JP2005321035A - Damping bearing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a damping bering device in which subharmonic resonance is hardly caused even though a radial clearance in a fluid-film damper is reduced to increase in a damping coefficient, and consequently the bearing part and a bearing housing are apt to collide with each other. <P>SOLUTION: The damping bearing device 1 includes the bearing part 20 rotatably supporting a rotor 2, the bearing housing 5 provided on the outer peripheral side of the bearing part 20, and a fluid film damper 15 forming a fluid film 6 in the clearance between the bearing part 20 and the bearing housing 5. A surface film 7 of low hardness is formed at least on either side of fluid film-forming surfaces of the bearing part 20 and the housing 5. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

  As interest in environmental issues increases, there is an increasing demand for downsizing and higher efficiency of turbomachinery.

  In order to reduce the size while securing the output, it is effective to increase the operating rotational speed. However, when the speed of the rotating body is increased, the stability is reduced due to unstable vibration represented by oil whirl. Further, due to the speeding up of the rotating body, it is generally necessary to pass a high-order critical speed with a high vibration response magnification.

  On the other hand, in order to increase the efficiency of turbomachinery, reduction of bearing loss is required. When a rolling bearing or a plain bearing using a low-viscosity fluid is used, the bearing loss is reduced, but there is a problem that the vibration response magnification of the critical speed is increased because the damping coefficient of the bearing is reduced.

  In order to solve these problems, it is effective to add a damping function having a high damping capacity to the shaft support portion, and there are many examples in which a fluid film damper is installed on the outer peripheral side of the bearing.

  The structure of the fluid film damper is disclosed in, for example, Japanese Patent Application Laid-Open No. 2001-50267 (Patent Document 1). This fluid film damper forms a fluid film in a gap between a damper bush fixed to the bearing and a bearing housing disposed on the outer peripheral side of the damper bush, and obtains a damping force by a squeeze action of the fluid film. For the purpose of stabilizing the damping characteristics of the fluid film, a structure in which a bearing support member that flexibly supports the damper bush is installed so as to reduce the eccentricity between the damper bush and the bearing housing has become the mainstream.

  A method for calculating the damping coefficient of such a fluid film damper is disclosed in, for example, “Hori, Vibration Engineering Handbook, Yokendo, (1976) 935” (Non-Patent Document 1). The damping coefficient C under the condition where there is no eccentricity is given by the following formula (1) from the short bearing width theory.

  Here, π is the circumference ratio, μ is the viscosity coefficient of the fluid, R is the damper diameter, L is the damper width, and c is the radial gap.

JP 2001-50267 A

Hori, Vibration Engineering Handbook, Yokendo, (1976) 935

  In the above-described damped bearing device, when the vibration amplitude of the rotor, which is the rotating shaft, increases and the damper bush and the bearing housing collide with each other, low-frequency vibration having a frequency that is an integral fraction of the rotational speed is generated. In particular, when the rotational speed is an integer multiple of the natural frequency of the rotor, there is a problem that subharmonic resonance occurs and the vibration amplitude of the rotor further increases. This phenomenon is attributed to the strong non-linearity that the rigidity of the fluid film damper increases rapidly due to the collision.

  As can be seen from Equation 1, in order to increase the damping coefficient of the fluid film damper, it is effective to reduce the radial gap of the fluid film damper. However, if the radial gap of the fluid film damper is reduced, the collision of the fluid film damper occurs even with a smaller vibration amplitude. Further, when the bearing support member of the damper bush is omitted for simplification of the structure, a collision occurs from a region where the vibration amplitude is relatively small.

  An object of the present invention is to provide a damping bearing device in which subharmonic resonance is unlikely to occur even when the radial gap of the fluid film damper is reduced and the damping coefficient thereof is increased so that the bearing portion and the bearing housing easily collide with each other. There is.

  In order to achieve the object, the present invention provides a fluid film in a bearing portion that rotatably supports a rotor, a bearing housing that is disposed on an outer peripheral side of the bearing portion, and a gap between the bearing portion and the bearing housing. A low-hardness surface film is formed on at least one of the bearing part and the fluid film forming surface of the bearing housing.

More preferred specific examples of the present invention are as follows.
(1) A low-viscosity liquid mainly composed of water is used as a working fluid for forming a fluid film of the fluid film damper.
(2) A surface film is formed on one of the bearing part and the fluid film forming surface of the bearing housing, and the contact rigidity between the surface film and the bearing part or the bearing housing facing the surface film is determined by the bearing part. And less than the contact rigidity between the bearing housing and the bearing housing.
(3) In addition to the above (2), the contact stiffness between the surface film and the bearing portion or the bearing housing facing the surface film is about half of the contact stiffness between the bearing portion and the bearing housing.
(4) The bearing portion is composed of a bearing and a damper bush fixed to the bearing, the outer peripheral surface of the damper bush is opposed to the inner peripheral surface of the bearing housing, and the surface film is formed on the outer peripheral surface of the damper bush. That formed.
(5) In addition to (4) above, the damper bush is provided in the bearing housing so as to be smoothly movable in the radial direction, and the bearing and the damper bush are detachably fixed.
(6) A bearing support member that flexibly supports the bearing portion is mounted on the bearing housing.

  According to the present invention, since the low hardness surface film is formed on at least one of the fluid film forming surfaces of the bearing part and the bearing housing, the radial gap of the fluid film damper is reduced and the damping coefficient thereof is increased to increase the bearing part and the bearing. Even if the housing easily collides, it is possible to provide a damped bearing device in which subharmonic resonance hardly occurs.

  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 damping bearing device according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a longitudinal sectional view showing a damping bearing device according to a first embodiment of the present invention. FIG. 2 is a diagram showing the rigidity characteristics of a fluid film damper in the damping bearing device of FIG. 3 is a diagram showing the vibration amplitude characteristics of the damping bearing device of FIG. 1 in comparison with the case without a surface film. 3A is a diagram showing the vibration amplitude of the conventional example, and FIG. 3B is a diagram showing the vibration amplitude of the present embodiment.

  As shown in FIG. 1, the damping bearing device 1 includes a bearing portion 20, a bearing housing 5, and a fluid film damper 15. The damping bearing device 1 of the present embodiment assumes a damping bearing device for a micro gas turbine.

  The rotor 2 that is a rotating shaft is rotatably supported by the bearing portion 20. The bearing portion 20 includes the bearing 3 and the damper bush 4. The bearing 3 is generally composed of a low-cost and highly reliable sliding bearing, and is disposed on the outer periphery of the rotor 2 to form a sliding portion with the rotor 2. The damper bush 4 is formed in a ring shape and is fixed to the outer periphery of the bearing 3. The bearing 3 and the damper bush 4 are detachably fixed by a bearing fixing bolt 10. By making these attachable and detachable, when either one is damaged or the performance is deteriorated, only the member whose damage or the performance is deteriorated can be replaced.

  A bearing housing 5 is disposed on the outer peripheral side of the damper bush 4. The damper bush 4 is flexibly supported by bearing support members 8 a and 8 b installed on both sides of the inner peripheral surface of the bearing housing 5. The support function of the bearing support members 8a and 8b and the fluid film 6 can be combined to support the bearing portion 20 satisfactorily. In this embodiment, a rubber O-ring is used as the bearing support member 8. Further, the damper bush 4 is restrained in the axial direction by the bearing cover 9. A slight gap is provided between the damper bush 4 and the bearing cover 9 so that the damper bush 4 can move smoothly in the radial direction. The bearing cover 9 is detachably fixed to the bearing housing 5 by bearing cover fixing bolts 11.

  The gap between the damper bush 4 and the bearing housing 5 is filled with the working fluid supplied from the fluid supply flow path 12, and a fluid film 6 is formed. The fluid supply flow path 12 extends radially inward from the outside of the bearing housing 5, and is opened at the center of the gap between the damper bush 4 and the bearing housing 5 so as to face the surface film 7.

  The vibration of the rotor 2 is transmitted to the damper bush 4 via the bearing 3 and functions as the fluid film damper 15 by changing the thickness of the fluid film 6. The working fluid of the fluid film damper 15 is discharged to the outside from a plurality of fluid discharge channels 14 provided in the damper bush 4. The fluid discharge channel 14 is provided on both the left and right sides of the fluid supply channel 12 so as to penetrate the surface film 7.

  In order to simplify the auxiliary machine configuration, the working fluid of the fluid film damper 15 and the lubricating fluid of the bearing 3 use the same fluid. From the viewpoint of reducing the loss of the bearing 3 and preventing freezing, a low viscosity liquid in which an antifreezing agent is mixed in water is used.

  A low hardness surface film 7 is formed on the surface of the damper bush 4 where the fluid film 6 is formed. The surface film 7 needs to be formed on at least one of the bearing film 20 and the fluid film forming surface of the bearing housing 5. In this embodiment, an inexpensive structure in which the surface film 7 is formed only on the outer peripheral surface of the damper bush 4 is employed. Specifically, the vibration isolating rubber is attached to the entire outer peripheral surface of the damper bush 4 and the surface. The film 7 is used. By providing the surface film 7 on the bearing portion 20 side, when the surface film 7 is damaged or the performance is lowered, the bearing portion 20 can be removed and replaced.

  FIG. 2 schematically shows the difference in rigidity characteristics of the fluid film damper 15 depending on the presence or absence of the low hardness surface film 7. When there is no surface film 7 with low hardness, as is apparent from the characteristics of the one-dot chain line in FIG. 2, the rigidity of the fluid film damper 15 is the bearing support member at the moment when the damper bush 4 and the bearing housing 5 collide. The rigidity of the damper bush 4 and the bearing housing 5 changes rapidly from the rigidity of FIG. 8 and the rigidity of the fluid film damper 15 has a strong non-linearity. Therefore, as shown in FIG. Wave resonance is likely to occur.

  On the other hand, when the low hardness surface film 7 is provided as in the present embodiment, the fluid film damper 15 has a rigidity from the rigidity of the bearing support member 8 to the low hardness surface film, as is apparent from the characteristics of the solid line in FIG. Since the transition to the contact stiffness between the damper bush 4 and the bearing housing 5 is made via the contact stiffness of 7, the nonlinearity of the stiffness of the fluid film damper 15 is alleviated, and as shown in FIG. Harmonic resonance is less likely to occur. As a result, vibrations caused by the damping bearing device 1 can be reduced and the reliability can be improved.

  FIG. 3A and FIG. 3B show calculation examples of the vibration frequency spectrum of the rotor 2 when there is no low hardness surface film 7 and when there is no surface film 7, respectively. The rotational speed of the rotor 2 in this calculation example is 200 Hz. In the calculation result when there is no surface film 7 with low hardness, as shown in FIG. 3 (a), due to the strong non-linearity of the fluid film damper 15, a fraction of the frequency of 100 Hz, which is half the rotational speed, is obtained. Harmonic resonance has occurred. On the other hand, as shown in FIG. 3B, the subharmonic resonance of the frequency of 100 Hz does not occur in the calculation result when the low hardness surface film 7 of this embodiment is present. From this, it can be seen that the subharmonic resonance can be suppressed by forming the low hardness surface film 7 on the surface on which the fluid film 15 is formed.

  In the present embodiment, since a low-viscosity liquid containing water as a main component is used as the working fluid of the fluid film damper 15, the fluid reaction of the fluid film damper is compared to the case of using high-viscosity oil or the like. The force is small, and collision between the damper bush 4 and the bearing housing 5 due to the breakage of the fluid film 6 is likely to occur. For this reason, while using a low-viscosity liquid as the working fluid of the fluid film 6, the effect of suppressing the subharmonic resonance when the surface film 7 with low hardness is formed on the surface on which the fluid film 6 is formed is remarkable. Further, since water is a fluid that easily causes corrosion, the surface film on the surface on which the fluid film 6 is formed is also effective from the viewpoint of preventing corrosion of the fluid film damper 15.

  The thickness of the low hardness surface film 7 is effective in the range of several tens of μm to several mm. That is, if the surface film 7 is too thin, the contact rigidity with the bearing housing 5 becomes too large, and if the surface film 7 is too thick, the damping capability of the squeeze film damper may be reduced. is there. When the contact rigidity of the low hardness surface film 7 is about ½ of the contact rigidity between the damper bush 4 and the bearing housing 5, the effect of suppressing the subharmonic resonance is the largest.

  The low hardness surface film 7 may be formed on the surface of the damper bush 4 where the fluid film 6 is formed as shown in FIG. 1, or may be formed on the surface of the bearing housing 5 where the fluid film 6 is formed. 4 and the bearing housing 5 may be formed. Further, a material other than rubber, such as a resin material, may be used as the material of the low-hardness surface film 7, a bearing metal material or the like may be used depending on use conditions, or a vibration-damping paint or the like may be applied. .

  In addition, depending on the use conditions, a fluid other than water, such as low-viscosity oil, may be employed as the working fluid of the fluid film damper 15, or another fluid may be used between the fluid film damper 15 and the bearing 3. good.

  Further, depending on use conditions, a bearing support member 8 other than a rubber O-ring such as a metal spring or a resin material may be used, or the bearing support member 8 may be omitted.

  Further, if the bearing 3 and the damper bush 4 are integrated without being divided, there is no advantage of the division, but the inexpensive bearing portion 20 can be obtained.

  Next, a second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a longitudinal sectional view of a damping bearing device according to a 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.

  In the second embodiment, the bearing portion 20 is composed only of the bearing 3, and a rolling bearing is used as the bearing 3. By using the rolling bearing 3, the loss of the bearing 3 can be reduced as compared with that using a sliding bearing. In the second embodiment, the outer peripheral surface of the rolling bearing 3 is the fluid film 6 forming surface, and the surface film 7 is directly formed on the outer peripheral surface. Therefore, the number of parts is reduced compared to the case where a damper bush is provided. it can. Furthermore, in the second embodiment, since the fluid discharge channel 14 is formed in the bearing housing 5 and the fluid discharge channel 14 is not formed in the rolling bearing 3, the rolling bearing 3 having a general structure can be used. . In the second embodiment, since the bearing support member 8 is omitted, the non-linearity of the rigidity of the fluid film damper 15 is increased, and subharmonic resonance is relatively likely to occur, but the number of components is reduced. it can.

  According to each of the above-described embodiments, since the surface film 7 having a low hardness is formed on the fluid film forming surface of the fluid film damper 15, a sudden change in rigidity due to the collision of the fluid film damper 15 can be reduced. It is difficult to generate wave resonance.

1 is a longitudinal sectional view showing a damping bearing device according to a first embodiment of the present invention. It is a figure which shows the rigidity characteristic of the fluid film | membrane damper in the damping bearing apparatus of FIG. 1 compared with the case where there is no surface film. It is a figure which shows the vibration amplitude characteristic of the attenuation | damping bearing apparatus of FIG. 1 compared with the case where there is no surface film. It is a longitudinal cross-sectional view of the damping bearing device of 2nd Example of this invention.

Explanation of symbols

1 ... Damping bearing device,
2 ... Rotor,
3 ... bearing,
4 ... Damper bush,
5 ... Bearing housing,
6 ... Fluid film,
7 ... low hardness surface film,
8 ... Bearing support member,
9 ... Bearing cover,
10: Bearing fixing bolt,
11 ... Bearing cover fixing bolt,
12 ... Fluid supply channel,
14 ... Fluid discharge channel,
15 ... Fluid film damper,
20 ... Bearing part.

Claims (7)

A bearing that rotatably supports the rotor;
A bearing housing disposed on the outer peripheral side of the bearing portion;
In a damping bearing device having a fluid film damper that forms a fluid film in a gap between the bearing portion and the bearing housing,
A low-hardness surface film is formed on at least one of the bearing part and the fluid film forming surface of the bearing housing.   2. The damping bearing device according to claim 1, wherein a low-viscosity liquid mainly composed of water is used as a working fluid for forming a fluid film of the fluid film damper.   The damping bearing device according to claim 1 or 2, wherein a surface film is formed on any one of the fluid film forming surfaces of the bearing part and the bearing housing, and the surface film and the bearing part facing the surface film or the A damping bearing device characterized in that a contact rigidity with a bearing housing is smaller than a contact rigidity between the bearing portion and the bearing housing.   4. The damping bearing device according to claim 3, wherein a contact rigidity between the surface film and the bearing portion or the bearing housing facing the surface film is about half of a contact rigidity between the bearing portion and the bearing housing. A damped bearing device.   The damping bearing device according to claim 1 or 2, wherein the bearing portion includes a bearing and a damper bush fixed to the bearing, and an outer peripheral surface of the damper bush is opposed to an inner peripheral surface of the bearing housing. A damping bearing device in which the surface film is formed on the outer peripheral surface of the damper bush.   6. The damping bearing device according to claim 5, wherein the damper bush is provided in the bearing housing so as to be smoothly movable in the radial direction, and the bearing and the damper bush are detachably fixed. Bearing device. 3. The damping bearing device according to claim 1, wherein a bearing support member that flexibly supports the bearing portion is attached to the bearing housing.

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