JPH08214480A - Spindle motor and method for machining its rotor yoke - Google Patents

Abstract

PURPOSE: To improve the productivity of a spindle motor by eliminating the occurrence of burrs and making the insertion of driving magnets easier and, at the same time, to easily make the main body of the motor thinner and prevent the breakage of the driving magnets. CONSTITUTION: A spindle motor is provided with a rotor frame 17 which is rotated while the frame 17 is mounted with a disk, rotor yoke 18 which is fixed to the frame 17 and composed of a magnetic material, driving magnets 19 fixed to the inner peripheral surface of the yoke 18, and stators 14 and 15 counterposed to the magnets 19. The yoke 18 is provided with a cylindrical section 18a, to the inner peripheral surface of which the magnets 19 are fixed, flange section 18c which is formed on the outer peripheral side of the opening end of the cylindrical section 18a by bending the opening end, cut face 18d which is formed by cutting the root of the flange section 18c in the axial direction, and curved section 18e formed on the inner peripheral edge of the opening end of the cylindrical section 18a.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to, for example, a spindle motor such as a magnetic disk drive, and a method of processing a rotor yoke of the spindle motor.

[0002]

2. Description of the Related Art FIG. 6 shows a conventional example of Japanese Patent Laid-Open No. 5-492.
The sectional view of the spindle motor published by the gazette No. 23 is shown. This spindle motor is provided with a rotor frame 1 on which a disk (not shown) is rotatably driven, a cylindrical rotor yoke 2 made of a magnetic material, which is fixed to an outer peripheral lower end surface of the rotor frame 1, and an inner peripheral surface of the rotor yoke 2. A drive magnet 3 fixed to the drive magnet 2a and a stator core 4 arranged to face the drive magnet 3 are provided. The rotor frame 1 is rotatably supported by bearings 7 and 7 ′ held by a stator frame 8. By energizing the coil 5 wound around the stator core 4, the rotor frame 1 is interposed between the stator core 4 and the drive magnet 3. Electromagnetic action works and the drive magnet 3, the rotor frame 1, and the disk rotate integrally. In this conventional example, the stator 6 is composed of the stator core 4 and the coil 5.

The conventional rotor yoke 2 is shown in FIG.
It was formed by the processing method as shown in (A) and (B). That is, first, a magnetic plate such as a cold rolled steel plate is attached to the die 30.
And punch 31 to form a cylinder with a bottom. At that time, the axial dimension L1 of the cylindrical portion is formed longer than the mounting dimension L2. This is because, even if it is attempted to obtain the mounting dimension L2 at one time by drawing, the dimensional variation becomes large, so it is necessary to form it longer than the mounting dimension L2 in advance and then cut it to a predetermined dimension. Because there is.

Next, the rotor yoke 2 was formed by cutting off the cylindrical portion in the radial direction with a blade 41 so that the height of the rotor yoke 2 became the mounting dimension L2. At the time of this cutting, as shown in FIG. 7 (B), while rotating the rotor yoke 2 which is the workpiece, a means for pressing the blade 6 against it and shearing it, or conversely fixing the rotor yoke 2 is fixed. And, the means to cut it by applying a rotary saw was taken.

[0005]

However, in the rotor yoke 2 formed as described above, since either the workpiece or the blade is rotated and cut, the open end 2b is cut. Then, scale-like burrs are generated at the opening end after cutting, which causes the burrs to fall off and become a cause of dust, which is a factor that significantly reduces the reliability of the apparatus. Further, as shown in FIG. 8A, a burr burr 2d is generated toward the center on the inner peripheral side of the open end 2c after cutting. The presence of the burr 2d not only causes the burr 2d to scrape the outer peripheral surface of the drive magnet 3 when the drive magnet 3 is inserted into the rotor yoke 2 later, but also causes debris of the magnet to be generated. Was also hindering the insertion of.

The drive magnet 3 has an adhesive 42 on the opening end 2c of the rotor yoke 2 as shown in FIG.
However, it is necessary to set the mounting dimension L2 in consideration of the blank dimension L3 for accumulating the adhesive 42 and ensuring the adhesive strength. Therefore, when such a rotor yoke 2 is applied to a spindle motor in which the stator frame 8 shown in FIG. 6 is a stator frame 8'as shown by a chain line, the height of the entire motor is increased by the margin size L3. However, there is a problem that the thickness cannot be reduced.

In view of the above situation, the present invention provides a spindle motor capable of eliminating the occurrence of burrs and improving the productivity by facilitating the insertion of the drive magnet by devising the shape of the rotor yoke and the processing method thereof. The purpose is to provide. Further, it is an object of the present invention to provide a spindle motor and a method of processing a rotor yoke thereof, which can reduce the thickness of the motor body and prevent damage to the drive magnet.

[0008]

In order to achieve the above object, in the invention according to claim 1, a rotor frame for rotating a disk mounted thereon, and a rotor yoke made of a magnetic material fixed to the rotor frame, In a spindle motor including a drive magnet fixed to the inner peripheral surface of the rotor yoke and a stator facing the drive magnet, the rotor yoke includes a cylindrical portion in which the drive magnet is fixed to the inner peripheral surface, and a cylindrical portion of the cylindrical portion. A flange portion that is bent and formed on the outer peripheral side of the opening end, a cut surface that is formed by axially cutting the root of the flange portion, and a curved portion that is formed at the inner peripheral edge portion of the opening end of the cylindrical portion. Is equipped with.

According to the second aspect of the invention, the first aspect is
In the spindle motor described above, a gap is formed between the curved portion formed on the inner peripheral edge of the opening end of the rotor yoke and the outer peripheral surface of the drive magnet, and the gap is filled with the adhesive.

Further, in the invention described in claim 3, in the spindle motor according to claim 1 or 2, the rotor yoke has a bottom portion at one end of the cylindrical portion, and a first hole formed in the center of the bottom portion. And a second portion having a diameter smaller than that of the first hole portion and having an inner peripheral surface fitted to the rotor frame.
And a hole portion.

Further, in the invention according to claim 4, a rotor frame which mounts a disk and is driven to rotate, a rotor yoke made of a magnetic material fixed to the rotor frame, and an inner circumference of a cylindrical portion of the rotor yoke. In a method of processing a rotor yoke of a spindle motor including a drive magnet fixed to a surface and a stator facing the drive magnet, a magnetic cylindrical plate is drawn into a hat shape to form a cylindrical cylindrical portion and the cylindrical portion. A flange is formed on the outer peripheral side of the open end, and the root of this flange is punched in the axial direction for cutting.

In the spindle motor and the method for processing the rotor yoke thereof of the present invention, the cylindrical portion of the rotor yoke to which the drive magnet is fixed and the flange portion following the cylindrical portion are formed by drawing the magnetic plate into a hat shape. are doing. Therefore, a burr does not occur at the opening end of the rotor yoke, and a curved portion is formed at the inner peripheral edge of the opening end, which facilitates insertion of the drive magnet and scrapes the drive magnet during insertion, thus debris is generated. It never happens. Further, since the root of the flange portion is axially punched and cut to form the rotor yoke, scaly burrs do not occur on the cut surface.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, an embodiment of a spindle motor of the present invention will be described with reference to FIGS.

In FIG. 1, reference numeral 12 is a stator frame 12 attached to the chassis of the main body apparatus, and a fixed shaft 13 is provided at the center thereof. Bearings 16 and 16 are fitted on the fixed shaft 13, and a rotor frame 17 is rotatably supported by these bearings 16 and 16. The rotor yoke 1 is attached to the lower end surface on the outer peripheral side of the rotor frame 17.
8 is fixed, and a drive magnet 19 is attached to the inner peripheral surface 18a of the rotor yoke 18. A stator core 14 having a plurality of radially protruding salient poles is fixed to the stator frame 12, and a coil 15 is wound around each salient pole. Then, the drive magnet 19
And the salient poles of the stator core 14 face each other with an appropriate interval. In this embodiment, the stator 21 is composed of the stator core 14 and the coil 15.

When the coil 15 is energized, the electromagnetic action of the stator core 14 and the drive magnet 19 causes
Drive magnet 19 and rotor yoke 1 that are rotating members
8, the rotor frame 17 and the disc are adapted to rotate.

Next, the shape of the rotor yoke 18 of the present invention and the processing method thereof will be described. Rotor yoke 18
First, as shown in FIG. 2 (A), a die 32 that is a female type of a magnetic plate such as a cold-rolled steel plate, and a cylindrical shape whose radius is smaller than the inner diameter of the die 32 by the thickness of the magnetic plate. Protrusion 33
It is drawn into a hat shape by the punch 33 having a. The rotor yoke 18 formed by this drawing process
A cross-sectional view of is shown in FIG. A curved sag (hereinafter referred to as a curved portion) 18e is formed on the inner peripheral edge of the opening end of the cylindrical portion by drawing.

Next, as shown in FIG.
A punch 35 having the same diameter as the inner diameter of the die 34 is used to axially punch the root of the collar portion 18c formed at the open end to shear the excess portion. At that time, unlike the conventional case, since no means for rotating and cutting one of the rotor yoke and the blade is used, no scaly burr is generated on the cut surface. Since the inner diameter of the die 34 is set to be slightly larger than the outer diameter of the rotor yoke 18, a short collar portion 18c is formed on the outer peripheral side of the opening end.

A sectional view of the rotor yoke 18 thus formed is shown in FIG. This rotor yoke 1
Reference numeral 8 denotes a cylindrical portion 18a, a bottom portion 18b, a flange portion 18c formed on the outer peripheral side of the open end of the cylindrical portion 18a, and the flange portion 1
The cutting surface 18d, which is the outer peripheral surface of 8c, and the curved portion 18e formed on the inner peripheral edge of the open end of the cylindrical portion 18a. Since the curved portion 18e is formed at the open end of the rotor yoke 18, there is no burr that tends toward the center unlike the conventional rotor yoke 2.

Next, FIG. 3B is a sectional view showing a state in which the drive magnet 19 is attached to the rotor yoke 18.
Since the rotor yoke 18 has the curved portion 18e formed on the inner peripheral edge portion of the opening end as described above, when the ring-shaped drive magnet 19 is fitted inside the rotor yoke 18,
Outer peripheral surface 19a of drive magnet 19 and rotor yoke 18
A gap P is formed between the curved portion 18e and the curved portion 18e. And
An adhesive 20 is filled in the gap P, and the drive magnet 19 is securely fixed to the rotor yoke 18. Since the curved portion 18e is formed on the inner peripheral edge portion of the opening end of the rotor yoke 18, the curved portion 18e serves as a guide when the drive magnet 19 is inserted, and the insertion work can be easily performed. Further, unlike the conventional example, since there is no burr toward the center direction, the drive magnet 19 is not scraped at the time of insertion, and no debris is generated. Further, since the adhesive agent 20 accumulates in the gap P formed by the curved portion 18e and the drive magnet 19, it is not necessary to set the axial length of the rotor yoke 18 to a size that takes into account the accumulation of the adhesive agent 20, and the opening of the rotor yoke 18 does not occur. The side end surface and the end surface of the drive magnet 19 can be made to have the same height, and the motor body can be made thinner.

Next, another embodiment of the rotor yoke according to the present invention is shown in FIG. In FIG. 4, the rotor yoke 18 has a first hole portion 18 formed at the center of the bottom portion 18b.
f and a second hole portion 18g having a diameter smaller than that of the first hole portion 18f. Such a stepped hole can be easily formed by providing convex portions 33a of the punch 33 shown in FIG. 2A with convex portions having different diameters.

As shown in FIG. 1, the inner peripheral surface of the second hole portion 18g is fitted into the rotor frame 17, and the peripheral portion thereof is joined to the rotor frame 17 by caulking or the like. This connection is made at the peripheral edge of the second hole 18g, which is one step lower than the first hole 18f, so that the connecting portion does not contact the drive magnet 19 and the fixed position of the drive magnet 19 is regulated. Without doing so, the rotor can be made thinner.

The above-described embodiments are examples of preferred embodiments of the present invention, but the present invention is not limited to these, and various modifications can be made without departing from the scope of the invention. Needless to say. For example, although the shaft fixed type spindle motor is shown in FIG. 1 in the above-described embodiment, the rotor yoke 18 according to the present invention can be applied to a shaft rotation type spindle motor as shown in FIG. Further, in the above embodiment, the rotor frame 1
Ball bearing 1 as a member for rotatably supporting 7
6 and 16, the dynamic pressure bearing or the slide bearing may be used separately from the ball bearing.

[0023]

As described above, the first and fourth aspects are provided.
In the spindle motor and the method for processing the rotor yoke thereof described above, burr does not occur at the opening end of the rotor yoke. Moreover, since the curved portion is formed at the inner peripheral edge of the opening end of the rotor yoke, the drive magnet can be easily inserted, and the drive magnet is not scraped during insertion to generate debris.

Moreover, in the method of processing the rotor yoke of the spindle motor according to the fourth aspect, since the root of the collar portion of the rotor yoke is punched in the axial direction for cutting, scale-like burrs do not occur on the cut surface. Therefore, the reliability of the main body device in which the spindle motor is incorporated can be improved.

Further, in the spindle motor of the second aspect, a gap is formed between the drive magnet and the curved portion formed on the inner peripheral edge of the opening end of the rotor yoke, and the gap is filled with an adhesive. Since the portion to which the adhesive is applied does not protrude to the outside, the motor can be downsized. Moreover, since this gap serves as a reservoir for the adhesive, the adhesive can be sufficiently filled and the fixing strength between the rotor yoke and the drive magnet is increased.

Furthermore, in the spindle motor of the third aspect, the rotor yoke has a first hole formed in the center of the bottom and a second hole formed with a diameter smaller than that of the first hole. Since the inner peripheral surface of the second hole is fitted to the rotor frame, the peripheral edge of the second hole can be joined to the rotor frame by caulking or the like.
The connecting part will not contact the drive magnet,
The rotor can be made thinner without restricting the fixed position of the drive magnet.

[Brief description of drawings]

FIG. 1 is a vertical sectional view of a spindle motor according to an embodiment of the present invention.

2A and 2B are cross-sectional views showing a process of processing a rotor yoke of the same spindle motor, FIG. 2A is a cross-sectional view showing how a magnetic plate is drawn, FIG. 2B is a vertical cross-sectional view of a rotor yoke after drawing, and FIG. [Fig. 4] is a cross-sectional view showing a state in which the collar portion is sheared.

FIG. 3 is a cross-sectional view showing a rotor yoke of the same spindle motor, FIG. 3A is a vertical cross-sectional view of a rotor yoke alone, and FIG.
FIG. 4 is a vertical cross-sectional view of a rotor yoke with a drive magnet attached.

FIG. 4 is a vertical sectional view showing another embodiment of the same rotor yoke.

FIG. 5 is a vertical cross-sectional view showing another embodiment of the same spindle motor.

FIG. 6 is a vertical sectional view of a conventional spindle motor.

7A and 7B are cross-sectional views showing a process of processing a rotor yoke of a conventional spindle motor, FIG. 7A is a cross-sectional view showing how a magnetic plate is drawn, and FIG. 7B is a sectional view showing an opening end of the rotor yoke after drawing. It is sectional drawing which shows a mode.

FIG. 8 is a sectional view showing a rotor yoke of the same spindle motor, FIG. 8A is a longitudinal sectional view of a rotor yoke alone, and FIG.
FIG. 4 is a vertical cross-sectional view of a rotor yoke with a drive magnet attached.

[Explanation of symbols]

 14 Stator core (stator) 15 Coil (stator) 17 Rotor frame 18 Rotor yoke 18a Cylindrical part 18c Collar part 18d Cut surface 18e Curved part 18f First hole part 18g Second hole part 19 Drive magnet 20 Adhesive

Claims (4)

[Claims] 1. A rotor frame that mounts a disk and is driven to rotate, a rotor yoke made of a magnetic material fixed to the rotor frame, a drive magnet fixed to an inner peripheral surface of the rotor yoke, and facing the drive magnet. In the spindle motor including the stator, the rotor yoke includes a cylindrical portion to which the drive magnet is fixed on an inner peripheral surface, a flange portion bent and formed on an outer peripheral side of an opening end of the cylindrical portion, and the flange portion. A spindle motor comprising: a cutting surface formed by axially cutting the root of the base and a curved portion formed on the inner peripheral edge of the open end of the cylindrical portion. 2. A gap is formed between the curved portion formed on the inner peripheral edge of the opening end of the rotor yoke and the outer peripheral surface of the drive magnet, and the gap is filled with an adhesive. Spindle motor. 3. The rotor yoke has a bottom portion at one end of the cylindrical portion, and has a first hole portion formed at the center of the bottom portion and an inner peripheral surface having a diameter smaller than that of the first hole portion. The spindle motor according to claim 1 or 2, further comprising a second hole portion that is fitted with the rotor frame. 4. A rotor frame that mounts a disk and is driven to rotate, a rotor yoke that is fixed to the rotor frame and is made of a magnetic material, and a drive magnet that is fixed to an inner peripheral surface of a cylindrical portion of the rotor yoke. In a method for processing a rotor yoke of a spindle motor including a stator facing the drive magnet, a magnetic plate is drawn into a hat shape to form a cylindrical cylindrical portion and an outer peripheral side of an opening end of the cylindrical portion. A method of processing a rotor yoke of a spindle motor, which comprises forming a flange portion to be located and punching a root of the flange portion in an axial direction to cut the flange portion.