JPH10318271A - Manufacture of dynamic pressure bearing device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the bubbles inside of the lubricating fluid by filling the lubricating fluid in a bottom surface inside a cylindrical hole of a bearing member, and inserting a shaft body having a shrunken diameter part into the cylindrical hole so that a specified diameter part of the shrunken diameter part firstly contacts with the lubricating fluid. SOLUTION: When the lubricating fluid 27 is filled in a bottom surface of a cylindrical hole 20 of a bearing member 22, a recessed spherical surface is formed in the surface by the surface tension. A radius R of a projecting spherical surface 21a of a shrunken diameter end of a shaft body 21 is smaller than the radius (r) of a recessed spherical surface of the fluid 27, and axial length L thereof is larger than the recessed spherical surface depth H. The shrunken diameter end has a diameter (d) at 3/4 or less of the diameter D of the shaft body 21. When the shaft body 21 is inserted into the cylindrical hole 20 in the condition that the shrunken diameter part thereof is headed, the diameter (d) part firstly contacts with the fluid 27, and the fluid 27 is transmitted through the spherical projecting surface 21a for raising without sealing the air in the end surface of the shaft body 21. When the shaft body 21 is inserted more, the fluid fills a radial bearing clearance, discharging air, and the end surface of the shaft body 21 contacts with a bottom surface of the cylindrical hole 20 of the thrust bearing. Assembling is thereby facilitated, and the assembling man-hours can be reduced.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of manufacturing a dynamic pressure bearing device used for information equipment such as a laser printer, an optical disk device, and a magnetic disk device, or acoustic and video equipment.

[0002]

2. Description of the Related Art Conventionally, a bearing device using a ball bearing or the like has been used as the above-mentioned device. However, in recent years, dynamic pressure has been increased due to demands for higher data density, higher speed transfer, and lower cost. A spindle motor using a bearing device has been studied. Fig. 1 shows a schematic longitudinal sectional view of the spindle motor
As shown in FIG. 1, a rotor 6 rotating around a stator 5 fixed to a bearing member 2 is fixed to a shaft 1, and the shaft 1 constitutes a dynamic pressure bearing device. The shaft 1 is inserted into a cylindrical hole 100 of the bearing member 2. The cylindrical hole 100 has a cylindrical inner surface constituting the radial dynamic pressure bearing 4 and a convex spherical surface for supporting the axial load of the shaft. And a bottom surface constituting the thrust bearing 3. In addition, the cylindrical hole 1 of the bearing member
In the gap between the shaft body 1 and the bearing member 2 formed at 00,
A lubricating fluid such as oil or liquid grease is injected to stabilize shaft rotation and improve durability when the spindle motor rotates.

[0003]

FIG. 2 (a), (b),
(C) and (d) show a cylindrical hole having a cylindrical inner surface forming the radial dynamic pressure bearing provided on the bearing member 12 and a bottom surface forming the thrust bearing when the conventional hydrodynamic bearing device is manufactured. The process of inserting the cylindrical shaft 11 into the shaft 10 will be described with reference to a schematic longitudinal sectional view of a hydrodynamic bearing device (note that FIGS.
In FIG. 7, stators, rotors, and the like other than the shaft body and the bearing member that are not directly involved in the present invention are omitted from the drawing.

[0004] First, a lubricating fluid 17 is injected into the cylindrical hole 10. The surface of the lubricating fluid 17 has a cylindrical shape as shown in FIG. The lubricating fluid surface rises along the inner surface of the shape to form a concave shape. Next, the shaft body 11 is inserted into the cylindrical hole 10 provided in the bearing member 12, and the shaft body end face 11a of the shaft body 11 as shown in FIG. Refers to the end surface of the shaft body facing the bottom surface provided in the following. In the following description, including the embodiment, the shaft body end surface means the same surface.) Forms a plane perpendicular to the axis. In this case, the outer peripheral portion of the shaft end face 11a comes into contact with the lubricating fluid 17 first as shown in FIG. Therefore, a large amount of air is trapped in the space 18 formed by the shaft end face 11a and the lubricating fluid 17.

As a result, the insertion of the shaft body 11 is further continued, and the bubbles 19 are lubricated even when the shaft body end face 11a shown in FIG. 2C is inserted until it comes into contact with the thrust bearing surface on the bottom surface of the cylindrical hole 10. A large amount remains in the fluid 17.
FIG. 2D is a schematic view showing the state of bubbles near the thrust bearing. Cylindrical hole 10 formed in bearing member 12
The bubbles 19 remaining in the lubricating fluid 17 existing between the cylindrical inner surface and the outer peripheral surface of the shaft 11 are slightly discharged as the shaft 11 rotates, but are not completely discharged. If a step of evacuating air bubbles is added after the end of the insertion step of the shaft 11, the air bubbles 19 are discharged but not completely discharged, and the air bubbles 19 near the shaft end face 11a, that is, near the thrust bearing are added.
Is hardly emitted.

As a result, during rotation of the spindle motor, whirling occurs due to unstable rotation due to the presence of the air bubbles 19, the load capacity is reduced, and the performance thereof is significantly reduced. An object of the present invention is to provide a high-performance hydrodynamic bearing device in which bubbles 19 inside the lubricating fluid 17 are reduced to such an extent that the performance of the spindle motor is not adversely affected, and which is easy to assemble.

[0007]

According to a method of manufacturing a dynamic pressure bearing device, a cylindrical hole having a cylindrical inner surface for forming a radial bearing surface and a bottom surface for forming a thrust bearing surface is provided. An injecting step of injecting a lubricating fluid into a bottom surface in the cylindrical hole of the bearing member, and after the injecting step, the outer peripheral portion has a cylindrical main body and a portion whose diameter decreases from the main body toward the tip. Inserting a shaft having a reduced diameter end into the cylindrical hole from the reduced diameter end. In the inserting step, the reduced diameter end is less than or equal to ／ of the diameter of the main body. A method for manufacturing a hydrodynamic bearing device, characterized in that a portion inside a circle centered on a shaft center having a diameter comes into contact with the lubricating fluid first.

Accordingly, the amount of bubbles in a lubricating fluid such as oil or liquid grease can be reduced to a level that does not adversely affect the performance of the spindle motor, and a high-performance hydrodynamic bearing device that is easy to assemble and can be provided. It becomes possible. Specifically, the shape of the reduced diameter end of the main body may be spherical.
Also, the reduced diameter end has a conical surface portion whose diameter decreases from the main body toward the distal end on the outer periphery, and the axial length of the reduced diameter end is adjusted to the cylindrical hole of the shaft body. Before the insertion, the lubricating fluid may be longer than the concave surface of the lubricating fluid formed by swelling along the inner surface of the cylindrical shape due to surface tension.

As a result, the reduced-diameter end is 3 mm of the diameter of the main body.
The portion inside the circle centered on the axis having a diameter of 以下 or less allowed the first contact with the lubricating fluid.
This makes it possible to eliminate or extremely reduce the space formed between the reduced diameter end of the shaft and the lubricating fluid in the shaft body inserting step. as a result,
Without going through a bubble discharging step such as vacuuming, the amount of bubbles in the lubricating fluid can be significantly reduced as compared with the prior art.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIGS. 3A, 3B, and 3C show a cylindrical inner surface and a radial dynamic pressure bearing provided on the bearing member 22 when the hydrodynamic bearing device is manufactured according to the first embodiment of the present invention. FIG. 3 is a schematic longitudinal sectional view of a hydrodynamic bearing device in a process of inserting a cylindrical shaft body 21 into a cylindrical hole 20 having a bottom surface forming a thrust bearing. First, a lubricating fluid 27 is injected into the bottom surface of the cylindrical hole 20, and the surface of the lubricating fluid 27 extends along the inner surface of the cylindrical hole 20 as shown in FIG. A concave surface of a substantially concave spherical surface is formed.

Next, the shaft body 21 is inserted into a cylindrical hole 20 provided in the bearing member 22. The shaft body 21 has a reduced diameter end portion of a cylindrical main body 21b and a convex spherical surface 21a connected to the main body 21b. Having. As shown in FIG. 3A, the convex spherical surface 21 a having the radius R of the end face of the shaft 21 is formed to be smaller than the radius r of the substantially concave spherical surface formed by the surface of the lubricating fluid 27. At the same time, the axial length L of the convex spherical surface 21a portion
Is set to be larger than the depth H of the substantially concave spherical surface formed on the surface of the lubricating fluid 27. The reduced-diameter end portion has a portion on the outer peripheral portion whose diameter decreases from the main body 21b toward the distal end, and the reduced-diameter end portion has a diameter d that is 3/4 or less of the diameter D of the main body of the shaft body. The inner part of the circle about the center will first contact the concave spherical surface of the lubricating fluid surface.

Therefore, as shown in FIG.
Is inserted into the cylindrical hole 20 from the reduced diameter end, the shaft 2
The first end face of the inner surface of the circle (in this case, the tip of the spherical surface) centered on the axis having the diameter d comes into contact with the lubricating fluid 27 first, and as the insertion of the shaft 21 continues, the lubricating fluid 27 The surface of the shaft 21 is raised while traveling along the convex spherical surface 21 a of the shaft 21, and the cylindrical hole 20 formed in the bearing member 22 is formed.
Reaching the lower portion of the radial bearing clearance forming a radial bearing between the cylindrical inner surface of the shaft member and the outer peripheral surface of the main body of the shaft body 21;
As a result, almost no air is trapped on the end face of the shaft 21.

As the insertion of the shaft 21 is further continued,
The lubricating fluid 27 which has reached the radial bearing clearance forming the radial bearing fills the radial bearing clearance while discharging air, and as shown in FIG. 3 (c), the end surface of the shaft body 21 forms a cylindrical shape forming a thrust bearing. Touches the bottom of the hole 20,
The step of inserting the shaft 21 ends. In the process described in the first embodiment described above, air is not trapped in the process of inserting the shaft, and the lubricating fluid is present between the cylindrical inner surface and the shaft outer surface. The lubricating fluid between the bottom surface of the cylindrical hole and the end surface of the shaft is sealed, so that almost no bubbles enter the lubricating fluid between the bearing member and the shaft.

That is, in this embodiment, a high-performance hydrodynamic bearing device in which bubbles in the lubricating fluid are greatly reduced can be easily obtained only by inserting the shaft into the cylindrical hole of the bearing member. . The depth H of the concave spherical surface formed by the lubricating fluid injected into the bottom surface of the cylindrical hole of the bearing member varies depending on the viscosity of the lubricating fluid and the size of the inner diameter of the cylindrical hole. The radius R and the axial length L of the convex spherical surface are the depth H of the concave surface.
May be appropriately determined according to the value of.

FIGS. 4 (a) and 4 (b) show the cylindrical inner surface of the radial dynamic pressure bearing provided on the bearing member 32 when the hydrodynamic bearing device is manufactured in the second embodiment of the present invention. FIG. 4 is a schematic longitudinal sectional view of a hydrodynamic bearing device in a process of inserting a cylindrical shaft body 31 into a cylindrical hole 30 having a cylindrical bottom surface constituting a thrust bearing. The difference from the first embodiment is that as shown in FIG. 3A, the shape of the thrust bearing surface on the bottom surface of the cylindrical hole 30 provided in the bearing member 32 is not a convex spherical surface but a flat surface. It is.

As a result, compared to the first embodiment, FIG.
The area where the end face of the shaft body 31 and the thrust bearing surface shown in (b) are in contact with each other is increased, and the surface pressure on the thrust bearing surface is reduced. In the second embodiment as well, the effect and action of preventing air bubbles from entering the lubricating fluid 37 are the same as in the first embodiment, and are high only in the step of inserting the shaft into the cylindrical hole provided in the bearing member. A high performance hydrodynamic bearing device is obtained.

FIGS. 5A and 5B show a cylindrical inner surface of a radial dynamic pressure bearing provided on a bearing member 42 when a hydrodynamic bearing device is manufactured according to a third embodiment of the present invention. A schematic longitudinal sectional view of a hydrodynamic bearing device is shown in a process of inserting a cylindrical shaft body 41 into a cylindrical hole 40 having a bottom surface constituting a thrust bearing. The difference from the second embodiment is that
As shown in FIG. 5A, the outer peripheral portion of the reduced diameter end portion of the shaft body 41 has a conical surface shape whose diameter decreases from the main body 21b toward the distal end, and the internal shape connected thereto is convex. It is a spherical point.

The radius of the convex spherical surface 41a on the end surface of the shaft 41 is increased by providing a conical surface 41b in the shape of the end surface of the shaft 41. By increasing the radius of the convex spherical surface 41a, the surface pressure applied to the thrust bearing surface on the bottom surface of the cylindrical hole 40 provided with the bearing member 42 shown in FIG. 5B can be reduced as compared with the first embodiment. It is possible to set the value of the axial length L of the reduced diameter end defined in the first embodiment to the value of the concave surface formed on the surface of the lubricating fluid 47 despite increasing the radius of the convex spherical surface 41a. It can be kept larger than the depth H.

In the third embodiment, the effect and action of preventing air bubbles from entering the lubricating fluid 47 are the same as those of the first embodiment, and a step of inserting a shaft into a cylindrical hole provided in a bearing member. Alone, a high-performance hydrodynamic bearing device can be obtained. In the step of inserting the shaft into the cylindrical hole, the reduced-diameter end portion is first formed by the inner portion of a circle centered on the axis having a diameter d of 3/4 or less of the diameter D of the main body 21b of the shaft. By contacting the lubricating fluid, no space is formed between the reduced diameter end of the shaft and the lubricating fluid. As a result, the amount of bubbles in the lubricating fluid that adversely affects the performance of the hydrodynamic bearing device can be significantly reduced without going through a bubble discharging step such as vacuuming, but the smaller the amount, the better.

As shown in Embodiments 1 to 3, in the case of a pivot bearing in which the reduced-diameter end of the shaft body is a convex spherical surface, the size of the spherical surface is simply changed (in the case of Embodiment 3, the taper angle and the size of the spherical surface are changed). ) Can easily bring the contact between the reduced diameter end and the lubricating fluid closer to the shaft center. If there is no problem with the surface pressure of the thrust bearing, the reduced diameter end of the shaft body should be It is preferred that the inner part of the circle about the axis having a diameter less than or equal to one-half the diameter of the body first contacts the lubricating fluid.

FIGS. 6 (a) and 6 (b) show the cylindrical inner surface and the radial dynamic pressure bearing provided on the bearing member 52 when the hydrodynamic bearing device is manufactured in the fourth embodiment of the present invention. A cylindrical hole 50 having a bottom surface constituting a thrust bearing
A schematic longitudinal cross-sectional view of a hydrodynamic bearing device is shown in a step of inserting a cylindrical shaft body 51 into the shaft. The difference from the third embodiment is that, as shown in FIG. 6 (b), the inner shape connected to the conical surface 51b of the outer peripheral portion of the reduced diameter end of the shaft becomes a plane perpendicular to the axis, and the bearing member The point is that a groove for generating dynamic pressure is formed in the thrust bearing surface on the bottom surface of the cylindrical hole 50 provided in 52.

As a result, dynamic pressure is generated on the thrust bearing surface when the shaft body 51 rotates, and the thrust bearing surface and the end face of the shaft body 51 can be brought into non-contact, so that the performance and durability are further improved. Although the amount of air bubbles in the lubricating fluid may slightly increase as compared with the case where the end surface of the shaft is spherical, air bubbles that adversely affect the performance of the bearing device due to the formation of the conical surface 51b are lubricated. Does not enter the fluid.

When a dynamic pressure bearing is used as the thrust bearing as in this embodiment, the flat portion of the end face of the shaft should be wide in order to secure the thrust load capacity, but there is a margin in the load capacity. In order to further reduce residual air bubbles, FIG.
In the reduced diameter end portion of the shaft body shown in (a), it is preferable that a portion inside a circle centered on an axis having a diameter equal to or less than half of the diameter of the main body comes into contact with the lubricating fluid first. Also in the fourth embodiment, the effect and action of preventing air bubbles from entering the lubricating fluid 57 are substantially the same as those of the first embodiment, and only the step of inserting the shaft into the cylindrical hole provided in the bearing member is performed. And a high-performance hydrodynamic bearing device can be obtained.

FIG. 7 shows a cylindrical inner surface constituting a radial dynamic pressure bearing provided on a bearing member 62 and a bottom surface constituting a thrust bearing when a hydrodynamic bearing device according to a fifth embodiment of the present invention is manufactured. A schematic vertical cross-sectional view of a dynamic pressure bearing device is shown in a process of inserting a cylindrical shaft body 61 into a cylindrical hole 60 formed by the method. The difference from the second embodiment is that the bearing member 62
Is composed of a sleeve 62b and a thrust bearing member 62a fixed to one end of the sleeve 62b. Even if the radial bearing component and the thrust bearing component are integrally formed or formed separately, the effect and action of preventing air bubbles from entering the lubricating fluid 67 are substantially the same as those of the second embodiment. A high-performance hydrodynamic bearing device can be obtained only by the step of inserting the shaft body into the cylindrical hole provided in the shaft.

FIG. 8 shows an example of a spindle motor using the hydrodynamic bearing device obtained according to the present invention. The spindle motor rotates around a stator 75 fixed to a bearing member 72. A rotor 76 is fixed to a shaft 71.
1 is a dynamic pressure bearing device. A shaft 71 serving as a rotating shaft is inserted into a cylindrical hole 70 of a bearing member 72. The cylindrical hole 70 has a cylindrical inner surface constituting a radial dynamic pressure bearing 74 and a convex spherical surface for supporting the axial load of the shaft. And a bottom surface constituting the thrust bearing 73 in which is formed. Herringbone-shaped grooves for generating dynamic pressure are provided at two locations separated in the axial direction on the inner surface of the cylindrical hole 70. As the dynamic bearing device of the spindle motor, the one obtained in the second embodiment is used.

The present invention is not limited to this embodiment. In the step of inserting the shaft into the cylindrical bore of the bearing member, the shape of the reduced diameter end of the shaft may be spherical, and the reduced diameter end may be the main body. The outer peripheral part has a conical surface part whose diameter decreases from the tip toward the tip, and the axial length of the reduced diameter end is increased by lubricating fluid rising along the cylindrical inner surface due to surface tension. It is preferable that the depth be longer than the depth of the concave surface of the formed lubricating fluid surface. As a result, the reduced-diameter end of the shaft body can first contact the lubricating fluid inside the circle centered on the axis having a diameter of 3/4 or less of the diameter of the main body, so that high-performance dynamic pressure can be obtained. Bearings can be obtained.

If the above process is satisfied, the thrust bearing surface may be a flat surface, a convex spherical surface, or a surface having a dynamic pressure generating groove as shown in the embodiment, and the shape of the reduced diameter end of the shaft body may be changed. The convex spherical surface may be a flat surface or a flat surface on which a groove for generating a dynamic pressure is formed except for the outer peripheral portion. Further, the thrust bearing surface and the reduced diameter end portion of the shaft may be a combination thereof as in the embodiment.

[0028]

According to the present invention, a shaft having a cylindrical body and a reduced-diameter end having an outer peripheral portion having a diameter decreasing from the main body toward the tip is provided by the reduced-diameter end. In the insertion step of inserting into the cylindrical hole of the bearing member from the portion, the reduced-diameter end portion has a portion inside the circle centered on the axis having a diameter of 3/4 or less of the diameter of the main body at the bottom of the cylindrical hole. The first contact with the lubricating fluid, such as oil or liquid grease, to eliminate or reduce air bubbles in the lubricating fluid that adversely affects the performance of the hydrodynamic bearing device. And a high-performance hydrodynamic bearing device can be obtained. Furthermore, since the bubbles in the lubricating fluid can be greatly reduced only by the step of inserting the shaft into the cylindrical hole of the bearing member, the assembly is facilitated and the number of assembly steps can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a spindle motor using a conventional dynamic pressure bearing device.

FIG. 2a is an explanatory view at the start of a process of inserting a shaft body into a bearing member cylindrical hole using a schematic longitudinal sectional view of a conventional dynamic pressure bearing device.

FIG. 2B is an explanatory view of an initial stage of contact between a shaft end face and a lubricating fluid in a step of inserting a shaft into a bearing member cylindrical hole using a schematic longitudinal sectional view of a conventional dynamic pressure bearing device.

FIG. 2c is an explanatory view at the end of the step of inserting a shaft body into a bearing member cylindrical hole using a schematic longitudinal sectional view of a conventional dynamic pressure bearing device.

2d is an explanatory view at the end of the step of inserting a shaft body into a bearing member cylindrical hole using a schematic longitudinal sectional view of a conventional dynamic pressure bearing device, and is an enlarged view of a thrust bearing portion in FIG. 2c. .

FIG. 3a is an explanatory view at the start of a process of inserting a shaft member into a cylindrical hole of a bearing member using a schematic longitudinal sectional view of the dynamic pressure bearing device according to the first embodiment of the present invention.

FIG. 3b is an explanatory view of the initial stage of contact between the end face of the shaft and the lubricating fluid in the step of inserting the shaft into the cylindrical hole of the bearing member using the schematic longitudinal sectional view of the dynamic pressure bearing device according to the first embodiment of the present invention; It is.

FIG. 3c is an explanatory view at the end of the step of inserting a shaft member into a cylindrical hole of a bearing member using a schematic longitudinal sectional view of the dynamic pressure bearing device according to the first embodiment of the present invention.

FIG. 4a is an explanatory view at the start of a process of inserting a shaft member into a cylindrical hole of a bearing member using a schematic longitudinal sectional view of a dynamic pressure bearing device according to a second embodiment of the present invention.

FIG. 4b is an explanatory view at the end of the step of inserting a shaft member into a cylindrical hole of a bearing member using a schematic longitudinal sectional view of a dynamic pressure bearing device according to a second embodiment of the present invention.

FIG. 5a is an explanatory view of an initial stage of contact between a shaft end face and a lubricating fluid in a step of inserting a shaft into a cylindrical hole of a bearing member using a schematic longitudinal sectional view of a dynamic bearing device according to a third embodiment of the present invention; It is.

FIG. 5b is an explanatory view at the end of the step of inserting a shaft member into a cylindrical hole of a bearing member using a schematic longitudinal sectional view of a dynamic pressure bearing device according to a third embodiment of the present invention.

FIG. 6a is an explanatory view of an initial stage of contact between a shaft end face and a lubricating fluid in a step of inserting a shaft into a cylindrical hole of a bearing member using a schematic longitudinal sectional view of a dynamic pressure bearing device according to a fourth embodiment of the present invention. It is.

FIG. 6B is an explanatory view at the end of the step of inserting a shaft member into a cylindrical hole of a bearing member using a schematic longitudinal sectional view of a dynamic pressure bearing device according to a fourth embodiment of the present invention.

FIG. 7 is a schematic longitudinal sectional view of a hydrodynamic bearing device according to a fifth embodiment of the present invention.

FIG. 8 is a schematic vertical sectional view of a spindle motor using a hydrodynamic bearing device according to a second embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 20 cylindrical hole 21 shaft body 21a convex spherical surface 21b main body 22 bearing member 27 lubricating fluid

Claims (1)

[Claims] 1. A method of manufacturing a hydrodynamic bearing device, comprising: a bearing member provided with a cylindrical hole having a cylindrical inner surface for forming a radial bearing surface and a bottom surface for forming a thrust bearing surface. An injecting step of injecting a lubricating fluid into the bottom surface of the cylindrical hole of the above, after the injecting step, a reduced diameter having a cylindrical main body and a portion whose diameter decreases from the main body toward the tip on the outer peripheral portion. And an insertion step of inserting a shaft having an end from the reduced diameter end into the cylindrical hole. In the inserting step, the reduced diameter end has a diameter of ／ or less of the diameter of the main body. A method for manufacturing a hydrodynamic bearing device, characterized in that an inner part of a circle centered on the shaft center first contacts the lubricating fluid.