JPH04181010A - Dynamic pressure bearing rotary device - Google Patents

Abstract

PURPOSE:To prevent partial contact with a simple structure and to steady the characteristic of a bearing with high precision by forming either of the end part of a shaft and the shaft supporting face of a thrust supporting member into a projecting shape protruding at its middle part. CONSTITUTION:A dynamic pressure radial bearing is formed of a herringbone shallow groove 14 and a spiral shallow groove 15 between a rotary shaft 1 and a sleeve 2 pressed in an outer cylinder 5, and a thrust supporting member 41 whose face opposite to the lower end face of the rotary shaft 1 is protruding and spherical is arranged on the lower end face of the rotary shaft 1. Thus each component does not require high accuracy and a complex shape, and can be prevented from deterioration caused by air mixing in bearing characteristic and the occurrence of seizure for its steadiness.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydrodynamic bearing rotating device, and relates to a rotating device used, for example, in a deflection scanning device such as a laser beam printer.

[Prior Art] In recent years, the demand for high-speed, high-precision rotating devices has increased, and in particular, high-precision, non-contact hydrodynamic rotary bearings are used in laser beam printers and the like. On the other hand, there is also a high demand for cost reduction.

FIG. 4 shows a deflection scanning rotation device for a laser beam printer using a conventional hydrodynamic bearing. The rotating shaft 1 and the sleeve 2 are rotatably fitted to each other. A thrust plate 3 is arranged at the lower end of the sleeve 2 together with a fixed plate 4, and is fixed to an outer cylinder 5. A flange 6 is fixed to the rotating shaft 1. A rotating polygon mirror 7 is attached to the upper part of the flange 6, and a yoke 9 to which a driving magnet 8 is fixed is fixed to the lower part.

A stator 1o fixed to the outer cylinder 5 is arranged at a position facing the drive magnet 8. A shallow groove 11 is cut into the thrust plate 3 on the surface facing the end of the rotating shaft 1 to form a dynamic pressure thrust bearing, and holes 12 and 13 for circulation of lubricating fluid are provided. Furthermore, a Heringhorn-shaped shallow groove 14 is carved on the outer circumferential surface of the rotating shaft 1 at a position facing the inner circumferential surface of the sleeve 2, thereby forming a hydrodynamic radial bearing. Furthermore, a shallow spiral groove 15 is cut in the vicinity of the sleeve opening to allow lubricating fluid to flow toward the dynamic pressure thrust bearing. Further, the sleeve 2 includes the herringhorn-shaped shallow groove 14 and the spiral shallow groove 15.
By providing the recess 16 and the small-diameter hole 17 between the two, the stability of the hydrodynamic bearing using liquid (oil, grease, etc.) as the lubricating fluid is ensured.

[Problem U to be solved by the invention] However, in the above conventional example, in order to ensure the characteristics and stability of the rotating device, the number of parts increases, the precision of each part must be high, and the shape becomes complicated. ,
Manufacturing costs such as processing and assembly were high. Furthermore, in order to ensure stable characteristics of the rotating device, it is necessary to retain lubricating fluid and prevent air from entering.

In particular, if air gets mixed in, the air expands and contracts as the environmental temperature changes, causing the lubricating fluid to be discharged from the bearing, deteriorating the bearing characteristics and causing failures such as caulking (uneven contact). was alive.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and it is an object of the present invention to provide a hydrodynamic bearing rotating device that has a simple structure, prevents problems such as uneven contact, and has highly accurate and stable characteristics.

[Means and Effects for Solving the Problems] In order to achieve the above object, the present invention provides a thrust bearing with a convex portion or a small area near the center of one end surface of the shaft or a surface facing the one end surface of the shaft. It has a convex spherical surface, and a hole communicating with the atmosphere is provided between the radial bearing part and the thrust bearing part. As a result, it is possible to prevent deterioration of bearing characteristics and occurrence of galling due to air entrainment, and to obtain a stable rotating device at low cost, without requiring high precision or having a complicated shape for each part. enable.

[Embodiment] FIG. 1 is a drawing showing one embodiment of the present invention. A sleeve 2 fixed to the rotating shaft 1 and the outer cylinder 5 by press fitting or the like is rotatably fitted to each other. A flange 6 is fixed above the rotating shaft 1 in the figure, and a rotating polygon mirror 7 is mounted above the flange 6.
is fixed.

In addition, a herringbone-shaped shallow groove 14 is carved in either the rotating shaft 1 or the sleeve 2 (in the embodiment, on the rotating shaft side) at a position where the outer circumferential surface of the rotating shaft 1 and the inner circumferential surface of the sleeve 2 face each other. A hydrodynamic radial bearing is formed. Furthermore, near the sleeve opening, there is a shallow spiral groove 1 that allows the fluid to flow downward in the figure to prevent the lubricating fluid from flowing out from the opening.
5 is similarly engraved. A yoke 9 to which a driving magnet 8 is fixed is fixed to the lower part of the flange 6. A stator 10 fixed to the outer cylinder 5 is arranged at a position facing the driving magnet 8. At the lower end of the sleeve 2,
A thrust support member 41 having a convex spherical surface facing the end surface of the rotating shaft 1 is arranged. The vicinity of the center of the lower end surface of the rotating shaft 1 is supported by the spherical portion of the thrust support member 41 . The thrust support member 41 is fixed to the inner surface of the sleeve 2 by a press-fit cap.

The sleeve 2 is provided with at least one hole 51 at a position between the dynamic pressure radial bearing forming part and the integrated part of the thrust support member 41, and the inside of the sleeve 2 is connected to the outside air through the hole 51. communicate with.

When the rotating shaft 1 is rotationally driven, the rotating shaft 1 and the sleeve 2 are supported in a non-contact manner by the dynamic pressure acting between them in the radial direction. Further, in the thrust direction, since a convex spherical surface is disposed on the surface facing the lower end surface of the rotating shaft 1, support is provided by point contact. Therefore, rotational loss and loss torque due to contact are extremely small, and the characteristics of the rotating device are close to those of non-contact support.

Furthermore, a hole 51 is provided in the sleeve 2 at a position between the dynamic pressure radial bearing forming part and the integrated part (convex spherical part) of the thrust support member 41, which communicates the inside of the sleeve 2 with the outside air. Therefore, if air is mixed in the lubricating fluid interposed in the gap between the sleeve 2 and the thrust support member 41 and the rotating shaft 1, the mixed air will be removed as the environmental temperature changes. Even if the lubricating fluid expands and contracts, since air enters and exits through the hole 51, the lubricating fluid is not forced out.

Note that it is desirable that the dynamic pressure radial bearing and the thrust support be filled with lubricating fluid (oil, etc.) present in the bearing, but it is not necessary that the parts other than the dynamic pressure radial bearing be filled with lubricating fluid. There isn't. Therefore, the hole 51 does not interfere with the rotational action. By providing such a hole 51, assembly can be carried out without consideration of air intrusion during assembly, which simplifies the assembly process and reduces cost.

Further, since the thrust support member 41 can be directly assembled into the sleeve 2, the number of parts can be reduced and the cost can be reduced. Since thrust bearings make point contact and do not maintain a non-contact state like hydrodynamic bearings, there is no need for recesses or small diameter holes to stabilize the thrust bearings.

FIG. 2 shows a main part of a second embodiment of the present invention.

The rotating shaft 1 and the sleeve 2 are rotatably fitted to each other.

A hole 51 is provided in the sleeve 2 at a position between the dynamic pressure radial bearing section and the thrust support member 41 to communicate the inside of the sleeve 2 with the outside air. A porous member 61 is disposed within this hole 51 .

By disposing this porous member 61 in the hole 51, when air is mixed in the lubricating fluid interposed in the gap between the sleeve 2 and the thrust support member 41 and the rotating shaft 1, the porous member 61 is arranged in the hole 51. Even if the mixed air expands or contracts, the air enters and exits through the porous member 61, so the lubricating fluid is not forced out as in the previous embodiment. Furthermore, since air enters and exits through the porous member 61, the porous member 61 functions as a filter.

Therefore, foreign matter, dust, etc. are prevented from entering the inside of the sleeve 2, the lubricating fluid can be kept clean, and the bearing characteristics will not deteriorate. In addition, since the amount of ventilation in the porous member 61 can be arbitrarily selected by selecting the material of the porous member, the particle size, or closing the holes, there is no need to tighten the machining accuracy of the holes 51 or to make the holes more than necessary (difficult to process). (I see) Since there is no need to reduce the size, it is possible to provide a stable rotating device at low cost.

FIG. 3 is a diagram showing essential parts of a third embodiment of the present invention.

Here, the thrust support member 42 has a sleeve at a position between the hydrodynamic radial bearing portion and a convex spherical surface provided on the surface facing the end surface of the rotary shaft 1 that supports the rotary shaft 1 in point contact. 2, a hole 52 is provided through which a space (gap) formed by the thrust support member 42 and the rotating shaft 1 communicates with the outside air. With this configuration, the hole 52 can be formed by an easy method such as molding, and the cost can be reduced.

Furthermore, a porous member may be placed in the hole 52 as in the second embodiment.

In the above embodiment, a case was described in which the surface facing the end surface of the rotating shaft 1 has a convex spherical surface, but even if a convex portion with a minute area is formed near the center instead of such a spherical surface, almost A similar effect can be obtained.

The same effect can also be obtained by forming a convex portion or a convex spherical surface with a small area at the center of the end on the rotating shaft side.

Further, although the case where the shaft rotates has been described, the present invention can also be applied to a case where the shaft is fixed and the sleeve rotates.

[Effects of the Invention] As explained above, the thrust bearing has a convex portion or a convex spherical surface with a minute area near the center of one end surface of the shaft or a surface facing the one end surface of the shaft, and the radial bearing portion and the thrust By providing a hole that communicates with the atmosphere between the bearing and the
A stable rotating device can be obtained at low cost by preventing deterioration of bearing characteristics and occurrence of galling due to air entrainment without requiring high precision or having a complicated shape for each part.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of an embodiment of the present invention, FIG. 2 is a block diagram of main parts of a second embodiment of the present invention, and FIG. 3 is a block diagram of main parts of a third embodiment of the present invention. FIG. 4 is a configuration diagram of a conventional hydrodynamic bearing rotating device. 1: Rotating shaft, 2 Ni sleeve, 7: Rotating polygon mirror, 14: Shallow herringbone groove, 41.42 Ni last support member, 51.52: Hole, 61: Porous member. Patent Applicant Canon Co., Ltd. Agent Patent Attorney Tetsuya Ito Agent Patent Attorney Tatsuo Ito Figure 1 Figure 2

Claims (5)

[Claims] (1) It has a shaft and a sleeve that rotatably fit into each other, a hydrodynamic radial bearing is configured between the outer peripheral surface of the shaft and the inner peripheral surface of the sleeve, and one end of the sleeve is attached to the shaft. A thrust support member is mounted to face and support the end portion, and one of the end portion of the shaft and the shaft support surface of the thrust support member is formed in a convex shape with a protruding central portion. Hydrodynamic bearing rotating device. (2) The hydrodynamic bearing rotation device according to claim 1, wherein a hole is provided around an end of the shaft to communicate the space between the shaft and the sleeve with the outside. (3) The dynamic pressure bearing rotation device according to claim 2, wherein a porous member is installed in the hole. (4) The hydrodynamic bearing rotating device according to claim 2, wherein the hole is provided in a sleeve. (5) The hydrodynamic bearing rotating device according to claim 2, wherein the hole is provided in the thrust support member.