JPH0842560A - Dynamic pressure gas journal bearing - Google Patents

Abstract

PURPOSE:To increase a load by a method wherein a groove is formed in the front edge in a rotation direction of the recessed curved surface of a pad and parts having no groove are formed at two end parts in an axial direction, the central part in an axial direction of the groove reaching the rear edge side in a peripheral direction from a pivot support point is shallow, and the curvatures of the two end parts are set to a value between the curvatures of the groove part and the rotary shaft. CONSTITUTION:Lands 6 remain at two end parts in an axial direction on the surface of a pad 2 and a shallow groove part 7 is formed. Rails 9 slightly deeper than a central part 8 are formed at the two ends of the groove part 7. The rail 9 is formed in such a manner that depth is gradually decreased toward the rear edge of the pad 2 and depth at the rear edge is set to a value equivalent to that of the central part 8 of the groove. When the radius of a rotary shaft is R, the curvature of the groove central part 8 is set approximate 1,001-1,003 R and the curvature of the land 6 is set to a value lower than that of the groove central part. When projection is effected from an axial direction, the groove central part 8 is prevented from protruding from the land part 6. This constitution prevents the generation of the stress of a bearing surface, making centralized contact, in the position of the pivot point, and improves load bearing ability of a bearing without damaging gas pressure generating performance of a gas bearing.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dynamic pressure gas journal bearing used in high speed turbomachines such as expansion turbines and compressors.

[0002]

2. Description of the Related Art In a conventional tilting pad type dynamic pressure gas journal bearing, as shown in the transverse sectional view of FIG. 3, each pad 02 is back-supported by a pivot 04, in which case the pivot is performed by a spherical surface. There are two types, a point support type and a line support type that is performed by line contact in the axial direction. Especially for bearings with a small load capacity such as gas bearings, the point support type is mainly used in order to eliminate the influence of one-sided contact. Further, the surface of the bearing pad 02 is manufactured to be as smooth as possible and to maintain its performance in gas lubrication with a small floating clearance by controlling the cylindricity.

[0003]

The conventional gas bearing has been mainly used for light load high speed rotation. By the way, if this is used with a higher load, there are the following problems. The solid contact condition between the pad surface and the rotary shaft surface, which is performed until the bearing pad 02 and the rotary shaft 01 are completely floated and separated from each other, is a line contact uniformly distributed in the axial direction when the load is light. However, as the load increases, the condition becomes closer to the concentrated contact with the pivot point 04 as the center, and the heat generated in that part increases, causing the pad to warp in the axial direction and further contact conditions. The bearing becomes severer and the damage becomes severe. For this reason, the projected surface pressure of the bearing at the time of design was limited to about 0.2 kgf / cm ² .

The present invention has been proposed in view of the above circumstances, and it is an object of the present invention to provide a high-performance dynamic pressure gas journal bearing which reduces heat generation in the pivot portion and damages to the bearing even when rotating under a high load. To aim.

[0005]

To this end, the present invention is directed to a pad in which a cylinder, which is arranged around a rotary shaft and is coaxially arranged with a clearance between the rotary shaft and the rotary shaft, is divided into a plurality of pieces in the circumferential direction. In the journal bearing that consists of (2) and can be supported in any position by supporting the convex curved back surface of each pad (2) with the pivot (5), the concave surface of the pad facing the rotation axis can be supported. Grooves (9) that open to the front edge in the rotational direction are provided on the curved surface, and portions (6) where grooves are not provided are provided at both ends in the axial direction of the pad. Process groove (7) up to
The depth of the groove (7) is made shallow in the central part in the axial direction, and the curvature of both end parts (6), (6) is set between the curvature of the groove part (7) and the curvature of the rotation axis. It is characterized by being set to a curvature.

[0006]

According to this structure, by providing a groove in the central portion of the pad in the axial direction until reaching the trailing edge side from the pivot position, when the weight of the rotating shaft acts on the pad, concentrated contact at the pivot point position occurs. No stress is generated on the bearing surface, and uniform line contact is realized at the two non-groove portions at both ends. Further, since the contact portions are located at both ends in the axial direction and the grooves are provided inside, the cooling effect of the pad is enhanced by the peripheral flow, and the local temperature rise can be suppressed. Further, by setting the curvature of the non-groove portion between the curvature of the groove portion and the curvature of the rotating shaft, the local contact surface pressure can be suppressed to be small. Furthermore, by reducing the groove depth at the center of the groove in the axial direction, it is possible to increase the bearing's gas film pressure generation capability while maintaining the cooling effect of the non-groove parts, and to reduce the bearing damage area due to contact to the gas film pressure. Since it can be limited to the bearing end portion that has little influence on the generation, the bearing proof strength can be significantly improved.

[0007]

Embodiments of the present invention will now be described with reference to the drawings.
1 and 2 are a perspective view and a vertical sectional view of the pad showing a first embodiment and a second embodiment, respectively.

First, the pad 2 of the first embodiment shown in FIG. 1 is used in place of the bearing pad 02 of the conventional tilting pad bearing shown in FIG. A shallow groove portion 7-1 is formed on the surface of the pad 2, leaving lands 6 at both axial end portions thereof, as shown in FIG. Rails 9 which are slightly deeper than the central portion 8 are formed along both ends of the groove. The rail 9 gradually becomes shallower toward the trailing edge of the pad, and the trailing edge is set at a depth comparable to that of the central portion of the groove, as shown in FIG. The curvature of the central portion of the groove is at the same level as in a normal bearing design, and when the radius of the rotating shaft is R, it is set to about 1.001 to 1.003R, and the land portion is set to a curvature less than that. At this time, the center of the groove does not protrude from the land when projected from the axial direction. Also,
The depth of the rail 9 is set to 0, which corresponds to the bearing clearance at the front edge portion with respect to the curved surface at the center of the groove so as not to hinder the pressure generation.
001 to 0.003R, and the trailing edge portion is set to almost zero.

Next, in the pad of the second embodiment shown in FIG. 2, as shown in FIG. 2A, the groove portion 7-2 does not reach the trailing edge of the pad, but gradually approaches the trailing edge as a whole. It takes the form of a so-called tapered land bearing that is shallowly formed. The end edge position of the taper needs to reach the trailing edge side with respect to the angle at which the pivot 4 exists, as shown in FIG. Further, the depth of the central portion of the groove is not uniform, and the gas film pressure can be promoted by making the depth shallower toward the trailing edge.

[0010]

According to the structure of the present invention, the bearing proof strength at the time of contact can be greatly improved without impairing the gas pressure generating performance of the gas bearing. Therefore, a large rotating body which cannot conventionally use the gas bearing is used. It becomes possible to apply to such as, and it becomes possible to reduce the equipment maintenance and downsize.

In short, according to the present invention, a pad (2) is formed by circumferentially dividing a cylinder, which is coaxially arranged around the rotary shaft with a gap between the rotary shaft and the rotary shaft, into a plurality of parts. In addition, in the journal bearing that can support the convex back surface of each pad (2) at any point by supporting each with the pivot (5), the direction of rotation on the concave curved surface of the pad facing the same rotation axis Grooves that open to the front edge (9)
In addition to the above, the pad (6) is provided at both ends in the axial direction of the pad, and the groove (7) is machined in the circumferential direction until it reaches the rear edge side from the pivot point, and the groove (7) is formed. The depth of should be such that the central part in the axial direction is made shallow, and the curvature of both end parts (6), (6) is set to the curvature between the curvature of the groove part (7) and the curvature of the rotation axis. As a result, a high-performance dynamic pressure gas journal bearing that reduces heat generation in the pivot part and damage to the bearing even when rotated under a high load is obtained, and therefore the present invention is extremely useful industrially.

[Brief description of drawings]

FIG. 1 shows a bearing pad according to a first embodiment of the present invention, in which FIG. 1A is an overall perspective view thereof, and FIGS. 1B and 1C are IB-IB of FIG. 1A, respectively. It is an arrow view and an IC-IC arrow view.

FIG. 2 shows a bearing pad according to a second embodiment of the present invention, in which FIG. 2A is an overall perspective view thereof, and FIGS. 2B and 2C are IIB-IIB of FIG. 2A, respectively. It is an arrow line view and a IIC-IIC arrow line sectional view.

FIG. 3 is an overall cross-sectional view of a conventional tilting pad bearing.

[Explanation of symbols]

 2 Pad 4 Pivot 5 Pivot rod 6 Land 7 Groove 7-1 Groove part 7-2 Groove part 8 Groove center part 9 Rail

Claims (1)

[Claims] 1. A pad (2) formed by circumferentially dividing a cylinder, which is arranged around the rotation shaft and coaxially with a clearance between the rotation shaft and the rotation shaft, into a plurality of parts, and each pad
In the journal bearing that can support the convex curved back surface of (2) at each point by the pivots (5), the concave surface of the pad facing the rotating shaft is opened at the front edge in the rotational direction. In addition to providing the groove (9), the pad (6) is provided at both ends of the pad in the axial direction, and the groove (7) is machined in the circumferential direction until it reaches the trailing edge side from the pivot point. The depth of the groove (7) is made shallow at the central part in the axial direction, and the curvature of both end parts (6), (6) is defined as the curvature between the curvature of the groove part (7) and the curvature of the rotation axis. A dynamic pressure gas journal bearing characterized by being set to.