JPH09217737A - Bearing device - Google Patents

Abstract

(57) [PROBLEMS] To provide a bearing device which can prevent the generation of 1/2 whirl with a simple structure without adding a special mechanism and which is also excellent in abrasion resistance. SOLUTION: The circular dynamic pressure bearings 5 and 6 are used as radial bearings that receive a load in the radial direction of a rotary shaft, and point contact type thrust bearings 7a and 18 are used as axial bearings that receive a load in the axial direction of the rotary shaft. In the bearing device using the above, the thrust projection 18 for point contact of the thrust bearing is provided with the rotation center O
To eccentricity by a predetermined amount ε.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a bearing device used in a device that rotates at a high speed such as a polygon scanner or a hard disk drive, and more particularly, to a radial bearing that supports a radial load of a rotary shaft and a true circular dynamic bearing. The present invention relates to a bearing device that uses a thrust bearing of a point contact type as an axial bearing that supports a load in the axial direction of a rotating shaft.

[0002]

2. Description of the Related Art Conventionally, rolling bearings called ball bearings have been used as bearing devices used in high-speed rotating devices such as polygon scanners and hard disk drives. The upper limit of the usable rotational speed of this ball bearing is at most about 17,000 rpm from the viewpoint of noise and life, and a non-contact type bearing is used when it is desired to support a higher rotational speed. There was a need. Therefore, a perfect circular dynamic pressure bearing is used as a low-cost non-contact bearing for achieving this.

6 and 7 show an example of a conventional perfect circular dynamic pressure bearing. FIG. 6 is a vertical sectional view showing the entire structure of a conventional polygon scanner using a perfect circular dynamic pressure bearing, and FIG. 7 is an enlarged sectional view of the perfect circular dynamic pressure bearing portion in FIG.

In the figure, reference numeral 1 is a polygonal polygon mirror made of aluminum alloy or the like having a peripheral surface as a mirror surface. This polygon mirror 1 is a flange portion 2 of a cylindrical rotary shaft 2.
It is attached to the upper surface of a and is configured to rotate integrally with the rotating shaft 2.

Further, a rotor yoke 3 and a rotor magnet 4 are attached to the lower surface of the flange portion 2a of the rotary shaft 2, and a cylindrical sleeve 5 is fitted and fixed to the inner peripheral surface of the cylinder of the rotary shaft 2. Has been done. The rotary shaft 2 to which the sleeve 5 is fitted and fixed is loosely rotatably fitted to the fixed shaft 6 to form a rotary body (rotor) 9 as a whole.

Between the inner peripheral surface 5a of the sleeve 5 and the outer peripheral surface 6a of the fixed shaft 6, a minute gap of several .mu.m to ten and several .mu.m is provided (see FIG. 7). The fixed shaft 5 and the fixed shaft 6 constitute a dynamic bearing which is a non-contact type radial bearing for supporting the radial load of the rotary shaft.

The upper end surface of the fixed shaft 6 is a spherical surface 8 having the center of rotation O as its apex. Further, a flat plate-shaped thrust receiving member 7a which is in point contact with the spherical surface 8 is fixedly provided on the lower surface of the thrust cover 7 of the rotary shaft 2 arranged so as to face the spherical surface 8. Member 7
The a and the spherical surface 8 constitute a thrust bearing which is a point contact type axial bearing for supporting a load in the axial direction of the rotary shaft.

The sleeve 5 and the thrust receiving member 7a described above are made of a member having excellent wear resistance and lubricity, for example, a resin material such as polyimide resin. The fixed shaft 6 is made of a metal material such as carbon steel or stainless steel.

An annular groove 2b is formed on the upper surface of the rotary shaft 2, and the outer peripheral edge of the rotor yoke 3 is bent upward to form an annular edge portion 3a. The annular groove 2b and the annular edge 3a are for attaching weights for balance adjustment, and as shown in the figure, by attaching the weights 2c, 3b to predetermined positions, the unbalance of the rotating body 9 is corrected. It is a thing.

The fixed shaft 6 is vertically attached to a base member 12 by a base collar 11. A printed circuit board 13 is disposed on the upper surface of the base member 12, on which the winding coil 14, the Hall element 15, the control IC 16, and the connector 17 are mounted.

The winding coil 14 is fixedly mounted on the printed circuit board 13 with a slight clearance from the rotor magnet 4 attached to the rotating body 9, and the rotating body 9 rotates detected by the hall element 15. Control IC 16 based on phase
The rotating body 9 is rotated as a motor by switching and controlling the exciting current of the winding coil 14.

When the rotating body 9 rotates as described above,
The air pressure in the gap formed between the inner peripheral surface 5a of the sleeve 5 and the outer peripheral surface 6a of the fixed shaft 6 increases, and the rotating body 9
, And rotate in a non-contact state with the outer peripheral surface of. For this reason, the rotational friction of the bearing peripheral surface is extremely small, and the bearing can be smoothly rotated up to a high rotational speed without noise.

A groove for pressure pumping is provided on the outer surface of the fixed shaft 6 for efficiently increasing the air pressure in the gap formed between the inner peripheral surface 5a of the sleeve 5 and the outer peripheral surface 6a of the fixed shaft 6. Is not formed at all, and its cross section is a perfect circle. As described above, a dynamic pressure bearing using a perfect circular shaft with no groove for pressure pumping is called a perfect circular dynamic pressure bearing. Further, a fluid which uses air as a fluid for generating a dynamic pressure is called a true circular dynamic pressure air bearing.

[0014]

As described above, the perfect circular dynamic bearing does not have any grooves for pressure pumping on the outer surface of the fixed shaft 6. For this reason, there is no need to perform high-precision groove processing on the outer surface of the fixed shaft 6, and there is an advantage that the manufacturing cost can be significantly reduced. However, on the other hand, since there is no groove for pressure pumping, there is a problem that the rotation of the rotating body 9 tends to be unstable.

In particular, when the fixed shaft 6 is arranged vertically as shown in the drawing, a so-called 1/2 whirl (a whirling and turning phenomenon of a 1/2 rotation component of the rotation frequency) occurs in the rotating body 9. If such a 1/2 whirl is caused, in the worst case, there is a possibility that the shaft may be locked and the rotation may become impossible.

Conventionally, in order to prevent the occurrence of this 1/2 whirl, air is laterally fed into the bearing to eccentrically rotate the shaft, or a spring spring is laterally pressed to eccentrically rotate the shaft. Is being developed. According to these methods, the center of rotation is decentered to change the radial bearing clearance, thereby reducing the whirling excitation force of the rotating body, stabilizing the rotation and reducing the generation of 1/2 whirl. Can be prevented.

However, according to these methods, it is necessary to newly add a mechanism for feeding air and a mechanism for pressing with a spring spring, which complicates the structure of the bearing portion and increases the cost. There was a problem.

Further, in the case of the conventional perfect circular dynamic pressure bearing, as shown in the figure, the spherical surface 8 is in point contact with the thrust receiving member 7a at one point of its rotation center O and is rotating. For this reason, there is a problem that the thrust receiving member 7a made of a synthetic resin such as a polyimide resin is severely worn and the life as a bearing is short.

The present invention has been made in order to solve the above problems, and can prevent the generation of 1/2 whirl with a simple structure without adding a special mechanism, and can also prevent abrasion. An object is to provide a bearing device having excellent properties.

[0020]

In order to solve the above problems, the present invention employs the following means. That is,
The invention according to claim 1 uses a perfect circular dynamic pressure bearing as a radial bearing that supports the radial load of the rotary shaft, and uses a point contact type thrust bearing as the axial bearing that supports the axial load of the rotary shaft. In the above bearing device, the thrust projection for point contact of the thrust bearing is provided eccentrically by a predetermined amount from the center of rotation.

The invention according to claim 2 is characterized in that, in the invention according to claim 1, the thrust projection is formed on the fixed shaft side.

The invention according to claim 3 is characterized in that, in the invention according to claim 1, the thrust projections are integrally formed on the rotary shaft side.

According to a fourth aspect of the invention, in the invention of the second or third aspect, the thrust protrusion is formed separately from the thrust bearing main body, and the thrust protrusion formed in the separate body is fixed to the fixed shaft or It is characterized in that it is fixed to a predetermined position of the rotary shaft.

The invention according to claim 5 is the same as claims 1 to 4.
In any one of the inventions described above, the outer shape of the thrust projection is a spherical surface.

Further, the invention according to claim 6 is characterized in that, in the invention according to any one of claims 1 to 5, a true circular dynamic pressure air bearing is used as the true circular dynamic pressure bearing. Is.

In the case of the invention described in claims 1 to 3, the rotating body is forcibly eccentrically rotated by the thrust projection to rotate. For this reason, the whirling excitation force is reduced, and the generation of 1/2 whirl is suppressed. Further, since the contact point of the thrust projection is rotationally moved due to this eccentricity, the conventional concentrated wear is eliminated and the wear resistance is also improved.

In the case of the present invention as defined in claim 4, since the thrust projection can be formed separately from the thrust bearing main body, the processing becomes easy, and any curved projection can be easily and accurately manufactured. You can Further, since the thrust protrusion can be made of a material different from that of the rotating shaft and the thrust receiving member, it is possible to adopt an optimum material while considering compatibility with the rotating shaft and the thrust member.

In the case of the present invention as defined in claim 5, since the thrust projection is a spherical surface having the simplest shape, the thrust projection can be easily manufactured.

In the case of the sixth aspect of the invention, since the fluid for generating the dynamic pressure is air, a seal structure for sealing the fluid is unnecessary, and the structure of the bearing portion can be simplified.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a first example of the bearing device of the present invention. FIG. 1 is an enlarged schematic view of the bearing portion in FIG. 2, and FIG. 2 is a polygon formed by using the bearing device of the present invention. FIG. 3 is a vertical sectional view showing the overall structure of the scanner. In these figures, the same or corresponding portions as those of the above-described conventional example (FIGS. 6 and 7) are designated by the same reference numerals, and detailed description thereof will be omitted.

The bearing device of the first example differs from the bearing device of the prior art in that the hemispherical thrust projection 18 formed on the upper end surface of the fixed shaft 6 is the center of rotation, as is clear from the drawing. It is formed by eccentricity from O by ε. For example, when the fixed shaft 6 is made of carbon steel and the thrust receiving member 7a is made of polyimide resin, the eccentricity ε is preferably 2 mm or less at a rotation speed of 20,000 rpm or less.

As described above, when the thrust projection 18 which makes point contact with the thrust receiving member 7a and constitutes the thrust bearing is provided eccentric from the rotation center O by ε, the rotor mounted on the thrust projection 18 is provided. 9 is tilted in the direction of the arrow and is forcibly eccentrically rotated. For this reason, the excitation force of whirling is reduced, the generation of 1/2 whirl is suppressed, and stable rotation is achieved.

Further, the point contact position between the thrust protrusion 18 and the thrust receiving member 7a is a radius ε as the rotating body 9 rotates.
Since the surface of the thrust receiving member 7a is rotationally moved while drawing a circle, the contact point is not fixed to one point of the rotation center O as in the conventional case. For this reason, concentrated wear does not occur, and the bearing has excellent wear resistance.

FIG. 3 shows a second example of the bearing device of the present invention. In the second example, contrary to the first example, a hemispherical thrust projection 19 is formed on the thrust receiving member 7a side. Even if the formation position of the thrust projection 19 is reversed in this way, the same effect can be obtained.

FIG. 4 shows a third example of the bearing device of the present invention. The third example is the thrust projection 1 in the example of FIG.
The shape of 8 is changed and the upper end surface of the fixed shaft 6 is formed into a spherical surface. That is, the thrust projection 20 formed of a large spherical surface having a radius R that contacts the thrust receiving member 7a at the eccentric position ε is formed on the entire upper end surface of the fixed shaft 6, and the thrust receiving member 7a is located at the apex position of the large spherical thrust projection 19.
It is configured to make point contact with. Also in this third example, the same operational effect as in the above-described first example can be obtained.

FIG. 5 shows a fourth example of the bearing device of the present invention. In the fourth example, contrary to the third example, the thrust projection 21 formed of a large spherical surface having a radius R is formed on the thrust receiving member 7a side. Thrust protrusion 1
Even if the formation position of 9 is reversed, the same effect can be obtained.

In each of the above examples, the case where air is used as the fluid for generating the dynamic pressure is taken as an example. However, if the bearing portion has a seal structure, fluid other than air is used as the fluid for generating the dynamic pressure. A liquid can also be used.

Further, the outer surface shape of the thrust projections 19 to 21 is also spherical, but any curved surface shape is applicable as long as it is a shape capable of point contact, not limited to a spherical surface.

Further, the thrust projections 18 to 21 are attached to the fixed shaft 6
Alternatively, although the thrust projections are integrally formed with the thrust receiving member 7a, these thrust projections are produced as separate members, and the thrust projections produced separately are fixed to the upper end surface of the fixed shaft 6 or the surface of the thrust receiving member 7a. You may do it.

Although the embodiments of the present invention have been described above, the present invention is not limited to these, and various modifications can be made in accordance with the gist of the invention.

[0041]

As described above, according to the invention described in claims 1 to 3, since the thrust projection for point contact of the thrust bearing is provided eccentric by a predetermined amount from the rotation center,
The whirling excitation force of the rotating body can be reduced to suppress the generation of 1/2 whirl, and stable rotation can be realized. Further, since the contact point of the thrust bearing is rotationally moved due to the eccentricity, concentrated wear is eliminated and wear resistance is also improved. Therefore, the 1/2 whirl can be prevented from occurring with a simple structure without adding a special mechanism, and the cost can be reduced.

Further, according to the invention of claim 4,
Since the thrust projection is formed separately from the bearing portion and the thrust projection formed in the separate body is fixed to a predetermined position of the fixed shaft or the rotary shaft, the thrust projection can be formed separately from the thrust bearing main body. Machining becomes easier, and thrust projections of any curved shape can be easily and accurately manufactured. Further, since the thrust protrusion can be made of a material different from that of the rotating shaft and the thrust receiving member, it is possible to adopt an optimum material in consideration of compatibility with the rotating shaft and the thrust member. Therefore, it is possible to obtain a bearing with extremely high accuracy.

According to the invention of claim 5,
Since the thrust projection is a spherical surface, which is the simplest shape,
Manufacturing of the thrust protrusion is facilitated. Therefore, cost reduction can be achieved.

Further, according to the invention of claim 6, since the true circular dynamic pressure air bearing is used as the true circular dynamic pressure bearing, a seal structure for sealing the fluid is unnecessary, and the structure of the bearing portion is It is simple and can be miniaturized and reduced in cost.

[Brief description of drawings]

FIG. 1 shows a first example of a bearing device of the present invention,
(A) is a schematic enlarged plan view of a bearing portion, and (B) is a schematic enlarged vertical sectional view of a bearing portion.

FIG. 2 is a vertical cross-sectional view showing the overall structure of a polygon scanner configured using the bearing device of the present invention.

FIG. 3 is an enlarged vertical sectional view of a second example of the bearing device of the present invention.

FIG. 4 is an enlarged vertical sectional view of a second example of the bearing device of the present invention.

FIG. 5 is an enlarged vertical sectional view of a second example of the bearing device of the present invention.

FIG. 6 is a vertical cross-sectional view showing the overall structure of a polygon scanner configured using a conventional bearing device.

FIG. 7 is an enlarged vertical sectional view of a bearing portion in FIG.

[Explanation of symbols]

 1 polygon mirror 2 cylindrical rotary shaft 3 rotor yoke 4 rotor magnet 5 sleeve 6 fixed shaft 7 thrust cover 7a thrust receiving member 9 rotor 11 base collar 14 winding coil 15 hall element 18-21 thrust protrusion O rotation center ε thrust protrusion Eccentricity of

Claims (6)

[Claims] 1. A bearing device using a perfect circular dynamic pressure bearing as a radial bearing for supporting a radial load of a rotary shaft and a point contact type thrust bearing as an axial bearing for supporting a radial load of a rotary shaft. 2. The bearing device according to claim 1, wherein the thrust projection for point contact of the thrust bearing is provided eccentric from the center of rotation by a predetermined amount. 2. The bearing device according to claim 1, wherein the thrust protrusion is formed on the fixed shaft side. 3. The bearing device according to claim 1, wherein the thrust protrusion is formed on the rotary shaft side. 4. The thrust protrusion formed as a separate body from the thrust bearing body, and the thrust protrusion formed as a separate body is fixed to a predetermined position of the fixed shaft or the rotary shaft. 3. The bearing device according to item 3. 5. The bearing device according to claim 1, wherein an outer surface shape of the thrust projection is a spherical surface. 6. The bearing device according to claim 1, wherein a perfect circular dynamic pressure air bearing is used as the perfect circular dynamic pressure bearing.