JP3077251B2 - Dynamic pressure bearing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a dynamic pressure bearing device used for video and information equipment such as a scanner unit for a laser printer.

[0002]

2. Description of the Related Art A mirror of a scanner unit for a laser printer is disposed on a flange provided on an outer peripheral surface of a rotating member supported by a support member of a bearing device via a dynamic pressure bearing. Conventionally, as a method of attaching the mirrors, which are known solid Teisu shall have the bolt stop.

[0003]

However, since the above-mentioned bearing device is used at a high speed rotation, when a mirror is bolted to a rotating member, a large centrifugal force at a high speed rotation or a mirror is required. Due to the effects of thermal expansion and the like caused by heat generation due to windage damage, problems such as rotational imbalance and deformation of the mirror occur .

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned conventional problems, and to fix a mirror to a rotating member by shrink fitting to prevent problems such as imbalance in rotation and deformation of the mirror. It is another object of the present invention to provide a dynamic pressure bearing device capable of further preventing deterioration of mirror surface accuracy and seizing of a bearing.

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a rotating member having a hollow portion at a shaft center supported by a supporting member via a dynamic pressure bearing, and a rotating member having a hollow portion on an outer peripheral surface of the rotating member. The present invention relates to a hydrodynamic bearing device in which a mirror provided on a provided flange portion is mounted on an outer diameter surface of a rotating member by shrink fitting.
An annular projection in the axial direction is provided on the flange, and a mirror is mounted on the outer diameter surface of the projection by shrink fitting.

[0006]

Even if the mirror is shrink-fitted with a large interference to the outer diameter surface of the annular projection of the flange of the rotating member, the deformation caused by the interference is absorbed by the annular projection, and the mirror is supported. Bearing clearance between members is too small,
There is no deformation of the mirror.

[0007]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a longitudinal sectional view of a first embodiment of the present invention. A shaft 2 serving as a support member is mounted on a base 1a of the housing 1.
One end of the sleeve 3 is fixed, and the sleeve 3 constituting the rotating member 70 having a hollow portion in the axis is fitted around the shaft body 2. Radial bearing surface 3 which is the inner diameter surface of sleeve 3
a and a radial receiving surface 4a, which is an outer diameter surface of the shaft body 2 provided with a groove 4 for generating dynamic pressure and opposed to the bearing via a bearing clearance C1, constitutes a dynamic pressure type radial fluid bearing R. The sleeve 3 is supported in the radial direction via the dynamic pressure type radial fluid bearing R. A thrust receiver 5 having an air vent hole 5 a is attached to one end of the sleeve 3, and the thrust receiver 5 also forms a rotating member 70. The thrust bearing surface 5b on the lower surface of the thrust receiver 5 and the thrust receiving surface 2a provided on the end face of the shaft body 2 facing the thrust bearing surface 5a constitute a thrust fluid bearing S. Through the thrust fluid bearing S, the thrust bearing 5 is It is supported in the axial direction.

A flange 3b is provided on the outer peripheral surface of the sleeve 3, and an annular axial projection 3c is projected from the upper surface of the flange 3b.
An annular groove 3d is formed between the outer peripheral surface and the outer peripheral surface. A polygon mirror (mirror) 6 is mounted on the outer diameter surface of the projection 3c by shrink fitting with a tightening margin of several μm to several tens μm, and the lower surface and the upper surface of the polygon mirror 6 are respectively formed by flange portions 3b.
And a mounting ring 7a mounted on the sleeve 3 from above. The polygon mirror 6 is attached to the flange 3b via a mounting ring 7a and a bolt (not shown) penetrating a hole provided in the mounting ring 7a. Installed.

A window 8 made of a transparent material is provided on the side wall 1b of the housing 1 at a position facing the polygon mirror 6 in the horizontal direction. As a result, the laser beam incident on the polygon mirror 6 is reflected, passes through the window 8, and is applied to an external photosensitive drum (not shown). Also, the flange 3b of the sleeve 3
The rotor magnet 9a fitted on the outer peripheral surface of the sleeve 3 is locked below the axial direction, and is fixed by a mounting ring 7b mounted on the sleeve 3 from below.
The rotor magnet 9a and the side wall 1c of the housing 1
Together with the stator coil 9b constitutes a drive motor having a peripheral surface facing type.

Next, the operation will be described. When the sleeve 3 of the dynamic pressure bearing device is rotated by energizing the stator coil 9b of the drive motor, the gas in the housing 1 is moved to the radial bearing surface 3a by the pumping action of the dynamic pressure generating groove 4 formed in the shaft body 2. The sleeve 3 is sucked into the radial clearance between the sleeve 3 and the radial receiving surface 4a, and the sleeve 3 is supported in the radial direction while maintaining the radial bearing clearance C1. At the same time, the gas sucked into the radial gap flows into the gap between the thrust bearing surface 5b and the opposing thrust receiving surface 2a, and the gas pressure causes the thrust receiver 5 to maintain a constant minute floating amount. While rotating in the thrust direction. The gas flowing into the thrust bearing gap is discharged into the housing 1 through the air vent hole 5a of the thrust receiver 5.

When the sleeve 3 rotates at a high speed, the polygon mirror 6 attached to the flange 3b of the sleeve 3 is rotated.
However, in this case, the polygon mirror 6 is fixed with a uniform force by shrink fitting, and the rotation is unbalanced and the mirror is deformed due to the large centrifugal force of the rotation and the heat generation. Is prevented from occurring. Moreover, the shrink fit of the polygon mirror 6 is performed by the flange 3 of the sleeve 3.
The deformation caused by the tightening of the shrink fit is absorbed by the diameter of the annular projection 3c being reduced toward the annular groove 3d, so that the sleeve 3b is absorbed by the shrink fit. 3 and sleeve 2 and shaft 2
The phenomenon that the radial clearance C1 between the first and second portions becomes locally too small to cause seizure is prevented. In addition, it is possible to prevent the outer surface of the polygon mirror 6 from being deformed and the mirror surface accuracy from being deteriorated.

FIG. 2 shows a second embodiment. The hydrodynamic bearing device of this embodiment has a structure in which a housing, which is a stationary member, rotatably supports a shaft, and the polygonal mirror 6 is attached to the shaft.
Is different from that of the first embodiment. That is, a cylindrical hole 11 is provided in the lower member 10b of the housing 10 which is a support member, and a cylindrical radial bearing surface 12 is provided on the inner peripheral surface of the cylindrical hole 11, and a central portion is provided on the bottom surface. A thrust bearing surface 13 having a convex spherical projection 13a is provided. A shaft 20 as a rotating member is disposed in the cylindrical hole 11 of the housing 10, and a radial receiving surface 22 facing the radial bearing surface 12 is provided on an outer peripheral surface of the shaft 20. Is provided with a spiral dynamic pressure generating groove 24 to form a dynamic pressure type radial fluid bearing R. Further, a flat thrust receiving surface 23 facing the thrust bearing surface 13 is provided on one end surface of the shaft body 20, and a portion between the outer peripheral portion of the thrust receiving surface 23 and the outer peripheral portion of the thrust bearing surface 13 is provided. A pressure chamber 30 is formed in the space to form a thrust fluid bearing S.

The shaft body 20 has a flow hole 40 as a hollow portion at the shaft center. The flow hole 40 has a very small diameter aperture hole 40a opened at the center of the thrust receiving surface 23 and a small diameter that gradually increases from the aperture hole 40a toward the other axial end surface opposite to the thrust receiving surface 23. A large-diameter hole 40 that is opened at the other end face through the hole 40b and the medium-diameter hole 40c.
d. Thrust receiving surface 23 of shaft body 20
Around the throttle hole 40a of the thrust bearing surface 13 when the shaft body 20 is stationary.
a.

The upper end of the shaft body 20 is provided with a flange 25. On the lower surface of the flange portion 25, an annular axial projection 25a protrudes, and an annular groove 25b is formed between the projection 25a and the outer peripheral surface of the shaft body 20. A polygon mirror 6 is provided on the outer diameter surface of the projection 25a.
And the upper and lower surfaces of the polygon mirror 6 are clamped by a flange 25 and a yoke 60, respectively. The polygon mirror 6 passes through the yoke 60 and holes (not shown) provided in the yoke 60. It is attached to the flange part 25 through a bolt. An annular rotor magnet 61 is attached to the yoke 60, and a stator coil 62 radially opposed to the rotor magnet 61 is attached to the lower member 10 b of the housing 10. 15 is the upper member 10 of the housing 10
a is a window provided to face the polygon mirror 6 in the horizontal direction.

The polygon mirror 6 of the second embodiment is also mounted on an annular projection 25a protruding from a flange 25 of a shaft 20 as a rotating member by shrink fitting. This is the same as the case of the example, and therefore has the same operation and effect as described above with respect to the mounting structure of the polygon mirror 6. In each of the above embodiments, the protrusions 3c and 25a of the flange portion may have a continuous annular shape or a discontinuous annular shape. Further, the polygon mirror 6 may be attached to the rotating members 70 and 20 only by shrink fitting.

The mounting rings 7a, 7a of the first embodiment
b and the rotor magnet 9a and the yoke 60 of the second embodiment are also shrink-fitted to the rotating members 70 and 20 in order to eliminate the influence of the rotational imbalance caused by the expansion and contraction caused by the centrifugal force and the temperature change. It is desirable to fix.

[0017]

As described above, in the dynamic pressure bearing device of the present invention, an annular axial projection is provided on the flange provided on the outer peripheral surface of the rotating member, and the mirror is provided on the outer diameter surface of the projection. The mirrors are mounted by shrink-fitting, which causes problems such as rotational imbalance and deformation of the mirrors due to high-speed rotation centrifugal force and thermal expansion, as in the case of conventional mirrors mounted with bolts on flanges. not only it can prevent further because collision raised portion absorbs the clamping, as a result or mirror surface accuracy is deteriorated by the outer diameter and the deformation of the mirror, and the inner diameter of the rotary member is deformed locally Problems such as the bearing clearance becoming too small and seizure occurring can also be prevented.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional side view showing a first embodiment of the present invention.

FIG. 2 is a vertical sectional side view showing a second embodiment of the present invention.

[Explanation of symbols]

 2,10 Support member 70,20 Rotary member R Dynamic pressure type radial fluid bearing S Thrust fluid bearing 3b, 25 Flange part 3c, 25a Projection part 6 Mirror

Claims (1)

(57) [Claims] 1. A rotating member having a hollow portion at an axial center is supported by a support member via a dynamic pressure bearing, and a mirror disposed on a flange portion provided on an outer peripheral surface of the rotating member has an outer diameter surface of the rotating member. In a hydrodynamic bearing device mounted by shrink fitting,
A hydrodynamic bearing device wherein an annular axial projection is provided on the flange, and a mirror is mounted on an outer diameter surface of the projection by shrink fitting.