JPH07190047A - High speed rotating body - Google Patents

Abstract

PURPOSE:To keep a prescribed rotating speed from the initial stage of rotation and provide stable rotating precision to using environmental temperature by shrinkage-fitting and fixing a metal outer circumferential member to a ceramic sleeve, and then working the bore into a prescribed hand drum form. CONSTITUTION:A sintering assistant and a molding assistant are added to and mixed with high purity alumina powder followed by pressing to provide a compact sleeve, which is then sintered after degreasing to form a high purity alumina sleeve material 11, and its outer diameter is made into a prescribed dimension. A high purity aluminium material 12 having a polygon mirror form whose bore is precisely cut into a prescribed dimension is shrinkage-fitted thereto, the bore is cut into a prescribed hand drum form, and the material 12 is precisely cut into the prescribed polygon mirror form with the bore 14 of the sleeve 3 as the standard to form a high speed rotating body 13. Thus, a precision necessary for general gas bearing is provided in the initial stage of rotation, thereby suppressing the unstable vibration at rotation starting, the bearing precision is enhanced under high speed rotation by the centrifugal stress of the high speed rotating body and the thermal expansion by the friction with the gas, and a stable rotating precision from speed to high speed can be kept.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-speed rotating body used for a gas dynamic pressure bearing, such as a polygon mirror, which requires high-speed and stable rotation.

[0002]

2. Description of the Related Art Gas dynamic bearings do not require a boosting device such as a hydraulic pump, can suppress vibrations and noises, can obtain stable rotation and excellent rotation accuracy, and are normally tens of thousands to several tens. From the fact that high-speed rotation of 100,000 rpm is possible,
For example, it is used as a bearing for equipment such as a polygon mirror that requires high-speed and stable rotation.

However, in the above-mentioned gas dynamic pressure bearing, the bearing portion is contacted at the time of starting and stopping, the load is limited, stable rotation is maintained, and the clearance between the fixed shaft and the rotating body (hereinafter referred to as "bearing"). There is a drawback that it depends on "clearance").

In order to solve these drawbacks, Japanese Patent Application Laid-Open No. 6-62
According to Japanese Patent Laid-Open No. 3-266420, in constructing a gas dynamic pressure bearing used for a polygon mirror having a constant and low load, a groove for dynamic pressure generation is provided in a fixed shaft and a rotating body to maintain stable rotation. At the same time, a magnet is provided on the rotating body corresponding to the stator coil of the fixed part to prevent contact with the bearing part at the time of starting and stopping, and the rotating body consisting of the ceramic sleeve and the outer peripheral member is shrink-fitted and fixed. There is disclosed a technique of canceling radial tension due to centrifugal stress to suppress crack generation and propagation and maintain stable rotation.

By the way, the high-speed rotating body used for the gas dynamic pressure bearing has been manufactured by the procedure shown in the schematic diagrams (a) to (d) of FIG. First, the sintered high-density ceramic sleeve material 20 shown in FIG. 2A is processed into inner and outer diameters to have a predetermined size, and the ceramic sleeve 2 as shown in FIG.
Get 0. Next, as shown in FIG. 2C, a metal outer peripheral member 21 having a larger coefficient of thermal expansion than that of the ceramic sleeve 20 and having an inner diameter processed into a predetermined dimension is shrink-fitted and fixed to the outer periphery 20b of the ceramic sleeve 20 as shown in FIG.

With reference to the inner diameter 22 of the ceramic sleeve 20 as shown in FIG. 2 (c), the shrink-fitted metal outer peripheral member 21 is attached to the rotary shaft 23 of the high-speed rotating body. Upper surface 21a of metal outer peripheral member 21
The lower surface 21b is processed at a right angle and the outer peripheral surface 21c is processed to be parallel to obtain a high-speed rotating body 24.

That is, the high-speed rotating body 24 has an inner diameter 20a and an outer diameter 20 of the sintered high-density ceramic sleeve 20.
After b is finished, since the metal outer peripheral member 21 having a larger thermal expansion coefficient than the ceramic sleeve 20 is shrink-fitted and fixed, the outer periphery 2 of the ceramic sleeve 20 is fixed.
From 0b, compressive stress due to shrinkage is applied, as shown in FIG.
As shown in FIG. 7, the inner diameter 22 of the ceramic sleeve is largely deformed into a staggered shape. Therefore, the bearing clearance between the ceramic sleeve 20 of the high-speed rotating body 24 and the ceramic fixed shaft having a dynamic pressure groove formed on the surface (not shown) is made nonuniform.

Generally, a gas dynamic pressure bearing used for supporting a high-speed rotating body uses a fluid having a small viscosity coefficient such as air, helium gas, nitrogen gas, etc., to generate pressure in the bearing clearance with rotation, and Since it supports a high-speed rotating body in a non-contact manner, it has features such as low friction loss due to rotation, low noise and high-accuracy high-speed rotation, but has the drawback of low load capacity and weak vibration resistance. .

Therefore, in order to obtain the bearing rigidity and rotation accuracy required for this type of high-speed rotating body, the bearing clearance is several μm.
The bearing shape such as roundness and cylindricity needs to be high accuracy of about 1 to 2 μm or less.

However, in the above-mentioned conventional high-speed rotating body, an uneven pressure distribution is easily generated in the bearing clearance at the start of rotation, and unpredictable unstable vibration is generated in the high-speed rotating body. It was difficult to obtain better rotation accuracy under steady rotation. Further, since the metal outer peripheral member 21 is processed on the basis of the inner diameter 22 of the ceramic sleeve 20 which has been deformed into the hook shape,
The processing accuracy of the metal outer peripheral member 21 with respect to the rotating shaft 23 is reduced, which is also a cause of rotational runout.

[0011]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and its purpose is to maintain a predetermined number of rotations from the initial stage of rotation and to achieve good rotation accuracy that is stable up to the ambient temperature of use. It is to provide a high-speed rotating body to achieve.

[0012]

SUMMARY OF THE INVENTION The main object of the present invention is to provide a conventional ceramic sleeve and a high-speed rotating body comprising a metal outer peripheral member fixed by shrink fitting to the outer periphery of the ceramic sleeve. After the member is shrink-fitted and fixed, the inner diameter of the ceramic sleeve is processed into a predetermined step shape. In addition, the clearance between the ceramic fixed shaft and the ceramic sleeve should be uniform according to the radial centrifugal force that acts depending on the rotational speed of the high-speed rotating body and the shrink-fit compressive stress that is relaxed by thermal expansion due to friction. In addition, there is also a place where a predetermined step shape of the inner diameter of the ceramic sleeve is determined.

Here, the inner diameter, outer diameter, Poisson's number, and Young's modulus of the metal rotating body are R ₁ , R ₂ , m ₁ , E _1, and the inner diameter, outer diameter, Poisson's number, Young's modulus of the ceramic sleeve are When R ₃ , R ₄ , m ₂ , E ₂ and the shrink fit allowance are δ, the shrink fit compressive stress P follows Equation 1, and the compressive deformation amount χ of the ceramic sleeve inner diameter at this time is Equation 2. Follow

[0014]

The predetermined shape of the ceramic sleeve changes according to the centrifugal stress in the radial direction based on the rotational speed of the high-speed rotating body. Therefore, in the present invention, the shape is determined by the amount of compressive deformation χ that is canceled by the centrifugal stress.

In the present invention, the shrinkage allowance δ is reduced by the thermal expansion of the metal outer peripheral member due to the heat generated by the friction with the gas due to the rotation of the high-speed rotating body, but it acts on the ceramic sleeve. The shrink fit compressive stress P thus obtained can be obtained by a shrink fit allowance δ so that the fixing of the ceramic sleeve and the metal rotating body is relaxed without loosening and rotating. Further, in the present invention, the shape is determined by the compressive deformation amount χ that is offset by the shrink fit compressive stress P that is relaxed by thermal expansion due to friction.

That is, according to the centrifugal stress and the shrinkage-compressive stress P, the predetermined zigzag shape becomes a better cylinder so that the bearing clearance is uniform. It has a shape that offsets the deformation that occurs.

[0018]

The high-speed rotating body of the present invention is arranged outside a ceramic fixed shaft having a dynamic pressure groove formed on the surface thereof, and is rotatably supported by a gas dynamic pressure bearing mechanism and has a uniform thickness in the radial direction. A metal outer peripheral member having a thermal expansion coefficient larger than that of the ceramic sleeve is shrink-fitted and fixed to the outer periphery of the ceramic sleeve, and shrink fit compressive stress P is applied from the outer periphery of the ceramic sleeve to compressively deform the ceramic sleeve. Then, the inner diameter of the ceramic sleeve under the shrinkage-fitting compression stress is processed to be equal to the amount of compressive deformation according to the above equation 2 in accordance with the relaxation of the shrinkage-fitting stress P at the operating speed and the operating environment temperature. Only the shape of the bearing will improve the initial bearing clearance in a uniform direction. Further, under high-speed rotation, the shrinkage compressive stress P is relaxed by centrifugal stress in the radial direction, the wrapping shape of the inner diameter of the ceramic sleeve is further improved, and good cylindrical accuracy is obtained under steady rotation.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. FIG. 3 is a schematic sectional view of a high speed rotating polygon mirror device according to the embodiment. Further, FIG. 1 is a schematic diagram for explaining a schematic manufacturing process of the same high-speed rotating polygon mirror rotating body and a change in the shape of the ceramic sleeve under high-speed rotation.

As shown in FIG. 1, high purity alumina (Al
₂ O ₃ ) Powder is mixed with a sintering aid and a molding aid and mixed, and the granulated powder is filled into a press molding die, and 500 kg / cm
^By pressing at a pressure of ² , an alumina molded body sleeve was obtained. 165 after degreasing the molded body according to a conventional method
Sintering was performed in an oxidizing atmosphere at 0 ° C. to obtain a high density alumina sleeve material 11 (FIG. 1 (a)).

Sintered high density alumina sleeve material 11
Cannot be used as it is as the ceramic sleeve 11 that constitutes the high-speed rotating body 13, so it must be ground into a predetermined shape using a diamond grindstone or diamond abrasive grains. The ceramic sleeve material 11 shown in FIG. 1 (a) was processed to have a predetermined outer diameter by a centerless grinder or a cylindrical grinder as shown in FIG. 1 (b). At this time, the outer diameter 11 of the ceramic sleeve 11 is
The shape accuracy of a was 1 μm in circularity and 2.0 μm in cylindricity.

Then, as shown in FIG. 1 (b), a ceramic sleeve 11 having the outer diameter 11a machined therein is provided with a high-purity aluminum material 12 which has been machined in advance into a polygon mirror shape by precision cutting the inner diameter to a predetermined dimension. Shrink fit (Fig. 1
(C)). The shrinkage allowance at this time (shrinkage allowance = inner diameter of metal rotating body−outer diameter of ceramic sleeve) is 16 to 2.
The shrink fitting temperature was 170 to 180 ° C.
At room temperature, the above high-purity aluminum polygon mirror material 12
Applies a compressive stress to the ceramic sleeve 11 from the outer circumference so that the inner diameter 11b of the ceramic sleeve 11 becomes 2 to 3
It was compressed and deformed by μm.

As shown in FIG. 1 (C), the high-purity aluminum polygon mirror material 12 is shrink-fitted onto the outer periphery of the ceramic sleeve 11, and the high-speed rotating body 13 has an inner diameter of a cylindrical inner diameter grinder and honing grinding. Figure 1 by the board
As shown in (d), it was ground into a predetermined step shape. At this time, the shape accuracy of the inner diameter was a rounded shape with a roundness of 0.6 μm and a cylindricity of 2 μm. Thereafter, the high-purity aluminum polygon mirror material 12 is precision-cut into a predetermined polygon mirror shape based on the inner diameter 14 of the ceramic sleeve 11, and the high-speed rotating body 13 (see FIG. 1).
(D)).

As shown in FIG. 3, the high-speed rotating polygon mirror manufactured as described above is provided with a magnet 31 at the lower part of the rotating body and a ceramic fixed shaft 32 having herringbone dynamic pressure grooves formed on the surface thereof. A motor is configured by providing a coil 34 and a circuit board 35 on an aluminum base 33, and the high-speed rotating polygon mirror 36 is rotated at 30,000 rpm by a rotation control device (not shown). As a result, the inner diameter of the high-speed rotating body in the steady rotation is as shown in FIG.
As shown in (e), the above-mentioned jagged shape is eliminated, unstable vibration of the rotating body that has been conventionally generated before reaching steady rotation is eliminated, and runout accuracy of the rotating body under steady rotation is eliminated. It was possible to stably achieve 0.03 μm.

[0025]

According to the present invention, in the initial stage of rotation, the bearing precision required for a normal gas bearing is obtained by machining, thereby suppressing unstable vibration that tends to occur at the start of rotation. Further, under high speed rotation, centrifugal stress of the high speed rotating body and thermal expansion due to friction with gas make the bearing accuracy of the high speed rotating body more accurate. As a result, stable rotation accuracy of the high-speed rotating body can be maintained from low speed to high speed.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining a schematic manufacturing process of the high-speed rotating polygon mirror rotating body and a change in shape of the ceramic sleeve under high-speed rotation.

FIG. 2 is a schematic view showing a schematic manufacturing process of a high-speed rotating polygon mirror device according to a conventional technique.

FIG. 3 is a schematic sectional view of a high-speed rotating polygon mirror device according to an embodiment.

[Explanation of symbols]

 11 ceramic sleeve 12 outer peripheral member 13 high-speed rotating body 14 inner diameter of ceramic sleeve 20 ceramic sleeve 21 outer peripheral member 22 inner diameter of ceramic sleeve 24 high-speed rotating body

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Kazushige Ohno 1-1, Kitagata, Ibikawa-cho, Ibi-gun, Gifu Prefecture Ibiden Co., Ltd. Ogakikita Factory

Claims (2)

[Claims] 1. A high-speed rotating body outside a ceramic fixed shaft that constitutes a gas dynamic pressure bearing together with the ceramic fixed shaft, wherein a ceramic sleeve having a constant thickness in the radial direction and an outer periphery thereof are baked. In a high-speed rotating body formed by a metal outer peripheral member having a larger coefficient of thermal expansion than the ceramic sleeve by fit-fitting, the ceramic sleeve is shrink-fitted and fixed to the metal outer peripheral member, and then the inner diameter of the ceramic sleeve is a predetermined step shape. High-speed rotating body characterized by being processed into. 2. A ceramic fixed shaft according to claim 2, wherein the predetermined stepped shape is in accordance with centrifugal stress in a radial direction that acts depending on the rotational speed of the high-speed rotating body and shrink-fit compressive stress that is relaxed by thermal expansion due to rotational friction. The high-speed rotating body according to claim 1, wherein a clearance between the ceramic sleeve and the ceramic sleeve is determined to be uniform.