Method for manufacturing an injection mold for a stator of a motor and injection mold for a stator of a motor

Abstract

Provided are a manufacturing method for an injection mold for a motor stator and an injection mold for a motor stator. An injection mold (1) used when performing molding for a motor stator having a core portion formed by stacking a plurality of annular electromagnetic steel sheets and a coil wound around a plurality of slots formed at an inner circumferential portion of the core portion at a prescribed interval, performs molding by injecting an insulating resin into at least a gap between the core portion and the coil and curing it. The injection mold (1) has a long main body portion (11) and a flange portion (12) extending outward from one end of the main body portion (11) in the length direction. After performing shot blasting on an outer circumferential surface (11a) of the main body portion (11) of the injection mold (1), electrolytic plating is performed.

Description

TECHNICAL FIELD

[0001] The present application relates to a manufacturing method of an injection mold for a motor stator used when performing mold forming with respect to a motor stator provided with a core portion formed by stacking a plurality of annular electromagnetic steel sheets, and a coil wound around a plurality of slots formed at an inner circumferential portion of the core portion at a prescribed interval, and injecting and curing an insulating resin at least to a gap between the core portion and the coil, and an injection mold for a motor stator manufactured by the manufacturing method. BACKGROUND

[0002] Conventionally, it is known that, when performing mold forming of a motor stator, an injection mold provided with a main body portion of a long size, and a flange portion extending outward from one end of the length direction of the main body portion is used (for example, refer to Patent Literature 1).

[0003] At the time of mold forming of the motor stator, the main body portion of the injection mold is inserted into the core portion of the motor stator in a state where the core portion of the motor stator is fitted into a cylindrical frame, and the one end of the length direction of the frame is overlapped with the flange portion. Then, a molten insulating resin is injected and filled into an inner cavity formed between the injection mold and the frame, and the filled insulating resin is heated and cured. After the insulating resin is cured, it is taken out of the injection mold, and a mold-formed motor stator is obtained.

[0004] However, the inner diameter size of each electromagnetic steel sheet forming the core portion is sometimes uneven due to a tolerance, and thus, it is rare that the radial size of the inner circumferential portion of the core portion is uniform in the entire length direction of the motor stator. In addition, since the insulating resin is injected from one end of the length direction of the motor stator to the other end via the slots of the core portion and the like, a part of the inner circumferential surface of the insulating resin cured in the inner cavity or the slots and the like is tightly joined to the outer circumferential surface of the main body portion of the injection mold.

[0005] Therefore, when the main body portion of the injection mold is inserted into the core portion, or when the motor stator is taken out of the injection mold after the mold forming, the outer circumferential surface of the main body portion of the injection mold rubs against a part of at least one of the inner circumferential portion of the core portion or the inner circumferential portion of the insulating resin after being cured, and causes abrasion of the main body portion of the injection mold. Thus, the injection mold for the conventional motor stator cannot sufficiently withstand repeated use.

[0006] PRIOR ART DOCUMENTS

[0007] PATENT LITERATURE

[0008] Patent Literature 1: Japanese Patent Application Laid-Open No. 2018-46710 SUMMARY

[0009] The present application has been made in view of the above-described problems, and has as its object to provide a manufacturing method of an injection mold for a motor stator that is sufficiently resistant to repeated use during molding of a motor stator, and an injection mold for a motor stator manufactured by the manufacturing method.

[0010] To achieve the above object, the manufacturing method of an injection mold for a motor stator according to the present application is a manufacturing method of an injection mold for a motor stator used when molding a motor stator, the motor stator including a core portion formed by stacking a plurality of annular electromagnetic steel sheets, and a coil wound around a plurality of insertion grooves formed at an inner circumferential portion of the core portion at regular intervals, and is characterized in that, when molding the motor stator by at least injecting an insulating resin into a gap between the core portion and the coil and curing the insulating resin, the injection mold is subjected to shot peening of an outer circumferential surface of a main portion, and then subjected to electroless plating.

[0011] Further, the injection mold for a motor stator according to the present application is manufactured by the above-described manufacturing method of an injection mold for a motor stator, and is characterized in that a plating layer based on the electroless plating is formed on the outer circumferential surface of the main portion after the shot peening.

[0012] According to the manufacturing method of an injection mold for a motor stator and the injection mold for a motor stator of the present application, the outer circumferential portion of the main portion of the injection mold is work-hardened by the shot peening, and the friction resistance is improved. Further, since the compressive stress at the time of the shot peening remains in the outer circumferential portion of the main portion of the injection mold, the fatigue strength of the outer circumferential portion of the main portion of the injection mold is improved. Furthermore, since the outer circumferential surface of the main portion of the injection mold is formed with fine irregularities, the adhesion of the plating layer formed on the outer circumferential surface of the main portion of the injection mold that has been subjected to the shot peening by the electroless plating is improved, so that peeling of the plating layer and the like are less likely to occur. Moreover, the plating layer is hard and has corrosion resistance. Therefore, when the main portion of the injection mold is inserted into the core portion, or when the motor stator is taken out of the injection mold after the molding, the plating layer formed on the outer circumferential surface of the main portion of the injection mold that has been subjected to the shot peening is able to suppress the abrasion of the main portion of the injection mold even if it comes into friction with a part of at least one of the inner circumferential portion of the core portion or the inner circumferential portion of the insulating resin after curing. Thus, the injection mold for a motor stator is able to be sufficiently resistant to repeated use during molding. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1is a perspective view of one embodiment of an injection mold for a motor stator of the present application.

[0014] Figure 2 (a) is a schematic cross-sectional view of a state at the time of mold formation, Figure 2 (b) is a schematic cross-sectional view at the time of taking out the motor stator from the injection mold.

[0015] Explanation of Reference Numerals

[0016] 1... injection mold; 11... main body portion; 11a... outer peripheral surface; 11c... plating layer; 12... flange portion; 2... motor stator; 21... core portion; 21a... insertion slot; 23... coil; 3... insulating resin. DETAILED DESCRIPTION

[0017] Reference Figure 1 , an injection mold 1 for a motor stator of the present embodiment will be described. The injection mold 1 is a hollow mold having a main body portion 11 of a long length and a cylindrical shape, and a flange portion 12 extending outward from one end of the main body portion 11 in the length direction. After mold formation, a refrigerant such as air flows in the hollow portion la of the injection mold 1, and the motor stator can be cooled together with the injection mold 1 by the refrigerant.

[0018] The main body portion 11 and the flange portion 12 of the injection mold 1 are each made of metal, and can be integrally formed by, for example, die casting of aluminum. In addition, as shown in the broken line circle in Figure 1 , the outer peripheral surface 11a of the main body portion 11 is subjected to shot blasting. Shot blasting is a metalworking method in which a plurality of spherical bodies made of metal or the like collide with the surface of a metal product at high speed. At the time of collision of the spherical bodies, a recess due to plastic deformation is formed in the collided portion of the metal product, and the surface of the metal product is formed with fine irregularities. On the other hand, the plastic deformation at the recess is restrained by portions other than the collided portion, or portions at a position closer to the inside of the surface portion than the recess, and a compressive residual stress is generated in the collided portion. As a result, the collided portion of the metal product after shot blasting is hardened by a change in the metal structure accompanying the plastic deformation, and the resistance to friction is improved. In addition, the fatigue strength is increased due to the residual of the compressive stress. Therefore, the outer peripheral portion 11b of the main body portion 11 of the injection mold 1 is improved in the resistance to friction and the fatigue strength compared with conventional products.

[0019] Furthermore, in the injection mold 1, the outer peripheral surface 11a of the main body portion 11, which has been subjected to the shot blasting treatment, is subjected to an electroless plating. The electroless plating is a plating method in which a plating object is immersed in a plating solution, and a surface of the plating object is caused to deposit a film by electrons released by oxidation of a reducing agent contained in the plating solution. The plating layer 11c, which is the deposited film, is hard and has corrosion resistance. In addition, since the outer peripheral surface 11a of the main body portion 11 of the injection mold 1, which has been subjected to the shot blasting treatment, is formed with fine irregularities, the adhesion of the plating layer 11c is improved, so that peeling of the plating layer 11c and the like are unlikely to occur. In addition, as a main component of the plating layer 11c, nickel is preferably cited.

[0020] The injection mold 1 of the stator for motor is manufactured by subjecting the outer peripheral surface 11a of the main body portion 11 to the shot blasting treatment and then subjecting it to the electroless plating. As the electroless plating, electroless nickel plating or the like can be cited.

[0021] Next, with reference to (a) and (b) of Fig. 2, the mold molding of the stator for motor 2 using the injection mold 1 shown in Fig. 1 is described. Figure 2 Figure 1 In the stator for motor 2, the core portion 21 is inserted into the cylindrical frame 22 by shrink fitting or the like, and the coil 23 is wound around the plurality of slots 21a formed at regular intervals in the inner peripheral portion of the core portion 21. At the time of the mold molding, the injection mold 1 is arranged with the flange portion 12 horizontally with the main body portion 11 upward, the main body portion 11 of the injection mold 1 is inserted into the core portion 21 of the stator for motor 2, and the lengthwise one end of the frame 22 is placed on the flange portion 12 of the injection mold 1 (a of Fig. 2). Figure 2 The main body portion 11 of the injection mold 1 is longer than the frame 22 in length, and inner cavities 4a and 4b for filling the insulating resin 3 are formed between the injection mold 1 and the stator for motor 2, and at the upper end portion and the lower end portion in the lengthwise direction of the frame 22, respectively.

[0022] Furthermore, the coil 23 of the stator for motor 2 is supplied with an alternating current from an alternating current power source (not shown) to heat the coil 23, and the heat is conducted to the core portion 21 and the frame 22, the injection mold 1, and the like, and the mold molding is performed after the preheating. At the time of the mold molding, the molten insulating resin 3 is injected from the inner cavity 4a at the position of the upper end portion in the lengthwise direction of the frame 22, and after the insulating resin 3 is filled into the inner cavity 4a, it is further filled into the inner cavity 4b at the position of the lower end portion in the lengthwise direction of the frame 22 through the gap between the core portion 21 and the coil 23 in the slot 21a, the gap between the conductors forming the coil 23, and the like. Thereafter, the stator for motor 2 is heated together with the injection mold 1 as with the preheating, so that the insulating resin 3 is cured.

[0023] ​After the insulating resin 3 is cured, a refrigerant such as air is circulated in the hollow portion la of the injection mold 1, and, if necessary, a refrigerant such as air is blown against the outer peripheral surface of the frame 22, or another method of refrigeration is performed, whereby the stator 2 for a motor is cooled together with the injection mold 1. Next, the stator 2 for a motor, which has been molded, is lifted upward and taken out of the injection mold 1. Figure 2

[0024] However, as described above, the inner diameter dimension of each electromagnetic steel sheet that forms the core portion 21 of the stator 2 for a motor is sometimes uneven due to a tolerance, and thus, the radial dimension of the inner peripheral portion of the core portion 21 is rarely uniform in the entire length direction of the stator 2 for a motor. In addition, since the insulating resin 3 is also filled into the inner cavity 4b via the inner cavity 4a and the insertion slot 21a of the core portion 21, a portion of the inner peripheral surface of the cured insulating resin 3 is tightly joined to the outer peripheral surface lid of the plated layer lie that is formed on the outer peripheral surface 11a of the main body portion 11 of the injection mold 1, which has been subjected to a shot peening treatment. Figure 1

[0025] However, in the injection mold 1 of the present embodiment, as described above, the outer peripheral portion lib of the main body portion 11 is work-hardened by the shot peening treatment, and the friction resistance is improved. In addition, since a compressive stress at the time of the shot peening treatment remains in the outer peripheral portion lib of the main body portion 11, the fatigue strength of the outer peripheral portion lib of the main body portion 11 is improved. Furthermore, since the outer peripheral surface 11a of the main body portion 11 of the injection mold 1 is formed with fine irregularities, the tightness of the plated layer lie that is formed on the outer peripheral surface 11a of the main body portion 11, which has been subjected to the shot peening treatment, by the electrolytic-less plating is improved, and thus, a peeling or the like of the plated layer lie is less likely to occur. Moreover, the plated layer lie is hard and has corrosion resistance. Therefore, when the main body portion 11 of the injection mold 1 is inserted into the core portion 21, or when the stator 2 for a motor is taken out of the injection mold 1 after the molding, even if a portion of at least one of the inner peripheral portion of the core portion 21 or the inner peripheral portion of the cured insulating resin 3 rubs against the plated layer lie that is formed on the outer peripheral surface 11a of the main body portion 11 of the injection mold 1, which has been subjected to the shot peening treatment, the wear of the main body portion 11 of the injection mold 1 can be suppressed. Thus, the injection mold 1 of the stator 2 for a motor can sufficiently withstand repeated use at the time of molding. Since the injection mold 1 can be repeatedly used, the manufacturing cost of the stator for a motor can be reduced.

[0026] ​​Although the embodiment of the present application has been described above, the present application is not limited to the above-described embodiment. The injection mold 1 can be pulled downward to extract the molded motor stator 2 from the injection mold 1. In addition, the injection mold 1 can have only the main body portion 11 and the flange portion 12, and other small portions can be appropriately changed. Furthermore, the metal forming the injection mold 1 is not limited to aluminum, and the main component of the plating layer 11c formed by the electroless plating is not limited to nickel.

Claims

1. A method of manufacturing an injection mold for a stator of a motor, the method of manufacturing an injection mold for a stator of a motor being a manufacturing method used when performing mold formation with respect to a stator of a motor that has a core portion formed by laminating a plurality of annular electromagnetic steel sheets, a coil wound around a plurality of slots formed at an inner circumferential portion of the core portion at a prescribed interval, and a cylindrical frame in which the core portion is inserted, and performs mold formation in which at least an insulating resin is injected into a gap between the core portion and the coil and cured with respect to the stator of a motor, characterized in that the injection mold has a main portion that is a long cylindrical shape and has a length longer than a length of the frame, and a flange portion that extends outward from one end of the main portion in the length direction, the injection mold also has a hollow portion, the flange portion is horizontally disposed with the main portion facing upward, the main portion is inserted into the core portion of the stator of a motor, and one end of the frame in the length direction is placed on the flange portion, an inner cavity for filling the insulating resin is formed between the injection mold and the stator of a motor and at an upper end portion and a lower end portion of the frame in the length direction, respectively, electroless plating is performed after shot blasting is performed on an outer circumferential surface of the main portion of the injection mold.

2. An injection mold for a stator of a motor, characterized in that the injection mold for a stator of a motor is manufactured by the method of manufacturing an injection mold for a stator of a motor according to claim 1, a plated layer based on electroless plating is formed on the outer circumferential surface of the main portion after shot blasting has been performed.

Images