Abstract:
A manufacturing method of a stator is a method for manufacturing the stator using molds. The stator is constructed so that a stator main body and resin molded portion are integrated. The stator main body includes a terminal portion and a core. The manufacturing method includes: arranging the stator main body such that the terminal portion is located on a top portion of the molds; and filling a cavity with resin. The terminal portion has a gas discharging port configured to discharge gas out of the cavity from inside the cavity in the molds.

Description:
INCORPORATION BY REFERENCE 
     The disclosure of Japanese Patent Application No. 2013-246017 filed on Nov. 28, 2013 including the specification, drawings and abstract is incorporated herein by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a manufacturing method of a stator, and the same stator and a motor. 
     2. Description of Related Art 
     There exists a stator which is obtainable by stacking a plurality of electromagnetic steel sheets and integrating them with resin. Injection molding method is used to integrate the electromagnetic steel sheet with resin. 
     For example, Japanese Patent Application Publication No. 2006-021329 (JP 2006-021329 A), has disclosed an injection molding method for forcibly discharging air inside a mold using a vacuum apparatus and injecting resin into the mold. Using such an injection molding method enables a resin molded portion having few defects to be obtained. Such injection molding can be used as the above-described manufacturing method of the stator. 
     By the way, another manufacturing method of a stator provided with the resin molded portion having few defects using a simpler apparatus has been demanded. Although the manufacturing method disclosed in the JP 2006-021329 can obtain such a resin molded product having few defects, it requires use of the vacuum apparatus. 
     Accordingly, the present invention provides a manufacturing method of the stator which contains the resin molded portion having few defects using the simpler apparatus. In addition, the present invention discloses the stator manufactured according to the above-described manufacturing method and a motor using the same stator. 
     SUMMARY OF THE INVENTION 
     The manufacturing method of a stator according to the present invention is a method for manufacturing the stator using molds. The stator is constructed so that a stator main body and resin molded portion are integrated and the stator main body includes a terminal portion and a core. The manufacturing method includes: arranging the stator main body such that the terminal portion is located on a top portion of the molds; and filling its cavity with resin. The terminal portion has a gas discharging port configured to discharge gas out of the cavity from inside the cavity in the molds. 
     With such a structure, the stator provided with a resin molded portion having few defects can be manufactured using a simpler apparatus. 
     The gas discharging port may be consist of a recess portion. The recess portion formed on a part of a plane of the terminal portion. The terminal portion contacts with the electromagnetic steel sheet in the plane. Further, the gas discharging port may be consist of a pipe which passes through the terminal portion. 
     A stator according to another aspect of the present invention comprises a stator main body. The stator main body includes a terminal portion and a core. The stator is constructed such that the stator main body and resin molded portion are integrated. The stator is manufactured by arranging the stator main body such that the terminal portion is located on a top portion of a molds, and filling the cavity with resin. The terminal portion has a gas discharging port configured to discharge gas out of the cavity from inside the cavity in the molds. A motor according to another aspect of the present invention comprising a stator. The stator includes a stator main body, and the stator main body includes a terminal portion and a core. The stator is constructed such that the stator main body and resin molded portion are integrated. The stator is manufactured by arranging the stator main body such that the terminal portion is located on a top portion of a molds, and filling the cavity with resin. The terminal portion has a gas discharging port configured to discharge gas out of the cavity from inside the cavity in the molds. 
     With such a structure, the stator provided with a resin molded portion having few defects can be obtained. Further, a motor having the stator provided with the resin molded portion having few defects can be obtained. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein: 
         FIG. 1  is a side view of a molded body according to a first embodiment; 
         FIG. 2  is a side view of a major portion of the molded body according to the first embodiment; 
         FIG. 3  is a front view of the major portion of the molded body according to the first embodiment; 
         FIG. 4  is a side view of the major portion of the molded body according to the first embodiment; 
         FIG. 5  is a top view of the major portion of the molded body according to the first embodiment; 
         FIG. 6  is a front view of the major portion of the molded body according to the first embodiment; 
         FIG. 7  is a flow chart of a manufacturing method according to the first embodiment; 
         FIG. 8  is a schematic view of the manufacturing method according to the first embodiment; 
         FIG. 9  is a schematic view of the manufacturing method according to the first embodiment; 
         FIG. 10  is a schematic view of the manufacturing method according to the first embodiment; 
         FIG. 11  is a side view of the major portion of a molded body according to a second embodiment; 
         FIG. 12  is a top view of the major portion of the molded body according to the second embodiment; 
         FIG. 13  is a schematic view of a manufacturing method according to the second embodiment; 
         FIG. 14  is a schematic view of an example of a terminal portion and a core; 
         FIG. 15  is a photograph showing the appearance of a resin portion; and 
         FIG. 16  is a photograph showing the appearance of the resin portion. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     First embodiment  1 . A molded body according to the first embodiment will be described with reference to  FIGS. 1 to 6 .  FIG. 1  is a side view of the molded body according to the first embodiment.  FIG. 2  and  FIG. 4  are a side view of a major portion of the molded product according to the first embodiment.  FIG. 3  and  FIG. 6  are a front view of the major portion of the molded product according to the first embodiment.  FIG. 5  is a top view of the major portion of the molded body according to the first embodiment. 
     As shown in  FIG. 1 , the molded body  9  includes a resin portion  1 , a core  2  and a terminal portion  3 . A stator main body includes the core  2  and the terminal portion  3 . The stator main body is a main component of the stator, or an assembly of such a components. The molded body  9  is used as a stator of a motor. 
     The resin portion  1  is a cylindrical body having an internal circumferential face  11 . The resin portion  1  is obtained by injection molding. 
     As shown in  FIG. 2 , the core  2  has a structure in which a plurality of electromagnetic steel sheets  21  are stacked. As shown in  FIG. 3 , the electromagnetic steel sheet  21  is an annular sheet which has a plurality of teeth  22  projecting toward a center C1 on its internal circumferential face. In the core  2 , the direction of the plural electromagnetic steel sheets  21  is fixed such that the teeth  22  are stacked. Referring to  FIG. 2  again, a coil  4  is wound around each of the stacked teeth  22 . The resin portion  1  (see  FIG. 1 ) is formed so as to cover the teeth  22  and the coils  4 . Further, the resin portion  1  is also formed so as to cover part of the terminal portion  3 . The core  2 , the terminal portion  3  and the coil  4  are joined by the resin portion  1  so that they are integrated. 
     As shown in  FIGS. 4 and 5 , the terminal portion  3  includes a terminal  31  and a base portion  32  which holds the terminal  31 . A face  33  of the base portion  32  makes contact with the core  2 . Referring to  FIG. 2  again, the terminal  31  is electrically connected to the coil  4 . Referring to  FIGS. 4 and 5  again, a slit  34  is formed in the face  33 . The slit  34  is a recess portion formed in part of the face  33  which makes contact with the core  2  of the base portion  32 , for example. The length t of a gap between the core  2  and the slit  34  has a size at least allowing gas to pass through. The range of the length t of the gap is preferably 0.01 to 0.2 mm. Here, it is assumed that gas flows in a direction G1 which goes upward from below the terminal portion  3 . Then, gas passes through the gap between the slit  34  and the core  2  and further, flows in a direction G2 which goes upward from the top side of the terminal portion  3 . Further, the resin portion  1  may invade into the gap between the core  2  and the slit  34 . The terminal  31  is made of conductive material, for example, copper or copper alloy. The base portion  32  is made of, for example, resin. 
     As shown in  FIG. 6 , the slit  34  extends in a zigzag manner. Comparing with a slit which extends upward in a linear manner, the slit  34  has a long passage on a plane of the same size and shape. 
     Next, a manufacturing method according to the first embodiment will be described with reference to  FIGS. 7 to 10 .  FIG. 7  shows a flow chart of the manufacturing method according to the first embodiment.  FIGS. 8 to 10  are a schematic view of the manufacturing method according to the first embodiment. 
     As shown in  FIG. 8 , the terminal portion  3  and the core  2  wound around the coil  4  are arranged on a movable mold  7  (arrangement step S 1 ). Here, the terminal portion  3  and at least a part of the core  2  are arranged such that they are positioned on a top portion of the movable mold  7 . Here, the top portion of the movable mold  7  may be located at any position as long as it is higher than the center of the movable mold  7 . It is more preferred, for example, to be at a position of the same height as the highest portion of a cavity in the movable mold  7 . The top portion is a portion which is located higher than the center of the movable mold  7  with respect to the vertical direction. By providing the slit  34  on the core  2 , a gap is formed between the core  2  and the terminal portion  3 . The gap is wide enough so that gas can pass through the gap. In the meantime, the terminal portion  3  may be held on the top portion of the core  2  by bonding or engagement. The movable mold  7  and a fixed mold  8  are installed on an injection molding apparatus (not shown) and is supplied with a power necessary for, injection molding. 
     Subsequently, as shown in  FIG. 9 , by moving the movable mold  7  toward the fixed mold  8 , the core  2  and the terminal portion  3  are sandwiched between the movable mold  7  and the fixed mold  8  (mold clamp step S 2 ). The core  2  and the terminal portion  3  are sandwiched by the movable mold  7  and the fixed mold  8  with a predetermined surface pressure. Here, a space inside the mold is closed by the movable mold  7 , the fixed mold  8 , the core  2  and the terminal portion  3  and a cavity is formed. The gap between the slit  34  and the core  2  is maintained wide enough so that gas can pass through the gap. 
     Subsequently, as shown in  FIG. 10 , the cavity is filled with resin L from a gate  81  of the fixed mold  8  so that the resin L is solidified (filling step S 3 ). Speaking in detail, the resin L flows to the fixed mold  8  side of the cavity, passes between the teeth  22  and the like and flows to the movable mold  7  side of the cavity. In this while, gas inside the cavity passes through the gap between the core  2  and the slit  34  and is discharged out of the cavity. The gap between the slit  34  and the core  2  in the terminal portion  3  functions as a gas discharging port. Subsequently, the cavity is filled with the resin L except the top portion of the fixed mold  8 , including the terminal portion  3  and the core  2 . Here, a surface Ls of the resin L reaches the vicinities of the terminal portion  3  and the core  2 . The air remaining in the cavity passes through the gap between the slit  34  and the core  2  so that the air continues to be discharged out of the cavity. Although the resin L further flows into the gap between the slit  34  and the core  2 , the resin L is solidified so as to stop the flow of the resin L. Here, because the slit  34  extends in a zigzag manner (see  FIG. 6 ), the resin L is solidified in the slit  34  without passing through the slit  34  thereby stopping the flow of the resin. As a result, the resin L can be prevented from leaking from outside of the cavity. Further, even if resin having a low viscosity is used as the resin L, the resin L can be prevented from leaking from outside of the cavity. 
     Because air inside the cavity is discharged successively out of the cavity in the above-described process, the cavity is filled with the resin L without containing much air. As a result, generation of poor appearance such as air trap and a defect such as void can be suppressed. After that, the resin L is solidified so as to form the resin portion  1 . 
     Finally, the movable mold  7  is moved in a direction of leaving the fixed mold  8  (mold opening step S 4 ). The molded body  9  (see  FIG. 1 ) is taken out of the fixed mold  8 . As required, unnecessary portions such as burr and a runner may be trimmed from the molded body  9 . 
     In the above-described manufacturing method of the first embodiment, a gas discharging port is provided on the top side of the mold which is filled with resin last and thereby gas can be discharged successively. Without using the vacuum apparatus, air inside the cavity can be discharged through the gap between the core and the terminal portion formed by provision of the slit, so that the molded body having few defects can be manufactured. Further, because the slit is provided between the terminal portion and the core which constitute the molded body, each time when molding is performed, gas inside the cavity can be discharged through a new slit. As a result, clogging of the slit due to repeated molding can be prevented and cleaning operation for the slit can be omitted, and generation of a defective product of the molded body due to the clogged slit can be prevented. 
     Further, according to the manufacturing method of the first embodiment, the stator provided with the molded body having few defects can be obtained. Further, a motor having this stator can be obtained. 
     Second embodiment Next, a molded body according to the second embodiment will be described with reference to  FIGS. 11 and 12 .  FIGS. 10 and 11  are a schematic view of the major portion of the molded body according to the second embodiment.  FIG. 12  is a schematic view of the major portion of the molded body according to the second embodiment. The manufacturing method of the second embodiment is different from the manufacturing method of the first embodiment in only the terminal portion. Description of other common structure is omitted. 
     As shown in  FIGS. 11 and 12 , the terminal portion  3  of the molded body holds a pipe  35  as well as the terminal  31 . The pipe  35  is mounted such that its bottom end  36  projects into the cavity. The bottom end is a lower end portion in the vertical direction of the pipe  35 . The length from the base portion  32  up to the bottom end  36  of the pipe  35  is adjusted appropriately. The pipe  35  is a pipe having a square section. In the meantime, the pipe  35  may be a pipe having a round section. The range of the length t of the gap of an opening of the pipe  35  is preferred to be 0.01 to 0.2 mm. Here, it is assumed that gas flows in a direction G1 from downward to upward of the pipe  35 . Then, gas passes through the gap of the opening from the bottom end  36  of the pipe  35  and further flows in a direction G2 which goes upward from the top side of the terminal portion  3 . Further, the resin portion  1  may invade into the gap of the opening of the pipe  35 . 
     Next, the manufacturing method of the second embodiment will be described with reference to  FIG. 13 .  FIG. 13  is a schematic view of the manufacturing method according to the second embodiment. 
     First, a manufacturing process passes the arrangement step S 1  and the mold clamp step S 2  (see  FIG. 7 ) like the manufacturing method according to the first embodiment. 
     Subsequently, resin is filled into the cavity from a gate  81  of the fixed mold  8  and solidified (filling step S 23 ) (see  FIG. 10 ). Like the filling step S 3 , the resin L flows into the cavity so that the cavity is filled with the resin L except the top side of the fixed mold  8 , particularly the terminal portion  3  and the core  2 . Here, a surface of the resin reaches the vicinities of the terminal portion  3  and the core  2 . In this while, air remaining inside the cavity passes through the pipe  35  and continues to be discharged out of the cavity. The pipe  35  functions as a gas discharging port. 
     Although the resin attempts to further flow into the pipe  35 , gas inside the cavity is discharged successively from the pipe  35 . The reason is considered to be that resin cannot flow into the pipe  35  easily or pressure is not applied to the resin easily because, for example, the bottom end  36  of the pipe  35  projects out of the base portion  32  as shown in  FIG. 13 . Subsequently, the resin flows into the pipe  35  and is solidified inside the pipe  35  to stop the flow of the resin. That is, no resin leaks out of the cavity through the pipe  35 . Because, as described above, air inside the cavity is discharged successively out of the cavity, the resin is filled in the cavity without swallowing air thereby preventing generation of poor appearance such as air trap and a defect such as void. After that, the resin is solidified so as to form the resin portion  1 . 
     Finally, a molded body  209  is obtained via the mold opening step S 4  like the manufacturing method according to the first embodiment. 
     According to the second embodiment, as described above, the gas discharging port is provided on the top side of the mold which is filled with resin at the end like the first embodiment. As a result, gas can be discharged successively. Without using the vacuum apparatus, air inside the cavity can be discharged so that a molded body having few defects can be manufactured. Further, because the pipe is provided on the terminal portion which constitutes the molded body as a gas discharging port, each time when molding is performed, gas inside the cavity can be discharged through a new pipe. As a result, clogging of the pipe due to repeated molding can be prevented and cleaning operation for the gas discharging port can be omitted, and generation of a defective product of the molded body due to the clogged gas discharging port can be prevented. 
     Further, according to the manufacturing method of the second embodiment, a stator provided with a molded body having few defects can be obtained like the manufacturing method of the first embodiment. Further, a motor having this stator can be obtained. 
     Prototype experiment. Next, a result of observation of the appearance of a prototype manufactured according to the manufacturing method of the first embodiment will be described with reference to  FIGS. 14 to 16 . A result of observation of the appearance of a comparative example manufactured according to the same manufacturing method as the manufacturing method of the first embodiment except using of a terminal portion having no slit also will be described for comparison.  FIG. 14  is a schematic view of an example of the terminal portion and the core.  FIGS. 15 and 16  are photographs showing the appearance of the resin portion. 
     An example was manufactured according to the manufacturing method of the first embodiment. In the example, the thickness t of a gap between the slit  34  and the core  2  is 0.2 mm as shown in  FIG. 14 . 
     As shown in  FIG. 15 , no defect such as air trap was recognized on the surface of the resin portion in the example, so that a mold shape was transferred accurately. The air trap mentioned here means a dent which is generated on the surface of the molded body because gas in the cavity cannot be discharged excellently. That is, in the example, the appearance of the resin portion was excellent and the resin portion had few defects. 
     On the other hand, as shown in  FIG. 16 , the air traps were recognized at a number of places of the surface of the resin portion of the comparative example. In the comparative example, the resin portion had poor appearance and defects were recognized. 
     In the meantime, the present invention is not restricted to the above-described embodiments but may be modified appropriately within a range not departing from the spirit of the invention.