JP2000065046A - Dynamic pressure bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily and reliably form a good lubrication coating surface in relation to a shaft body and a dynamic pressure surface in a shaft body or a shaft fitting body. SOLUTION: A lubrication coating having good lubricity based on the uniform coating action of electrodeposition coating is easily obtained by electrodeposition coating either one of front surfaces of both dynamic pressure bearing surfaces of a shaft body 21 and a shaft fitting body 31, the film thickness on the end of the coated surface is uniformed by forming a film thickness adjusting surface on the end of the electrodeposition coating, and therefore, reliability of electrodeposition coating is improved.

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 device which generates a dynamic pressure in a lubricating fluid and supports a shaft body and a shaft fitting body so as to be relatively rotatable by the dynamic pressure.

[0002]

2. Description of the Related Art In recent years, polygon mirrors, magnetic disks,
Various proposals have been made for hydrodynamic bearing motors that rotationally drive various rotating plates such as optical disks. In this hydrodynamic bearing device, the hydrodynamic bearing surface on the shaft body side and the hydrodynamic bearing surface on the shaft fitting body side are provided so as to oppose each other in the radial direction with a predetermined gap therebetween. A dynamic pressure bearing is formed. A groove for generating dynamic pressure is formed on one of the two opposed dynamic pressure bearing surfaces, so that a lubricating fluid such as air or oil injected into the dynamic pressure bearing portion is rotated during rotation. The pressure is generated by the pumping action of the pressure generating groove, and both members of the shaft body and the shaft fitting body are relatively rotatably supported by the dynamic pressure of the lubricating fluid.

In general, a lubricating paint is applied to one surface of both hydrodynamic bearing surfaces of the shaft body or the shaft fitting body in such a hydrodynamic bearing device, and a plating is applied to the other surface. And both are used in combination.

For example, in order to apply a lubricating paint to a shaft fitting body, first, a shaft fitting body as shown in FIG. 4A is cast or die-cast using aluminum and an aluminum alloy material. Is formed. Then, as shown in FIG. 4B, a base treatment 2 such as a chromate treatment or an anodic oxidation treatment for improving corrosion resistance and coating adhesion is performed, and a masking 3 is applied to a part of the outer surface. , And as shown in FIG.
For the inner peripheral surface of the blank 1, for example, PTFE
After applying and drying the (polytetrafluoroethylene) -containing lubricating paint 4 by spraying or the like, the same spray coating is repeated three to five times again to perform thick coating. The reason why such thick coating is performed is that there is foaming or unevenness in the layer thickness of the coating, and the material having the uneven coating is laced as shown in FIG. Processing 5 and the like are performed to finish the coating 4 so that the thickness of the coating 4 becomes about 15 microns, and to perform the accuracy of the inner diameter dimension. The same applies when a lubricating paint is applied to the shaft body side.

[0005] On the other hand, when plating the dynamic pressure bearing surface on the shaft body side, if there is a dynamic pressure generating groove, the dynamic pressure generating groove is formed before plating. That is, the blank 6 shown in FIG.
As shown in FIG. 5B, masking printing 7 is applied to portions other than the portion where the dynamic pressure generating grooves are formed, and as shown in FIG. , The dynamic pressure generating groove 9 is processed.

Next, a plating process is performed, and after performing pretreatments such as degreasing and activation as shown in FIG. 5 (d), the plating process is again performed as shown in FIG. 5 (e). A cap 8 is provided on the end face to replace the surface with zinc, and a plating process such as electroless nickel plating is performed as shown in FIG.

[0007]

However, such a conventional hydrodynamic bearing device and its manufacturing method have the following problems. First, in the lubricating paint coating process, the coating process itself takes time to perform thick coating, and a finishing process such as lace processing for forming a uniform thickness must be performed. Further, since a very large number of steps (about 50 steps) must be performed in the plating process, the conventional hydrodynamic bearing device has a problem that the productivity is low and the product cost is high.

Further, plating treatment is not sufficient in durability against corrosion, and the surface grows granularly, so that the surface roughness (smoothness) is not good and wear powder is easily generated during use. In the case of an apparatus requiring cleanliness, a serious problem may occur.

Accordingly, the present invention provides a dynamic pressure bearing device in which a dynamic pressure bearing surface having high quality and excellent durability can be formed on a shaft body or a shaft fitting body in a simple process. With the goal.

[0010]

In order to achieve the above object, according to the first aspect of the present invention, an outer peripheral surface of a shaft body and a shaft fitting body mounted rotatably relative to the shaft body are provided. At least one pair of radially opposed dynamic pressure bearing surfaces is formed by the peripheral surface, and a dynamic pressure generating groove of a predetermined shape is formed on one of the dynamic pressure bearing surfaces of the shaft body and the shaft fitting body. In the hydrodynamic bearing device in which the lubricating film is formed by electrodeposition coating on either one of the dynamic pressure bearing surfaces of the shaft body and the shaft fitting body, A film thickness adjusting surface for making the film thickness uniform at the time of electrodeposition coating is formed on the edge portion of the surface on which the lubricating film is formed.

Further, in the invention according to claim 2, the electrodeposition coating lubricating film according to claim 1 is formed with a thickness in the range of 5 μm to 30 μm, and the film thickness adjustment surface has a curvature radius of 0 μm. It is formed from an R curved surface shape of 0.3 mm or more.

Further, according to the third aspect of the present invention, the film thickness adjusting surface according to the first aspect is formed in a tapered surface shape.

Further, in the invention according to claim 4, the edge portion having the film thickness adjusting surface according to claim 1 is provided on the outer peripheral surface of the shaft body and the inner peripheral surface of the shaft fitting body which face each other in the radial direction. In any one of the above.

According to the fifth aspect of the present invention, the film thickness adjusting surface of the first aspect has at least an edge portion on a reference surface when the shaft body or the shaft fitting body is attached to a predetermined member. Including.

Further, in the invention according to claim 6, the film thickness adjusting surface according to claim 1 has a convex surface provided at the corner of the edge so as to maintain the film thickness of the electrodeposition coating, and a convex surface provided on the convex surface. It has a concave surface provided so as to make the film thickness of the electrodeposition coating uniform with respect to a continuous adjacent surface.

Further, in the invention according to claim 7, the thickness adjustment surface according to claim 6 has an R-curved surface shape approximating a convex surface and a concave surface.

According to the first to seventh aspects of the present invention, the lubricating coating can be easily obtained with a uniform thickness over the entire circumference by the uniform coating effect of the electrodeposition coating. Since the lubricating particles (PTFE) float on the surface of the coating at the time of electrodeposition coating, the lubricating particles (PTFE) are formed so as to have extremely good lubricating properties, and the bearing characteristics are improved.

In the dynamic pressure bearing device, the shaft body and the bearing body are opposed to each other with a small clearance therebetween. The swelling phenomenon caused by anyone cannot be ignored. In other words, the swelling of the coating tends to occur equal to or more than the fitting clearance between the shaft body and the shaft fitting body.Accordingly, in the present invention, the film thickness adjusting surface is provided on the edge portion of the coating surface. The thickness of the electrodeposition coating is made uniform even at the edge part by the function of equalizing the thickness of the film thickness adjustment surface so that a good lubricating film can be easily obtained without performing post-processing such as lace processing. Has become.

At this time, if the film thickness and the film thickness adjusting surface are formed within the scope of the present invention, good electrodeposition coating can be performed without generating "undulation" or the like. ing.

[0020]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below. Prior to that, the structure of a shaft-rotating polygon mirror driving motor having an air dynamic pressure bearing to which the present invention is applied will be described with reference to the drawings. It is explained based on.

FIG. 2 shows an example of an outer rotor type motor provided with a fixed shaft type air dynamic pressure bearing device for rotationally driving a polygon mirror. This air dynamic pressure bearing motor includes a stator set 20 as a fixing member assembled on the frame 10 side,
And a rotor set 30 as a rotating member fitted so as to be fitted from the upper side in the figure. Among these, the stator set 20 is a fixed shaft (shaft) mounted so as to stand upright at a substantially center position of the frame 10. And a bearing holder 22 that surrounds the fixed shaft 21 in a cylindrical shape at a constant distance in the radial direction from the outer peripheral surface of the fixed shaft 21. A stator core 23 is fitted around the outer periphery of the bearing holder 22, and a drive coil 24 is wound around salient pole portions of the stator core 23.

On the outer peripheral surface of the fixed shaft 21, a herringbone type dynamic pressure generating groove 25 is axially divided into two blocks and is annularly recessed. , 25, a cylindrical body (shaft fitting body) 31 of the rotor set 30 is rotatably mounted with a gap of several μm to several tens of μm. The air bearing is generated between the outer peripheral surface of the fixed shaft 21 and the inner peripheral surface of the cylindrical body 31 of the rotor set 30 to form a radial bearing. The fixed shaft 21 has an air supply hole 26 extending in the axial direction from a shaft end (upper end in the figure) of the fixed shaft 21, and the air supply hole 26 generates the dynamic pressure of the two blocks. Groove 2
The portion between 5, 25 is open toward the outside of the fixed shaft 21.

Further, an outer peripheral portion of the shaft end (upper end in the figure) of the fixed shaft 21 projects axially by a predetermined amount, and a fixed-side magnet 27 for thrust floating is annularly formed on an inner peripheral wall of the projected portion. It is attached to. On the other hand, a porous air orifice 32 having a predetermined air flow resistance penetrates axially as a damper means at a center portion of the cylindrical body 31 of the rotor set 30 at a base side (upper end side in the figure). The damping action of the air orifice 32 due to the airflow resistance reduces the impact on the rotor set 30 in the axial direction. The air inside the rotor set 30 is supplied to the portion between the dynamic pressure generating grooves 25 by the air supply holes 26, and the pumping action of the dynamic pressure generating grooves 25, 25 causes the air to flow outward in the vertical direction in the drawing. And discharged to the outside.

Further, around the air orifice 32, a rotary magnet 33 for thrust floating is annularly mounted. The rotating magnet 33 is magnetized in the axial direction (vertical direction in the drawing) so as to mutually generate a magnetic attraction with the fixed magnet 27 on the fixed shaft 21. The set 30 is configured to be held in a state of floating by a predetermined amount in the thrust direction.

On the other hand, a flat hexagonal polygon mirror 34 as a rotary plate is fitted around the outer periphery of the cylindrical body 31 of the rotor set 30 on the base side (upper end side in the figure) so as to form a rotary plate. I have. The polygon mirror 34 has a holding unit 38 extending radially outward from the cylindrical body 31.
It is mounted on the upper side in the axial direction, and is fixed from the outside in the axial direction by a pressing spring 39 serving as a clamping means.

A rotor flange portion 35 extends outward from the holding portion 38 in the radial direction. The rotor flange portion 35 includes the cylindrical body portion 31 and the holding portion 3.
8, and is arranged so as to separate a space inside the rotor where the drive coil 24 is arranged and a space outside the rotor where the polygon mirror 34 is arranged.

Further, a driving magnet 37 is provided on the inner peripheral wall surface of an annular mounting plate 36 projecting from the outer peripheral portion of the rotor flange portion 35 in the axial direction (downward in the figure) via a back yoke made of a magnetic material. It is mounted in a ring.
The drive magnet 37 is connected to the stator core 23 described above.
Is arranged so as to face the outer peripheral surface in the radial direction,
It constitutes a motor drive unit.

In the embodiment shown in FIG. 2, the holding portion 38,
Although the cylindrical body portion 31, the rotor flange portion 35, and the mounting portion 36 are integrally formed, each of them may be formed separately.

When a predetermined drive voltage is applied to the drive coil 24, the polygon mirror 34 and the cylindrical body 31 are moved together.
Is rotated, and the laser light converged on the polygon mirror 34 by the rotation of the polygon mirror 34 scans an image recording medium (not shown). At this time, the cylindrical body 31 is supported in the radial direction by the dynamic pressure of the air generated between the cylindrical body 31 and the fixed shaft 21, and the magnetic force between the rotating magnet 33 and the fixed magnet 27 is increased. Due to the suction action, the rotor set 30 is held in a state of floating by a predetermined amount in the thrust direction.

The fixed shaft 21 is made of an aluminum material such as aluminum or an aluminum alloy.
As described later, a lubricating film is formed on the outer peripheral surface including the dynamic pressure bearing surface by electrodeposition coating. The detailed structure of the fixed shaft 21 as such a shaft will be described together with the manufacturing method.

First, a fixed shaft 2 as shown in FIG. 1 is formed by casting using aluminum, an aluminum alloy material or a magnesium alloy, die casting or other processing methods.
When the first blank 21a is formed and a dynamic pressure generating groove is provided, masking printing is performed on a portion other than the dynamic pressure generating groove forming portion, and an etching process or the like is performed, so that the dynamic pressure generating groove 25 (see FIG. 2). ) Is first processed and formed.

Next, the blank 21a of the fixed shaft 21
Before the electrodeposition coating is performed on the outer peripheral surface, a film thickness adjustment surface 21b of the electrodeposition coating is formed on the edge portion of the step provided on the blank 21a.
The film thickness adjusting surface 21b is for making the film thickness uniform at the time of electrodeposition coating. In the present embodiment, the film thickness adjusting surface 21b has an R curved surface shape having a curvature radius of 0.3 mm or more. The film thickness adjusting surface 21b is formed at least on the edge portion of the outer peripheral surface corresponding to the dynamic pressure surface and the edge portion of the surface A corresponding to the mounting reference surface for the frame 10. The radius of curvature of the curved surface constituting the surface 21b is set to a radius of curvature of 0.5 mm or more so as to provide a stronger film thickness uniforming action.

When performing the electrodeposition coating, the outer surface of the blank 21a having the above-mentioned film thickness adjusting surface 21b is subjected to a chromate treatment (allodin treatment) or the like for improving corrosion resistance and coating adhesion. A base treatment is performed. Next, the blank 21a is immersed in an electrodeposition tank (not shown), and the entire surface of the blank 21a is coated by electrodeposition (electric swimming). In this electrodeposition coating, a blank 21a is put in a paint dispersed in water,
A paint is applied to the blank 21a by passing an electric current so that the blank 21a and the other metal body become both poles.

The thickness of the lubricating coating formed by the electrodeposition coating forming portion is adjusted by the time and voltage of electrodeposition. In the present embodiment, the thickness is about 5 μm to 30 μm. I have. If the thickness is 5 μm or less, there is a problem in the wear resistance of the electrodeposition coating film.
If the film thickness is more than m, problems such as "undulation" will occur on the electrodeposition coated surface. After the electrodeposition coating, a heat treatment is performed to cure the resin, and a portion corresponding to the dynamic pressure bearing surface is subjected to a predetermined lubrication process.

According to such an embodiment, a lubricating film having a uniform thickness can be easily obtained on the surface of the fixed shaft 21 by the uniform coating effect of the electrodeposition coating. Since the lubricating film formed of the electrodeposition coating portion is formed so as to have extremely good lubricity since lubricating particles float on the surface of the coating at the time of electrodeposition coating, the bearing characteristics are improved. Is achieved. Furthermore, in this electrodeposition coating, even if there is a defect such as a nest in the material of the coating partner, the coating enters the inside, so that the formed lubricating film has strong adhesion. . The fixed shaft 21 having a lubricating film formed by electrodeposition coating having such good lubricating properties.
Is used, the wear resistance on the dynamic pressure bearing surface is improved, the generation of wear powder is significantly reduced, and the bearing gap is maintained and seizure is prevented.

On the other hand, in the dynamic pressure bearing device, the fixed shaft 21 as the shaft and the cylindrical body 31 as the shaft fitting body are opposed to each other with a small clearance (several μm to several tens μm). Even with electrodeposition coating having uniform coating properties, the swelling phenomenon due to paint dripping at the edge of the coating surface cannot be ignored. In other words, since the swelling of the coating tends to be equal to or larger than the fitting clearance between the fixed shaft 21 and the cylindrical body 31, in the present invention, the swelling of the coating surface The film thickness adjusting surface 21a is provided, and the film thickness of the electrodeposition coating is made uniform even at the edge portion by the film thickness uniforming function of the film thickness adjusting surface 21a. Thus, a good lubricating coating can be easily obtained without performing post-processing such as lace processing.

At this time, an R-curved surface having a film thickness within a range (5 μm to 30 μm) as in the present embodiment and a radius (0.3 mm or more, preferably 0.5 mm or more) as in the present embodiment. Film thickness adjustment surface 21 made of
By forming b, good electrodeposition coating can be performed without generating "undulation" or the like. The inventor of the present application has confirmed that the “undulation” is 1 μm or less when the R-curved surface shape of the film thickness adjusting surface 21b is 0.3 mm or more.

The electrodeposition coating on which the film thickness adjusting surface 21a for making the film thickness uniform is not limited to the fixed shaft 21a as in the above-described embodiment, but may be a cylindrical body as a shaft fitting body. 31 can be similarly applied.

The film thickness adjusting surface 21c in the embodiment shown in FIG. 3 is formed in a tapered shape.
The tapered surface of the film thickness adjusting surface 21c in the present embodiment is formed so as to form an angle of about 15 degrees with respect to the axial direction. In such an embodiment, substantially the same operation and effect as in the above-described embodiment can be obtained. The inventor of the present application has determined that the dynamic pressure surface is 15 degrees, 30 degrees,
"Waviness" in the case of forming a tapered surface is
It was confirmed that it was within the range of 4 μm.

Further, the film thickness adjusting surface according to the present invention can be formed from an uneven surface. In other words, the uneven surface constituting the curved surface of the film thickness adjusting surface is formed by electro-depositing a convex surface provided at the corner of the edge so as to maintain the film thickness of the electrodeposition coating and a surface portion adjacent to the convex surface. A concave surface provided so as to make the thickness of the coating uniform, and the film thickness of the electrodeposition coating film having a tendency to be thin at the corners of the edge is increased by the film thickness holding action of the convex surface. It is drawn into the edge, where it is held at the appropriate thickness. On the other hand, the surface portion adjacent to the corner of the edge where the convex surface is provided tends to decrease the film thickness by the above-mentioned effect of drawing in the film thickness of the convex surface, but the leveling effect of the concave surface provided in the same portion The predetermined film thickness is maintained by the (film uniforming action). As a result, a substantially uniform film thickness is formed over the entire edge portion.

In order to approximate such a concave-convex surface and obtain efficient productivity, an R-curved surface shape similar to the above-described embodiment can be obtained, and substantially the same operation and effect can be obtained. it can.

Although the embodiments of the present invention made by the inventor have been specifically described above, the present invention is not limited to the above-described embodiments, and can be variously modified without departing from the gist thereof. Needless to say.

For example, the present invention can be applied not only to the case where the dynamic pressure generating groove is provided on the shaft body side but also to the case where the dynamic pressure generating groove is formed on the shaft fitting body side as in each of the above-described embodiments. it can. Further, the present invention can be similarly applied to a case where electrodeposition coating is performed on the shaft fitting body side.

Further, each of the above embodiments is a case of a hydrodynamic bearing device using air as a lubricating fluid, but the present invention can be similarly applied to a device using a liquid such as oil. it can.

Further, the present invention is similarly applied to a dynamic pressure bearing device used for a motor other than the above-described motor, for example, a dynamic pressure bearing device provided in a hard disk drive (HDD) motor. be able to. Shown in 6

[0046]

As described above, the invention according to each of the claims is characterized in that the electrodeposition coating is performed by applying the electrodeposition coating to either one of the surfaces of the dynamic pressure bearings of the shaft body and the shaft fitting body. It is possible to easily obtain a lubricating film having extremely good lubricity based on a uniform coating action, and to improve bearing characteristics.
In addition, when the electrodeposition coating is performed, the swelling portion of the minute coating that is likely to be generated at the edge portion is also made uniform by providing a film thickness adjustment surface on the edge portion, and post-processing such as lace processing is performed. A highly reliable electrodeposition coating surface can be easily and reliably obtained without performing.

At this time, if the film thickness and the film thickness adjusting surface are particularly set as in the second aspect of the present invention, it is possible to obtain a good electrodeposited surface free from "undulation" and the like. Can be even higher.

[Brief description of the drawings]

FIG. 1 is an explanatory side view showing a blank state of a fixed shaft according to an embodiment of the present invention.

FIG. 2 is an explanatory cross-sectional view showing an example of a fixed shaft type polygon mirror driving motor provided with a dynamic pressure bearing to which the present invention is applied.

FIG. 3 is an explanatory side view showing a blank state of a fixed shaft according to another embodiment of the present invention.

FIG. 4 is an explanatory view showing a conventional shaft manufacturing process.

FIG. 5 is an explanatory view showing a manufacturing process of a conventional shaft fitting body.

[Explanation of symbols]

 21 Fixed Shaft (Shaft) 25 Groove for Generating Dynamic Pressure 31 Cylindrical Body (Shaft Fitting Body) 21a Fixed Shaft Blank 21b, 21c Film Thickness Adjusting Surface

Claims (7)

[Claims] At least one pair of radially opposed hydrodynamic bearing surfaces is formed by an outer peripheral surface of a shaft body and an inner peripheral surface of a shaft fitting body rotatably mounted on the shaft body. And a hydrodynamic bearing device in which a dynamic pressure generating groove having a predetermined shape is formed in one of the two dynamic pressure bearing surfaces of the shaft body and the shaft fitting body. A lubricating film is formed by electrodeposition coating on one of the surfaces of the hydrodynamic bearing surface, and a film at the time of electrodeposition coating is formed on an edge portion of the surface on which the lubricating film is formed by the electrodeposition coating. A hydrodynamic bearing device, wherein a film thickness adjusting surface for making the thickness uniform is formed. 2. The electrodeposition coating lubricating film according to claim 1, wherein
A hydrodynamic bearing device having a thickness in the range of [mu] m to 30 [mu] m, and wherein the film thickness adjusting surface is formed of an R curved surface having a radius of curvature of 0.3 mm or more. 3. The dynamic pressure bearing device according to claim 1, wherein the film thickness adjusting surface is formed in a tapered shape. 4. The edge portion having the film thickness adjusting surface according to claim 1, wherein the edge portion is any one of an outer peripheral surface of a shaft body and an inner peripheral surface of a shaft fitting body opposed in a radial direction. A dynamic pressure bearing device. 5. The dynamic pressure bearing according to claim 1, wherein the film thickness adjusting surface includes at least an edge portion on a reference surface when the shaft body or the shaft fitting body is attached to a predetermined member. apparatus. 6. The film thickness adjusting surface according to claim 1, wherein the convexity surface is provided at a corner of the edge so as to maintain the film thickness of the electrodeposition coating;
A hydrodynamic bearing device comprising a concave surface provided so as to make the film thickness of the electrodeposition coating uniform with respect to an adjacent surface continuous with the convex surface. 7. The dynamic pressure bearing device according to claim 6, wherein the thickness adjustment surface has an R-curved surface shape approximating a convex surface and a concave surface.