WO2018190528A1

WO2018190528A1 - Centrifugal casting apparatus for manufacturing rotor of motor

Info

Publication number: WO2018190528A1
Application number: PCT/KR2018/003326
Authority: WO
Inventors: In Gyu Jung
Original assignee: Hangnam Co., Ltd.
Priority date: 2017-04-11
Filing date: 2018-03-22
Publication date: 2018-10-18
Also published as: KR101860933B1

Abstract

The centrifugal casting apparatus for manufacturing a rotor of a motor according to the present invention comprises a lower mold 10 in which a rotor core 110 is held, and having a lower end ring molding part 11 for molding a lower end ring which is formed on the bottom of the rotor core; an upper mold 20 being positioned on the top of the lower mold 10 and having a hollow part 21; and a dummy pin 30 being combined to the center of the top of the rotor core 110, characterized in that on the top of the dummy pin 30, a molten metal injecting channel 34 is formed, so that a passage through which the molten metal is supplied is formed together with the inner upper surface 23 around the hollow part 21 of the upper mold 20.

Description

CENTRIFUGAL CASTING APPARATUS FOR MANUFACTURING ROTOR OF MOTOR

The present invention relates to an apparatus for manufacturing a rotor of a motor. More specifically, the present invention relates to a centrifugal casting apparatus which can reduce the number of unnecessary processes and lower costs for raw materials, thereby improving productivity and reducing the production cost, when molding an end ring made of copper, etc. in a rotor core.

Generally, the centrifugal casting method is a method of injecting high-temperature dissolved metal (molten metal) while rotating a mold, and casting a hollow-shaped product by centrifugal force. Such centrifugal casting method is applied to various products, and this method is applied also for the manufacture of a rotor of a motor.

Fig. 1 illustrates a rotor core 110 of a motor. The rotor core 110 is made by vertically laminating a plurality of core sheets 111, which consist of thin silicon steel sheets. In the rotor core 110, a plurality of slots 112, which are radially formed, are axially penetrated and formed, and in the center of the rotor core 110, a shaft hole 115 to which a rotary shaft is combined is formed. Such rotor core 110 is held on the mold of the centrifugal casting apparatus, and copper or aluminum molten metal is injected into the slots 112 by the centrifugal casting method, and as a result, the rotor in which an upper end ring 120 and a lower end ring 130 are formed is manufactured, as illustrated in Fig. 2.

As such, as the centrifugal casting method for manufacturing a rotor, greatly, the horizontal method and the vertical method are applied. The horizontal method is a method of obtaining a cast by rotating around the horizontal rotary shaft in the state where the rotary shaft is placed horizontally. This method is applied also for the manufacture of a rotor. However, the horizontal method has a problem that homogeneity inside the cast is low or porosity is increased, so the method has a disadvantage that the reliability of a product is so low.

For this reason, the vertical method is widely applied for the manufacture of a rotor. Korean Patent No. 10-1220890 and Korean Patent Laid-Open Nos. 10-2015-0028517 and 10-2016-0082087 disclose a rotor manufacturing apparatus using the vertical method. However, in the rotor manufacturing apparatus presented in theses prior art documents, because molten metal is injected from the top of an upper end ring, as illustrated in Fig. 3, in the rotor 100' manufactured by centrifugal casting, a considerable sized biscuit 140 is formed on the top of the upper end ring 120. Thus, the process of removing the biscuit 140 should be necessarily followed, and the waste of a material due to the formation of the biscuit cannot be prevented. Furthermore, in case where the size of the centrifugal casting mold is so small, it is difficult to take out the rotor 100' in which the biscuit 140 is formed, from the mold; thus, a process of cutting the biscuit 140 and then removing the rotor 100' from the mold, and thereafter removing the remaining biscuit 140 again is added. In addition, there is also a case where during the process of removing the biscuit 140, the upper end ring 120 is damaged, which causes a problem that the productivity is deteriorated due to the occurrence of the faulty of a product.

In particular, in case of using copper which price is high, reducing the amount of biscuits is very helpful for production cost, and because the speed that copper is coagulated is fast, if the process of removing the biscuit can be reduced, this is advantageous in the aspect of productivity. Furthermore, recently, the size of a high-powered motor which is applied to electric automobiles, etc. is getting medium and large; in case where an end ring is to be molded with copper in the medium- and large-sized motor, the prior art technology is improper because of the aforementioned problems.

Accordingly, the present inventors would like to propose a centrifugal casting apparatus having a new structure which can modify the passage into which molten metal is injected, thereby preventing the formation of biscuits so as to reduce the number of processes, improve productivity and reduce the production cost.

The object of the present invention is to provide a centrifugal casting apparatus for manufacturing a rotor of a motor, which can prevent the formation of biscuit, thereby lowering the production cost.

Another object of the present invention is to provide a centrifugal casting apparatus for manufacturing a rotor of a motor, which can reduce the number of the manufacturing processes, thereby lowering the production process and the production cost.

One another object of the present invention is to provide a centrifugal casting apparatus for manufacturing a rotor of a motor, which is suitable for applying molten metal made of copper to the centrifugal casting method.

The other object of the present invention is to provide a centrifugal casting apparatus for manufacturing a rotor of a motor, which can minimize the amount of air entered into the cast.

The centrifugal casting apparatus according to the present invention comprises

a lower mold 10 in which a rotor core 110 is held, and having a lower end ring molding part 11 for molding a lower end ring which is formed on the bottom of the rotor core;an upper mold 20 being positioned on the top of the lower mold 10 and having a hollow part 21; and

a dummy pin 30 being combined to the center of the top of the rotor core 110, characterized in that

on the top of the dummy pin 30, a molten metal injection channel 34 is formed, so that a passage through which the molten metal is supplied is formed together with the inner upper surface 23 around the hollow part 21 of the upper mold 20.

In the present invention, it is preferred that in the center of the dummy pin 30, an upwardly open-shaped molten metal retention part 33 is formed.

In the present invention, in the center of the lower mold 10, a collet which is combined to the center of the bottom of the rotor core 110 can be positioned.In the present invention, it is preferred that 6 molten metal injection channels 34 are radially formed.

In the present invention, it is preferred that the molten metal injection channel 34 which is formed on the dummy pin is connected only to the inner surface of the upper end ring 120 which is formed on the top of the rotor core 110.

The present invention has the following effects.

(1) The present invention prevents the formation of biscuits, thereby reducing the production cost for manufacturing a product.

(2) Since the present invention does not require a process of removing biscuits, the number of manufacturing processes can be reduced, thereby lowering the production cost.

(3) The present invention provides a centrifugal casting apparatus suitable for molding an end ring made of copper in a rotor core.

(4) A product which minimizes the porosity of casting and has high homogeneity can be obtained.

Fig. 1 is a perspective view illustrating a rotor core;

Fig. 2 is a perspective view illustrating a rotor in which the upper and lower end rings are molded on the rotor core;

Fig. 3 is a perspective view showing a rotor molded by the conventional centrifugal casting apparatus, i.e. the shape where biscuit is molded;

Fig. 4 is a cross section view separately illustrating the lower mold and the upper mold of the centrifugal casting apparatus according to the present invention;

Fig. 5 is a cross section view illustrating the state where the lower mold of the centrifugal casting apparatus according to the present invention is positioned on the upper mold; and

Fig. 6 is a plane view showing the structure of the dummy pin of the centrifugal casting apparatus according to the present invention.

Hereinafter, the present invention will be explained in detail with reference to the attached drawings.

Fig. 4 is a cross section view separately illustrating that the lower mold 10 and the upper mold 20 of the centrifugal casting apparatus 1 according to the present invention, and Fig. 5 is a cross section view illustrating the state where the lower mold 10 of the centrifugal casting apparatus according to the present invention is risen and positioned on the upper mold 20.

As illustrated in Figs. 4 and 5, the centrifugal casting apparatus 1 according to the present invention greatly comprises the lower mold 10, the upper mold 20, the rotor core 110 held on the lower mold, and the dummy pin 30 combined to the top of the center of the rotor core 110.

The lower mold 10 is movable upwardly and downwardly in the state where the rotor core 110 is held thereon, and when the lower mold 10 moves to the top, the rotor core 110 held on the lower mold 10 is positioned in engagement with the upper mold 20 as illustrated in Fig. 5. In this state, the lower mold 10 and the upper mold 20 rotate together on the basis of the center axis of the rotor core 110, and at the same time, high-temperature molten metal such as dissolved copper or aluminum is injected from a molten metal supply part (not shown), which is positioned on the top of the upper mold 20, into the top of the dummy pin 30 through a molten metal injection nozzle 40. Through the molten metal injection channel 34 of the dummy pin 30, the molten metal is injected through slots 112 of the rotor core 110. The injected molten metal is filled in the lower end ring 130 through the respective slots 112 and molds the shape of the upper end ring 120.

To this end, in the lower mold 10, a lower end ring molding part 11 corresponding to the shape of the lower end ring 130 is formed. In order to support the outside of the lower part of the rotor core 110, in the lower mold 10, a lower side wall part 12 is formed towards the upper side, and it is preferred that the end of the upper part of the lower side wall part 12 contacts with the end of a upper side wall part 20 of the upper mold 20 as illustrated in Fig. 5 when centrifugal casting, but it is not necessary to have a height such that the lower and upper

side wall parts

12, 22 contact with each other, and they can be positioned at a certain distance. Meanwhile, in the center where the rotor core 110 of the lower mold 10 is received, a collet 15 is formed. The collet 15 is pressed in the lower part of a shaft hole 115 of the rotor core 110 so serves as a role for fixing the rotor core 110 on the lower mold 10.

In the upper mold 20, a hollow part 21 is penetrated into the center. The molten metal injection nozzle 40 is positioned on the hollow part 21, and has the structure which allows to supply the molten metal to the rotor core 110 positioned inside the lower mold 10 and the upper mold 20. Around the lower part of the upper mold 20, an upper side wall part 22 protruding downwardly is provided. The surface around the hollow part 21 inside the upper side wall part 22 is an inner upper surface 23. This inner upper surface 23 contacts with the top of the dummy pin 30 which will be explained below, so as to form a passage through which the molten metal can flow and at the same time provide the shape of the upper surface of the upper end ring. The upper side wall inside the upper side wall part 22 is an upper end ring outer wall molding part 24, which has the shape corresponding to the shape of the outside wall 122 of the upper end ring 120.

The dummy pin 30 has the structure where it is combined to the center of the top of the rotor core 110 and at the same time combined to the hollow part 21 of the upper mold 20. That is, on the power part of a body part 32 of the dummy pin 30, a lower protruding part 31, which protrudes downwardly from the center and is pressed in the top of the shaft hole 115 of the rotor core 110, is formed. In addition, on the top of the body part 32 of the dummy pin 30, an upper protruding part 35, which protrudes upwardly from the center and is pressed in the hollow part 21 of the upper mold 20, is formed.

The outer circumference surface of the body part 32 has an upper end ring inner wall molding part 32a having the shape corresponding to the inner wall 121 of the upper end ring 120.

Meanwhile, in the center of the body part 32, an upwardly open molten metal retention part 33 is formed. At the upper side of the molten metal retention part 33, the body part 32 is penetrated into and is connected to the molten metal injection channel 34 which is formed on the top. Thus, if the molten metal supplied at the molten metal injection nozzle 40 is filled in the molten metal retention part 33 at a predetermined height, the molten metal is supplied to the molten metal injection channel 34. The reason why the molten metal is first filled in the molten metal retention part 33 is because this can reduce bubbles which may be occurred when directly supplying the molten metal to the molten metal injection channel 34.

On the top of the molten metal injection channel 34, a part of the inner upper surface 23 of the upper mold 20 is positioned, so that the molten metal stably flows into the space made by them. Of course, during this process, the supply of the molten metal is carried out in the state where the lower mold 10, the upper mold 20, the rotor core 110 and the dummy pin 30 all rotate at the same speed. Here, it is important that the supply of the molten metal is carried out towards the inner surface of the upper end ring 120. That is, in the conventional technologies, because the supply of the molten metal is carried out towards the upper surface of the upper end ring 120, the molten metal is filled and then biscuit is formed. According to the present invention, the supply of the molten metal is carried out only towards the inner surface, not the upper surface of the upper end ring 120, thereby preventing biscuit from being formed.

The molten metal supplied to the molten metal injection channel 34 is injected into the lower end ring molding part 11 of the lower mold 10 through the slots 112 of the rotor core 110. When the molten metal is continuously supplied, the respective slots 112 are filled with the molten metal, and thereafter, for the molding of the upper end ring 120, the molten metal is filled in the space made by the upper end ring outer wall molding part 24 inside the upper mold 20, the part of the inner upper surface 23, and the upper end ring inner wall molding part 32a of the body part 32 of the dummy pin 30. A small amount of the molten metal which is filled in the shape of the upper end ring 12 may overflow and flow backward towards the molten metal injection channel 34; however, the portion which flows backward and is coagulated, i.e. burr, is naturally removed when removing the dummy pin 30 from the rotor core 110. Thus, the present invention does not require a process of removing biscuit because biscuit is not formed unlike in the conventional art.

Fig. 6 is a plane view showing the structure of the dummy pin 30 of the centrifugal casting apparatus 1 according to the present invention.

Referring to Fig. 6, the dummy pin 30 of the present invention has the body part 32, and is provided with the molten metal retention part 33 in its center. The body part 32 has the upper end ring inner wall molding part 32a corresponding to the shape of the inner wall 121 of the upper end ring on its outer circumference surface. The molten metal injection channel 34 is formed in the form of a groove on the top of the body part 32, and is penetrated at the upper protruding part 35 and is connected to the molten metal retention part 33. The number of the molten metal injection channels 34 is not particularly limited, but it is preferred that 6 molten metal injection channels are formed at a predetermined angle, as shown in Fig. 6.

Please note that the explanation of the present invention above is just given to help the understanding of the present invention, and the explanation does not define the scope of protection of the present invention. The scope of protection of the present invention is defined by the attached claims, and it should be interpreted that a simple change or modification of the present invention within this scope falls within the scope of the present invention.

Claims

A centrifugal casting apparatus comprising:

a lower mold 10 on which a rotor core 110 is held, and having a lower end ring molding part 11 for molding the lower end ring formed on the lower part of the rotor core;

an upper part mold 20 being positioned on the top of the lower mold 10 and having a hollow part 21; and

a dummy pin 30 being combined to the center of the top of the rotor core 110, characterized in that

on the top of the dummy pin 30, a molten metal injection channel 34 is formed, so that a passage through which the molten metal is supplied is formed together with the inner upper surface 23 around the hollow part 21 of the upper mold 20.
The centrifugal casting apparatus according to claim 1, characterized in that in the center of the dummy pin 30, an upwardly open-shaped molten metal retention part 33 is formed.
The centrifugal casting apparatus according to claim 1, characterized in that in the center of the lower mold 10, a collet 15 which is combined to the center of the bottom of the rotor core 110 is positioned.
The centrifugal casting apparatus according to claim 1, characterized in that the molten metal injection channels 34 are radially formed.
The centrifugal casting apparatus according to claim 1, characterized in that the molten metal injection channel 34 which is formed on the dummy pin is connected only to the inner surface of the upper end ring 120 which is formed on the top of the rotor core 110.