JPH11195267A - Spindle motor for information equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance a rotational accuracy by mounting an immobilized member on the outer circumference of a housing made of sintered metal and directly forming a bearing surface having tilt dynamic pressure grooves to be opposed to the outer peripheral surface of a rotary shaft while interposing bearing gaps to be supported on the inner peripheral surface of the housing and impregnating lubricating oil or the like insided the housing to prevent the grooves from being collapsed. SOLUTION: The rotary shaft 1 of a turntable on which a disk is to be loaded is revolved with the electromagnetic force between the rotor 5 of a rotor case 9 being integrated with the shaft 1 and a stator coil 6 fixed covering a housing 3. The housing 3 is the porous body made of sintered metal and lubricating oil or lubricating grease is impregnated in its inside and bearing surfaces 3c to be opposed to the outer peripheral surface 1a of the rotary shaft 1 while interposing a bearing gap (c) are formed on its inner peripheral surface 3b. Then, this housing is applied to a sealing treating so that the oil is not leaked to the outer surface by providing plural inclined dynamic pressure grooves on these two bearing surfaces 3c and forming dynamic pressure oil films in the bearing gaps (c). Thus, the lowering of the manufacturing cost of the spindle motor and the miniaturizing of the motor and the making light in weight of the motor can be attained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spindle motor for information equipment, and more particularly to a laser beam printer (LB).
P) polygon mirror, magnetic disk drive (HDD)
The present invention relates to a spindle motor for a device that requires high rotational accuracy at high speeds, such as a DVD, a CD-ROM, etc., and a spindle motor for a device that is driven at a high speed by applying a large unbalance load when a disc is mounted thereon.

[0002]

2. Description of the Related Art In such small spindle motors related to information equipment, further improvement in rotational performance and cost reduction are required. The ball bearing used for the bearing part of the spindle is composed of a number of components such as inner ring, outer ring, ball, cage, seal, etc., so there is a limit to cost reduction. The sound of the ball rolling on the raceway) and the self-excited vibration of the cage generate noise.
Noise reduction has reached its limit. Therefore, replacement of the bearing portion of the spindle from a ball bearing to a porous oil-impregnated bearing, particularly a sintered oil-impregnated bearing, is being studied.

[0003] A sintered oil-impregnated bearing is one in which a bearing body made of sintered metal is impregnated with lubricating oil or lubricating grease. Oil circulating between the bearing gap and the bearing body forms an oil film in the bearing gap. It supports the rotating shaft in a non-contact manner, but because it is a kind of round bearing, unstable vibrations are likely to occur where the eccentricity of the shaft is small. There are drawbacks such as easy occurrence of Therefore, it has been attempted to provide a dynamic pressure groove such as a herringbone type or spiral type on the bearing surface, and to generate a dynamic pressure oil film in the bearing gap by the action of the dynamic pressure groove accompanying the rotation of the shaft, and to float and support the shaft. (Dynamic pressure type oil-impregnated bearing).

As shown in FIG. 5, in a conventional small spindle motor related to information equipment, this type of sintered oil-impregnated bearing 11 has a housing 14 in which a stationary member such as a stator 12 and a lower frame 13 is mounted. It is fixed to the peripheral surface by means such as press fitting or bonding.

[0005]

The conventional structure has the following points to be improved.

When the bearing is pressed into the inner peripheral surface of the housing or the like, the dynamic pressure grooves on the bearing surface may be broken.

After the bearing is pressed into the inner peripheral surface of the housing or the like, the degree of shrinkage of the bearing (due to uneven thickness of each part of the bearing, difference in density, etc.) depends on the bearing accuracy and the shape of the housing (change in wall thickness, etc.). And the cylindricity and coaxiality of the bearing surface may be deviated.

[0008] The fact that the housing and the bearing are separate bodies,
This increases the number of parts and the number of assembly steps.

[0009] Each of the housing and the bearing requires a design for securing strength, and there is a limit in reducing the size and weight.

Accordingly, an object of the present invention is to solve the above-mentioned problems in the conventional spindle motor.

[0011]

In order to solve the above-mentioned problems, according to the present invention, the housing and the dynamic pressure type oil-impregnated sintered bearing are integrated. That is, the housing of the present invention is a housing made of sintered metal, a stationary member is mounted on the outer periphery thereof, and faces the outer peripheral surface of the rotating shaft to be supported on the inner peripheral surface thereof via a bearing gap, and In addition, a bearing surface having an inclined dynamic pressure groove is directly formed, and the housing is impregnated with lubricating oil or lubricating grease.

A rotating shaft on which a rotating element of an information device is mounted is inserted into a bearing surface of a housing, and is driven to rotate by an electromagnetic force generated between a rotor and a stator. that time,
The oil held in the housing circulates between the bearing gap and the inside of the housing, and forms a dynamic pressure oil film in the bearing gap by the action of the dynamic pressure groove on the bearing surface. Are supported in a non-contact manner with respect to the bearing surface of the housing.

In order to prevent the oil impregnated inside the housing from leaking to the outside, it is desirable to perform a sealing treatment on the outer surface except the inner peripheral surface.

[0014]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 illustrates a spindle motor A for a CD-ROM. The spindle motor A mainly includes a rotating shaft 1, a housing 3 into which the rotating shaft 1 is inserted, a rotor 5 and a stator coil 6, which are arranged to face each other via a radial gap.

At the upper end of the rotating shaft 1, a turntable 8 for mounting a disk as an information recording medium is mounted.
A cylindrical rotor case 9 is attached to the lower surface of the turntable 8, and the rotor 5 is fixed to the inner peripheral surface thereof.

The housing 3 is a substantially cylindrical porous body made of a sintered metal, and is impregnated with lubricating oil or lubricating grease inside.

The housing 3 is a substantially cylindrical porous body made of sintered metal obtained by compacting and firing metal powder. Specifically, it is formed of a copper-based or iron-based, or a sintered metal mainly containing both of them.
It is formed so as to have a density of 6.4 to 7.2 g / 3 using 95 wt%. It is preferable that the outer surface of the housing 3 be subjected to a sealing treatment except for the inner peripheral surface 3b so that the oil impregnated therein does not leak to the outside.

A rotating shaft 1 is provided on an inner peripheral surface 3b of the housing 3.
A bearing surface 3c is formed opposite to the outer peripheral surface 1a of the bearing 3 with a predetermined bearing gap c therebetween. The outer peripheral surface 3d of the housing 3
The collar 3d1 is integrally formed, the stator coil 6 is externally fixed to the upper side with the collar 3d1 interposed therebetween, and the frame 10 is externally fixed to the lower side. In the case of the present embodiment, the rotor 5 and the stator coil 6 are mounted via a predetermined radial gap so as to exert an electromagnetic force in the radial direction with respect to each other.

As shown in FIG. 2, on the inner peripheral surface 3b of the housing 3, two axially spaced bearing surfaces 3c are formed, and both of the two bearing surfaces 3c are inclined with respect to the axial direction. The plurality of dynamic pressure grooves 3e are arranged in the circumferential direction. The step (depth of the dynamic pressure groove 3e) between the dynamic pressure groove 3e and the other area 3f on the bearing surface 3c is, for example, 3 to 5
It is about μm. It is sufficient that the dynamic pressure groove 3e is formed to be inclined with respect to the axial direction, and the shape is not limited to the shape shown in FIG.

Various molding methods can be applied to the molding of the bearing surface 3c as described above. For example, an inner peripheral surface 3b 'of a sintered metal material 3' having a predetermined shape as shown in FIG.
Then, by pressing a forming die having a shape facing the bearing surface 3c of the finished product 3, the formation region of the dynamic pressure groove 3e of the bearing surface 3c and the other region 3f can be simultaneously formed. This step is as follows.

FIG. 4 illustrates a schematic structure of a forming apparatus used in a bearing surface forming step. This apparatus includes a cylindrical die 20, a core rod 21 forming an inner peripheral surface 3b 'of a sintered metal material 3', and upper and lower primary punches 22, 23 for pressing both end surfaces of the sintered metal material 3 'from above and below. And upper and lower secondary punches 24 and 25 for pressing the sintered metal material 3 'from the outer peripheral surface.
Is composed as a main element. On the outer peripheral surface of the core rod 21, two forming dies 21a having an uneven shape corresponding to the shape of the bearing surface 3c of the finished product are provided at a distance in the axial direction. The first forming portion 21a1 of each forming die 21a which is convex.
Molds the region of the dynamic pressure groove 3e on the bearing surface 3c, and the concaved second molded portion 21a2 is formed in the region 3 other than the dynamic pressure groove 3e.
f is formed. The step between the first forming portion 21a1 and the second forming portion 21a2 in the forming die 21a is 3 to 5 μm, which is the same as the depth of the dynamic pressure groove 3e in the bearing surface 3b.

After the core rod 21 is inserted into the circumferential surface 3b 'of the sintered metal material 3' with a gap therebetween to perform positioning,
The upper primary punch 22 and the core rod 21 are lowered, and the sintered metal material 3 ′ is pressed into the die 20 and further pressed against the lower primary punch 23. Then, the upper and lower secondary punches 24.2
5, and press the sintered metal material 3 'from the outer peripheral side.

The sintered metal material 3 ′ is composed of upper and lower primary punches 22.
The inner peripheral surface 3b 'of the sintered metal material 3' undergoes plastic flow on the side of the core rod 21 to bite the forming die 21a. Thus, the shape of the mold 21a is transferred to the inner peripheral surface 3b 'of the sintered metal material 3', and the bearing surface 3c is
Is formed into the shape shown in FIG.

After the molding of the bearing surface 3c is completed, the upper and lower secondary punches 24 and 25 are removed, the upper primary punch 22 is raised, and the lower primary punch 22 is inserted with the core rod 21 inserted into the sintered metal material 3 '. Next, the punch 23 and the core rod 21 are raised in conjunction with each other, and the sintered metal material 3 ′ is pulled out of the die 20. When the sintered metal material 3 'is pulled out of the die 20, the sintered metal material 3'
As a result, the core rod 21 can be removed from the inner peripheral surface 3b 'of the sintered metal material 3' without breaking the dynamic pressure groove 3e. Thus, the housing 3 having the shape shown in FIG. 2 is completed.

The spindle motor A comprises a housing 3 formed as described above, a thrust receiver 4, a stator coil 6 and the like attached thereto, and then a rotary shaft 1 on which a turntable 8, a rotor case 9, and a rotor 5 are mounted. 3 to complete.

With the spindle motor A, the oil retained inside the housing 3 is transferred to the bearing surface 3 with the rotation of the rotating shaft 1.
b oozes out into the bearing gap c from both axial sides. Further, the oil is drawn toward the axial center of the bearing gap c by the dynamic pressure groove 3e. Due to this oil drawing action, the pressure of the oil film interposed in the bearing gap c is increased, and a dynamic pressure oil film is formed. By the dynamic pressure oil film, the rotating shaft 1 is supported by floating (non-contact support) with respect to the bearing surface 3b without causing unstable vibration such as whirl. The oil that has oozed into the bearing gap c is generated by the pressure generated by the rotation of the rotating shaft 1.
b returns to the inside of the housing 3 from the surface opening (the portion where the pores of the porous body tissue are opened on the outer surface), circulates inside the housing 3, and returns from the bearing surface 3b to the bearing gap c again. Seep out.

The spindle motor in this embodiment is
Since the configuration is for a CD-ROM, the shape of the housing 3 and other components, the structure of the motor, and the like shown above are suitable for a CD-ROM. These are changed and used according to the application.

In the above embodiment, the method of manufacturing the housing has been described in which the method of extracting the housing from the core rod using the springback of the sintered metal material without breaking the dynamic pressure groove is described. However, the present invention is not limited to this manufacturing method. Another method is to use a core rod configured to be freely expandable and contractable by forming a slit (slit) at the tip of the core rod, reducing the diameter of the core rod after molding the housing, and removing the housing from the core rod. May be.

[0030]

According to the present invention, since the bearing surface is formed directly on the inner peripheral surface of the housing, the operation of fixing the bearing, which is required in the conventional spindle motor, becomes unnecessary. For this reason, the problems of fixing the bearing, such as the collapse of the dynamic pressure groove on the bearing surface and the deviation of the cylindricity and coaxiality of the bearing surface, do not occur. Therefore, high-speed rotation performance and rotation accuracy of the spindle motor can be improved.

Further, since the housing and the bearing are integrally formed, the number of parts and the number of assembling steps can be reduced, and the manufacturing cost can be reduced. Since it is sufficient to design the integrated product of the housing and the bearing to secure the strength, it is possible to further reduce the size and weight.

Further, by sealing the outer surface except the inner peripheral surface of the housing, it is possible to prevent the oil impregnated inside the housing from leaking to the outside.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a spindle motor for a CD-ROM according to an embodiment of the present invention.

FIG. 2 is a longitudinal sectional view of a housing of a spindle motor for a CD-ROM according to an embodiment of the present invention.

FIG. 3 is a longitudinal sectional view of a sintered metal material according to an embodiment of the present invention.

FIG. 4 is a schematic sectional view of a housing forming apparatus according to an embodiment of the present invention.

FIG. 5 is a longitudinal sectional view of a conventional small spindle motor related to information equipment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Rotating shaft 3 Housing 3b Inner peripheral surface 3c Bearing surface 3d Outer peripheral surface 3d1 Collar 3e Dynamic pressure groove 3f Area other than groove of bearing surface 4 Thrust receiver 5 Rotor 6 Stator coil 8 Turntable c Bearing gap

Claims (4)

[Claims] 1. A rotating shaft on which a rotating element of an information device is mounted, a rotor and a stator coil opposed to each other via a predetermined gap, and a stationary member mounted on the outer periphery of the rotor and the stator coil. Is formed on the inner peripheral surface, which faces the outer peripheral surface of the rotary shaft via a bearing gap, and has a bearing surface having an inclined dynamic pressure groove,
A housing made of a sintered metal impregnated with lubricating oil or lubricating grease therein, wherein the rotating shaft is rotationally driven by electromagnetic force generated between the rotor and the stator coil; A spindle motor for an information device, wherein the rotating shaft is rotatably supported in a non-contact manner with respect to a bearing surface of the housing by a formed dynamic oil film of oil. 2. The spindle motor according to claim 1, wherein a sealing process is performed on an outer surface of the housing except an inner peripheral surface of the housing. 3. A stationary member is mounted on an outer peripheral surface thereof, and an inner peripheral surface into which a rotating shaft on which a rotating element of an information device is mounted is inserted, facing an outer peripheral surface of the rotating shaft via a bearing gap, and ,
A housing for an information equipment spindle motor, which is formed of a sintered metal having a bearing surface having an inclined dynamic pressure groove and impregnated with lubricating oil or lubricating grease. 4. A housing for a spindle motor of an information equipment according to claim 3, wherein a sealing treatment is applied to an outer surface excluding the inner peripheral surface.