JP2006266437A - Journal bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress abnormal vibration of a rotation shaft by improving linearity of the support spring constant of the rotation shaft, in a journal bearing using a tilting pad. <P>SOLUTION: This journal bearing 11 is formed by having a holding member 2, a plurality of the tilting pads 1 rotatably supported with respect to the holding member 2. A fluid lubricating film 4 is formed in a gap between the rotation shaft 3 and the tilting pad 1 to support the rotation shaft. In addition, a softly supporting member 5 to radially and softly support the tilting pad 1 is mounted to the holding member 2. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a journal bearing, and more particularly to a journal bearing suitable for a high-speed rotating machine such as a gas turbine or a turbo compressor.

  As a journal bearing for supporting a rotating shaft, for example, one described in JP-A-11-303864 (Patent Document 1) is known. This journal bearing constitutes a journal bearing by a holding member and a plurality of tilting pads rotatably supported by the holding member. The journal bearing is supported by the housing via a spring material, and a fluid film damper is formed between the outer peripheral surface of the journal bearing and the inner peripheral surface of the housing via an O-ring.

JP-A-11-303864

  Generally, when the fluid lubrication film of the journal bearing becomes thin, the spring constant of the fluid lubrication film increases rapidly. In journal bearings, when a low-viscosity lubricating fluid such as water is used, or when the vibration amplitude is large, the fluid lubrication film becomes thin, so the nonlinearity of the support spring constant of the rotating shaft becomes stronger, and vibration amplitude jumps. Phenomenon and abnormal vibration such as subharmonic resonance and harmonic resonance are likely to occur on the rotating shaft. In Patent Document 1, since the entire journal bearing is supported on the housing by a spring material, it is difficult to sufficiently suppress abnormal vibration of the rotating shaft.

  In the journal bearing of Patent Document 1, since the fluid film damper portion is formed between the inner peripheral surface of the housing and the outer peripheral surface of the journal bearing, the damper movable portion is the entire journal bearing, and the fluid film damper portion For this to function, the entire journal bearing must vibrate with the rotating shaft. Since the vibration frequency increases during high-speed rotation, the inertial force of the journal bearing increases and the journal bearing becomes difficult to move. For this reason, the vibration damping capability of the fluid film damper portion is reduced.

  Further, in order to obtain a predetermined damping coefficient in the journal bearing of Patent Document 1, it is necessary to precisely adjust the inner diameter of the housing, the outer diameter of the journal bearing, and the width of the fluid film damper portion. There was a problem that it was difficult to adjust.

  An object of the present invention is to provide a journal bearing that can improve the linearity of a support spring constant of a rotating shaft and suppress abnormal vibration of the rotating shaft.

  Another object of the present invention is to provide a journal bearing capable of suppressing the abnormal vibration of the rotating shaft by ensuring the linearity of the supporting spring constant of the rotating shaft while ensuring the vibration damping capability of the fluid film damper. It is in.

  Still another object of the present invention is to provide a journal bearing that can easily adjust the damping coefficient of a fluid film damper and improve the linearity of the support spring constant of the rotating shaft to suppress abnormal vibration of the rotating shaft. There is to do.

  In order to achieve the above-mentioned object, the present invention comprises a holding member and a plurality of tilting pads that are rotatably supported by the holding member, and a fluid is provided in a gap between the rotating shaft and the tilting pad. In a journal bearing that supports the rotating shaft by forming a lubricating film, a flexible support member that flexibly supports the tilting pad in the radial direction is attached to the holding member.

A more preferable specific configuration example of the present invention is as follows.
(1) The flexible support member is formed of a number of plate-like members corresponding to the tilting pads, and the tilting pads are rotatably attached to the central portions of these flexible support members, and the end portions of the flexible support members Is attached to the holding member.
(2) The flexible support member is formed of a plate-like member, and a fluid film damper is formed between the flexible support member and the holding member.
(3) The flexible support member is formed of a plate-like member, a plurality of fluid chambers are formed between the flexible support member and the holding member, and the fluid chambers communicate with each other via a thin tube.

  In addition, said (2) is a structure for achieving the another objective mentioned above, and said (3) is a structure for achieving the another objective mentioned above.

  According to the journal bearing of the present invention, it is possible to improve the linearity of the support spring constant of the rotating shaft and to suppress abnormal vibration of the rotating shaft.

  According to the journal bearing of the present invention, it is possible to improve the linearity of the support spring constant of the rotating shaft and suppress the abnormal vibration of the rotating shaft while ensuring the vibration damping capability of the fluid film damper.

  According to the journal bearing of the present invention, it is possible to improve the linearity of the support spring constant of the rotating shaft and to suppress abnormal vibration of the rotating shaft while facilitating the adjustment of the damping coefficient of the fluid film damper.

  Hereinafter, a plurality of embodiments of the present invention will be described with reference to the drawings. The same reference numerals in the drawings of the respective embodiments indicate the same or equivalent.

  First, a journal bearing according to a first embodiment of the present invention will be described with reference to FIGS.

  The overall configuration of the journal bearing 11 of the present embodiment will be described with reference to FIG. FIG. 1 is a sectional view showing a journal bearing 11 according to a first embodiment of the present invention.

  The journal bearing 11 includes a holding member 2, a tilting pad 1, and a flexible support member 5.

  The holding member 2 has a cylindrical portion concentric with the rotating shaft 3 and side wall portions provided on both sides of the cylindrical portion. The rotating shaft 3 passes through the center of the holding member 2.

  The tilt pad 1 has an inner peripheral surface having a slightly larger diameter than the outer peripheral surface of the rotating shaft 3 and an outer peripheral surface substantially concentric with the inner peripheral surface. A fluid lubricating film is formed in a gap between the inner peripheral surface of the tilting pad 1 and the outer peripheral surface of the rotating shaft 3, and the rotating shaft 3 is supported by the tilting pad 1 through the fluid lubricating film. The tilt pad 1 is divided into a plurality (four in the illustrated example) in the circumferential direction of the rotating shaft 3. Each tilt pad 1 is supported by the flexible support member 5 so as to rotate around its central portion.

  The flexible support members 5 are constituted by plate-like members (flat plate members in the illustrated example), and are provided in the same number corresponding to the outer side of the tilting pad 1 in the circumferential direction of the rotating shaft 3. The tilt pad 1 and the flexible support member 5 are configured as a pair, and a plurality of sets are provided. Then, both ends of the flexible support member 5 are fixed to the holding member 2, and the holding member 2 is flexibly supported in the radial direction by the central portion of the flexible support member 5 having flexibility. Therefore, the tilt pad 1 is supported by the holding member 2 via the flexible support member 5.

  The function and effect of the journal bearing 11 of the present embodiment will be described with reference to FIGS. 2 is a schematic diagram showing a spring constant calculation model of the journal bearing 11 of FIG. 1, and FIG. 3 is a schematic diagram showing the relationship between the eccentricity and the spring constant in the journal bearing.

  In the journal bearing 11 of the present embodiment, as shown in FIG. 2, the rotating shaft 3 is arranged such that the spring 7 of the flexible support member 5 and the spring 6 of the fluid lubricating film 4 are in series via the tilting pad 1. It is supported by the holding member 2.

  In the journal bearing using the fluid lubrication film 4, the fluid lubrication film 4 becomes thinner as the eccentricity between the rotating shaft 3 and the tilting pad 1 increases, and when the eccentricity approaches 1, as shown in FIG. The lubricating film spring constant increases rapidly. In journal bearings that do not use the flexible support member 5, the fluid lubrication film spring constant directly corresponds to the rotation shaft support rigidity, and therefore the nonlinearity of the rotation shaft support rigidity has increased.

  On the other hand, the rotational shaft support rigidity of the journal bearing 11 of this embodiment corresponds to the series sum of the spring constant 7 of the flexible support member 5 and the spring constant 6 of the fluid lubricating film 4. In the example of FIG. 3, since the tilting pad 1 is supported by the flexible support member 5 having a spring constant of 10 (N / m), even if the eccentricity is close to 1, as shown in FIG. The change in the support stiffness is small, and the rotation shaft support stiffness does not exceed the flexible support member spring constant. Therefore, in the journal bearing 11 of the present embodiment, the linearity of the rotation shaft support rigidity is improved, and abnormal vibration of the rotation shaft due to the non-linearity of the rotation shaft support rigidity can be suppressed.

  In this embodiment, the flexible support member 5 has a planar shape, but the flexible support member 5 may have a curved surface shape.

  Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a cross-sectional view of the journal bearing 11 according to the second embodiment of the present invention. The second embodiment is different from the first embodiment in the following points, and is basically the same as the first embodiment in other points.

  The second embodiment is different from the first embodiment in that a fluid film damper 8 is provided by forming a fluid film in the gap between the flexible support member 5 and the holding member 2. In the second embodiment, the vibration of the rotating shaft 3 is transmitted to the tilting pad 1, and the tilting pad 1 vibrates in the radial direction, whereby the damping force by the fluid film damper 8 is obtained. Compared with the case where the fluid film damper is provided on the outer peripheral side of the journal bearing 11, the mass of the movable part of the damper is very small, so that the vibration damping ability of the fluid film damper 8 can be improved even in a high vibration frequency state at high speed rotation. Can be maintained.

  Therefore, according to the second embodiment, it is possible to provide a journal bearing in which the linearity of the support spring constant is good and the vibration damping characteristics are good.

  In the present embodiment, the fluid film damper 8 has a planar shape, but the fluid film damper 8 may have a curved surface shape. Further, in this embodiment, the fluid supply hole and the fluid discharge hole are not shown in the fluid film damper 8, and the fluid supply hole and the fluid discharge hole are provided in the fluid film damper 8 to circulate the working fluid. Yes. When the working fluid of the fluid film damper 8 is circulated, the temperature rise of the working fluid of the fluid film damper 8 can be suppressed.

  Next, a third embodiment of the present invention will be described with reference to FIG. FIG. 5 is a sectional view of a journal bearing 11 according to the third embodiment of the present invention. The third embodiment is different from the first embodiment in the following points, and is basically the same as the first embodiment in other points.

  The third embodiment is different from the first embodiment in that a fluid chamber 9 is provided between the flexible support member 5 and the holding member 2 and the fluid chambers 9 are connected by a thin tube 10. In the third embodiment, when the tilting pad 1 moves in the radial direction due to the vibration of the rotating shaft 3, the volume of the fluid chamber 9 on the back of the tilting pad 1 decreases, so that the fluid in the fluid chamber 9 passes through the thin tube 10. It moves through to another fluid chamber 9. At this time, the vibration of the rotating shaft 3 is attenuated by the flow path resistance of the thin tube 10. The damping coefficient of the damper can be easily adjusted by adjusting the flow resistance of the thin tube 10 using an orifice or the like. Therefore, according to the third embodiment, it is possible to provide a journal bearing in which the linearity of the support spring constant is good and the vibration damping characteristics are good.

  In the third embodiment, the thin tube 10 connecting the fluid chamber 9 is provided inside the journal bearing 11, but the thin tube 10 may be provided outside the journal bearing 11.

It is sectional drawing of the journal bearing which concerns on 1st Example of this invention. It is a schematic diagram showing the spring constant calculation model of the journal bearing of FIG. It is a schematic diagram which represents the relationship between the eccentricity of the journal bearing of this invention, and a spring constant compared with a prior art example. It is sectional drawing of the journal bearing which concerns on 2nd Example of this invention. It is sectional drawing of the journal bearing which concerns on 3rd Example of this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Tilting pad, 2 ... Holding member, 3 ... Rotating shaft, 4 ... Fluid lubrication film, 5 ... Flexible support member, 6 ... Spring of fluid lubrication film, 7 ... Spring of flexible support member, 8 ... Fluid film damper, 9 ... Fluid chamber, 10 ... Narrow tube, 11 ... Journal bearing.

Claims (4)

A journal comprising a holding member and a plurality of tilting pads that are rotatably supported with respect to the holding member, and forming a fluid lubrication film in a gap between the rotating shaft and the tilting pad to support the rotating shaft In bearings,
A journal bearing, wherein a flexible support member that flexibly supports the tilting pad in a radial direction is attached to the holding member.   The journal bearing according to claim 1, wherein the flexible support member is formed of a number of plate-like members corresponding to the tilting pads, and the tilting pads are rotatably attached to a central portion of the flexible support members. A journal bearing, wherein an end of the flexible support member is attached to the holding member.   The journal bearing according to claim 1, wherein the flexible support member is formed of a plate-like member, and a fluid film damper is formed between the flexible support member and the holding member.   2. The journal bearing according to claim 1, wherein the flexible support member is formed of a plate-like member, a plurality of fluid chambers are formed between the flexible support member and the holding member, and the fluid chambers are interposed via thin tubes. Journal bearings characterized in that they communicate with each other.

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