JPH01210611A - Fluid bearing apparatus - Google Patents

Abstract

PURPOSE:To prevent a seizure and facilitate formation of a dynamic pressure generating slot at a low cost by constructing a shaft body from an shaft core, whose material has the same line expansion coefficient as that of a sleeve, and from a lining layer provided with a dynamic pressure generating channel made of a soft metallic material. CONSTITUTION:A Liner 6 which is made of soft metallic material such as copper, aluminum etc. is shrink-fitted to a steel shaft core 5 for constructing a shaft body, and helling bone shaped dynamic pressure generating channels 8 are formed on peripheral bearing faces 7a and 7b of the liner 6. Therefore even if the shaft body and inside face of a sleeve may come in contact with each other, no seizure occurs, and the dynamic pressure generating channels 8 can be easily formed at a low cost.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is applicable to polygon mirror scanners and hard disk vcs.
The present invention relates to a hydrodynamic bearing device equipped with a dynamic pressure generating groove used in a main shaft portion of Wi, etc., and particularly to a hydrodynamic bearing device that can be suitably used in a gas bearing for high-speed rotation.

BACKGROUND OF THE INVENTION Various configurations of hydrodynamic bearings equipped with dynamic pressure generating grooves have been proposed in the past, but for example, one applied to a polygon mirror scanner is one with the configuration shown in Figure 3. It has been known.

In the rjSs diagram, 21 is a disc-shaped main body, and the lower end of the shaft body 22 is fitted and fixed to a boss 21a formed in the center of the main body. A motor 2 is mounted on the outer periphery of the main body 21.
No. 3 stator 24 is fixed. The shaft body 22 is formed with a lower bearing surface 25a and a lower bearing surface 2S& with an intermediate small diameter portion 22a, and a herringbone-shaped dynamic pressure generation @26 is formed on each of them, and a sleeve (described later) is formed at the upper end. A large-diameter collar 27 is formed to serve as a stopper.

A sleeve 28 is rotatably fitted to the shaft body 22 with an appropriate gap 29 between the upper and lower bearing surfaces 25a and 25b. A gas such as oil or air is interposed in this gap 29 as a lubricating fluid. A rotor 30 of the motor 23 is fixed to the lower outer periphery of the sleeve 28 so as to face the stator 24 . Also,
A polygon mirror 32 is placed on a 7-run no. 31 protruding from the middle portion of the sleeve 28, and is fixed by a port 34 via a fixing plate 33.

By the way, in a polygon mirror scanner having such a configuration, when gas is used as a lubricating fluid to cope with high-speed rotation, the gap 29 between the shaft body 22 and the sleeve 28 should be small in order to obtain the necessary load capacity. Therefore, if the gap 29 changes due to temperature changes, the bearing function may be impaired. Therefore, both the shaft body 22 and the sleeve 28 are made of steel so that the gap remains constant even if the temperature changes. The linear expansion coefficients are the same.

Furthermore, Japanese Utility Model Publication No. 61-46256 discloses a hydrodynamic bearing in which a sleeve made of synthetic resin is fitted and fixed to the shaft, a dynamic pressure generating groove is formed on the inner periphery, and a shaft is inserted through the sleeve. Disclosed.

Problem to be Solved by the Invention However, in the conventional example shown in FIG. 3, the shaft body 22 and the sleeve 28 are made of the same material, so if they come into contact during rotation, seizure may occur and the bearing may be damaged. There is also the problem that forming dynamic pressure generating grooves on a steel shaft is expensive.

Furthermore, if vibration is applied from the outside, the sleeve 28
The end surface of r! is the upper end of the sleeve body 22! There is also the problem of damage caused by collision with J27.

Therefore, as disclosed in the above publication, it is possible to use a synthetic resin sleeve for the steel shaft, but if the shaft is rotated at high speed using gas as a lubricating fluid as described above, However, there is a problem that even if there is a slight contact for a moment, the sleeve will melt and the bearing will be damaged immediately, making it unusable.Furthermore, it is difficult to perform high-precision machining to accommodate gas bearings. There's a problem.

In view of the above-mentioned conventional problems, the present invention provides a fluid that does not cause seizing or damage due to contact between the shaft body and the sleeve even when gas is used as a lubricating fluid, and can easily form a dynamic pressure generating groove. The purpose is to provide bearing devices. A further object of the present invention is to provide a hydrodynamic bearing device that is free from damage caused by vibration.

Means for Solving Deep Layer Problems In order to achieve the above object, the present invention includes a sleeve and a shaft body that are fitted together so as to be able to rotate relative to each other, and a lubricating fluid is provided in the gap between the inner circumferential surface of the sleeve and the outer circumferential surface of the shaft body. In a hydrodynamic bearing in which dynamic pressure generation grooves are formed on the outer peripheral surface of the shaft body,
The curved shaft body is composed of a core shaft made of a material having approximately the same linear expansion coefficient as the sleeve, and a lining layer integrally formed on the outer periphery of the core shaft, and this lining layer is formed of a soft metal material, and the outer periphery thereof It is characterized in that the dynamic pressure generating groove is formed in.

The lining layer can be formed by plating or thermal spraying the core shaft, but it can also be easily formed by fitting a cylindrical liner by shrink fitting or the like.

Further, the dynamic pressure generating groove can be easily formed by plastic working.

Further, a stopper facing the end face of the sleeve body is attached to the sleeve, and a synthetic resin bipot member is attached to the face of the stopper facing the end face of the shaft body.

According to the above structure of the present invention, since the outer circumferential surface of the shaft tree is formed of the lining layer made of a soft metal material, there is no risk of seizure even if it comes into contact with the inner circumferential surface of the sleeve.
Moreover, since the thickness of the lining layer is smaller than the diameter of the core shaft, there is almost no difference in the spacing due to temperature changes compared to when the shaft body and sleeve are made of the same material. Since it only needs to be formed on the material, it can be easily formed by plastic working such as ball rolling, and the rigidity can be ensured by the core shaft.

Furthermore, even if vibration is applied from the outside, the stopper of the sleeve and the end face of the shaft collide via the synthetic resin pivot member, so there is no damage caused by the vibration.

EXAMPLE Hereinafter, an example in which the present invention is applied to a polygon mirror scanner will be described with reference to FIG. 1 and tjS2.

In FIG. 1, reference numeral 1 denotes a disc-shaped main body, and the lower end of a shaft 2 is fitted and fixed to a boss portion 1a formed in the center of the main body. On the outer periphery of the main body 1 is a stator 4 of the motor 3.
is fixed. As shown in FIG. 2, the shaft body 2 is made by baking a cylindrical liner 6 made of a soft metal material such as copper, aluminum, an alloy thereof, or other metal bearing material on a core shaft 5 made of steel. A lower bearing surface 7a and a lower bearing surface 7b are formed on the outer periphery of the liner 6 with an intermediate small diameter portion 6a in between, and a herringbone-shaped dynamic pressure generating groove 8 is formed in each of the lower bearing surfaces 7a and 7b. ing. The depth of the dynamic pressure generating grooves 8 is about several micrometers to several tens of micrometers, and it is sufficient that the thickness of the liner 6 is about 10 times or more.

A sleeve 10 made of steel is rotatably fitted to the shaft body 2 with a suitable gap 9 of about 2 to 5 μm between the upper and lower bearing surfaces 7a and 7b. Gas such as air exists in this gap 9 as a lubricating fluid. In addition, a 7-run no. 1 protruding from the middle part of the sleeve 10
A polygon mirror 12 is mounted on the mirror 1. Also, a stopper 13 is arranged at the upper end of the sleeve 10 to cover the opening. The polygon mirror 12 is sandwiched between the seven flange 11 and a pressing portion 14 formed on the outer periphery of the polygon mirror 12, and is fixed with bolts 15.

Further, a pivot member 16 made of synthetic resin is attached to a portion of the stopper 13 facing the upper end surface of the shaft body 2. A rotor 17 of the motor 3 is fixed to the lower outer periphery of the sleeve 10 so as to face the stator 4 .

In the above configuration, when the stator 4 of the motor 3 is energized, the rotor 17 is rotationally driven, and the polygon mirror 12 is rotated via the sleeve 10 at a high speed of, for example, 10,000 r, p, at. In this rotating state, the upper and lower bearing surfaces 7a of the shaft body 2 are
, 7b and the inner peripheral surface of the sleeve 10, the pressure of the air as a lubricating fluid is increased, and the sleeve 10 rotates at high speed without contacting the upper and lower bearing surfaces 7a and 7b. . At this time, when a laser beam (not shown) is incident on the polygon mirror 12, it can be reflected and scanning with the laser beam can be performed.

Furthermore, even if the inner circumferential surface of the sleeve 10 comes into contact with the upper or lower bearing surface 7a or 7b of the shaft body 2 immediately after starting, immediately before stopping, or during high-speed rotation, although the sleeve 10 is made of steel, Since the liner 6 that forms the bearing surfaces 7a and 7b is made of soft, dissimilar metal materials, there is no risk of seizure due to the surface lubrication properties of these metals.Therefore, even if contact occurs, the bearing It is possible to return to normal rotation and rotate without loss of function. Furthermore, since the core shaft 5 and the sleeve 10 are made of the same type of metal, the bearing gap is kept constant from high to low temperatures.
Bearing performance is stable.

Moreover, even if the sleeve 10 is moved downward by shock due to external vibration, the stopper 1 at the upper end of the sleeve 10
3 and the upper end of the shaft body 2 are synthetic trees! ! lit pivot member 1
6, so there is no damage.

In addition, in the above embodiment, an example was shown in which the liner 6 was shrink-fitted to the outer periphery of the core shaft 5 to form a lining layer. Therefore, it can also be formed by plating, thermal spraying, etc.

Further, it goes without saying that the present invention is applicable not only to bearings using air as a lubricating fluid but also to fluid bearings using oil.

Effects of the Invention According to the hydrodynamic bearing device of the present invention, since the outer peripheral surface of the shaft body is formed of a lining layer made of a soft metal material,
There is no risk of seizing even if it comes into contact with the inner peripheral surface of the sleeve, and the dynamic pressure generating grooves can be formed on soft metal materials, so they are easier to form than on hard materials such as steel. can be formed.

Further, by fitting a cylindrical liner to the core shaft, a second inning layer can be easily formed.

Further, if the dynamic pressure generating groove is formed by plastic working such as ball rolling, it can be formed extremely easily and at low cost.

Further, even when vibration is applied from the outside, the stopper of the sleeve and the end face of the shaft collide via the synthetic resin pivot member, so there is no damage caused by the vibration.

[Brief explanation of the drawing]

FIG. 1 and FIG. 2 show an embodiment of the present invention, and! jS1
The figure is a vertical front view, FIG. 2 is a cross-sectional view of the shaft, and FIG. 3 is a vertical front view of a conventional example. 2・・・・・・・・・・・・・・・Shaft body 5...
・・・・・・・・・・・・・・・Core shaft 6・・・・・・・
...... Liners 7a, 7b...Bearing surface 8......Dynamic pressure generation groove 9
・・・・・・・・・・・・・・・Gap 10...
・・・・・・・・・・・・・・・Sleeve 13・・・・
・・・River・・・・・・Stopper 16・・・・・・
・・・・・・・・・・・・Pivot member. Acting patent attorney Toshio Nakao (1 person)

Claims (4)

[Claims] (1) Equipped with a sleeve and a shaft that are fitted to allow relative rotation, a lubricating fluid is interposed in the gap between the inner circumferential surface of the sleeve and the outer circumferential surface of the shaft, and a dynamic pressure generating groove is provided on the outer circumferential surface of the shaft. In the hydrodynamic bearing, the shaft body is composed of a core shaft made of a material having substantially the same coefficient of linear expansion as the sleeve, and a lining layer integrally formed on the outer periphery of the core shaft, and the lining layer is made of a soft metal material. A hydrodynamic bearing device having the hydrodynamic groove formed on its outer circumferential surface. (2) The hydrodynamic bearing device according to claim 1, wherein the lining layer is constituted by a cylindrical liner fitted to the core shaft. (3) The hydrodynamic bearing device according to claim 1 or 2, wherein the dynamic pressure generating groove is formed by plastic working. (4) The hydrodynamic bearing device according to claim 1, 2 or 3, wherein a stopper facing the end face of the shaft body is attached to the sleeve, and a pivot member made of synthetic resin is attached to the face of the stopper facing the end face of the shaft body.