JPH03121306A - Tilting pad shaped dynamic pressure gas bearing - Google Patents

Abstract

PURPOSE:To secure resistance against wearing and vibration stability for improving durability against damage and improving bearing performance at the time of a high temperature by forming a pad with a material the same as that for a rotor, coating a solid lubricating material on an inner face of a ceramic coating and performing thickness reducing treatment on the outer periphery of the pad. CONSTITUTION:A pad 21 is formed of a material the same as that of a rotor. Therefore compared with a case where the pad 21 is made of a single ceramic material, durability against damage of the pad 21 is raised and the pad 21 exhibits thermal expansion approximately equal to that of the rotor so that bearing clearance can be maintained well even with respect to a wide variation in temperature for improving bearing performance at the time of a high temperature. Further a ceramic coating 24 is applied to an inner face of the pad 21 and solid lubricant 25 is coated to also maintain resistance against wearing of the pad 21 well. In addition, respective angle parts are subjected to thickness reducing treatment by a cut 27 on the outer periphery of the pad 21 to reduce a moment of inertia of the pad 21, resulting in improvement of follow-up property of the pad 21 as well as maintaining vibration stability well.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a tilting pad type hydrodynamic gas bearing that supports a rotor that rotates at an extremely high speed under high temperatures.

(Conventional technology) In recent years, rotors that rotate at extremely high speeds have been developed without using oil or water.
Tilting pad type hydrodynamic gas bearings, which use surrounding gas for support, are being adopted.

FIGS. 3A and 3B are cross-sectional views showing the structure of this conventional tilting pad type dynamic pressure gas bearing. A pad 3 is connected to the outside of the bearing bracket 1 via a pivot 2.
is supported. This pad 3 is circumferentially divided into, for example, three parts, and each of the divided pad bases 4 is supported by the bearing bracket 1 by one pivot 2, respectively.

The pivot 2 includes one that is directly fixed to the bearing bracket 1 with a lock nut 5, and one that is elastically supported by the bearing bracket 1 via a leaf spring 6.

The rotor 7 is supported on the inner peripheral surface of each pad base 4 of this pad 3 via a gas film, and rotates at an extremely high speed.

By the way, in the dynamic pressure lubrication system of the tilting pad type hydrodynamic gas bearing as described above, the rotor 7 is
and the inner circumferential surface of the pad 3 must come into direct contact with each other. At this time, since the gas does not have boundary lubricity unlike liquids such as ura, there is a risk that the rotor 7 and the inner circumferential surface of the pad 3 may seize. Therefore, a hard material such as ceramic is selected for the pad 3.

FIGS. 2(A) and 2(B) are configuration diagrams showing essential parts of another conventional tilting pad type hydrodynamic gas bearing. In this other conventional tilting pad type hydrodynamic gas bearing, a rotor 10 made of steel is supported by a pad 12 made of a pad base 11 made of a single ceramic material. The advantage of this conventional example is that the pad 12 is made of ceramic, so it has excellent wear resistance.
Since the specific gravity of the material is small, the moment of inertia of the pad 12 is small, and as a result, the followability of the pad 12 is good, resulting in excellent vibration stability.

(Problem to be Solved by the Invention) However, in the other conventional tilting pad type hydrodynamic gas bearing shown in FIG. Extremely low and easy to break. In addition, the coefficient of linear expansion of the pad 12 is extremely small, about 1/3 compared to the rotor 10 made of steel.
When the temperature change is large, the radius (Rp) of the pad 12 becomes smaller than the radius (Rr) of the rotor 10, and the bearing clearance C (C=Rp-Rr) is lost, which may significantly reduce bearing performance. .

This invention was made in consideration of the above circumstances, and provides a tilting pad that ensures good wear resistance and vibration stability, has a high fracture toughness value, and can improve bearing performance even at high temperatures. The purpose of the present invention is to provide a shaped dynamic pressure gas bearing.

[Structure of the invention]

(Means for Solving the Problems) The present invention provides a tilting pad type hydrodynamic gas bearing in which a pad is supported within a bearing bracket and a rotor is supported via a gas film on the inner peripheral surface of the pad. The pad is made of the same material as the rotor, its inner circumferential surface is coated with a ceramic coating, the inner circumferential surface of the ceramic coating is coated with a solid lubricant, and the outer circumference of the pad is thinned. It is characterized by this.

(Function) Therefore, according to the tilting pad type hydrodynamic gas bearing according to the present invention, since the pad is made of the same material as the rotor, the fracture toughness value of the pad is lower than when the pad is made of a single ceramic material. It can be made higher. In addition, since the pad is made of the same material as the rotor, the pad exhibits the same degree of thermal expansion as the rotor, allowing good bearing clearance to be maintained even under wide temperature changes, improving bearing performance at high temperatures. I can do it.

Furthermore, since the inner peripheral surface of the pad is coated with a ceramic coating, the wear resistance of the pad can also be maintained well.

Furthermore, since the outer periphery of the pad is thinned, the moment of inertia of the pad can be lowered, and as a result, the followability of the pad is improved, and vibration stability can also be maintained favorably.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1(A) is a front view of main parts of a tilting pad type hydrodynamic gas bearing according to the present invention, and FIG.
) is a sectional view taken along line IB-IB of FIG. In this embodiment, parts similar to those in the conventional example are given the same reference numerals.

The pad 21 is composed of a pad base 22 divided into, for example, three parts in the circumferential direction. A pivot hole 23 is formed in each outer periphery of each pad base 21, and the tip of the pivot 2 is fitted into this pivot hole 23.

Each pad base 22 of the pad 21 has a pivot 2
The bearing bracket 1 is directly rigidly supported by the bearing bracket 1 or elastically supported by a leaf spring 6.

The rotor 7 is supported on the inner peripheral surface of the pad base 22 of the pad 21 as described above. The rotor 7 is made of steel. Further, each ballad base 22 of the pad 21 is also formed from steel.

The inner circumferential surface of each pad base 22 is coated with a ceramic coating 24 of titanium nitride (T i N), which has a relatively strong bonding property with metal, by vapor deposition. Furthermore, the inner surface of this ceramic coating 24 is coated with a solid lubricant 25 such as molybdenum disulfide.

The thickness of each of the ceramic coating 24 and the solid lubricant 25 is about several microns, whereas the thickness of the pad base 22 is about 10-.

The rotor 7 contacts this solid lubricant 25 via a gas film.

Further, on the outer peripheral surface of each pad base 22 of the pad 21, a plurality of, for example two, grooves 26 are formed along the circumferential direction of the pad base 22, as shown in FIG. 1(B). Furthermore, the outer periphery of each pad base 22 is processed by cutting 27 inside both corners, as shown in FIG. 1(A). These grooves 26 and cuts 27 are the thickness reduction processing of the pad 21.

Here, the moment of inertia of the pad 21 is I, and the pad 21
Assuming that the mass of the minute portion of the (pad base 22) is dm, and the distance between the mass point position of this minute portion and the center of gravity of the pad 21 is R, then there is the following relationship: (1)=ΣR2dm. The grooves 26 of the pad base 22 as described above reduce the mass of the pad 21, and the pad 27 reduces the distance R, so these grooves 26 and cuts 27
This reduces the moment of inertia I of the pad 21.

According to the above embodiment, since the pad 21 is made of the same material (steel material) as the rotor 7, the fracture toughness value of the pad 21 can be increased compared to the case where the pad 21 is made of a single ceramic material.

In addition, since the pad 21 is made of the same material as the rotor 7, the pad 21 exhibits the same degree of thermal expansion as the rotor 7, and the bearing clearance C can be maintained well even under a wide range of temperature changes. Bearing performance can be improved.

Furthermore, since the ceramic coating 24 is applied to the inner peripheral surface of each pad base 22, the wear resistance of the pad base 22 can be maintained well.

Additionally, a groove 26 and a cut 27 are provided on the outer periphery of the pad base 22.
Since the thickness reduction process has been performed, the moment of inertia (2) of the pad 21 can be reduced.

As a result, the followability of the pad 21 improves, and vibration stability can be maintained favorably.

By the way, in general, the moment of inertia I of the pad 21 is
Affects the limit speed of the rotor. In other words, as the moment of inertia I of the pad 21 increases, the rotational speed at which magnetically excited vibrations occur in the pad 21 decreases, so when the rotor 7 is rotated at high speed, the moment of inertia (I) of the pad 21 must be made as small as possible. . In this embodiment, since the moment of inertia of the pad 21 is reduced, the rotational speed at which magnetically excited vibrations occur in the pad 21 can be increased, and the bearing performance at high speeds can be improved.

Furthermore, the inner peripheral surface of the pad base 22 is coated with a solid lubricant 25, and the rotor 7 comes into contact with this solid lubricant 25 via a gas film, so that the solid lubricant 25 improves lubricity. In particular, the lubrication performance of the rotor 7 and pad 21 during starting and stopping can be improved.

〔Effect of the invention〕

As described above, according to the tilting pad type hydrodynamic gas bearing according to the present invention, the pad that is supported within the bracket and supports the rotor through the gas film on the inner peripheral surface is made of the same material as the rotor. The inner circumferential surface of the ceramic coating is coated with a solid lubricant, and the outer circumference of the pad is thinned to provide wear resistance and vibration stability. It is possible to increase fracture toughness while ensuring good properties, and to improve bearing performance at high temperatures.

[Brief explanation of drawings]

FIG. 1(A) is a front view of the main part of the tilting pad type hydrodynamic gas bearing according to the present invention, and FIG. 1(B) is
A) is a sectional view taken along the IB-IB line, FIG. 2(A) is a front view of the main part of another conventional tilting pad type hydrodynamic gas bearing, and FIG. 2(B) is a cross-sectional view of FIG. 2(A). 3(A) is a sectional view taken along line IIB-IIB of FIG. 3(A), and FIG. 3(B) is a sectional view showing the structure of a conventional tilting pad type hydrodynamic gas bearing.
is a sectional view taken along line I[IB-IIIB of FIG. 3(A). 1... Bearing bracket, 2... Pivot, 7...
Rotor, 21... Pad, 22... Pad base, 2
4...Ceramic coating, 25...Solid lubricant, 26...Groove, 27...Cut.

Claims (1)

[Claims] In a tilting pad type hydrodynamic gas bearing in which a pad is supported within a bearing bracket and a rotor is supported via a gas film on the inner peripheral surface of the pad, the pad is made of the same material as the rotor, and the pad is made of the same material as the rotor. A tilting pad type hydrodynamic gas bearing characterized in that a ceramic coating is applied to the inner circumferential surface, a solid lubricant is coated on the inner circumferential surface of the ceramic coating, and a thinning process is applied to the outer circumference of the pad. .