JPH01150018A - Dynamic pressure fluid bearing - Google Patents

Abstract

PURPOSE:To prevent and control the generation of abrasion powder to the most extent so as to improve the sliding property of the bearing in the caption by forming a thin film made of synthetic resin on at least one side of opposite faces making relative rotation, in a dynamic pressure bearing in which grooves for leading lubricating oil in a fixed direction are formed. CONSTITUTION:In a dynamic pressure fluid bearing in which lubricating oil is used as fluid, a SUS 304 made shaft 2 having herringbone grooves 5 is dipped in painting liquid in polyester resin is dispersed by methyl-ethyl-ketone and is burned to be formed in a film 4 of about 1mum thickness. Accordingly, synthetic resin thin film on the shaft surface prevents this surface from contact with metal and wear is eliminated so that rotational torque can be stabilized.

Description

[Detailed description of the invention] [Industrial application field] This invention relates to a hydrodynamic bearing.

[Conventional technology]

In recent years, there has been a strong demand for bearings for polygon mirror rotation shafts used in laser beam printers, VTR cylinder head spindles, magnetic disk spindles, etc. to rotate at high speed and with high precision. Hydrodynamic bearings that use oil or grease as a lubricant have been used to maintain bearing performance with very little unevenness (and stable rotational torque). The bearing is characterized by generating a high-pressure fluid layer between the stationary side and the rotating side during steady rotation, and rotating without contact while maintaining a minute gap (about 2 to 10μ). Accuracy, rotational unevenness, rotational torque, etc.) are also derived from this.In addition, the guarantee of such a small gap is due to the deterioration of bearing performance due to deterioration of grease, oil, etc. due to wear particles on the fixed side and rotating side. This is extremely important to prevent fatal problems for bearings such as seizure.However, since the affinity between lubricating oil and metal surfaces is poor, lubricating oil is discharged during rotation and metal-to-metal contact can occur. This has the drawback of causing wear.

Therefore, in order to minimize the surface wear caused by this contact, it was necessary to harden the facing surface by hardening or hard plating, but hardening causes distortion in the bearing, and in the case of hard plating, the plating layer Since it is not easy to control the thickness of the plate with high precision, it was necessary to refinish the surface by polishing or other methods. Even if such hardening means are used, abrasion particles from the surface will accelerate the deterioration of grease and other lubricating oils, and often cause changes in rotational torque, so it is never a desirable condition in actual use. In addition, since these metal surfaces have a large surface energy, there is a large resistance to the movement of liquid, and there are also inherent disadvantages such as a long time from the start of operation until steady rotation is reached.

[Problem that the invention seeks to solve]

As mentioned above, the problem with conventional technology is that it is not possible to obtain a dynamic pressure liquid bearing that prevents and suppresses the generation of wear particles as much as possible through simple processing, and that takes a short time from start of operation to steady rotation. was there.

[Means for solving problems]

In order to solve the above problems, the present invention provides a means for forming a thin film made of synthetic resin on at least one of the opposing surfaces that rotate relatively in a hydrodynamic bearing having grooves that guide lubricating oil in a fixed direction. was adopted.

First, the synthetic resin in this invention is a general-purpose resin that can be applied in liquid form.

Examples include epoxy resins, polyurethane resins, polycarbonate resins, polyimide resins, phenol resins, polyether sulfone resins, acrylic resins, polyester resins, etc., and these may be used alone or in combination.

By forming such a thin film of synthetic resin on at least one opposing surface, metal contact does not occur and wear does not occur. Further, when a lubricating oil having a functional group or an oil with an oiliness improver added thereto is used, an adsorption film on the level of a monomolecular film is formed on the thin film of the synthetic resin. Although this adsorption film can be formed on a metal surface, it is possible to form an adsorption film stronger against shearing force on a thin film of synthetic resin. When this adsorption film is formed, the surface energy is reduced, the resistance to movement of the liquid is small, and the time from the start of operation to steady rotation is short and stable.
This can be said to be a more preferable combination. Here, the synthetic resin thin film is 0.01 to 5
．． The thickness is about 0 μm. The lubricating oil having a functional group is a fluorine-containing polymer such as a fluoropolyether polymer or a fluoroalkyl polymer, or an organopolysiloxane, and the oiliness improver is a saturated fatty acid, an amino compound, or the like.

〔Example〕

Example 1: In a dynamic pressure fluid bearing as shown in the figure in which lubricating oil is used as a fluid, a shaft 2 made of 5US304 with a herringbone groove 5 is coated with polyester resin (Vylon 150A manufactured by Toyobo Co., Ltd.) with 0.5 weight of methyl ethyl ketone. The shaft 2 was immersed in a coating solution dispersed in 50% of the total concentration, pulled up at a speed of 80 mm per minute, and fired at 120° C. for 30 minutes to form a film 4 of about 1 μm. inserted into. In addition, a hydrocarbon oil (hexadecane) with 10-2 mol/I of mystylinic acid added as an oiliness improver was used as a lubricating oil, and this was operated continuously for 2000 hours, and the torque (g-cn+) was measured every 400 hours. did. Those with large fluctuations in torque (x mark) and those with small fluctuations (O
After the 2000 hour test, it was examined whether there were any wear marks on the sliding parts. The results obtained are summarized in a table. Although the film 4 is shown as being formed on the outer peripheral surface of the shaft 2 in the illustrated example, it may be provided on the inner surface of the housing 1 and the upper surface of the thrust bearing 3 that receives the thrust force of the shaft 2.

Example 2: A test was conducted in exactly the same manner as in Example 1, except that a fluoropolyether polymer having a carboxy group at the end (manufactured by Monte Fluos, Italy: Huonpurin/Z-DIACID) was used as the surface lubricating oil. . The obtained results are also listed in the table.

Comparative Example: The same test as in Example 1 was conducted except that the shaft 2 was not coated with polyester resin, and the obtained results are also shown in the table.

From the results in the table, the comparative example in which stainless steels were rotated in lubricating oil without forming the synthetic resin film 4 on the shaft 2 showed a low rotational torque value immediately after rotation, but it showed a tendency to gradually increase. Ta. Further, sliding marks (wear marks) were observed on the shaft 2 and the housing 1 in the circumferential direction.

On the other hand, both Examples 1 and 2 in which the synthetic resin film 4 was formed on the shaft 2 continued to maintain a low rotational torque immediately after the start of rotation. Furthermore, no wear marks were observed on the coating 4 and metal surfaces of the shaft 2 and housing 1.

From the above, the synthetic resin thin film on the shaft surface can prevent contact with metal, prevent wear, and stabilize rotational torque.

〔effect〕

The hydrodynamic bearing of this invention is a bearing with excellent sliding characteristics, such as controlling the generation of wear particles as much as possible and achieving steady rotation in a short time after the start of operation.The significance of this invention is therefore It can be said that it is extremely large.

[Brief explanation of the drawing]

The figure is a schematic cross-sectional view showing the structure of a hydrodynamic bearing used in an example. 1...Housing, 2...Shaft,
3... Thrust bearing, 4... Film,
5... Herringbone groove.

Claims (1)

[Claims] 1. A hydrodynamic bearing characterized in that a thin film made of synthetic resin is formed on at least one of opposing surfaces of the hydrodynamic bearing which uses lubricating oil as a fluid.