Abstract:
In a method of manufacturing a laminated core, a laminated core body  14  including magnet insertion holes  12  and  13  with magnet pieces  15  inserted therein is placed between a molding (upper) die  10  and a retaining (lower) die  11 , and a molding resin  19  is filled from resin reservoir portions (pots)  16  to fix the pieces  15  in the holes  12  and  13 . Between the die  10  and the body  14 , a guide member  18  is placed, which includes resin passages  31  provided from the portions  16  to the holes  12  and  13  and gates  30  connecting to the holes  12  and  13  on downstream sides of the passages  31 . The method can reduce lead time of a production line without replacing the molding dies for different laminated rotor cores and thus without preparing different types of molding dies.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a method of manufacturing a laminated core for a motor, the laminated core with a magnet piece resin-sealed in each of a plurality of magnet insertion holes axially-penetrating therethrough. 
       BACKGROUND ART 
       [0002]    Conventionally, as described in Patent Literature 1, a magnet molding method A is known, in which a plurality of magnet insertion holes are provided for a laminated core body of a laminated rotor core, and a magnet piece is inserted and fixed in each of the magnet insertion holes. In this method, as shown in FIG. 8, magnet pieces 72 are inserted in a plurality of magnet insertion holes 71 provided in a radially-outward region of a laminated rotor core 70. After the laminated rotor core 70 is heated to a certain temperature, a molding resin 75 is injected from an upper die 73 (or a lower die 74) into the magnet insertion holes 71. By curing the molding resin 75, the magnet pieces 72 are fixed to a laminated core body 76. A reference numeral 77 denotes a carrier fixture, a reference numeral 78 denotes an upper fixing plate, a reference numeral 79 denotes a lower fixing plate, a reference numeral 80 denotes a guide post, and a reference numeral 81 denotes a plunger. 
         [0003]    However, in the method described in Patent Literature 1, the molding resin 75 remains on a resin passage portion of a surface of the laminated rotor core and a gate portion which connects to the magnet insertion hole 71. Therefore, after the molding resin is filled, a process to remove the resin remained on the surface is needed. Thus, Patent Literature 2 discloses a magnet molding method B wherein a dummy plate is used. 
         [0004]    In the magnet molding method B, as shown in FIG. 9, a dummy plate 82 is disposed on a top surface of a laminated core body 76. The molding resin 75 is injected through a gate 83, a resin injection hole, provided on the dummy plate 82. Thus, the injected molding resin 75 adheres to and remains on a surface of the dummy plate 82, not on the top surface of the laminated core body 76. Therefore, by removing the dummy plate 82 from the laminated core body 76, the residual molding resin is also removed at the same time. A reference numeral 84 denotes a resin passage provided in the upper die 73. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         [Patent Literature 1] Japanese Patent No. 3786946 
         [Patent Literature 2] Japanese Patent No. 4414417 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0007]    However, in the magnet molding methods described in Patent Literature 1 and 2, it is necessary to change a shape of a molding die (upper die or lower die) including a resin reservoir portion and a dummy plate according to a given laminated core body whenever the positions or the numbers of the magnet insertion holes of the laminated core body are changed. Therefore, if the molding die is prepared according to a type of a laminated rotor core, manufacturing cost increases. Moreover, in a production line, the molding die must be replaced whenever the type of the laminated rotor core is changed. Accordingly, including adjustment after replacing the molding die, it takes several dozens of minutes to several hours to restart production, resulting in a hindrance to a reduction of production time. 
         [0008]    The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a method of manufacturing a laminated core, which can reduce lead time of the production line without changing the molding die for each different laminated rotor core and thus without preparing another type of molding device. 
       Solution to Problem 
       [0009]    To accomplish the above object, the present invention provides a method of manufacturing a laminated core, the laminated core formed by placing a laminated core body having magnet pieces inserted in magnet insertion holes thereof between a molding die and a retaining die, filling a molding resin from resin reservoir portions of the molding die to the magnet insertion holes, and thereby fixing the magnet pieces in the magnet insertion holes, the method including: placing a guide member between the molding die and the laminated core body, the guide member including: a) groove-type resin passages provided from the resin reservoir portions to the magnet insertion holes; and b) gates on downstream sides of the resin passages, the gates connected to the magnet insertion holes. 
         [0000]    Here, if the laminated core body stands vertically, the molding die is disposed at a top or a bottom of the laminated core body. The guide portion is correspondingly disposed at the top or the bottom of the laminated core body. 
         [0010]    In the method of manufacturing the laminated core according to the present invention, it is preferable that the guide member be made of one flat plate (e.g., stainless steel plate or steel plate), the resin passage include a groove opened to the molding die, and the gate be a through-hole provided at an end of the resin passage. 
         [0011]    Also, in the method of manufacturing the laminated core according to the present invention, it is preferable that the guide member include at least two flat plates (e.g, stainless steel plate or steel plate), and the resin passage be formed by penetrating through one of the flat plates adjoining the molding die. It is further preferable that the gate be formed in another flat plate adjoining the laminated core body, and be a through-hole connected to the downstream side of the resin passage. 
         [0012]    In the method of manufacturing the laminated core according to the present invention, it is preferable that when viewed in plan, the gate be smaller than the magnet insertion hole, and overlap with the magnet insertion hole on a radially-inward region thereof. Here, the term “when viewed in plan” means to look at the laminated core body in an axial direction. Accordingly, the resin at where the magnet insertion hole and the gate abut each other can be broken easily, and the unnecessary resin can be removed easily. 
         [0013]    In the method of manufacturing the laminated core according to the present invention, it is preferable that the molding die include a plurality of the resin reservoir portions, from which the molding resin be supplied to a plurality of groups of the magnet insertion holes (including one or a plurality of the magnet insertion holes) formed in the laminated core body. 
         [0000]    In addition, in the method of manufacturing the laminated core according to the present invention, it is preferable that a diameter of the guide member be larger than a diameter of the laminated core body. Accordingly, the guide member can be easily removed after resin-sealing. 
       Advantageous Effects of Invention 
       [0014]    The method of manufacturing a laminated core according to the present invention has the following effects: 
         [0000]    (1) In a production line in operation, even if a type of the product to be molded (i.e., laminated core) is changed during the operation, molding is enabled only by setting a guide member corresponding to the product without replacing a molding die, it is thus possible to manufacture the product continuously without stopping the production line.
 
(2) Thus, for a specific product type, it is only necessary to replace the guide member as the type of the product is changed, and it is therefore possible to reduce lead time.
 
(3) It is further possible to significantly reduce costs for dies and production because it is not necessary to manufacture a molding die for each product type.
 
         [0015]    Specifically, by using at least two flat plates for the guide member, it is possible to prevent the resin from remaining on a surface of the product. Further, by separating the at least two flat plates, the residual resin can be removed very easily. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0016]      FIG. 1  is an explanatory diagram showing a method of manufacturing a laminated core according to a first embodiment of the present invention. 
           [0017]      FIG. 2  is a plan view showing a carrier fixture used in the method. 
           [0018]      FIG. 3(A)  is a plan view showing a guide member used in the method, and FIG.  3 (B) is a plan view showing a laminated core manufactured by the method. 
           [0019]      FIG. 4(A)  is a plan view showing a guide member used in a method of manufacturing a laminated core according to a second embodiment of the present invention, and  FIG. 4(B)  is a plan view showing a laminated core manufactured by the method. 
           [0020]      FIG. 5  is an explanatory diagram showing a method of manufacturing a laminated core according to a third embodiment of the present invention. 
           [0021]      FIGS. 6(A) and 6(B)  are explanatory diagrams showing a guide member used in the method, and  FIG. 6(C)  is a plan view showing a laminated core manufactured by the method. 
           [0022]      FIGS. 7(A) and 7(B)  are plan views showing a guide member used in a method of manufacturing a laminated core according to a fourth embodiment of the present invention, and  FIG. 7(C)  is a plan view showing a laminated core manufactured by the method. 
           [0023]      FIG. 8  is an explanatory diagram showing a method of manufacturing a laminated core according to a conventional example. 
           [0024]      FIG. 9  is an explanatory diagram showing a method of manufacturing a laminated core according to a conventional example. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0025]    As shown in  FIG. 1 , in a method of manufacturing a laminated core according to a first embodiment of the present invention, a laminated core body  14  is placed between an upper die  10 , which is an example of a molding die, and a lower die  11 , which is an example of a retaining die. The laminated core body  14  has a plurality of pairs of magnet insertion holes  12  and  13  vertically penetrating therethrough (see  FIG. 3(B) ) in a radially-outward region thereof. The laminated core body  14  is placed with a magnet piece (unexcited permanent magnet)  15  inserted in each of the magnet insertion holes  12  and  13 . Further, a molding resin  19  is filled via a guide member  18  into the magnet insertion holes  12  and  13  from resin reservoir pots  16 , which are examples of resin reservoir portions formed in the upper die  10 , to fix the magnet pieces  15  in the magnet insertion holes  12  and  13 . Here, a height of the magnet piece  15  is equal to a height of the laminated core body  14  or smaller than the height of the laminated core body  14  with a slight difference (0.1 to 2 mm). 
         [0026]    The laminated core body  14  includes a plurality of pairs (8 pairs in this embodiment) of the paired magnet insertion holes  12  and  13  (which form a group of the magnet insertion holes), and a through-hole  21  as a lightening hole is formed in each radially-inward region between the magnet insertion holes  12  and  13 , which are arranged in a chevron shape when viewed in plan. At a center of the laminated core body  14 , a shaft hole  22  is formed, and inside the shaft hole  22 , projecting portions  23  and  24  (see  FIG. 3 ) are formed. The projecting portions  23  and  24  are rectangular when viewed in plan and are disposed opposite each other. The laminated core body  14  is formed by caulking and laminating core sheets  25 , which are pressed from a magnetic metal sheet (e.g., silicon steel plate) and have an identical shape. 
         [0027]    As shown in  FIG. 3(A) , the upper die  10  includes the resin reservoir pots  16  having circular sections at the positions radially inward of the paired magnet insertion holes  13  and  12  in a V-shape when viewed in plan. A liquefied molding resin (thermosetting resin)  19  filled inside each of the resin reservoir pots  16  is extruded to the laminated core body  14  by a plunger  27  moved up and down by an unillustrated cylinder. 
         [0028]    The guide member  18  is made of one flat plate (e.g., stainless steel plate or steel plate) with a thickness, for example, of 0.2 to 3 mm. The guide member  18  includes resin passages  31 , which are bottomed grooves opened to the upper die  10 . Upstream ends of the resin passages  31  are connected to the resin reservoir pots  16 , and downstream ends thereof are connected to gates  30 , which are through-holes each formed in a radially-inward region of the magnet insertion holes  12  and  13  (shown in dotted lines). A depth of the resin passage  31  is 30 to 70% of a thickness of the guide member  18 . The gates  30  formed at the downstream ends of the resin passages  31  are rectangular holes, and are provided at centers of the radially-inward regions of the magnet insertion holes  12  and  13  below the resin passages  31 . Here, the gates  30  are not limited to be rectangular holes, but may be circular holes, triangular holes, etc. 
         [0029]    A length of a long side of the gate  30  is 0.3-fold to 0.7-fold of a length of a long side of the magnet insertion holes  12  and  13 . Also, a length of a short side of the gate  30  is 0.3-fold to 0.7-fold of a length of a short side of the magnet insertion holes  12  and  13 . 
         [0000]    A diameter of the guide member  18  is larger than a diameter of the laminated core body  14  by 1 to 10%. Inside the guide member  18 , a shaft hole  32 , which has a diameter identical to a diameter of a shaft hole  22  of the laminated core body  14 , is provided. Inside the shaft hole  32 , projecting portions  33  and  34 , which are identical to projecting portions  23  and  24  provided inside the shaft hole  22 , are provided. 
         [0030]    In this embodiment, the laminated core body  14  is mounted on a carrier fixture  36 , and positioned and held between the lower die  11  and the upper die  10 . 
         [0000]    As shown in  FIG. 2 , the carrier fixture  36  includes a mounting portion  37  and a guide shaft  38  disposed at a center thereof. A length of the guide shaft  38  is longer than a height of the laminated core body  14 , and a chamfer  39  is formed at an upper end of the guide shaft  38 . The upper die  10  includes a hole  40  into which the guide shaft  38  is inserted. At both sides in a radial direction of the guide shaft  38 , key slots  41  and  42  are provided, into which the projecting portions  23 ,  24 ,  33 , and  34  are inserted in close contact therewith. Alternatively, key slots may be formed in an outer circumference of a shaft hole of a laminated core, and projecting portions, which are inserted into the key slots, may be provided on a guide shaft. 
         [0031]    Hereinafter, a method of manufacturing a laminated core using a resin sealing apparatus constituted as described above will be described. 
         [0032]    After the guide member  18  is stacked on the laminated core body  14  preheated and mounted on the carrier fixture  36 , they are together placed between the upper die  10  and the lower die  11 . The laminated core body  14  and the guide member  18  are positioned by lowering the upper die  10  to insert the guide shaft  38  of the carrier fixture  36  into the hole  40  of the upper die  10 . 
         [0033]    Here, the plungers  27  are pushed down by the unillustrated cylinders to extrude the liquefied molding resin  19  in the resin reservoir pots  16  downward. The molding resin  19  is filled in each of the magnet insertion holes  12  and  13  from the resin passage  31  via the gate  30 . Since the gates  30  are provided in a way that they overlap radially-inward regions of the magnet insertion holes  12  and  13 , the magnet pieces  15  are pushed to radially-outward regions of the magnet insertion holes  12  and  13 . 
         [0034]    Since the molding resin  19  is a thermosetting resin, it is heated and cured by the preheated laminated core body  14 . 
         [0000]    The upper die  10  is then lifted and the guide member  18  is removed from the laminated core body  14 , and the cured molding resin  19  is broken at or near the gates  30 . This procedure can be performed on the lower die  11 . Alternatively, this procedure can be performed after the carrier fixture  36  is moved to another place. 
         [0035]    Next, by referring to  FIGS. 4(A) and 4(B) , a method of manufacturing a laminated core according to a second embodiment of the present invention will be described only for parts different from the method according to the first embodiment of the present invention. The upper die  10 , the lower die  11 , and the carrier fixture  36 , which are the same as those described in the first embodiment of the present invention, are used. In a laminated core body  44 , magnet insertion holes  45  are provided in addition to the magnet insertion holes  12  and  13 , forming eight groups of the magnet insertion holes. Therefore, in a guide member  47  to be mounted on the laminated core body  44 , resin passages  48  and gates  49  corresponding to the magnet insertion holes  45  are provided. 
         [0036]    Detailed descriptions of procedures for the method of manufacturing the laminated core according to the second embodiment are omitted because the procedures are the same as those of the method of manufacturing the laminated core according to the first embodiment. 
         [0000]    In these embodiments, the resin is filled from one resin reservoir pot to two or three magnet insertion holes. Further, the present invention is applicable to a case where the resin is filled from one resin reservoir pot to one magnet insertion hole or to four or more magnet insertion holes. 
         [0037]    Next, by referring to  FIGS. 5 and 6 , a method of manufacturing a laminated core according to a third embodiment of the present invention will be described. Hereunder, detailed descriptions of an upper die and a lower die will be omitted because they are the same as those used in the method of manufacturing the laminated core according to the first embodiment. Also, although a carrier fixture for a laminated core body is omitted (not used) in the third embodiment, it is preferable to use the carrier fixture as described in the first embodiment. In addition, elements which are the same as those in the above-mentioned embodiments are numbered accordingly, and repetitive descriptions of the elements will be omitted (likewise in a fourth embodiment of the present invention). 
         [0038]    As shown in  FIG. 5  and  FIGS. 6(A) to 6(C) , the laminated core body  14  with a guide member  51  mounted thereon is placed between the upper die  10  and the lower die  11 . In the laminated core body  14 , the magnet insertion holes  12  and  13  are provided as described above. In this embodiment, the guide member  51  includes two annular flat plates  52  and  53  made of stainless-steel, and a thickness of each of the flat plates  52  and  53  is, for example, 0.2 to 2 mm. The flat plate  52  adjoining the resin reservoir pots  16  includes resin passages  55 , each formed from the resin reservoir pot  16  to a gate  54  on a downstream side of the resin passage  55 . The flat plate  53  adjoining the laminated core body  14  includes the gates  54 , through which the resin is filled into the magnet insertion holes  12  and  13  formed in the laminated core body  14 . 
         [0039]    The resin passage  55  is formed by vertically penetrating through the flat plate  52 , and the gate  54  is formed by vertically penetrating (as a through-hole) through the flat plate  53 . The gate  54  is provided at a radially-inward center of each of the magnet insertion holes  12  and  13  when viewed in plan. The upstream side of the resin passage  55  is connected to the resin reservoir pot  16 , and the downstream side thereof is connected to the gate  54 . 
         [0000]    Accordingly, the two flat plates  52  and  53  are integral with each other, working in the same way as the guide member  18  provided with the resin passages  31  and the gates  30  in the first embodiment. Here, diameters of the flat plates  52  and  53  are larger than a diameter of the laminated core body  14 , thus the flat plates  52  and  53  can be removed easily. 
         [0040]    The guide member  51  is used in the same way as described in the first embodiment. By removing the guide member  51 , which means removing the flat plates  52  and  53  simultaneously, and further by separating the flat plates  52  and  53 , the molding resin remained in the resin passage  55  can be easily removed. 
         [0000]    In addition, it is preferable to use the carrier fixture  36  (not shown in  FIG. 5 ), but if a positioning means (e.g., recessed portion and projecting portion) to position the guide member  51  and the laminated core body  14  is provided, the carrier fixture can be omitted. In  FIGS. 6(A) and 6(B) , reference numerals  57  and  58  denote projecting portions and reference numerals  59  and  60  denote shaft holes. 
         [0041]    Next, by referring to  FIGS. 7(A) to 7(C) , a method of manufacturing a laminated core according to a fourth embodiment of the present invention will be described. In this embodiment, the laminated core body  44  used in the second embodiment of the present invention is used. In the fourth embodiment of the present invention, two flat plates  63  and  64  are used to form a guide member  62 . In the flat plate  63 , the resin passages  55  and  66  are provided. The resin passages  55  and  66  are connected from the resin reservoir pots provided in the upper die to the gates  54  and  65  on downstream sides. In the flat plate  64 , the gates  54  and  65  are provided. The gates  54  and  65  are located at radially-inward centers of the magnet insertion holes  12 ,  13 , and  45  of the laminated core body  44 . 
         [0042]    The predetermined magnet pieces  15  are inserted in the magnet insertion holes  12 ,  13 , and  45 , and the guide member  62  is positioned and mounted on the laminated core body  44 . The laminated core body  44  and the guide member  62  are then held together by the upper die and the lower die. After that, the molding resin is filled from the resin reservoir pots to the magnet insertion holes  12 ,  13 , and  45  via the resin passages  55  and  66  and the gates  54  and  65 . Accordingly, the magnet pieces  15  are fixed in the magnet insertion holes  12 ,  13 , and  45 . When the guide member  62  is removed, the molding resin is removed without remaining on the laminated core body  44 . 
         [0043]    As described above, by manufacturing the guide members  18 ,  47 ,  51 , and  62  in accordance with a shape of the laminated core body, it is not necessary to modify a shape of the molding die, thus manufacturing cost for the molding die can be reduced. 
         [0000]    In addition, since the guide members  18 ,  47 ,  51 , and  62  are replaceable in accordance with the shape of the laminated core body, the device (resin sealing apparatus) can be easily changed even when the shape of the laminated core body is changed. 
         [0044]    Furthermore, if the guide member includes two or more flat plates, it may be sufficient that only one of the flat plates is replaced in accordance with the shape of the laminated core body. 
         [0045]    In the above embodiments, the resin reservoir pots are provided in the upper die, but the resin reservoir pots can also be provided in the lower die to fill the molding resin from below to each of the magnet insertion holes. Moreover, although specific dimensions are shown in descriptions of the above embodiments, it is possible to change the values of the specific dimensions without departing from the scope of the present invention. 
         [0000]    Furthermore, although the method of manufacturing the laminated core according to the present invention is described by referring to the first to fourth embodiments above, a part or all of the above embodiments can be combined to constitute the present invention. 
       REFERENCE SIGNS LIST 
       [0046]      10 : upper die,  11 : lower die,  12 ,  13 : magnet insertion hole,  14 : laminated core body,  15 : magnet piece,  16 : resin reservoir pot,  18 : guide member,  19 : molding resin,  21 : through-hole,  22 : shaft hole,  23 ,  24 : projecting portion,  25 : core sheet,  27 : plunger,  30 : gate,  31 : resin passage,  32 : shaft hole,  33 ,  34 : projecting portion,  36 : carrier fixture,  37 : mounting portion,  38 : guide shaft,  39 : chamfer,  40 : hole,  41 ,  42 : key slot,  44 : laminated core body,  45 : magnet insertion hole,  47 : guide member,  48 : resin passage,  49 : gate,  51 : guide member,  52 ,  53 : flat plate,  54 : gate,  55 : resin passage,  57 : projecting portion,  58 : projecting portion,  59 : shaft hole,  60 : shaft hole,  62 : guide member,  63 ,  64 : flat plate,  65 : gate,  66 : resin passage