JPH029536A - Manufacture of rotor and hub for motor - Google Patents

Abstract

PURPOSE:To improve production efficiency and to prevent production of burrs by a method wherein inner and outer cylinder bodies are molded by hot forging, and after the cylinder bodies are cooled in an interference fit state, a through-hole for a motor shaft is formed in each of the bottom walls of the two cylinder bodies by a machining work. CONSTITUTION:Inner and outer cylinder bodies 14 and 15 are molded such that a billet 13 of a low density quenching solidifying metallic powder material contained in a molding die 6 and having the coefficient of thermal expansion higher than that of a magnetic material is hot-forged by a punch 10 engaged internally of a premolded inner cylinder body 12 made of a magnetic material. The inner and the outer cylinder bodies 14 and 15 are brought into an interference fit state by cooling. Thereafter, a through-hole 18 for a motor shaft is formed in each of bottom walls 16 and 17 of the inner and outer cylinder bodies 14 and 15 by a machining work. Thus, there is no need for engagement after individual molding, and production efficiency can be improved. Since formation of the through-hole 18 for a motor shaft is effected after interference fit of the inner and outer cylinder bodies 14 and 15, displacement is prevented from occurring, and since formation of the through-hole is made by a machining work burrs produced as in a blanking work is prevented from production.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method of manufacturing a hub that also serves as a rotor for a motor used for rotating a magnetic disk or the like.

(Prior Art) FIGS. 6 and 7 each show a so-called DC motor for a hard disk drive, in which a motor shaft 22 is supported by a fixed case 20 via a bearing 21, and an armature 23 is attached to the fixed case 20. , a permanent magnet 25 is attached to the rotor 24. A rotor/rotor hub 19 is inserted and attached to the motor shaft 22 so as to rotate together with the motor shaft 22, and this hub 19 becomes the rotation center of the magnetic disk 26.

The rotor hub 19 has a composite structure in which an inner cylindrical body 14 and an outer cylindrical body 15 are fitted onto the outside. This is the inner cylinder body 14
This is to prevent leakage of magnetic flux by making the outer cylinder 15 a magnetic material such as stainless steel, and to reduce the capacity and size of the motor by making the outer cylindrical body 15 a lightweight material such as aluminum.

Conventionally, the above-mentioned rotor hub 19 has been manufactured by separately molding the inner cylinder 14 and the outer cylinder 15 and then fitting them together.

(Problem to be Solved by the Invention) In the conventional manufacturing method of the hub 19 which also serves as a rotor, it is difficult to fit the inner cylindrical body 14 and the outer cylindrical body 5, especially when precision is required such as for rotating a magnetic disk. Precise work requires careful work, which reduces efficiency.

In addition, the fitting operation becomes more difficult as the thickness of the hub becomes thinner in order to reduce the size and weight.

Furthermore, the through hole 18 of the motor shaft 22 is connected to the inner cylinder 14 and the outer cylinder 15.
If you attempt to open the holes individually after they are separated, there is a risk that the positions of the holes will not match when they are fitted.

It is also necessary to apply adhesive between the inner and outer cylinders.

In view of the above, the present invention aims to solve the above problems by focusing on the excellent deformability of rapidly cooled a solid metal powder, forming an inner cylinder and an outer cylinder by forging, and simultaneously fitting them together. The purpose is to

(Means for Solving the Problems) The present invention is characterized in that a preformed inner cylindrical body 12 made of a magnetic material is fitted onto the bunch 10, and the coefficient of thermal expansion is higher than that of the magnetic material housed in the molding die 6. A large, low-density rapidly solidified metal powder billet 13 is hot-forged with a punch 10 into which a preformed inner curved body 12 is fitted to form an inner cylinder 14 and an outer cylinder 15, and then By cooling, the inner and outer cylindrical bodies 14 and 15 are tightly fitted, and then both cylindrical bodies 1
The point is that a through hole I8 for the motor shaft is opened in the bottom wall 16.17 of 4.15 by machining.

(Function) Since the material of the outer cylinder 15 has a larger coefficient of thermal expansion than the material of the inner cylinder 14, by cooling both cylinders 14.15 after hot forging, both cylinders 14.15 It becomes a tight fit.

Since the material of the outer cylindrical body I5 is a rapidly solidified metal powder, its plastic deformability is excellent.
When the billet 13 is forged, the billet 13 can be brought into close contact with the outer peripheral surface of the inner cylinder 14 when it is formed into the outer cylinder I5.

After the inner and outer cylinders 14 and 15 are tightly fitted, the motor shaft through hole I8 is machined in both bottom walls 16 and 17 of the inner and outer cylinders. , there is no misalignment of the hole. Also, if the through holes are punched out, burrs will occur, but machining will not cause burrs.

(Example) Embodiments of the present invention will be described below based on the drawings.

In this example, the first molding step shown in FIGS. 1 and 2 and the second molding step shown in FIGS. 3 and 4 were performed using a transfer press.

In FIGS. 1 and 2, numeral 1 denotes a first molding die, the four central parts of which form a cavity 2, and the lower surface of this cavity 2 is formed by the upper surface of a first push-up block 3. This first push-up block 3 is moved up and down by a first knockout punch 4. Reference numeral 5 denotes a first punch, which is moved up and down by a drive mechanism not shown.

In FIGS. 3 and 4, reference numeral 6 denotes a second molding die, with a concave portion in the center serving as a cavity 7, and the lower surface of this cavity 7 is formed by the upper surface of a second push-up block 8. This second push-up block 8 is moved up and down by a second non-knockout punch 9. 10 is a second punch, which is moved up and down by a drive mechanism not shown.

Further, the second punch 10 can be magnetic, and therefore includes an electromagnet, for example.

In addition, the transfer press is equipped with a transport mechanism (not shown) that transports the forged product extracted from the first forming die 2 to a position above the second forming die 6.

In the forging with the above configuration, first, the magnetic material billet 1-11 is placed in the cavity 2 of the first forming die 1. In this example, the pinhole 1 is made of stainless steel (for example, 5US41
6).

Next, the billet 11 is forged with the first punch 5 to form the preformed inner cylinder body 12. In this embodiment, the preformed inner cylindrical body 12
The inner circumferential surface of the tube is an inclined surface that gradually becomes radially outward as it goes upward.

Next, the first punch 5 and the first non-kout bunch 4 are raised, and the first push-up bronch 3 pushes the preformed inner cylindrical body 12 into the first
Pull it out from molding die 1.

Then, the conveying mechanism moves the preformed inner cylindrical body 12 to the upper part of the second molding die 6 along with the hump, and as shown in the third figure, the preformed inner cylindrical body 12 is
Fit it onto the punch 10. At this time, the second punch 10 is made magnetic to prevent the preformed inner cylindrical body 12 from coming off.

Furthermore, a billet 13 made of rapidly solidified metal powder material having a higher coefficient of thermal expansion and lower density than stainless steel is housed in the cavity 7 of the second forming die 6 . In this example, 104 to 1
Non-magnetic aluminum powder produced at a cooling rate of 0.06°/sec was extruded.Also, rapidly solidified powders of aluminum alloys and titanium alloys may also be used. The reason why a powder material is used is that it has excellent plastic deformability.For example, an aluminum elephant as used in this example, a cold solidified powder is used at an extrusion ratio of 5 to 2.
0. When processed at an extrusion temperature of 250 to 480°C, the powder in the molded body is subjected to a strong shearing effect, resulting in a few inert and stable /V, 0. The film is fragmented and destroyed, and the crystallized substances and precipitates in the N base (for example, eutectic Si in the case of A/-Si alloy powder) are fragmented into fine particles, and these are uniformly distributed in the N base. When dispersed, crystal grains become finer and stronger, resulting in significantly improved plastic deformability.

Then, as shown in FIG. 4, the billet 13 is hot forged using the second punch 10 into which the preformed inner cylindrical body 12 is fitted. As a result, the preformed inner cylindrical body 12 is formed into the inner cylindrical body 14, and the grooves 3 are formed into the outer cylindrical body 15. Thereafter, the second punch 10 and the second knock-out punch 9 are raised, and the second push-up block 8 extracts both the cylindrical bodies 14 and 15 from the second forming die 6, followed by cooling. Due to this cooling, the two cylindrical bodies 14 and 15 are tightly fitted due to the difference in thermal expansion coefficients.

When an extrusion molding agent of rapidly solidified aluminum powder is used as the billet 13 and magnetic stainless steel is used as the inner cylinder 14, the molding temperature is 350 to 480'C, and the molded product is taken out at 250 to 430°C. It is better to do so. If the molding temperature is high, the unloading temperature will also be high, and since the product is cooled from a high temperature, the cooling temperature difference will be large, and the amount of shrinkage due to cooling will be excessive.If the side wall is made thinner than 1iIII11, the crank will easily enter. Become.

The molding temperature can be easily controlled by embedding a heater or the like in the die and installing an appropriate temperature control device. It is desirable that the preformed inner cylindrical body 12 and the billet 13 are also preheated.

If the inner and outer cylindrical bodies 14 and 15 are tightly fitted, the bottom walls 16°1 of both the cylindrical bodies 14 and 15 as shown in FIG.
7, the through hole 18 of the motor shaft is opened by machining.

In the rotor hub 19 manufactured by the above manufacturing method, no peeling boundary line was observed at the joint interface between the inner and outer cylinders 14 and 15 even when observed at a magnification of 3000 times. In addition, since the opening of the through hole 18 of the motor shaft is performed after the inner and outer cylindrical bodies 14 and 15 are tightly fitted, there is no misalignment between the inner and outer cylindrical bodies 14 and 15, and the opening of the through hole 18 is Since this is done by machining, there is no burr that occurs when punching is done.

(Effects of the Invention) According to the present invention, the inner and outer cylindrical bodies of the rotor hub are fitted together at the same time as they are molded, and there is no need to fit them together after individual molding as in the past, improving production efficiency. There is no need to apply adhesive or the like. Furthermore, the opening of the motor shaft through-hole is done after the inner and outer cylinders are tightly fitted, so there is no misalignment between the inner and outer cylinders, and the opening is done by machining, so there is no need for punching. There is no occurrence of Paris as in the case.

[Brief explanation of the drawing]

1 to 4 are sectional views sequentially showing the manufacturing process of a rotor-cum-hub according to an embodiment of the present invention, FIG. 5 is a sectional view of the rotor-cum-hub, and FIGS. 6 and 7 are different from each other. FIG. 1... first forming goo, 5... first punch, 6...
Second forming die, 10... Second punch, 11... Billet made of magnetic material, 12... Preformed cylindrical body, 13... Billet made of rapidly solidified powder material, 14... Inner cylinder body, 15...
・Outer cylinder body, 16.17...Bottom wall, 18...Through hole, 1
9...Rotor dual use hub.

Claims (1)

[Claims] (1) A preformed inner cylindrical body 12 made of a magnetic material is fitted onto the punch 10, and a billet 13 made of rapidly solidified metal powder material having a higher coefficient of thermal expansion and lower density than the magnetic material placed in the forming die 6
is hot-forged with a punch 10 into which a preformed inner cylinder 12 is fitted, thereby forming an inner cylinder 14 and an outer cylinder 15,
Next, the inner and outer cylindrical bodies 14 and 15 are tightly fitted by cooling, and then the bottom walls 16 and 1 of both the cylindrical bodies 14 and 15 are closed.
7. A method for manufacturing a hub that also serves as a rotor for a motor, which comprises opening a through hole 18 of a motor shaft by machining.