inner circumferential surface of the above described frame  11 . The slots  31  correspond to the teeth  34  with rectangular transverse cross-sectional shapes, and are each formed so as to be fan-shaped with the transverse cross-sectional shape narrowing toward the radial-direction inside. 
     At this time, the above described coils  41  (48 coils in this example) is formed in advance as one substantially cylindrical coil resin structure  45 , as shown in  FIG. 3 . The following describes the coil resin structure  45  formed by the 48 coils  41 , and the detailed structures of and the respective coils  41 , using  FIG. 4  and  FIG. 5 . 
     Structure of Coil 
     Each of the coils  41  is formed as a hexagonal air-core coil, as shown in  FIG. 4 . That is, first a conductor  42  covered by a suitable insulating film (not shown) is wound multiple times (4 times, for example) into a long rectangular frame shape. Note that a flat rectangular wire with a rectangular transverse cross-sectional shape is used as the conductor  42  in this example. Nevertheless, the present disclosure is not limited thereto, allowing use of a lead wire with another shape (a round lead wire with a substantially circular transverse cross-sectional shape, for example). At this time, the conductor  42  is wound while layered from the lowermost layer in the direction of the upper layers on one of the long sides of the rectangular frame that face each other, and while layered from the uppermost layer in the direction of the lower layers on the other of the long sides. Further, at that time, the conductor  42  is wound while inverting the front and back so as to create a loop within a plane surface orthogonal to the plane surface of the above described rectangular frame, in the centre area of the two short sides that face each other. After the above described winding, the wound body of the conductor  42  is widened in the width direction and longitudinal direction as indicated by arrows (a1, a2, a3, a4) in  FIG. 4 , plastically deforming into a hexagonal shape, thereby achieving the above described coil  41 , which is a hexagonal air-core coil. 
     That is, the coil  41  has a substantially linear first linear part ( 41   a ) (one side portion in a circumferential direction) positioned on the upper right side in  FIG. 4  that leads to a winding start end  41   s  of the conductor  42 , a substantially linear second linear part ( 41   b ) (other side portion in a circumferential direction) positioned on the lower left side in  FIG. 4  that leads to a winding finish end ( 41   e ) of the conductor  42 , inclined parts ( 41   f ,  41   g ) that respectively connect one end of the first linear part ( 41   a ) and the second linear part ( 41   b ) (upper left side in  FIG. 4 ), one turn part ( 41   c ) disposed in the middle area of these inclined parts ( 41   f ,  41   g ), and another turn part ( 41   d ) (hereinafter “nose part”) that continues to the inclined parts that connect the other end of the first linear part ( 41   a ) and the second linear part ( 41   b ). 
     Four-Layer Layered Structure of Conductor 
     In each of the above described parts ( 41   a - 41   g ) of the coil  41 , the conductor  42  is wound multiple times (4 times in this example). As a result, in each of the above described parts ( 41   a - 41   g ), the conductor  42  is layered in multiple layers (4 layers in this example; hereinafter the same) in the radial direction (up-down direction in  FIG. 4 ) of the stator core  32 . Then, the first linear part ( 41   a ) and the second linear part ( 41   b ) of the coil  41  are disposed away from each other so as to substantially extend along the direction that is the circumferential direction of the stator core  32  when the stator core  32  is mounted to the slots  31  (in other words, when the coil resin structure  45  is mounted to the stator core  32 ). 
     Hence, during the above described mounting, the first linear part ( 41   a ) (or the second linear part ( 41   b )) of a certain coil  41  included in the coil resin structure  45  is disposed well on the radial-direction inside (indicated by the “inner circumferential step” in  FIG. 4 ) of each of the slots  31 , and the first linear part ( 41   a ) (or the second linear part ( 41   b )) of another coil included in the coil resin structure  45  is disposed well on the radial-direction outside (indicated by the “outer circumferential step” in  FIG. 4 ) of each of the slots  31 , as shown in the enlarged explanatory views inside the circles in  FIG. 4 . That is, with the coil resin structure  45  assembled to the stator core  32 , in each of the 48 coils  41 , the first linear part  41  is disposed well on the radial-direction inside (on the “inner to circumferential step” in  FIG. 4 ) of a certain slot  31  while the second linear parts ( 41   b ) is disposed well on the radial-direction outside (on the “outer circumferential step” in  FIG. 4 ) of another slot  31 , four slots away in the circumferential direction. To achieve such a disposition, a separation distance (L) between the first linear part ( 41   a ) and the second linear part ( 41   b ) of the respective coils  41  described above (refer to  FIG. 3 ) is substantially equal to a separation distance (X) equivalent to four slots  31  in the substantially circumferential direction (with the difference in the inner/outer radial-direction positions described above taken into account; refer to  FIG. 2 ) when the aforementioned coil resin structure  45  is mounted to the stator core  32 . 
     Pressure Molding 
     Further, as described above, the slot  31  is fan-shaped, with a transverse cross-sectional shape narrowing toward the radial-direction inside. Correspondingly, at least the first linear part ( 41   a ) and the second linear part ( 41   b ) of each of the coils  41  are pressure-molded in advance so that the outer shape agrees with the transverse cross-sectional shape of each of the slots  31  prior to being molded as described later. That is, the second linear part ( 41   b ) disposed well on the radial-direction outside of the slot  31  is molded into a flatter shape than the first linear part ( 41   a ) disposed well on the radial-direction inside of the slot  31 . Specifically, in the four layer conductor  42  (conductors ( 42 - 1 ,  42 - 2 ,  42 - 3 ,  42 - 4 ) from the radial-direction inside toward the outside) having the first linear part ( 41   a ), the conductor ( 42 - 1 ) has the smallest circumferential-direction (the left-right direction in the enlarged view in  FIG. 4 ) dimension and the largest radial-direction (the up-down direction in the enlarged view in  FIG. 4 ) dimension. Then, the cross-sectional shape becomes increasingly flat for conductors further on the radial-direction outside, in the order of the conductor ( 42 - 2 ), the conductor ( 42 - 3 ), and the conductor ( 42 - 4 ), with the conductor ( 42 - 4 ) having the largest circumferential-direction dimension and the smallest radial-direction dimension. Similarly, in the four layer conductor  42  (conductors ( 42 - 5 ,  42 - 6 ,  42 - 7 ,  42 - 8 ) from the radial-direction inside toward the outside) having the second linear part ( 41   b ), the conductor ( 42 - 5 ) has the smallest circumferential-direction dimension and the largest radial-direction dimension. Then, the cross-sectional shape becomes increasingly flat for conductors further on the radial-direction outside, in the order of the conductor ( 42 - 6 ), the conductor ( 42 - 7 ), and the conductor ( 42 - 8 ), with the conductor ( 42 - 8 ) having the largest circumferential-direction dimension and the smallest radial-direction dimension. Note that the conductor ( 42 - 5 ) has a larger circumferential-direction dimension and a smaller radial-direction dimension than the conductor ( 42 - 4 ). 
     Forming Coil Resin Structure 
     Then, as conceptually shown in  FIG. 5 , an air gap  43  where the above described tooth  34  of the stator core  32  is fitted is formed between two coils  41  during the above described mounting, and each of the 48 coils  41  is shifted in position and overlapped while extended along the circumferential direction of the stator core  32  during the above described mounting. This overlapping mode is repeated so as to extend across the entire circumferential direction of the stator core  32  during the above described mounting (equivalent to the lap-winding step). Then, the 48 coils  41  thus lap-wound across the entire circumferential-direction circumference are integrally resin-molded and hardened by mold resin (not shown), thereby forming one substantially cylindrical coil resin structure  45  made of the 48 coils  41  (equivalent to the resin molding step), as shown in the above described  FIG. 3 . 
     Attaching Coil Resin Structure to Stator Core 
     Subsequently, the teeth  34  of the divided core element  33  are fitted (across the entire circumference of the coil resin structure  45 ) from the outer circumference side of the coil resin structure  45  into each of the air gaps  43  between adjacent coils ( 41 ,  41 ) of the coil resin structure  45  formed as described above. With this arrangement, the annular stator core  32  is constructed by the divided core elements  33  (48 elements in this example). Further, the coil resin structure  45  and the above described stator core  32  are integrally assembled while the first linear part ( 41   a ) of the coil  41  of the coil resin structure  45  is housed in the above described inner circumferential step of each of the slots  31  formed between the teeth ( 34 ,  34 ) of two adjacent divided core elements ( 33 ,  33 ), and the second linear part ( 41   b ) of the another coil  41  of the coil resin structure  45  is housed in the above described outer circumferential step of each of the slots  31  (equivalent to the assembly step). In this manner, the stator  30  is assembled. 
     As described above, according to the rotating electrical machine  10  in embodiment 1, each of the coils  41  has an air-core coil, and the first linear part ( 41   a ) and the second linear part ( 41   b ) are disposed in a so-called lap-winding mode in which the circumferential-direction position is sequentially shifted while the parts are separately inserted into different slots  31 . At this time, the coils  41 , which are air-core coils subjected to lap-winding and arranged around the entire circumferential-direction circumference as described above, are integrally resin-molded in advance while not inserted into the slots  31  to form one coil resin structure  45 . On the other hand, the stator core  32  is structured by arranging the divided core element  33  in multiple across the entire circumferential-direction circumference. Each of the core elements  33  has the tooth  34 , and the above described slot  31  is formed between two divided core elements  33  that are adjacent when arranged in multiple. Then, the divided core elements  33  are assembled from the outer circumference side of the coil resin structure  45  while each of the coils  41  included in the coil resin structure  45  is inserted into two corresponding slots  31 . With this arrangement, the stator  30  with the lap-wound coils  41  inserted into the slots  31  of the stator core  32  is manufactured. 
     As described above, according to this embodiment, before being individually inserted into the slots  31 , the coils  41  are constructed as one coil resin structure  45  and the stator core  32  with the divided structure is inserted into the one coil resin structure  45 . With this arrangement, the coils are not inserted into the slots and molded by mold resin on the main line of the manufacturing process, but rather the coils  41  can be prepared as one resin structure  45  in advance on a sub-line of the manufacturing process. By constructing the coil resin structure  45  at a high space factor by the coils  41  on a sub-line that is a separate line from the main line, it is possible to decrease the generation of heat of the coil  41  itself, thereby improving the cooling performance of the rotating electrical machine  10 . 
     Further, since the work is performed for assembling each of the coils  41  of the coil resin structure  45  constructed in advance on the sub-line while housing them into the slots  31 , the mold resin molding work is no longer necessary on the main line, making it possible to significantly reduce the manufacturing time. 
     Then, the stator  30  is structured by the assembly body of the stator core  32  with a divided structure such as described above and one coil resin structure  45 , thereby making it possible to perform disassembly easily when the rotating electrical machine  10  is no longer needed and is to be discarded. In particular, the iron material used on the core  32  side and the copper material used in the conductor  42  of the coil  41  can be easily separated, for example, making it possible to rapidly improve recyclability. 
     Further, in particular, according to this embodiment, each of the coils  41  is pressure-molded, thereby making the external shape thereof agree with the transverse cross-sectional shape of the corresponding slot  31 . With this arrangement, there is also the advantage of more reliably improving the space factor, which is the actual disposition capacity of the coil  41  that occupies the slot  31 , which is the disposition space of the coil  41 . Further, there is also the advantage of improving the cooling performance by the decrease in coil heat generation resulting from the increase in the space factor of the rotating electrical machine  10 . 
     Embodiment 2 
     Overview of Rotating Electrical Machine 
     Next, the rotating electrical machine in embodiment 2 will be described using  FIG. 6  to  FIG. 12 . The components that are the same as those in embodiment 1 will be denoted using the same reference numerals, and descriptions thereof will be suitably omitted or simplified. As shown in  FIG. 6 , a rotating electrical machine  10 A in this embodiment has a coil resin structure  60  in the stator  30 . 
     The coil resin structure  60 , as schematically shown in  FIG. 7 , is formed by lap-winding the coils  41  (48 coils in this example, the same as described above; refer to  FIG. 8  described later), which are the same air-core coils as the above described embodiment 1, across the entire circumferential-direction circumference of the stator core  32  (refer to the aforementioned  FIG. 4  and  FIG. 5  as well), and integrally resin-molding by mold resin and hardening the lap-wound coils  41 . Each of the coils  41  is pressure-molded so that the external shape agrees with the transverse cross-sectional shape of the corresponding two slots  31 . A load-side end surface ( 41 A) of the coil  41  is formed so as to have a partial conical surface corresponding to an inside surface ( 12   a ) by the above described pressure-molding so as to be closely fitted to the inside surface ( 12   a ) of the load-side bracket  12 . 
     Overview of Coil Resin Structure 
       FIG. 8  shows the overall outer appearance of the coil resin structure  60 . The coil resin structure  60 , as shown in  FIG. 8 , has a short, cylindrical load-side coil end part  62  positioned on the load side (equivalent to one axial-direction side of the rotor), a short, cylindrical counter-load side coil end part  63  positioned on the counter-load side (equivalent to the other axial-direction side of the rotor), and a middle part  64  positioned between the load-side coil end part  62  and the counter-load side coil end part  63 . At this time, the coil resin structure  60 , as shown in  FIG. 7  and  FIG. 8 , has a nearly cylindrical reel shape overall, with the outer diameter of the middle part  64  smaller than the outer diameter of the above described coil end parts ( 62 ,  63 ) on both sides. 
     The load-side coil end part  62 , as indicated by the dashed lines in  FIG. 8 , is an area where the portion of the turn part ( 41   c ) and the like on the above described one end side of each of the coils  41  is covered and contained (details described later). The counter-load side coil end part  63 , as indicated by the dashed lines in  FIG. 8 , is an area where the above described winding start end ( 41   s ), the above described winding finish end ( 41   e ), the above described nose part ( 41   d ), and the like on the above described other end side of each of the coils  41  are covered (details described later). 
     In the middle part  64 , multiple slot insertion parts  61  with a substantially rectangular plate shape, housed in the slots  31  of the stator core  32 , are arranged in the circumferential direction. Note that, as described later, this slot insertion part  61  is an area where the above described first linear part ( 41   a ) and the above described second linear part ( 41   b ) of each of the coils  41  are covered and contained. 
     Molding by Primary Covering and Secondary Covering 
     This coil resin structure  60  is formed by performing resin-molding by mold resin twice on the front surface of each of the coils  41  disposed in advance in a substantially annular shape. That is, a primary covering layer  700  that covers the outside of each of the coils  41  (refer to  FIG. 9  and the like described later) is generated by a first resin molding, thereby forming a primary molding  50 . Subsequently, a secondary covering layer  800  that covers the outside of the primary covering layer  700  (refer to  FIG. 12 , described later) is generated by a second resin molding, thereby forming the above described coil resin structure  60 . The following describes the details of the formation of the above described primary covering layer  700  and secondary covering layer  800 , in order. The primary covering layer  700  links to means for covering an outside of the air-core coil. The secondary covering layer  800  links to means for covering an outside of the means for covering an outside of the air-core coil. 
     Formation of Primary Molding 
     The following describes the above described primary molding  50  using  FIG. 9 ,  FIG. 10 , and  FIG. 11 . The primary molding  50 , as described above, is structured by covering the outside of each of the coils  41  disposed in a substantially annular shape with the primary covering layer  700  (refer to  FIG. 11  and  FIG. 10 ). That is, the primary molding  50 , as shown in  FIG. 9 , has a load-side coil end part  52  corresponding to the load-side coil end part  62  of the above described coil resin structure  60 , a counter-load side coil end part  53  corresponding to the counter-load side coil end part  63  of the above described coil resin structure  60 , and a middle part  54  corresponding to the middle part  64  of the above described coil resin structure  60 , positioned between the load-side coil end part  52  and the counter-load side coil end part  53 . 
     When the above described primary molding  50  is molded, the coils  41  disposed in the above described substantially annular shape is set in the primary mold, which is a split mold, and mold resin is poured into the interior of the mold, thereby forming the above described primary covering layer  700  by mold resin on the outside of each of the coils  41  (equivalent to the primary covering step). With this arrangement, regardless of the position and posture of each of the coils  41  inside the interior space of the above described primary mold, it is possible to achieve the above described primary molding  50  having the load-side coil end part  52  and the counter-load side coil end part  53  with a specified outer diameter dimensions determined in advance, and further having the identically shaped slot insertion parts  51  with a specified outer diameter dimension determined in advance in the middle of the coil ends parts ( 52 ,  53 ). 
     Middle Part 
     In the middle part  54 , multiple slot insertion parts  51  with a substantially rectangular plate shape, respectively corresponding to the slots insertion parts  61  of the above described coil resin structure  60 , are arranged in the circumferential direction. As shown in  FIG. 10A , the second linear part ( 41   b ) of a certain coil  41  and the first linear part ( 41   a ) of another coil  41  are overlapped and layered in the radial direction in the slot insertion part  51 . That is, in this example, the above described second linear part ( 41   b ) is disposed on the radial-direction outside (the upper side in  FIG. 10A ,  FIG. 10C ) of the slot insertion part  51 , and the above described first linear part ( 41   a ) is disposed on the radial-direction inside (the lower side in  FIG. 10A ,  FIG. 10C ) of the slot insertion part  51  (refer to  FIG. 4  and  FIG. 8  as well). Then, by covering the outside of the layered first linear part ( 41   a ) and the second linear part ( 41   b ) with the primary covering layer  700 , the slot insertion part  51  has a substantially rectangular plate shape with multiple protrusion portions (described later). 
     Specifically, the slot insertion part  51  has outer surface parts ( 701   a ,  701   a ) with a rectangular plane surface and the outer surface parts  701   b ,  701   b  with a long, narrow rectangular plane surface, as the outer surface resulting from the primary covering layer  700 . 
     The outer surface part ( 701   a ) is respectively formed on both sides (the upper side and the lower side in  FIG. 10B , the far side and the near side in  FIG. 10A , and the left side and the right side in  FIG. 10C ) of the slot insertion part  51  along the circumferential direction. Each of the outer surface parts ( 701   a ) has at least one protrusion portion ( 701   a   1 ) (two portions in this example) resulting from the primary covering layer  700 , protruded from the outer surface part ( 701   a ) in the above described circumferential direction in an amount equivalent to a predetermined dimension. 
     The outer surface part ( 701   b ) is respectively formed on both sides (the near side and the far side in  FIG. 10B , the upper side and the lower side in  FIG. 10A , and the upper side and the lower side in  FIG. 10C ) of the slot insertion part  51  along the radial direction. Each of the outer surface parts  701   b  has at least one protrusion portion ( 701   b   1 ) (one portion in this example) resulting from the primary covering layer  700 , protruded from the outer surface part ( 701   b ) in the above described radial direction in an amount equivalent to a predetermined dimension. 
     Load-Side Coil End Part 
     The load-side coil end part  52  is formed into a substantially cylindrical shape having multiple protrusion portions (described later) by covering the outside of the turn part ( 41   c ) and the like on one axial-direction side of the coils  41  with the primary covering layer  700 . 
     Specifically, the load-side coil end part  52  has an outer surface part ( 702   a ) with a substantially circular plate shape, an outer surface part ( 702   b ) with an annular curved surface, and an outer surface part ( 702   c ) with an annular curved surface, as the outer surface resulting from the primary covering layer  700 . 
     The outer surface part ( 702   a ) is formed on the aforementioned other axial-direction side (corresponding to the above described counter-load side; the left side in  FIG. 10B  and  FIG. 10A , and the near side in  FIG. 10C ). The outer surface part  702   a  has at least one protrusion portion ( 702   a   1 ) (two portions in this example) resulting from the primary covering layer  700 , protruded from the outer surface part ( 702   a ) in an amount equivalent to the same dimension as the above described protrusion portion ( 701   a   1 ). 
     The outer surface part ( 702   b ) is formed on the radial-direction outside (the near side in  FIG. 10B , and the upper side in  FIG. 10A  and  FIG. 10C ). The outer surface part ( 702   b ) has at least one protrusion portion ( 702   b   1 ) (one portion in this example) resulting from the primary covering layer  700 , protruded from the outer surface part ( 702   b ) in an amount equivalent to the same dimension as the above described protrusion portion ( 701   b   1 ). 
     The outer surface part ( 702   c ) is formed on the radial-direction inside (the far side in  FIG. 10B , and the lower side in  FIG. 10A  and  FIG. 10C ). The outer surface part ( 702   c ) has at least one protrusion portion ( 702   c   1 ) (one in this example) resulting from the primary covering layer  700 , protruded from the outer surface part ( 702   c ) in an amount equivalent to the same dimension as the above described protrusion portion ( 701   b   1 ). 
     Counter-Load Side Coil End Part 
     The counter-load side coil end part  53  is formed into a substantially cylindrical shape having multiple protrusion portions (described later) by covering the outside of the nose part ( 41   d ) and the like on the other axial-direction side of the coils  41  with the primary covering layer  700 . 
     Specifically, the counter-load side coil end part  53  has an outer surface part ( 703   a ) with a substantially circular plate shape, an outer surface part ( 703   b ) with an annular curved surface, and an outer surface part ( 703   c ) with an annular curved surface, as the outer surface resulting from the primary covering layer  700 . 
     The outer surface part ( 703   a ) is formed on the aforementioned one axial-direction side (corresponding to the above described load side; the right side in  FIG. 10B  and  FIG. 10A ). The outer surface part ( 703   a ) has at least one protrusion portion ( 703   a   1 ) (two portions in this example) resulting from the primary covering layer  700 , protruded from the outer surface part ( 703   a ) in an amount equivalent to the same dimension as the above described protrusion portion ( 701   a   1 ) and the like. 
     The outer surface part ( 703   b ) is formed on the radial-direction outside (the near side in  FIG. 10B , and the upper side in  FIG. 10A ). The outer surface part  703   b  has at least one protrusion portion ( 703   b   1 ) (one portion in this example) resulting from the primary covering layer  700 , protruded from the outer surface part ( 703   b ) in an amount equivalent to the same dimension as the above described protrusion portion ( 701   a   1 ) and the like. 
     The outer surface part ( 703   c ) is formed on the radial-direction inside (the far side in  FIG. 10B , and the lower side in  FIG. 10A ). The outer surface part ( 703   c ) has at least one protrusion portion ( 703   c   1 ) (one portion in this example) resulting from the primary covering layer  700 , protruded from the outer surface part ( 703   c ) in an amount equivalent to the same dimension as the above described protrusion portion ( 701   a   1 ) and the like. 
     Molding Coil Resin Structure 
     The covering when the coil resin structure  60  is molded from the above described primary molding  50  will now be described using  FIG. 12  and  FIG. 8 . After the primary molding  50  is molded as described above, the primary molding  50  is set in a secondary mold, which is a split mold, and the mold resin is poured into the interior of the mold to cover each of the outer surface parts ( 701   a ,  701   b ,  702   a ,  702   b ,  702   c ,  703   a ,  703   b ,  703   c ) of the primary covering layer  700  of the primary molding  50  with the secondary covering layer  800  at a specified thickness determined in advance, thereby forming the above described coil resin structure  60  (equivalent to the secondary covering step). At this time, the primary molding  50  is supported on the above described both radial-direction sides, the above described both circumferential-direction sides, and the above described both axial-direction sides with respect to the inner wall of the secondary mold via the aforementioned protrusion portions ( 701   a ,  701   b   1 ), the protrusion portions ( 702   a   1 ,  702   b   1 ,  702   c   1 ), the protrusion portions ( 703   a   1 ,  703   b   1 ,  703   c   1 ), in the interior of the above described secondary mold. As a result, with the above-described resin pouring, the secondary covering layer  800  having the same thickness as the height-direction dimension of each of the protrusion portions ( 701   a ,  701   b   1 ,  702   a   1 ,  702   b   1 ,  702   c   1 ,  703   a   1 ,  703   b   1 ,  703   c   1 ) (equivalent to the above described predetermined thickness) is formed on the entire outer front surface of the primary molding  50  (excluding the above described respective protrusion portions), thereby completing the above described coil structure  60 . Note that the height-direction dimension of each of the protrusion portions ( 701   a ,  701   b   1 ,  702   a   1 ,  702   b   1 ,  702   c   1 ,  703   a   1 ,  703   b   1 ,  703   c   1 ) may be mutually the same or not the same. 
     The coil resin structure  60 , as described above using  FIG. 8 , has the middle part  64 , the load-side coil end part  62 , and the counter-load side coil end part  63 . At this time, in the middle part  64 , the rectangular plate-shaped slot insertion part  61  where the outside of the primary covering layer  700  of the above described slot insertion part  51  of the primary molding  50  is covered by the secondary covering layer  800  is arranged in the circumferential direction. The load-side coil end part  62  is formed by covering the outside of the primary covering layer  700  of the above described load-side coil end part  52  of the primary molding  50  with the secondary covering layer  800 . The counter-load side coil end part  63  is formed by covering the outside of the primary covering layer  700  of the above described counter-load side coil end part  53  of the primary molding  50  with the secondary covering layer  800 . 
     Middle Part 
     As described above, in the middle part  64 , the slot insertion parts  61  with the substantially rectangular plate shape are arranged in the circumferential direction. The slot insertion part  61  has rectangular outer surface parts ( 801   a ,  801   a ) and long, narrow rectangular outer surface parts ( 801   b ,  801   b ), as the outer surface resulting from the covered above described secondary covering layer  800  that further covers the outside of the above described primary covering layer  700 . 
     The outer surface part ( 801   a ) is formed by further covering the outer front surface of the outer surface part ( 701   a ) resulting from the primary covering layer  700  of the above described primary molding  50  with the secondary covering layer  800  having a thickness equivalent to the height dimension of the protrusion portion ( 701   a   1 ) using the aforementioned technique, on both sides (the upper side and the lower side in  FIG. 12B , the far side and the near side in  FIG. 12A , and the left side and the right side in  FIG. 12C ) of the slot insertion part  61  along the circumferential direction. 
     The outer surface part ( 801   b ) is formed by further covering the outer front surface of the outer surface part ( 701   b ) resulting from the primary covering layer  700  of the above described primary molding  50  with the secondary covering layer  800  having a thickness equivalent to the height dimension of the protrusion portion ( 701   b   1 ) using the aforementioned technique, on both sides (the near side and the far side in  FIG. 12A , the upper side and the lower side in  FIG. 10A , and the upper side and the lower side in  FIG. 10C ) of the slot insertion part  61  along the radial direction. 
     Load-Side Coil End Part 
     The load-side coil end part  62  has an outer surface part ( 802   a ) with a substantially circular plate shape, an annular outer surface part ( 802   b ), and an outer surface part ( 802   c ) with an annular curved surface, as the outer surface resulting from the above described secondary covering layer  800  that further covers the outside of the above described primary covering layer  700 . 
     The outer surface part ( 802   a ) is formed by further covering the outer front surface of the outer surface part ( 702   a ) resulting from the primary covering layer  700  of the above described primary molding  50  with the secondary covering layer  800  having a thickness equivalent to the height dimension of the protrusion portion ( 702   a   1 ) using the aforementioned technique, on the above described other axial-direction side (the left side in  FIG. 12A  and  FIG. 12B , and the near side in  FIG. 12C ). 
     The outer surface part  802   b  is formed by further covering the outer front surface of the outer surface part ( 702   b ) resulting from the primary covering layer  700  of the above described primary molding  50  with the secondary covering layer  800  having a thickness equivalent to the height dimension of the protrusion portion ( 702   b   1 ) using the aforementioned technique, on the above described radial-direction outside (the near side in  FIG. 12B , and the upper side in  FIG. 12A  and  FIG. 12C ). 
     The outer surface part ( 802   c ) is formed by further covering the outer front surface of the outer surface part ( 702   c ) resulting from the primary covering layer  700  of the above described primary molding  50  with the secondary covering layer  800  having a thickness equivalent to the height dimension of the protrusion portion ( 702   c   1 ) using the aforementioned technique, on the above described radial-direction inside (the far side in  FIG. 12B , and the lower side in  FIG. 12A  and  FIG. 12C ). 
     Counter-Load Side Coil End Part 
     The counter-load side coil end part  63  has an outer surface part ( 803   a ) with a substantially circular plate shape, an outer surface part ( 803   b ) with an annular curved surface, and an outer surface part ( 803   c ) with an annular curved surface, as the outer surface resulting from the above described secondary covering layer  800  that further covers the outside of the above described primary covering layer  700 . 
     The outer surface part ( 803   a ) is formed by further covering the outer front surface of the outer surface part ( 703   a ) resulting from the primary covering layer  700  of the above described primary molding  50  with the secondary covering layer  800  having a thickness equivalent to the height dimension of the protrusion portion ( 703   a   1 ) using the aforementioned technique, on the above described one axial-direction side (the right side in  FIG. 12A  and  FIG. 12B ). 
     The outer surface part ( 803   b ) is formed by further covering the outer front surface of the outer surface part ( 702   b ) resulting from the primary covering layer  700  of the above described primary molding  50  with the secondary covering layer  800  having a thickness equivalent to the height dimension of the protrusion portion ( 702   b   1 ) using the aforementioned technique, on the above described radial-direction outside (the near side in  FIG. 12B , and the upper side in  FIG. 12A  and  FIG. 12C ). 
     The outer surface part ( 803   c ) is formed by further covering the outer front surface of the outer surface part ( 703   c ) resulting from the primary covering layer  700  of the above described primary molding  50  with the secondary covering layer  800  having a thickness equivalent to the height dimension of the protrusion portion ( 703   c   1 ) using the aforementioned technique, on the above described radial-direction inside (the far side in  FIG. 12B , and the lower side in  FIG. 12A  and  FIG. 12C ). 
     The same advantages as those of the above described embodiment 1 are achieved according to this embodiment structured as described above as well. That is, by constructing the coil resin structure  45  at a high space factor by the coils  41  on a sub-line that is a separate line from the main line, it is possible to decrease the generation of heat of the coil  41  itself, thereby improving the cooling performance of the rotating electrical machine  10 . Further, the mold resin molding work on the main line is no longer required, making it possible to significantly reduce the manufacturing time. Further, the rotating electrical machine  10  can be easily disassembled when it is no longer needed and is to be discarded. In particular, the iron material used on the stator core  35  side and the copper material used in the conductor  42  of the coil  41  can be easily separated, for example, making it possible to rapidly improve recyclability. 
     Further, according to this embodiment, the following advantages are achieved in addition to the above. That is, according to this embodiment, the coil resin structure  60  is manufactured by forming the primary covering layer  700  on the outside of the coil  41 , which is an air-core coil, and then further forming the secondary covering layer  800  on the outside thereof. In the primary covering step, the coil  41  is housed into the above described primary mold, resin is poured into the interior of the mold, and the coil  41  is covered by the primary covering layer  700 . At this time, the outer shape dimensions of the primary molding  50  that contains the coils  41  covered by the primary covering layer  700  (in other words, the shape dimensions of the space formed in the interior of the above described mold) are controlled. That is, in the interior of the primary molding  50 , the skew and the position of each of the coils  41  do not matter. 
     Then, the above described primary molding  50  is further housed into a different secondary mold, resin is poured into the interior of the mold, and the primary molding  50  is covered by the secondary covering layer  800 . As described above, the outer shape dimensions of the primary molding  50  are controlled by the above described primary mold with high precision (all outer shape dimensions of the primary molding  50  are the same, regardless of the position of the each of the coils  41  in the interior of the primary molding  50 ), thereby making it possible to form the secondary covering layer  800  on the outside of the above described primary molding  51  at a uniform thickness. 
     As described above, the secondary covering layer  800  is uniformly formed on the outside of the primary molding  50  wherein the outer shape dimensions are controlled by the primary covering layer  700  with high precision. With this arrangement, it is possible to maintain the minimum required thickness in the covering layer of the resin formed on the outer circumference side of the coil  41  (the primary covering layer  700 + the secondary covering layer  800 ). 
     Further, when the winding (the conductor  42 ) is wound during the manufacture of the coil  41 , which is a preliminary stage of formation of the above described primary covering layer  700  (or when the coil  41  is subsequently pressure-molded), winding lift may occur, for example, causing the coil  41  to stick out from the outside of the primary mold or to become distorted in shape, and therefore the primary molding  50  to not always achieve the preferred external dimensions with high precision (hereinafter suitably referred to as “irregular shape”). According to this embodiment 2, even in such a case, the coil  41  with the above described irregular shape is housed in the interior of the primary mold and the primary mold is closed, making it possible to forcibly achieve the aforementioned high-precision outer shape dimensions of the primary molding  50 . However, in this case, resin does not flow into areas of the coil  41  that are contacted and pressed by the above described primary mold, resulting in a thickness of the primary covering layer  700  of zero (or near that value). Nevertheless, as described above, the secondary covering layer  800  having a predetermined thickness is subsequently uniformly formed across the entire outside area of the primary covering layer  700 , thereby making it possible to reliably form the resin covering layer in these areas as well. 
     As a result of the above, according to this embodiment, it is possible to suppress variance in thickness in the covering layer when the coil  41  is covered, improving the uniformity. 
     Further, in particular, according to this embodiment, in the primary covering layer  700 , multiple protrusion portions (the protrusion portions ( 701   a   1 ,  701   b   1 ), the protrusion portions ( 702   a   1 ,  702   b   1 ,  702   c   1 ), and the protrusion portions ( 703   a   1 ,  703   b   1 ,  703   c   1 ) are protruded from each outer surface part in an amount equivalent to a predetermined dimension on the outer surface (the outer surface part ( 701   a ) and the outer surface part  701   b ) of the slot insertion part  51 , on the outer surface (the outer surface part  702   a , the outer surface part ( 702   b ), and the outer surface part  702   c ) of the load-side coil end part  52 , and on the outer surface (the outer surface part  703   a , the outer surface part ( 703   b ), and the outer surface part ( 703   c )) of the counter-load side coil end part  53 . Then, the secondary covering layer  800  is disposed so as to cover the outside of the above described primary covering layer  700  at a thickness equal to the above described predetermined dimensions (the height-direction dimension of each of the protrusion portions). 
     That is, in this embodiment, each of the outer surface parts of the primary molding  50  after the primary covering layer  700  is formed has the above described protrusion portions ( 701   a   1 ,  701   b   1 ,  702   a   1 ,  702   b   1 ,  702   c   1 ,  703   a   1 ,  703   b   1 ,  703   c   1 ) having a predetermined dimension (equivalent to the thickness dimension of the secondary covering layer  800 ). With this arrangement, when the primary molding  50  is housed in the secondary mold to form the secondary covering layer  800 , it is possible to reliably support the entire primary molding  50  with respect to the inner wall of the secondary mold by the above described protrusion portions ( 701   a   1 ,  701   b   1 ,  702   a   1 ,  702   b   1 ,  702   c   1 ,  703   a   1 ,  703   b   1 ,  703   c   1 ), as described above. 
     Further, in particular, according to this embodiment, resin is poured and filled in the area around the primary molding  50  supported by the above described protrusion portions ( 701   a   1 ,  701   b   1 ,  702   a   1 ,  702   b   1 ,  702   c   1 ,  703   a   1 ,  703   b   1 ,  703   c   1 ), thereby causing the above described secondary covering layer  800  to cover the outside of the above described primary covering layer  700 , excluding the above described protrusion portions, at a thickness equal to the above described predetermined dimension. With this arrangement, it is possible to reliably uniformly form the secondary covering layer  800  in the area around the primary molding  50  housed in the secondary mold other than the protrusion portions ( 701   a   1 ,  701   b   1 ,  702   a   1 ,  702   b   1 ,  702   c   1 ,  703   a   1 ,  703   b   1 ,  703   c   1 ). 
     Further, in particular, according to this embodiment, in the coil resin structure  60 , the outer diameter of the middle part  64  having the slot insertion part  61  housed in the slots  31  is smaller than the outer diameter of the coil end parts ( 62 ,  63 ) on both sides of the rotor  30  along the axial direction. This has the following significance. 
     That is, when the coils  41  are disposed on the stator core  32  as described above, the rotor  20  is disposed on the radial-direction inside of the portion of each of the coils  41  housed in the slot  31  (the middle part  64  other than the coil end parts ( 62 ,  63 )), and a support structure of the housing of the rotating electrical machine ( 10 A) is disposed on the radial-direction outside of the above described slot insertion part  61  of the above described middle part  64  of each of the coils  41 , as shown in  FIG. 6 . Hence, according to this embodiment, in the coil resin structure  60 , the outer diameter of the middle part  64  where other members and structures are disposed on the radial-direction inside and outside as described above is made smaller than the outer diameter of the coil end parts ( 62 ,  63 ) where there is no such disposition. With this arrangement, it is possible to prevent the overall rotating electrical machine ( 10 A) from increasing in size in the radial direction, and thus decrease the size. 
     Embodiment 3 
     Next, the rotating electrical machine in embodiment 3 will be described using  FIG. 13 . As shown in  FIG. 13 , a rotating electrical machine ( 10 B) in this embodiment is a reluctance motor having the rotor  20  inside the stator  30 . The components that are the same as those in embodiment 1 will be denoted using the same reference numerals, and descriptions thereof will be suitably omitted or simplified. 
     In the rotating electrical machine ( 10 B) shown in  FIG. 13 , the stator  30  has a stator core  35 . In the stator core  35 , similar to the above described embodiment 1, multiple divided core elements  36  (72 elements in this example) are arranged across the entire circumference while extending along the inner circumferential surface of the frame  11  of the stator  30  (refer to the above described  FIG. 2 ). Each of the divided core elements  36  has a tooth  37  with a transverse cross-section having a tapered trapezoidal shape on the radial-direction inside. Then, a slot  38  with a rectangular (shaped like a long rectangular) transverse cross-section is formed between the above described teeth ( 37 ,  37 ) of adjacent divided core elements ( 36 ,  36 ). 
     According to this embodiment, similar to the above described embodiment 1, the coils  41  (72 coils in this example) are inserted (housed) in the above described slots  38  (72 slots in this example). At this time, similar to the above, each of the coils  41  is shifted in position and lap-wound so that the air gap  43  where the tooth  37  of the divided core element  36  is fit is formed between two coils ( 41 ,  41 ). Then, 72 lap-wound coils  41  are integrally resin-molded using mold resin (not shown), forming one substantially cylindrical coil resin structure  45  (not shown; refer to the above described  FIG. 8  as well). 
     At this time, according to this embodiment, the transverse cross-sectional shape of the tooth  37  is tapered, and thus the transverse cross-sectional shape of the slot  38  is left rectangular (shaped like a long rectangle) as is. As a result, the pressure-molding with respect to the outer shape such as in the above described embodiment 1 is not performed on the first linear part ( 41   a ) and the second linear part ( 41   b ) of the coil  41 . 
     In this embodiment as well, similar to the above described embodiment 1, the teeth  37  of the divided core element  36  are fitted (across the entire circumference of the coil resin structure  45 ) from the outer circumference side of the coil resin structure  45  into each of the air gaps  43  between adjacent coils ( 41 ,  41 ) of the coil resin structure  45 . With this arrangement, the annular stator core  35  is constructed by the 72 divided core elements  36 . Further, the coil resin structure  45  and the above described stator core  35  are assembled while the first linear part of the coil  41  of the coil resin structure  45  is housed in the above described inner circumferential step of each of the slots  38  formed between the teeth ( 37 ,  37 ) of two adjacent divided core elements ( 36 ,  36 ), and the second linear part of another coil  41  of the coil resin structure  45  is housed in the above described outer circumferential step of each of the slots  38 . Note that while the above described first linear part in this embodiment is equivalent to the first linear part ( 41   a ) in the above described embodiment 1, each layer of the four layer conductor  42  has the same substantially rectangular transverse cross-sectional shape. Further, while the above described second linear part in this embodiment is equivalent to the second linear part ( 41   b ) in the above described embodiment 2, each layer of the four layer conductor  42  has the same substantially rectangular transverse cross-sectional shape. In this manner, the stator  30  is assembled. 
     Note that a total of 24 air gap parts  25  are disposed on the rotor core  22  of the rotor  20 , three per each of multiple poles (8 poles in this example) along the circumferential direction. The air gap part  25  curves in a convex manner on the radial-direction inside. This air gap part  25  can cause a difference in the magnetic path resistance of the rotor core, resulting in a reluctance torque. 
     The same advantages as those of the above described embodiment 1 are achieved according to this embodiment structured as described above as well. That is, by constructing the coil resin structure  45  at a high space factor by the coils  41  on a sub-line that is a separate line from the main line, it is possible to decrease the generation of heat of the coil  41  itself, thereby improving the cooling performance of the rotating electrical machine ( 10 B). Further, the mold resin molding work on the main line is no longer required, making it possible to significantly reduce the manufacturing time. Further, the rotating electrical machine ( 10 B) can be easily disassembled when it is no longer needed and is to be discarded. In particular, the iron material used on the stator core  35  side and the copper material used in the conductor  42  of the coil  41  can be easily separated, for example, making it possible to rapidly improve recyclability. 
     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 disclosure may be practiced otherwise than as specifically described herein.