JPH04366012A - Dynamic pressure bearing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention relates to a hydrodynamic bearing device.
For example, the invention relates to a rotating device used in a deflection scanning device such as a laser beam printer.

0002

BACKGROUND OF THE INVENTION In recent years, there has been an increasing demand for rotating devices that perform high-speed and high-precision rotation, and in order to obtain high-speed and high-precision rotating devices, especially for laser beam printers, etc.
A hydrodynamic bearing that rotates without contact is used.

FIG. 5 shows a rotary bearing section of a deflection scanning device of 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 and a fixed plate 4 are disposed at the lower end of the sleeve 2, and the fixed plate 4 is fixed to an outer cylinder 5. A flange 6 is fixed to the rotating shaft 1, a rotating polygon mirror 7 is fixed to the upper part of the flange 6, and a yoke 9 is fixed to the lower part. A driving magnet 8 is attached to the inner surface of the yoke 9, and a stator 10 is provided on the outer cylinder 5 side facing the magnet 8. A shallow groove 11 is formed in the thrust plate 3 so as to face the lower end surface of the rotary shaft 1, thereby forming a hydrodynamic thrust bearing. Furthermore, two herringbone-shaped shallow grooves 14 are formed on the outer circumferential surface of the rotating shaft 1 so as to face the inner circumferential surface of the sleeve 2, thereby forming a dynamic pressure thrust bearing. moreover,
Near the upper opening of the sleeve, a shallow spiral groove 15 is formed in the direction in which lubricating fluid flows toward the dynamic pressure thrust bearing inside the sleeve. The sleeve 2 also includes the herringbone-shaped shallow groove 14 and the spiral shallow groove 1.
5, and a small diameter hole 17 is formed therein. This ensures the stability of the hydrodynamic bearing when a liquid such as oil or grease is used as the lubricating fluid.

0004

[Problems to be Solved by the Invention] However, the above-mentioned prior art has the following drawbacks. That is, when inserting the rotating shaft into the sleeve during assembly,
In some cases, the lubricating fluid that was previously injected into the sleeve overflowed from the opening of the sleeve. This overflowing lubricating fluid is scattered by the centrifugal force of the rotating body, staining the optical system including the reflecting surface of the rotating polygon mirror, and deteriorating the performance of the deflection scanning device.

[0005] Furthermore, even if bubbles such as air are mixed into the lubricating fluid, the bubbles may expand due to temperature changes and a portion of the lubricating fluid may overflow from the sleeve opening.

The present invention has been made in view of the above-mentioned drawbacks of the prior art, and provides a hydrodynamic bearing capable of returning lubricating fluid leaking from a sleeve that fits into a rotating shaft during assembly and manufacturing into a bearing portion. For the purpose of providing.

[0007]

[Means and operations for solving the problems] In order to achieve the above object, in the present invention, the end face of the sleeve is sloped so as to be concave from the outer circumference toward the inner circumference. Returns lubricating fluid overflowing to the bearing.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a cross section of an embodiment of a hydrodynamic bearing according to the present invention. Components that are the same as those of the bearing shown in FIG. 5 and have the same functions are given the same numbers, and description thereof will be omitted. Rotating axis 1
A conical surface 102a having an inclination concave from the outer circumference toward the inner circumference is formed on the end surface of the opening of the sleeve 102 which is rotatably fitted into the sleeve 102. Such a conical surface 102a
By providing this, even if the lubricating fluid overflows from between the rotating shaft 1 and the sleeve 102 when the rotating shaft 1 is inserted into the sleeve 102 during bearing assembly and manufacture, the lubricating fluid will flow within the conical surface of the sleeve opening. It stays there and does not scatter to the outside, or it can return to the gap between the rotating shaft 1 and the sleeve 102 again.

[0009] Furthermore, if bubbles such as air get mixed into the lubricating fluid, the bubbles expand due to temperature changes and some of the lubricating fluid overflows to the end surface of the sleeve opening, but once the air bubbles are expelled, The lubricating fluid returns to the gap between the rotating shaft 1 and the sleeve 102 again.

By using the above configuration, even if the lubricating fluid overflows during assembly, the lubricating fluid will not scatter due to the centrifugal force of the rotating body and will not contaminate the optical system or deteriorate the performance of the deflection scanning device. .

FIG. 2 shows another embodiment of the invention. A conical surface 202a having an inclination concave from the outer periphery toward the inner periphery is formed on the opening end surface of the sleeve 202 that rotatably fits on the rotating shaft 1, and further includes a plurality of grooves 218.
is provided. By providing such a groove,
The lubricating fluid overflowing from the end face of the sleeve easily and reliably returns to the gap between the rotating shaft 1 and the sleeve 202.

FIGS. 3A-3C show a pattern of a plurality of grooves 218 formed in the conical surface 202a of the sleeve opening. FIG. 3(a) shows a pattern in which linear grooves are formed from the outside to the inside. FIG. 3(b) shows a pattern in which spiral grooves are formed in a direction opposite to the direction of centrifugal force applied to the lubricating oil by rotation of the rotating shaft 1. Figure 3(c)
) shows a pattern in which linear grooves are formed in the same direction as in FIG. 3(b). FIG. 3(d) shows a cross section of a sleeve opening formed with such a pattern.

FIG. 4 shows yet another embodiment of the invention. An auxiliary sleeve 319 molded from synthetic resin or the like is fixed by press-fitting or the like into the opening of the sleeve 302 which rotatably fits into the rotating shaft 1 . The auxiliary sleeve 319 includes a step 316 for forming a recess at a position between the shallow grooves 14 and 15 formed on the rotating shaft 1, a groove 317a with a small cross-sectional area for communicating the recess with the outside air,
317b is provided. This ensures the stability of the hydrodynamic bearing. Further, a conical surface 319a having an inclination concave from the outer circumference toward the inner circumference is formed on the end surface of the upper opening of the auxiliary sleeve 319, and the plurality of grooves 318 shown in the above embodiment are formed. provided. By adopting such a configuration, the above-mentioned embodiments (Figs. 1 and 2
), and since the auxiliary sleeve 319 is manufactured by molding, there is no need to perform troublesome processing on the sleeve 302, leading to a reduction in manufacturing costs.

[0014] Also, the grooves 317a, 317 of the auxiliary sleeve
b communicates with the outside air on the conical surface of the opening end surface, so even if the lubricating fluid leaks from these grooves, the lubricating fluid will flow back along the conical surface 319a or its groove 318 to the bearing section (inside the sleeve 302). ). Therefore, the stability of the bearing is further improved.

In each of the above embodiments, a configuration in which the shaft rotates is shown, but similar effects can be obtained in a configuration in which the shaft is fixed and the sleeve rotates.

[0016]

Effects of the Invention As explained above, since the end face of the sleeve opening has a concave slope from the outer circumference to the inner circumference, even if the lubricating fluid overflows from the bearing part during assembly, the lubricating fluid can be re-lubricated. The fluid can be returned to the bearing, and the lubricating fluid is not scattered due to the centrifugal force of the rotating body, preventing contamination of the surrounding area.

Furthermore, by providing an auxiliary sleeve made of synthetic resin at the sleeve opening, costs can be reduced.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of an embodiment of a hydrodynamic bearing device according to the present invention.

FIG. 2 is a sectional view of another embodiment of the hydrodynamic bearing device according to the present invention.

FIGS. 3(a), 3(b), and 3(c) are top views showing different examples of groove patterns formed on the end surface of the sleeve, respectively;
d) is a sectional view of the sleeve end.

FIG. 4 is a sectional view of still another embodiment of the hydrodynamic bearing device according to the present invention.

FIG. 5 is a sectional view of a conventional hydrodynamic bearing device.

[Explanation of symbols]

1; Rotating shaft, 2, 102, 202, 302; Sleeve,
102a, 202a, 319a; conical surface, 218, 31
8; groove, 14; herringbone-shaped shallow groove, 15; spiral-shaped shallow groove.

Claims (3)

[Claims] 1. A dynamic pressure generating unit comprising a shaft and a sleeve that are rotatably fitted to each other, and a shallow groove is formed between the outer circumferential surface of the shaft and the inner circumferential surface of the sleeve to form a dynamic pressure generating section. 1. A dynamic pressure bearing device, characterized in that an end surface on the opening side of the sleeve is conically inclined so as to be concave from an outer circumference toward an inner circumference. 2. The hydrodynamic bearing device according to claim 1, wherein a plurality of grooves are formed substantially radially on the end surface of the conical sleeve opening. 3. The hydrodynamic bearing device according to claim 1, wherein the sleeve opening is provided with an auxiliary sleeve molded from synthetic resin.