JPH0464709A - Device for rotating dynamic pressure fluid bearing - Google Patents

Abstract

PURPOSE:To prevent the vibration at the time of high speed rotation, and restrict generation of the heat, and improve the stability by providing at least two dynamic pressure generating parts along an axial line, and forming a clearance and a length of one of the two dynamic pressure generating parts, which is closer to a center of gravity of a rotating body, wider and longer than that of the other dynamic pressure generating part. CONSTITUTION:A first and a second herringbone shallow channels 141, 142 are provided in the outer peripheral surface of a rotating shaft 1, which is supported by a sleeve 21 freely to rotate, opposite to the inner peripheral surface of the sleeve 21. An axial length of the first herringbone shallow channel 141 in a center of gravity G side of a rotating member and a clearance between the rotating shaft 1 and the sleeve 21 is made longer and wider than that of the second herringbone shallow channel 142. Consequently, even if whirling of the rotating body is large at the time of high speed rotation, a touch of the first herringbone shallow channel 141 can be prevented, and increase of an eccentricity quantity and a loss by the viscosity of the fluid are prevented without lowering the dynamic pressure, and scoring is prevented to reduce the generated heat.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a hydrodynamic bearing rotating device, and more particularly to a rotating device used in a deflection scanning device used in a laser beam printer or the like.

[Prior Art] In recent years, demands for high-speed and high-precision rotating devices have increased, and for this reason, hydrodynamic bearings that rotate without contact are being used, particularly in laser beam printers and the like. FIG. 4 shows a rotation device of a deflection scanning device of a THE BEAM printer using a conventional hydrodynamic bearing.

The rotating shaft 1 and the sleeve 2 are rotatably fitted to each other, and a thrust plate 3 or a fixed plate 4 is attached to the lower end of the sleeve 2. The sleeve 2 is fixed to the outer cylinder 5 together with the fixing plate 4. A flange 6 is fixed to the upper part of the rotating shaft 1. A rotating polygon fi7 is fixed to the upper side of the flange 6. A yoke 9 to which a driving magnet 8 is fixed is fixed to the lower surface of the flange 6. A stator 10 fixed to the outer cylinder 5 is located on the inner side facing the drive magnet 8.
is located. A shallow groove 11 is cut into the thrust plate 3 on the surface facing the lower end of the rotary shaft 1, and a dynamic pressure thrust bearing is formed by kneading. Furthermore, shallow herringbone grooves 14 are formed on the outer circumferential surface of the rotating shaft 1 at two locations, upper and lower, at positions facing the inner circumferential surface of the sleeve 2, thereby forming a dynamic pressure radial bearing. A shallow spiral groove 15 is formed near the opening (upper part) of the sleeve 2 so that the lubricating fluid flows in the direction of the dynamic pressure thrust bearing.

The sleeve 2 also has a recess 16 located between the upper herringbone-shaped shallow groove 14 and the spiral shallow groove 15.
A small diameter hole 17 communicating with this recess 16 is provided.
will be established. This increases the stability of hydrodynamic bearings that use liquid (oil, grease, etc.) as the lubricating fluid.

[Problems to be Solved by the Invention] However, in the conventional example described above, when the hydrodynamic fluid bearing rotating device is used for high-speed rotation, the whirling becomes large due to the imbalance in the dynamic balance of the rotating body (rotating shaft 1), and the rotation There have been cases where the rotating shaft and the sleeve come into contact with each other at the dynamic pressure generating portion on the center of gravity side, resulting in so-called galling. Furthermore, heat is generated due to resistance loss due to the viscosity of the fluid interposed between the rotating shaft and the sleeve, increasing the temperature of the fluid and lowering the viscosity of the fluid. As a result, rotation became unstable due to the influence of external vibrations.

The present invention was developed in view of the above-mentioned drawbacks of the prior art, and it prevents vibrations during high-speed rotation to obtain stable rotation, suppresses heat generation, prevents a decrease in the viscosity of the lubricating fluid, and improves rotational stability. The purpose of the present invention is to provide a hydrodynamic bearing rotation device with increased hydrodynamic pressure.

[Means and effects for solving the problem] In order to achieve the above-mentioned object, the present invention provides that among the plurality of dynamic pressure generating parts forming a radial bearing, the dynamic pressure generating part on the side of the center of gravity of rotation or the other By widening the bearing gap and increasing the axial length of the dynamic pressure generating section compared to the dynamic pressure generating section, galling during high speed rotation is prevented and heat generation is reduced.

[Embodiment] FIG. 1 is a drawing showing an embodiment of the present invention. Components that are the same as those in FIG. 4 and have the same functions are designated by the same numbers and their explanations will be omitted. The rotating shaft 1 and the sleeve 21 are rotatably fitted together. A flange 6 is fixed above the rotating shaft 1 in the drawing. A rotating polygon mirror 7 is fixed above the flange 6. A first herringbone-shaped shallow groove 141 and a second shallow groove 141 are provided at a position where the outer circumferential surface of the rotating shaft 1 and the inner circumferential surface of the sleeve 21 face each other.
A herringbone-shaped shallow groove 142 is carved in either one of the rotating shaft 1 or the sleeve 21 (in the embodiment, on the rotating shaft side). The first one on the side (upper side) of the center of gravity G (marked by X in the figure) of the rotating body.
The herringbone-shaped shallow groove 141 has a longer axial length than the lower second herringbone-shaped shallow groove 142. Regarding the gap between the rotating shaft 1 and the sleeve 21, the gap 211 in the upper dynamic pressure generating part in which the first herringbone-shaped shallow groove 141 is carved is the second herringbone-shaped shallow groove 14.
It is wider than the gap 212 of the lower dynamic pressure generating part where 2 is carved.

Near the opening (upper end) of the sleeve 21, a shallow spiral groove 15 is formed so that the lubricating fluid flows downward in the figure in order to prevent the lubricating fluid from flowing out from the opening. It is desirable that the gap 213 in this part be the same as or wider than the gap 212 in the carved part of the first herringbone-shaped shallow groove 141.

When a rotating device with the above configuration is driven at high speed, the amount of whirling may increase due to an imbalance in the dynamic balance of the rotating body.
Even if external vibrations are applied, an increase in eccentricity is prevented. This is due to the following reasons. That is, in order to support the moment force applied to the center of gravity of the rotating body (X-axis in the figure) with the two radial bearing parts, the force applied to the radial bearing by the first herringbone-shaped shallow groove 141 becomes stronger, and The amount of eccentricity tends to increase. However, in the configuration of the present invention, the first herringbone-shaped shallow dipping 141
By widening the gap in the radial bearing and increasing the axial length to compensate for the decrease in dynamic pressure generation force due to the widening, the dynamic pressure generation force can be equalized or exceeded. This can prevent the amount of eccentricity from increasing. Further, since the gap is wide, contact is prevented, and galling of the radial bearing portion by the first herringbone-shaped shallow groove 141 on the side closer to the rotational center of gravity is prevented.

Furthermore, by widening the gap, the loss due to the viscosity of the fluid intervening in the gap 211 is reduced, so it is possible to suppress the temperature rise of the fluid, and it is possible to prevent the viscosity of the fluid from decreasing, which in turn prevents a decrease in bearing rigidity. becomes. therefore,
The influence of external vibrations, etc. is suppressed and stable rotational operation is achieved.

FIG. 2 is a drawing showing a second embodiment of the present invention. The rotating shaft 1 is rotatably fitted to the sleeve 22.

A first modified herringbone-shaped shallow groove 143 and a second shallow groove 143 are provided at positions where the outer circumferential surface of the rotating shaft 1 and the inner circumferential surface of the sleeve 22 face each other.
A herringbone-shaped shallow groove 142 is carved in either the rotating shaft 1 or the sleeve 22 (in the embodiment, on the rotating shaft side). The first deformed herringbone-shaped shallow groove 143 on the side of the center of gravity G (marked by X in the figure) of the rotating body is the one closer to the center of gravity (upper side)
The axial length of the shallow groove portion 143a is longer than the axial length of the shallow groove portion 143b on the opposite side (lower side). As for the gap, the gap 221 of the dynamic pressure generating part in which the shallow groove part 143a near the center of gravity of the first herringbone-shaped shallow groove 143 is carved is the gap 221 of the first modified herringbone-shaped shallow groove 143. A gap 222 in the dynamic pressure generating part in which a shallow groove part 143b on the side far from the center of gravity and a second Heringhorn-shaped shallow part 11!142 are carved.
It is wider than .

Such a configuration prevents the eccentricity of the first deformed Herringhorn-shaped shallow groove 143 from increasing due to moment force due to runout during high-speed driving, vibration from the outside, or the like. Additionally, the gap between the dynamic pressure generating section on the center of gravity side is wide, which prevents galling of the bearing. Furthermore, since the axial length of the first modified herringbone-shaped shallow groove portion 143 can be made shorter than that of the first embodiment, it is possible to reduce loss and also to make the rotating device thinner. It is possible.

FIG. 3 is a diagram showing a third embodiment of the present invention. The rotating shaft 1 is rotatably fitted to the sleeve 23.

The sleeve facing the outer peripheral surface of the rotating shaft 1 is tapered upward so that the closer it is to the center of gravity of the rotating body (marked by X in the figure), the wider the gap 232 with the rotating shaft 1 becomes. on the other hand,
At a position where the outer circumferential surface of the rotating shaft 1 and the inner circumferential surface of the sleeve 23 face each other, a first modified herringbone-shaped shallow groove 144 and a second modified herringbone-shaped shallow groove 145 are provided. It is engraved on either one of the sleeves 23 (in the embodiment, on the rotating shaft side). In the first modified herringbone-shaped shallow groove 144 on the side of the center of gravity of the rotating body, the axial length of the shallow groove portion 144a closer to the center of gravity is longer than the axial length of the shallow groove portion 144b on the opposite side. In addition, a second deformed herringbone-shaped shallow groove 1
45 is a first modified Herringhorn-shaped shallow groove 144a;
The axial length of the shallow groove 145a that is shorter than that of the shallow groove 144b and closer to the center of gravity is that of the shallow groove 145b on the opposite side.
longer than Even with such a configuration, the same effects as those of the first and second embodiments can be obtained. Also sleeve 2
Since the inner circumferential surface of No. 3 can be easily processed, the cost is low.

Although the description has been given of a configuration in which the dynamic pressure generating groove is provided on the rotating shaft 1, the same effect can be obtained by providing the dynamic pressure generating groove on the sleeve.

Further, the same applies to a dynamic pressure fluid bearing rotating device in which the shaft is fixed and the sleeve rotates.

[Effects of the Invention] As explained above, among the plurality of dynamic pressure generating parts forming a radial bearing, the dynamic pressure generating part on the center of gravity side of the rotating body has a wider bearing gap than the other dynamic pressure generating parts. In addition, by increasing the axial length of the dynamic pressure generating portion, there is an effect of preventing galling during high speed rotation and reducing heat generation.

[Brief explanation of drawings]

1 is a block diagram showing one embodiment of the present invention, FIG. 82 is a block diagram showing a second embodiment of the present invention, FIG. 3 is a block diagram showing a third embodiment of the present invention, The figure is a configuration diagram showing a conventional hydrodynamic bearing rotating device. 1... Rotating shaft, 2 21 22 23... Sleeve, 14.141,
142, 143, 144, 145...shallow groove, 211.
212, 221, 222, 232... Gap. Patent applicant Canon Co., Ltd.

Claims (3)

[Claims] (1) It has a shaft and a sleeve that are rotatably fitted to each other, and has a dynamic pressure generating section consisting of a group of shallow grooves provided on one side of the shaft and the sleeve at a position where the shaft and the sleeve face each other. At least two locations are provided along the axial direction, and the gap between the shaft and the sleeve of the dynamic pressure generating section on the side closer to the center of gravity of the rotating body including the shaft that rotates with the shaft is equal to the axis of the other dynamic pressure generating section. and a dynamic pressure fluid bearing rotating device characterized in that the gap is wider than the gap between the sleeves and the length in the axial direction is longer than other dynamic pressure generating parts. (2) The gap between the sleeve and the shaft of the dynamic pressure generating section on the side closer to the center of gravity is widened by providing a step in the inner diameter of the sleeve to enlarge the inner diameter. Dynamic pressure fluid bearing rotating device as described in . (3) A patent characterized in that the inner diameter of the sleeve is formed into a tapered shape that continuously expands in the direction of the center of gravity, thereby widening the gap between the shaft of the dynamic pressure generating section on the side closer to the center of gravity and the sleeve. A dynamic pressure fluid bearing rotating device according to claim 1.