JPH08254210A - Dynamic pressure bearing device - Google Patents

Abstract

PURPOSE: To secure stable bearing performance of a dynamic pressure bearing by assuredly suppressing outflow of lubricant to the outside. CONSTITUTION: An annular second tapered surface 42 for lubricant seal is communicatingly formed on an outer peripheral part of a lower side tapered surface 40 on a lower end of a sleeve 6, through an annular narrow portion 44 between the sleeve 6 and a thrust receiver 8. A volume between an upper tapered surface 38 and a shaft 10 is formed larger than that between the lower tapered surface 40 and the shaft 10. Grooves are formed on the upper surface of the thrust receiver 8 which is opposed to the shaft 10 for generating dynamic pressure. Oil repellent agent is applied to the upper surface of the thrust receiver 8, on its outer peripheral part than the groove thereupon.

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 used for a polygon motor used for optical scanning of a copying machine or a laser beam printer (LBP), a spindle motor for a hard disk, or the like.

[0002]

2. Description of the Related Art A polygonal motor, which rotates a polygonal mirror, that is, a polygonal mirror by a motor, irradiates a laser beam on a polygonal reflecting surface of the polygonal mirror to scan the reflected light, is used as a light beam of a copying machine or a laser beam printer. Used in the scanning unit. Various types of polygon motors have been conventionally used, but dynamic pressure bearings have been conventionally used to meet the demands for downsizing and speeding up of polygon motors.

In this case, the shaft is inserted inside a cylindrical sleeve fixed to the substrate, and the end portion of the shaft is supported on a thrust receiver whose lower end opening is closed.
The rotor is fixed to the upper part of the shaft, the polygon mirror is fixed to this rotor, and the rotor is rotated together with the shaft to rotate the polygon mirror at high speed. Herringbone-shaped grooves for generating dynamic pressure are formed on one or both of the inner peripheral surface of the sleeve and the outer peripheral surface of the shaft, and a lubricant is filled between the sleeve and the shaft.

For example, FIG. 7 shows a part of the dynamic pressure bearing portion of the polygon motor described above. A vertical sleeve A fixed to the circuit board of the polygon motor has a cylindrical inner peripheral surface B, and a thrust receiver C is fitted to the lower end opening of the cylindrical inner peripheral surface B so as to close it. The shaft D, to which the rotor is fixed at the upper end, is provided with herringbone-shaped grooves F and G for generating dynamic pressure in the upper and lower portions of the outer peripheral surface E thereof. Both grooves F and G are inserted into the peripheral surface B so as to face the cylindrical inner peripheral surface B, and the lower end surface H of the shaft D formed into a curved surface faces the spiral groove formed in the central portion of the thrust receiver C. are doing. A lubricant such as oil is filled between the cylindrical inner peripheral surface B of the sleeve A and the outer peripheral surface E of the shaft D.

At the upper end and the lower end of the inner peripheral surface B of the sleeve A, an annular upper taper surface for lubricant sealing, in which a gap between the inner peripheral surface B of the sleeve A and the outer peripheral surface E of the shaft D expands outward in the axial direction. I and the lower taper surface J are formed, and the outflow of the lubricant filled between the cylindrical inner peripheral surface B of the sleeve A and the outer peripheral surface E of the shaft D is prevented at both taper surfaces I and J. Held in. Both taper surfaces I and J are formed in a substantially symmetrical shape, and a lubricant reservoir is formed on the taper surfaces I and J, and their holding volumes are substantially equal. A lubricant is also filled between the thrust receiver C and the lower end surface H of the shaft D.

[0006]

By the way, in the above-mentioned dynamic pressure bearing device, when the lubricant is filled between the cylindrical inner peripheral surface B of the sleeve A and the outer peripheral surface E of the shaft D, the inner diameter of the sleeve A is reduced. In a state where only the lower end portion of the shaft D is inserted into the peripheral surface B from above, a lubricant is annularly applied across the upper end opening surface of the sleeve A and the outer peripheral surface E of the shaft D, and the shaft D is removed from this state. It is lowered, that is, inserted into the sleeve A, the lubricant is gradually drawn into the gap between the sleeve A and the shaft D, and finally filled between the tapered surfaces I and J.

However, if the lubricant filling method described above is adopted, the peripheral surface of the lower end portion of the shaft D gets wet with the lubricant. Therefore, even if the lubricant is sealed by the lower taper surface J, the lubricant of the shaft D remains. Due to the wettability of the lower end portion, the lubricant easily flows out along this peripheral surface, and due to the action of gravity, the lubricant does not stay on the tapered surface J but flows out, and the lubricant is exhausted on the upper tapered surface I. There is no stable rotation performance. In addition, since the shaft D rotates at a high speed when the motor rotates, the lubricant on the peripheral surface of the shaft D is likely to be scattered, resulting in the further depletion of the lubricant described above.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to prevent the depletion of the lubricant and to retain the lubricant. An object of the present invention is to provide a hydrodynamic bearing device that can be increased and can secure stable rotation performance.

[0009]

In order to achieve the above object, in a hydrodynamic bearing device of the present invention, a vertical sleeve having a cylindrical inner peripheral surface and an inner peripheral surface of the sleeve are inserted. An inner peripheral surface of the sleeve and an outer peripheral surface of the shaft, the vertical shaft having a cylindrical outer peripheral surface facing the inner peripheral surface, and a thrust receiver mounted on the lower opening of the sleeve to support the lower end of the shaft. A groove for dynamic pressure generation is engraved on one or both of the surfaces and a lubricant is filled between the inner peripheral surface of the sleeve and the outer peripheral surface of the shaft so that the shaft is rotatably supported with respect to the sleeve. In the bearing device,
At the upper and lower ends of the inner peripheral surface of the sleeve, annular upper and lower tapered surfaces for lubricant sealing are formed so that the gap between the inner peripheral surface of the sleeve and the outer peripheral surface of the shaft expands outward in the axial direction. On the outer peripheral portion of the lower taper surface of the lower end portion of the sleeve, an annular second taper surface for lubricant sealing is formed so that the gap between the thrust receiver and the thrust receiver expands outward in the radial direction. The surface and the second tapered surface are communicated with each other through an annular narrow portion between the sleeve and the thrust receiver.

In this case, the volume between the upper tapered surface and the shaft is preferably larger than the volume between the lower tapered surface and the shaft. Further, it is preferable that a groove for generating a dynamic pressure is formed in a portion of the upper surface of the thrust receiver facing the shaft, and an oil repellent agent is applied to an outer peripheral portion of the groove on the upper surface of the thrust receiver. Further, an oil repellent may be applied to the surface of the narrow portion and the surface of the second tapered surface.

[0011]

In the dynamic pressure bearing device configured as described above, the thrust bearing is provided on the outer peripheral portion of the lower tapered surface of the lower end portion of the sleeve via the annular narrow portion between the sleeve and the thrust bearing. Since the annular second taper surface for the lubricant seal is formed so that the gap between
Even if the lubricant held on the lower tapered surface tries to flow out from this seal part due to the weight of the lubricant itself or some other reason, the narrow part of the lubricant acts as a resistance against the outflow. It cannot easily flow out from the side tapered surface, and even if the lubricant flows out through the narrow portion, the lubricant is taper-sealed by the second tapered surface located on the outer peripheral side, so that the lubricant is not Outflow is greatly suppressed.

Here, if the volume between the upper taper surface and the shaft is made larger than the volume between the lower taper surface and the shaft, the upper taper surface is preliminarily lubricated so as to retain excess lubricant. It is possible to fill a large amount of lubricant, and if the lubricant temporarily passes through the narrow part from the lower taper surface,
Even if the lubricant flows out to the tapered surface, the lubricant is not depleted, and the bearing performance can be maintained for a long time. If a groove for generating dynamic pressure is formed in a portion of the upper surface of the thrust receiver facing the shaft and an oil repellent agent is applied to the outer peripheral portion of the groove on the upper surface of the thrust receiver, the lubricant on the thrust receiver is It is possible to easily prevent the oil from flowing out from the portion in the outer peripheral direction. Furthermore, if an oil repellent agent is applied to the surface of the narrow portion and the surface of the second taper surface, the lubricant can be more effectively discharged from the lower taper surface. Can be suppressed to.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a sectional view of a main part of a first embodiment of the present invention, FIG. 2 is a sectional view showing the entire structure, FIG. 3 is a partially enlarged view of FIG.
5 is a perspective view of the thrust receiver, FIG. 5 is a process explanatory view of the surface treatment of the thrust receiver, and FIG. 6 is a sectional view showing the overall configuration of the second embodiment of the present invention.

First, the overall structure of the polygon motor M to which the present invention is applied will be described with reference to FIG. A vertical cylindrical sleeve 6 made of copper alloy or the like and having a cylindrical inner peripheral surface 4 is fixed to the circuit board 2 made of an iron plate or the like by caulking or the like. A substantially disk-shaped thrust receiver 8 is fitted into the lower end opening of the sleeve 6, the shaft 10 is inserted through the upper end opening of the sleeve 6, and the thrust receiving surface 12 at the lower end of the shaft 10 is supported on the thrust receiver 8. ing.

At the upper end of the shaft 10, the rotor hub 1
4 is fixed by press fitting or the like.
A substantially covered cylindrical rotor yoke 16 is fixed to the lower surface of the rotor yoke, an annular magnet 18 is attached to the inner peripheral surface of the cylindrical portion of the rotor yoke 16, and a stator 20 fixed to the central portion of the outer peripheral surface of the sleeve 6 by caulking or the like is a rotor magnet. It opposes to 18 through the radial gap. An annular concave portion 2 is formed by bending at the outermost peripheral portion of the rotor yoke 16, and a dynamic balance is achieved by filling an appropriate amount of the annular concave portion 22 with a weight such as putty.

For example, a regular hexagonal polygon mirror 24 is fitted around the outer periphery of the rotor hub 14, and is clamped between the rotor hub 14 and the rotor hub 14 by a clamp spring 28 attached to the upper end of the shaft 10 by a screw 26. There is.

Shaft 10 inserted in sleeve 6
Is a cylindrical outer peripheral surface 30 facing the inner peripheral surface 4 of the sleeve 6.
Herringbone-shaped dynamic pressure generating grooves 32 and 34 are formed in the upper and lower portions of the outer peripheral surface 30. Sleeve 6
As shown in FIG. 3, a lubricant 36 such as oil is filled between the inner peripheral surface 4 of the shaft 10 and the outer peripheral surface 30 of the shaft 10, and the groove 32 is formed by relative rotation of the sleeve 6 and the shaft 10. The lubricant pressure in the central portions of the bearings 34 and 34 becomes high, and each constitutes a radial dynamic pressure bearing portion.

At the upper end and the lower end of the inner peripheral surface 4 of the sleeve 6, an annular upper taper surface for lubricant sealing is formed so that a gap between the inner peripheral surface 4 of the sleeve 6 and the outer peripheral surface 30 of the shaft 10 expands outward in the axial direction. 36 and the lower taper surface 38 are formed, and the upper taper surface 36 has a larger volume than the lower taper surface 38. The upper taper surface 36 and the lower taper surface 38 prevent the lubricant 36 from flowing out from the inner peripheral surface 4 of the sleeve 6, and the lubricant 36 is filled between the inner and outer peripheral surfaces 4 and 30 therebetween. Become. The lower taper surface 40 is closer to the lower end side of the shaft 10 than in the conventional case, and is adjacent to the thrust bearing portion.

The lower taper surface 4 at the lower end of the sleeve 6
An annular second tapered surface 42 for a lubricant seal is formed on the outer peripheral portion of 0 for expanding a gap between the thrust receiver 8 and the radial direction outward. The two taper surfaces 42 communicate with each other via the annular narrow portion 44 between the sleeve 6 and the thrust receiver 8.

The thrust bearing 8 is made of cermet such as alumina having excellent wear resistance, and a portion of the upper surface of the thrust bearing 8 facing the shaft 10 has a spiral motion as shown in FIG. A pressure generating groove 46 is engraved. An oil repellent is applied to the outer peripheral portion of the upper surface of the thrust receiver 8 with respect to the groove 46, that is, the portion facing the open end of the lower tapered surface 40. In this case, it is necessary to apply the oil-repellent agent to the outer peripheral portion of the groove 46 accurately and in an appropriate amount. If the amount is small, the lubricant filled between the thrust receiver 8 and the shaft 10 tends to flow out, and a large amount of oil-repellent agent may be applied. For example, there is a problem that the oil repellent itself may flow out.

Therefore, in this embodiment, the following lubricant application method is adopted. That is, first, as shown in FIG. 5A, the lubricant 36 is applied to the thrust bearing portion, that is, the groove 46, on the upper surface of the thrust receiver 8 after the groove 46 is processed.
Apply a thinly. Next, as shown in FIG.
A predetermined amount of the oil repellent 48 is applied to the outer peripheral portion of the above and baked. At this time, the oil repellent 48 does not flow into the groove 46 due to the lubricant 36a. Thereafter, as shown in FIG. 7C, a prescribed amount of the lubricant 36b is applied to the upper surface of the lubricant 36a, that is, the inside of the oil repellent 48. As a result, the oil repellent 48
Can be applied without invading the groove 46,
The management of the applied amount becomes easy.

On the outer peripheral portion of the thrust receiver 8, as shown in FIG. 4, three notches 50 for removing air are formed at equal intervals. As shown in FIGS. 1 and 3, each of the notches 50 faces the second tapered surface 42 of the sleeve 6, and the expansion and contraction of the lubricant or the like due to air venting and temperature change when the lubricant 36 is filled. It also serves as a breathing port for time.

In the dynamic pressure bearing device having such a structure, when the lubricant 36 is injected, the thrust bearing portion is
The thrust bearing 8 is filled with an appropriate amount of the lubricant 36 in the manner described above, and the radial bearing portion is filled with the lubricant 36 in the manner described in the related art. In this embodiment, the lower tapered surface 40 of the sleeve 6 is the shaft 10
Since the shaft 10 is opposed to the lower end of the shaft 10, even if the lower end of the shaft 10 is wet with the lubricant when the lubricant is filled, as shown in FIG. Then, the lubricant 36 is prevented from flowing out. Further, the lubricant 36 is filled in a necessary amount or more, and the excess lubricant is held by the upper tapered surface 38.

When the motor M is driven, the shaft 10 rotates at a high speed, and with this rotation, the lubricant 36 on the lower taper surface 40 partially flows out toward the lower end along the peripheral surface of the shaft due to centrifugal force. Then, the other lubricant 36 tries to flow out along the tapered surface 40 in the outer peripheral direction. The lubricant 36, which tends to flow out to the lower end side of the shaft, is prevented from further spreading due to the action of the oil repellent on the thrust receiver 8.
In addition, the lubricant 36 that is about to flow out in the outer peripheral direction has the narrow portion 44 between the sleeve 6 and the thrust receiver 8 that is the lubricant 36.
This serves as resistance against the outflow, and the outflow of the lubricant 36 is stopped by the narrow portion 44.

Even if the lubricant 36 flows out from the narrow portion 44, since the second taper seal structure by the second tapered surface 42 exists on the outer peripheral side of the narrow portion 44,
The lubricant 36 that has flowed out is taper-sealed as shown by the chain double-dashed line in FIG. 3 to reliably prevent it from flowing out. Here, the excess lubricant 36 retained on the upper tapered surface 38 has an amount such that the lubricant between the sleeve 6 and the shaft 10 is not depleted even when the lubricant 36 flows out to the second tapered surface 42. It is set.

In the above embodiment, the thrust bearing 8
If the oil repellent treatment is applied to not only the outer peripheral portion of the upper surface but also the surface of the sleeve 6 and the second taper surface 42 forming the narrow portion 42, the above-described sealing effect becomes more reliable.

Next, FIG. 6 shows a second embodiment in which the present invention is applied to an inner rotor type polygon motor M '. In the figure, the same reference numerals as those used above denote the same or corresponding ones.

The sleeve 6 fixed to the circuit board 2 includes:
As in the case of the first embodiment, the shaft 10 is supported by the dynamic pressure bearings in the radial direction and the thrust direction, and the shaft 1
A cylindrical portion 14 ′ is provided on the rotor hub 14 fixed to the upper end of the sleeve 0 near the outer circumference of the sleeve 6. A rotor magnet 18 is attached to the outer peripheral surface of the cylindrical portion 14 ′ via a cylindrical yoke 16.

A rotor magnet 18 is provided on the circuit board 2.
An annular stator 20 is arranged so as to face the outer peripheral surface of the, and is fixed to the circuit board 2 by an annular holder 52 made of resin.

Although the embodiments of the dynamic pressure bearing device of the present invention have been described above, the present invention is not limited to such embodiments and various modifications can be made without departing from the spirit of the present invention. Needless to say.

[0031]

Since the present invention is constructed as described above, it has the following effects. Since the annular second taper surface for the lubricant seal is formed to communicate with the outer peripheral portion of the lower taper surface of the lower end portion of the sleeve through the annular narrow portion between the sleeve and the thrust receiver, the lower taper surface is formed. Even if the retained lubricant tries to flow out from this seal part for some reason, the lubricant can be stopped first in the narrow part, and even if the lubricant passes through the narrow part and flows out, it will reach the outer peripheral side. The lubricant can be taper-sealed by the second taper surface located, the outflow of the lubricant to the outside can be surely suppressed, and the stable bearing performance of the dynamic pressure bearing can be secured.

Further, if the volume between the upper taper surface and the shaft is made larger than the volume between the lower taper surface and the shaft, the lubricant may be retained in advance on the upper taper surface. Can be filled a little, and even if the lubricant flows from the lower taper surface to the second taper surface through the narrow part, the lubricant will not be exhausted and the bearing performance will be maintained for a long time. It is possible.
Further, if a groove for generating dynamic pressure is formed in a portion of the upper surface of the thrust receiver facing the shaft and an oil repellent agent is applied to the outer peripheral portion of the groove on the upper surface of the thrust receiver, the lubricant on the thrust receiver is It is possible to prevent the oil from easily flowing out from the part in the outer peripheral direction, and by applying an oil repellent to the surface of the narrow portion and the surface of the second taper surface, it is possible to more effectively suppress the outflow of the lubricant from the lower taper surface. It is possible.

[Brief description of drawings]

FIG. 1 is a sectional view of essential parts showing a first embodiment when a dynamic pressure bearing device of the present invention is applied to a polygon motor.

FIG. 2 is a sectional view showing an overall configuration of a polygon motor of a first embodiment.

FIG. 3 is an enlarged sectional view of a lower tapered surface portion of FIG.

4 is a perspective view of the thrust receiver of FIG. 1. FIG.

5 is a front view of each step for explaining the oil repellent process of the thrust receiver of FIG. 1. FIG.

FIG. 6 is an overall sectional view showing a second embodiment when the dynamic pressure bearing device of the present invention is applied to a polygon motor.

FIG. 7 is a partial cross-sectional view showing a conventional dynamic pressure bearing device.

[Explanation of symbols]

 4 Cylindrical inner peripheral surface 6 Sleeve 8 Thrust receiving 10 Shaft 30 Cylindrical outer peripheral surface 32, 34, 46 Groove 36 Lubricant 38 Upper taper surface 40 Lower taper surface 42 Second taper surface 44 Narrow part

Claims (4)

[Claims] 1. A vertical sleeve having a cylindrical inner peripheral surface, a vertical shaft having a cylindrical outer peripheral surface which is inserted through the inner peripheral surface of the sleeve and faces the inner peripheral surface, and a lower end of the sleeve. A thrust receiver that is mounted in the opening and supports the lower end of the shaft, and a dynamic pressure generating groove is engraved on one or both of the inner peripheral surface of the sleeve and the outer peripheral surface of the shaft. In a dynamic pressure bearing device in which a lubricant is filled between an inner peripheral surface and an outer peripheral surface of the shaft, and the shaft is rotatably supported with respect to the sleeve, in an upper end portion and a lower end portion of the inner peripheral surface of the sleeve. Is formed with an annular upper taper surface and a lower taper surface for a lubricant seal in which a gap between the outer peripheral surface of the shaft and the outer peripheral surface of the shaft expands outward, and the lower side of the lower end portion of the sleeve is formed. Outer circumference of tapered surface , The annular second lubricant seal gaps between said thrust receiving is expanded radially outwardly
A dynamic bearing device, wherein a tapered surface is formed, and the lower tapered surface and the second tapered surface communicate with each other through an annular narrow portion between the sleeve and the thrust receiver. 2. The hydrodynamic bearing device according to claim 1, wherein the volume between the upper tapered surface and the shaft is larger than the volume between the lower tapered surface and the shaft. 3. A groove for generating a dynamic pressure is engraved in a portion of the upper surface of the thrust receiver facing the shaft,
The hydrodynamic bearing device according to claim 1, wherein an oil repellent agent is applied to an outer peripheral portion of the upper surface of the thrust receiver from the groove. 4. The hydrodynamic bearing device according to claim 1, wherein an oil repellent agent is applied to the surface of the narrow portion and the surface of the second tapered surface.