JPH08308172A - Motor using dynamic pressure bearing - Google Patents

Abstract

PURPOSE: To provide a motor using dynamic pressure bearing which is suitable for FDD, HDD, etc., and has a small size, light weight, high strength, and excellent physical properties. CONSTITUTION: In a fixed bearing/rotating shaft type motor using dynamic bearing, a supporting frame 8 and dynamic pressure bearing 9 are integrally constituted of a sintered body of metal powder and a dynamic pressure generating groove is formed on the inner peripheral surface of a fixed bearing section 3. Therefore, materials can be used effectively and the diameter and machining time of the motor can be reduced and the strength and machining accuracy of the motor can be improved by eliminating overlapping sections and bonding sections at the time of assembly.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure bearing motor suitable for FDD (floppy disk drive device), HDD (hard disk drive device) and the like, and more particularly to improvement of a dynamic pressure bearing structure.

[0002]

2. Description of the Related Art FDDs and HDDs are used as peripheral devices for electronic devices such as computers. These peripheral devices have a built-in spindle motor for rotationally driving an FD (floppy disk) or HD (hard disk).

In recent years, there has been a demand for high speed rotation, low noise, high precision, improved vibration resistance, downsizing, flatness, and high reliability of these electronic devices. As a motor that meets these demands, an oil dynamic pressure bearing motor (or a fluid bearing) is drawing attention.

In the dynamic pressure bearing, a dynamic pressure generating groove is formed on the inner peripheral surface of the bearing, and oil (lubrication oil) is provided between the rotary shaft and the inner peripheral surface of the bearing.
Is enclosed, and the rotary shaft is rotatably supported in a non-contact state by the pumping action of the dynamic pressure generated by the dynamic pressure generating groove as the rotary shaft rotates.

FIG. 5 shows an example of a conventional dynamic pressure bearing motor.
As shown in the figure, the dynamic pressure bearing motor is roughly composed of a rotating rotor assembly 1 and a fixed stator assembly 2, and has a so-called shaft rotation / bearing fixed type structure. In the rotor assembly 1, a hub 4 is attached to the upright rotating shaft 3. A drive magnet 5 is attached to the inner surface of the lower portion of the hub 4 via a back yoke 6.

As shown in FIG. 5, the support frame 100 includes a frame portion 80 and a fixed bearing portion 90 which are separately provided.
Consists of The frame portion 80 has an outer tubular portion 81 that surrounds the outside of the rotating shaft 30, and the fixed bearing portion 9 is provided inside the outer tubular portion 81.
0 is fitted. The fixed bearing portion 90 has a hollow cylindrical shape, the rotary shaft 3 is rotatably inserted into an inner hole of the fixed bearing portion 90, and a dynamic pressure generating groove (not shown) is formed on the inner peripheral surface by rolling molding (plastic working) or the like. .) Has been formed. A status core 10 is mounted on the outer peripheral surface of the fixed bearing portion 90 so as to face the drive magnet 5, and a stator winding 11 is wound around the status core 10. Reference numeral 12 is a thrust plate, and 13 is a retaining plate for preventing oil leakage.

[0007]

The dynamic pressure bearing motor is suitable for the specifications of light load and high speed rotation such as a spindle motor, but has the following problems.

That is, in the case of a dynamic pressure bearing motor, the clearance between the dynamic pressure bearing and the rotary shaft 3 is on the order of several microns, and the inner diameter of the bearing and the inner surface roughness must be finished on the order of submicron. In addition, strict precision is required for the reference plane for processing or assembly. In order to secure such accuracy in a combination of a plurality of parts such as a combination of the outer cylinder portion 81 and the fixed bearing portion 90, it is necessary to repeat machining and adjustment, which requires machining labor and machining time. This is a cause of increase in production efficiency, decrease in production efficiency, and rise in production cost. In addition, since the dynamic pressure bearing motor uses oil, there is a problem in terms of temperature characteristics due to oil leakage and oil clay. An object of the present invention is to solve the above problems and to provide a dynamic bearing motor that is small in size and light in weight, has high strength, and is excellent in various physical characteristics.

[0009]

In order to solve the above-mentioned problems, the present invention as set forth in claim 1, is a fixed bearing in which a rotary shaft of a rotor is rotatably fitted to a support frame made of a sintered body of metal powder. And a dynamic pressure generating groove is formed on the inner peripheral surface of the fixed bearing portion to integrally configure the support frame and the dynamic pressure bearing.

According to a second aspect of the present invention, in the dynamic pressure bearing motor according to the first aspect, the support frame is made of a magnetic material having a coefficient of thermal expansion lower than that of the rotary shaft.

According to a third aspect of the present invention, in the dynamic pressure bearing motor according to the first aspect, a resin layer or a metal layer is formed on the inner peripheral surface of the fixed bearing portion.

According to a fourth aspect of the present invention, in the dynamic pressure bearing motor according to the first aspect, at least the fixed bearing portion of the support frame is impregnated with resin.

According to a fifth aspect of the present invention, in the dynamic pressure bearing motor according to the first aspect, the sintered density of the support frame is 85% or more.

According to a sixth aspect of the present invention, in the dynamic pressure bearing motor according to the first aspect, the dynamic pressure generating groove is formed by plastic working.

According to a seventh aspect of the present invention, a fixed shaft on which the rotary bearing portion of the rotor is rotatably fitted is formed on a support frame made of a sintered body of metal powder, and a dynamic pressure is applied to the outer peripheral surface of the fixed shaft. The generating groove is formed to integrally configure the support frame and the dynamic pressure bearing.

[0016]

According to the invention described in claim 1, in the fixed bearing / rotary shaft type dynamic pressure bearing motor, the support frame and the dynamic pressure bearing are integrally formed of a sintered body of metal powder, and the fixed bearing is used. Since a dynamic pressure generating groove is formed on the inner peripheral surface of the part, there is no waste of material, eliminating stacking and joining parts during assembly to reduce the diameter, improve strength, reduce processing time, improve processing accuracy. It will be possible.

According to the second aspect of the invention, since the support frame is made of a magnetic material having a coefficient of thermal expansion lower than that of the rotary shaft, the clearance between the fixed bearing portion and the rotary shaft is narrow at high temperature and wide at low temperature. It is possible to improve the temperature dependence of the driving force of the motor by canceling out the viscosity of the oil that decreases at high temperature and increases at low temperature.

According to the third aspect of the invention, since the resin layer or the metal layer is formed on the inner peripheral surface of the fixed bearing portion, the resin layer or the metal layer has a function of sealing the porous material generated in the sintered body. However, since the inner peripheral surface of the fixed bearing portion can be hermetically sealed, oil leakage prevention and rust prevention effects are exhibited.

According to the fourth aspect of the present invention, since at least the fixed bearing portion of the support frame is impregnated with the resin, it is possible to close the inner surface of the fixed bearing portion by closing the porous body. Can prevent leakage.

According to the fifth aspect of the present invention, the sintered density of the support frame is set to 85% or more, whereby the degree of sealing of the inner peripheral surface of the fixed bearing portion is improved, and resin impregnation or resin or metal coating is performed. Oil leakage can be prevented even without applying.

According to the invention described in claim 6, since the dynamic pressure generating groove is formed by plastic working, the porous is closed by a kind of crushing action and the hermeticity of the inner peripheral surface of the fixed bearing portion is improved. It can prevent oil leakage.

According to the invention of claim 7, the same operation as that of the invention of claim 1 can be exerted also on a fixed rotary shaft / rotary bearing type dynamic pressure bearing motor.

[0023]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, preferred embodiments of the present invention will be described with reference to the drawings. (I) First Embodiment FIG. 1 shows a first embodiment of the present invention. FIG. 1 is a half sectional view of a dynamic pressure bearing motor. As shown in the figure, the dynamic pressure bearing motor is roughly composed of a rotating rotor assembly 1 and a fixed stator assembly 2, and has a so-called rotating shaft / fixed bearing type structure.

In the rotor assembly 1, a hub 4 is mounted on a rotating shaft 3 which stands upright. A drive magnet 5 is fixed to the inner surface of the lower portion of the hub 4 via a back yoke 6.

As shown in FIG. 2, the support frame 7 is composed of a frame portion 8 and a fixed bearing portion 9 and is formed by firing a metal powder made of a magnetic material such as Invar (iron-nickel alloy) or SUS (stainless alloy). It is united and formed integrally. The average density of the sintered body is preferably 85% or more.

Here, the reason why the average density of the sintered body is set to 85% or more is as follows. That is, the pores of the sintered body include open pores (pores connected to the surface) and closed pores (closed pores). As shown in FIG. 3A, in the case of a sintered body without recompression processing (sizing), most of the pores are closed pores at a porosity of 10% or less (= sintered body density of 90% or more). Oil absorption rate (content rate)
Is very low and therefore oil-free support frame 7
Can be formed. However, if a sintered body having a low sintered density, that is, a sintered body having a porosity of about 15% (= sintered body density of 85%) is considered for the purpose of practically reducing the weight of the support frame 7, it is more Since the open pores are included, the oil content increases as shown in A of FIG. 2 and oil leakage occurs. Therefore, the surface density is increased by recompressing the sintered body having a porosity of 15% (= sintered body density of 85%), and the oil content is set to a practical level as shown in FIG. 2B. It is possible to prevent oil leakage.

By adopting this integral structure by sintering, superposition and coupling of members as in the prior art are eliminated,
The processing time is shortened, the strength is improved, and further strength reduction enables further downsizing. Further, since the basic shape is determined, it is easy to obtain the dimensional accuracy, and only the final finishing is required for the processing, so that the man-hours, the productivity and the cost can be reduced.

The support frame 7 is impregnated with resin, and the resin permeates into the porous material existing inside the sintered body to block the porous material. This resin impregnation prevents leakage of oil filled between the rotary shaft 3 and the fixed bearing portion 9. As another method for preventing oil leakage, at least the fixed bearing portion 9 may be coated with a resin or a metal.

The material of the support frame 7 is preferably one having a coefficient of thermal expansion lower than that of the rotating shaft 3 in order to improve temperature characteristics. That is, the driving performance of a dynamic pressure bearing motor is likely to depend on the temperature dependence of the viscosity of oil, the dynamic pressure decreases (that is, the bearing rigidity decreases) when the viscosity decreases at high temperature, and conversely the rotation increases when the viscosity increases at low temperature. The rotation loss on the shaft 3 increases.
On the other hand, in the relationship between the rotary shaft 3 and the fixed bearing portion 9, the dynamic pressure increases when the clearance between the rotary shaft 3 and the fixed bearing portion 9 becomes narrower, and conversely when the clearance becomes wider, the rotation loss increases. Therefore, this is because the temperature dependence of the viscosity of the oil and the thermal characteristics of the rotating shaft 3 and the fixed bearing portion 9 that cancel each other are combined so that the clearance is narrow at high temperatures and wide at low temperatures. As such a material, the above-mentioned Invar or SUS is suitable.

As shown in FIG. 2, the fixed bearing portion 9 has a hollow cylindrical shape, the rotary shaft 3 is rotatably inserted through the inner hole, and the inner peripheral surface is formed by rolling (plastic working). The dynamic pressure generating groove 29 is formed by the above. In this manner, by plastically processing the inner peripheral surface of the fixed bearing portion 9 by rolling or the like, the inner peripheral surface is crushed and the porous is closed, and at the same time a smooth surface is obtained and fixed to the rotating shaft 3. Leakage of the oil enclosed between the bearing 9 and the bearing 9 is prevented. Further, the dynamic pressure generating groove 29
During molding, swells are generated between adjacent dynamic pressure generating grooves, but by smoothing the swells by sizing (recompression) or burnishing by rolling, a smoother surface can be obtained. Thus, the effect of preventing oil leakage is promoted.

A stator core 10 is mounted on the outer peripheral surface of the fixed bearing portion 9 so as to face the drive magnet 5, and a stator winding 11 is wound around the stator core 10. Reference numeral 12 indicates a thrust plate that serves as a thrust bearing, and 13 indicates a retaining plate for preventing oil leakage.

(II) Second Embodiment FIG. 4 shows a second embodiment of the present invention. FIG. 4 is a half sectional view of the dynamic pressure bearing motor. As shown in the figure, the dynamic pressure bearing motor is roughly divided into a rotating rotor 14 and a fixed stator assembly 20, and has a so-called fixed shaft / rotary bearing type structure. The structure is opposite to that of the bearing motor.

In the rotor 14, the hub 16 is formed in the shape of a double cylinder, and the fixed shaft portion 22 of the support frame 20 is rotatably fitted to the inner cylinder portion 19 of the hub 16 and the inner cylinder surface of the outer cylinder. A magnet 17 is attached via a back yoke 18.

The support frame 20 is composed of a frame 21 and a fixed shaft portion 22, and is integrally formed of a sintered body obtained by firing metal powder made of a magnetic material such as Invar or SUS. The average density of the sintered body is 85% or more. The reason is the same as in the first embodiment.

The support frame 20 is impregnated with resin, the resin permeates into the porous material existing inside the sintered body, and the porous material is sealed, and is sealed between the fixed shaft portion 22 and the inner cylindrical portion 19. Prevents oil leakage. As another method for preventing this oil leakage, at least the fixed shaft portion 2
The outer peripheral surface of 2 may be resin-coated or metal-coated.

The material of the support frame 20 is preferably one having a coefficient of thermal expansion higher than that of the inner tubular portion 19 in order to improve temperature characteristics. That is, the driving performance of the dynamic pressure bearing motor is easily affected by the temperature dependence of oil clay, and the dynamic pressure decreases (that is, the bearing rigidity decreases) due to the decrease in viscosity at high temperature.
Conversely, the increase in viscosity at low temperature increases the rotation loss in the inner cylinder portion 19. On the other hand, in the relationship between the support frame 22 and the inner tubular portion 19, the dynamic pressure increases when the clearance between the support frame 22 and the inner cylindrical portion 19 decreases, and conversely, the rotation loss increases when the clearance increases. Therefore,
This is because the clearance is narrowed at a high temperature and widened at a low temperature by combining the temperature dependence of the viscosity of the oil with the thermal characteristics of the support frame 22 and the inner tubular portion 19 that cancel each other out. As such a material, the above-mentioned Invar or SUS is suitable.

A dynamic pressure generating groove (not shown) is formed on the outer peripheral surface of the support frame 22 by rolling (plastic working) or the like. In this way, by plastically processing the outer peripheral surface of the support frame 22 by rolling or the like, the porous surface of the outer peripheral surface is crushed and the porous is closed, and at the same time a smooth surface is obtained. The leakage of the oil enclosed between and is prevented.

Further, when molding the dynamic pressure generating groove, a swelling portion is generated between the adjacent dynamic pressure generating grooves, and the swelling portion is surface-finished by sizing (recompression) or burnishing by rolling pressure. By doing so, a smoother surface is obtained, and the oil leakage prevention effect is promoted.

A cylindrical stator holder 23 extends coaxially with the support frame 22 from the support frame 22, and a stator core 24 is mounted on the outer peripheral surface of the support frame 22 so as to face the drive magnet 17 and the stator core 24.
A stator winding 25 is wound around. Reference numerals 26 and 2
Reference numerals 7 and 28 denote magnetic fluids for preventing oil leakage.

[0040]

As described above, according to the invention described in claims 1 to 7, dimensional accuracy is improved, cost is reduced, strength is improved, size is reduced, temperature characteristics are improved, oil leakage is prevented, and productivity is improved. An improvement can be achieved.

[Brief description of drawings]

FIG. 1 is a half sectional view showing a rotary shaft / fixed bearing type dynamic pressure bearing motor of a first embodiment of the present invention.

FIG. 2 is a sectional view of a support frame in the first embodiment of the present invention.

FIG. 3 is a characteristic diagram showing a correlation between porosity and oil content of a sintered body according to the present invention.

FIG. 4 is a half cross-sectional view showing a fixed shaft / rotary bearing type dynamic pressure bearing motor of a second embodiment of the present invention.

FIG. 5 is a sectional view showing a conventional rotary shaft / fixed bearing type dynamic pressure bearing motor.

[Explanation of symbols]

 1 rotor assembly 2 stator assembly 3 rotary shaft 4 hub 5 drive magnet 6 back yoke 7 support frame 8 frame part 9 fixed bearing part 10 stator core 11 stator winding 12 thrust plate 13 retaining plate 14 rotor assembly 15 stator assembly 16 hub 17 drive magnet 18 Back Yoke 19 Inner Cylinder 20 Support Frame 21 Frame 22 Fixed Shaft 23 Stator Holder 24 Stator Core 25 Stator Winding 26 Magnetic Fluid 27 Magnetic Fluid 28 Magnetic Fluid 29 Dynamic Pressure Generation Groove

Claims (7)

[Claims] 1. A fixed bearing portion on which a rotary shaft of a rotor is rotatably fitted is formed on a support frame made of a sintered body of metal powder, and a dynamic pressure generating groove is formed on an inner peripheral surface of the fixed bearing portion. The dynamic pressure bearing motor is characterized in that the supporting frame and the dynamic pressure bearing are integrally formed. 2. The dynamic pressure bearing motor according to claim 1, wherein the support frame is made of a magnetic material having a coefficient of thermal expansion lower than that of the rotating shaft. 3. The dynamic pressure bearing motor according to claim 1, wherein a resin layer or a metal layer is formed on an inner peripheral surface of the fixed bearing portion. 4. The dynamic pressure bearing motor according to claim 1, wherein at least the fixed bearing portion of the frame is impregnated with resin. 5. The dynamic pressure bearing motor according to claim 1, wherein the supporting frame has a sintered density of 85% or more. 6. The dynamic pressure bearing motor according to claim 1, wherein the dynamic pressure generating groove is formed by plastic working. 7. A support frame made of a sintered body of metal powder is provided with a fixed shaft on which a rotary bearing portion of a rotor is rotatably fitted, and a dynamic pressure generating groove is formed on an outer peripheral surface of the fixed shaft for support. A dynamic pressure bearing motor characterized in that a frame and a dynamic pressure bearing are integrally configured.