JP7482000B2 - Tilting pad journal bearing and rotating machine equipped with same - Google Patents

Description

The present invention relates to a tilting pad journal bearing and a rotating machine equipped with the same.

Generally, a rotating machine is composed of a rotating rotor, a journal bearing that supports the rotor so that it can rotate freely, and a stator such as a casing that fixes the journal bearing.

For example, in high-speed, large rotating machinery such as centrifugal compressors and turbines, tilting pad journal bearings are often used when the bearing surface pressure is relatively low. This is because, compared to other types of bearings such as circular bearings and elliptical bearings, the force that destabilizes the whirling vibration of the rotor caused by the oil film pressure in the bearing is smaller, making unstable vibration of the rotor less likely to occur.

As shown in FIG. 1 of Patent Document 1, for example, a tilting pad journal bearing has a structure in which multiple pads that support a rotor are arranged in the circumferential direction of the rotor. The pads are supported by the housing via pivots provided on the back surfaces of the pads. The pads can tilt in the circumferential direction around the pivots, making it possible to suppress the forces that destabilize the whirling vibration of the rotor.

In addition, if the gap formed by the rotor and the bearing becomes uneven in the axial direction due to rotor deflection or bearing misalignment, the oil film thickness becomes uneven in the axial direction, and the temperature of the oil film may rise locally. Generally, the rotor is unbalanced, and this unbalance causes unbalanced vibration. If the oil film thickness is uneven in the axial direction and the rotor vibrates unbalanced, an uneven temperature distribution occurs in the circumferential direction of the rotor's bearing part, and thermal bending may occur in the rotor. This thermal bending of the rotor causes further unbalance, and the vibration gradually increases. This is the thermal bending vibration phenomenon called the Morton effect, reported in Non-Patent Document 1.

In order to prevent thermal bending vibration, it is effective to make the oil film thickness uniform in the axial direction. For example, as disclosed in Fig. 1 of Patent Document 2, a method is known in which the pivot of the tilting pad is made a spherical pivot so that it tilts not only in the circumferential direction but also in the axial direction. This prevents the pad from tilting along the rotor, which would cause the oil film thickness to become non-uniform in the axial direction.
Also, as disclosed in FIG. 2 of Patent Document 2, for example, a method is known in which the entire housing supporting the tilting pad is tilted by a spherical liner to keep the oil film thickness uniform in the axial direction.

JP 2011-256773 A Japanese Patent Application Laid-Open No. 5-332355

deJongh, F. M., and Morton, P. G. “The synchronous instability of a compressor rotor due to bearing journal differential heating.” ASME Paper 94-GT-35 1-13. 1994

When a single-axis pivot is used in which the pads are tilted only in the circumferential direction, the portion supporting the load is in line contact. However, when a spherical pivot as shown in FIG. 1 of Patent Document 2 is used, the portion supporting the load is in point contact. For this reason, the spherical pivot's structure means that the surface pressure at the contact portion is large, which can be a design constraint. Therefore, if an attempt is made to change a tilting pad journal bearing with a single-axis pivot that is in line contact to a tilting pad journal bearing with a spherical pivot in order to suppress thermal bending vibration, it may become necessary to significantly reconsider the design.

The structure using a spherical liner as shown in Figure 2 of Patent Document 2 is considered to be effective against static non-uniformity such as initial deflection of the rotor and misalignment of the bearings. However, this structure has a relatively large movable range that covers the entire housing, and its mass is also large, so it has poor follow-up ability to the rotor and may not be able to deal with oil film non-uniformity in the axial direction that occurs dynamically due to vibration.

The object of the present invention is to provide a tilting pad journal bearing and a rotating machine equipped with the same that easily suppresses unevenness in the bearing oil film in the axial direction while suppressing the forces that destabilize the whirling vibration of the rotor, thereby preventing the occurrence of thermal bending vibration.

In order to achieve the above-mentioned object, the present invention provides a tilting pad type journal bearing comprising: a housing through which a rotor passes; a plurality of tiltable pads arranged between the rotor and the housing; and two non-contacting surfaces existing between the outer surfaces of the pads and the inner surface of the housing, wherein the two surfaces each have a single-axis pivot with an axis that serves as the tilt center oriented in a different direction from each other, and comprising a liner, an inner cleat, and an outer cleat arranged between the pads and the housing in that order from the radially inside, and the two surfaces being the outer surface of the inner cleat and the outer surface of the outer cleat .
The present invention also relates to a rotary machine including the tilting pad journal bearing and the rotor.

The present invention provides a tilting pad journal bearing and a rotating machine equipped with the same that easily suppresses unevenness in the bearing oil film in the axial direction while suppressing the forces that destabilize the whirling vibration of the rotor, thereby preventing the occurrence of thermal bending vibration.

1 is a cross-sectional view perpendicular to the central axis of a rotor in a tilting pad journal bearing according to a first embodiment of the present invention. FIG. FIG. 2 is an enlarged cross-sectional view parallel to the central axis of the rotor, showing details of the tilting structure and the housing in the tilting pad journal bearing according to the first embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view perpendicular to the central axis of the rotor, showing details of a tilting structure in the tilting pad journal bearing according to the first embodiment of the present invention. FIG. 1 is a longitudinal sectional view of a case where the present invention is applied to a centrifugal compressor, which is a representative rotary machine, as an example of a rotary machine of the present invention, and is a diagram showing an overall structure of a centrifugal compressor as a rotary machine. FIG. 5 is an enlarged cross-sectional view of a main portion of a tilting pad journal bearing according to a second embodiment of the present invention, taken along a line parallel to the central axis of a rotor.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described in detail with reference to the accompanying drawings.
In the drawings shown below, the same reference numerals are used to refer to common or similar components, and duplicated explanations will be omitted as appropriate. Furthermore, the size and shape of the components may be exaggerated or distorted for ease of explanation.

First Embodiment
FIG. 1 is a cross-sectional view perpendicular to the central axis CL (see FIG. 4) of a rotor 2 in a tilting pad journal bearing 1 according to a first embodiment of the present invention.

As shown in Figure 1, the tilting pad journal bearing 1 comprises a housing 7 through which the rotor 2 passes, and a number of tiltable pads 3 arranged between the rotor 2 and the housing 7. The housing 7 is annular. The rotor 2 and the housing 7 share a common central axis CL (see Figure 4). Hereinafter, the direction along the central axis CL will be referred to as the "axial direction", the direction extending perpendicular to the central axis CL from a point on the central axis CL as the "radial direction", and the circumferential direction centered on a point on the central axis CL as the "circumferential direction".

The tilting pad journal bearing 1 has a liner 4 and a cleat 5 arranged between the pad 3 and the housing 7, in that order from the inside in the radial direction. The pad 3 supports the rotor 2 via an oil film. The pad 3, the liner 4, and the cleat 5 constitute the tilting structure 6.

The tilting structure 6 is arranged in the circumferential direction around the rotor 2, for example, five places in FIG. 1. The tilting pad journal bearing 1 shown in FIG. 1 is a bearing with a load on pad structure in which one of the pads 3 is installed in the load direction of the rotor 2, indicated by W.

The tilting structure 6 is supported by a housing 7 arranged radially outward of the tilting structure 6 via a convex 1-axis pivot P1 provided on the outer surface 5a of the cleat 5. Here, the outer surface refers to the surface facing radially outward. The 1-axis pivot refers to a pivot that has only one axis that serves as the center of tilting and forms a line contact. The 1-axis pivot P1 allows the pad 3 to tilt in the circumferential direction. In other words, the axis that serves as the center of tilting of the 1-axis pivot P1 is a linear axis that is parallel to the central axis CL.

The housing 7 has a split structure and is made up of a pair of members that are split at the split surfaces 7a, 7a and joined together.

FIG. 2 is an enlarged cross-sectional view showing the tilting structure 6 and the housing 7 in detail, taken along a line parallel to the central axis CL of the rotor 2 (see FIG. 4).
The tilting structure in Fig. 2 is drawn with a slightly different dimensional relationship from the tilting structure in Fig. 1, but is essentially the same. Therefore, the tilting structure 6 and the housing 7 will be described in detail with reference to Fig. 2, which has the same reference numerals as those in Fig. 1.

As shown in FIG. 2, when assembling, first, the protruding parts 9, 9 provided on both axial sides of the cleat 5 of the tilting structure 6 are inserted into the grooves 8, 8 provided in the housing 7 from the half-split surface 7a of the housing 7 (see FIG. 1). Then, the tilting structure 6 is moved to a predetermined position in the circumferential direction. After moving, a pin 10 is inserted from the radial outside of the housing 7, and the tip of the pin 10 is inserted into a hole 11 provided in the cleat 5 of the tilting structure 6, thereby preventing the circumferential position of the tilting structure 6 from shifting. The pin 10 is fixed to the housing 7, for example, by screw fastening. Both the groove 8 and the hole 11 have dimensions such that a gap is formed that allows the tilting structure 6 to tilt. As a result, the circumferential position and radial position of the tilting structure 6 are maintained while allowing the tilting structure 6 to tilt (swing) in the circumferential direction.

The liner 4 and the cleat 5 are integrated together, for example by screwing them together with bolts (not shown). The outer surface 3a of the pad 3 contacts the liner 4 via a convex uniaxial pivot P2 provided on the inner surface 4b of the liner 4. Here, the inner surface refers to the surface facing radially inward. The uniaxial pivot P2 allows the pad 3 to tilt in the axial direction. In other words, the axis that is the center of tilting of the uniaxial pivot P2 is the axis tangential to a circle centered on a point on the central axis CL.

FIG. 3 is an enlarged cross-sectional view showing the tilting structure 6 in detail, taken along a line perpendicular to the central axis CL of the rotor 2. As shown in FIG.
As shown in FIG. 3, the pad 3 has a concave shape that is concave toward the outside in the radial direction, and has grooves 14, 14 facing each other on both sides in the circumferential direction of the pad 3 on the inner surface of the concave shape. In the liner 4 and the cleat 5 that are screwed together, the width of the liner 4 is longer than the width of the cleat 5. During assembly, both ends 13, 13 in the circumferential direction of the liner 4 are inserted into the grooves 14, 14. The grooves 14 provided in the pad 3 and the both ends 13 in the circumferential direction of the liner 4 hold the radial positions of the liner 4 and the cleat 5 relative to the pad 3. Then, the screwed liner 4 and the cleat 5 are slid from the axial end face of the pad 3 to the axial center position of the pad 3. After the movement, a pin 15 is inserted from the cleat 5 side, and the tip of the pin 15 is inserted into a hole 16 provided in the outer surface 3a of the pad 3, thereby preventing the pad 3 from being misaligned with the liner 4 and the cleat 5. The pin 15 is fixed to the cleat 5 or the liner 4 by, for example, screw fastening. Both the groove 14 and the hole 16 have dimensions such that a gap is formed that allows the pad 3 to tilt in the axial direction. For example, the groove 14 has a groove width that allows the liner 4 to tilt in the axial direction within the groove 14. These allow the pad 3 to tilt (swing) in the axial direction while maintaining the axial position of the pad 3.

The single-axis pivot P1, which allows tilting in the circumferential direction, and the single-axis pivot P2, which allows tilting in the axial direction, are both single-axis pivots that support loads through line contact. Therefore, the contact surface pressure at the pivot can be reduced compared to a spherical pivot, which is a point contact. This also makes it possible to replace existing journal bearings that use single-axis pivots that can tilt (swing) only in the circumferential direction without making major design changes. In addition, because the tilting structure 6 can be disassembled into the pad 3, liner 4, and cleat 5, in the event of a malfunction such as bearing burnout, the number of parts that need to be replaced can be minimized.

As described above, the tilting pad journal bearing 1 according to this embodiment includes a liner 4 and a cleat 5 arranged between the pad 3 and the housing 7 in that order from the inside in the radial direction. The outer surface 5a of the cleat 5 and the inner surface 4b of the liner 4 each have one-axis pivots P1 and P2 whose axes serving as the tilting centers are oriented in different directions.

In this embodiment, the two single-axis pivots P1 and P2 can be pivots on which the pad 3 can tilt in the circumferential direction and pivots on which the pad 3 can tilt in the axial direction, respectively. Therefore, the single-axis pivot P1 that can tilt in the circumferential direction can suppress the force that destabilizes the whirling vibration, while the single-axis pivot P2 that can tilt in the axial direction can suppress the oil film from becoming uneven in the axial direction. Furthermore, the single-axis pivots P1 and P2 and the surfaces that support the single-axis pivots P1 and P2 are in line contact, so that the contact surface pressure can be reduced. In addition, the movable range of the single-axis pivots P1 and P2 is limited to the vicinity of each pad 3 inside the housing 7, so that it is possible to follow the dynamic oil film unevenness in the axial direction and prevent thermal bending vibration.
Therefore, according to this embodiment, a tilting pad type journal bearing 1 can be provided that suppresses the forces that destabilize the whirling vibration of the rotor 2 while simply suppressing unevenness in the bearing oil film in the axial direction, thereby preventing the occurrence of thermal bending vibration.

In this embodiment, the outer surface 5a of the cleat 5 and the inner surface 4b of the liner 4 each have one-axis pivots P1, P2 whose axes serving as the center of tilting have different orientations, but the present invention is not limited to this.
That is, the tilting pad journal bearing 1 may have two surfaces (indicated as 4b and 5a in Figs. 1 to 3) that are not in contact with each other and are present between the outer surface 3a of the pad 3 and the inner surface 7b of the housing 7, and the two surfaces each have one-axis pivots P1 and P2 whose axes serving as the tilting centers are oriented in different directions. The two surfaces are surfaces of a plurality of members that constitute the tilting pad journal bearing 1. For example, in the case where the tilting pad journal bearing 1 is configured to include a liner 4 and a cleat 5, the two surfaces may be any one of the inner surface 4b of the liner 4, the outer surface 4a of the liner 4, the inner surface 5b of the cleat 5, and the outer surface 5a of the cleat 5. With such a configuration, the same effects as those of the above-mentioned embodiment can be achieved.

It is also possible to change the single-axis pivot P1 to a pivot that allows the pad 3 to tilt in the axial direction, and the single-axis pivot P2 to a pivot that allows the pad 3 to tilt in the circumferential direction.

FIG. 4 is a vertical sectional view of a centrifugal compressor 101, which is a representative rotary machine, as an example of the rotary machine of the present invention, and shows the overall structure of the centrifugal compressor 101 as a rotary machine.
As shown in Fig. 4, the centrifugal compressor 101 includes a casing 102 formed into a cylindrical shape or the like and serving as a stationary part (stator). A rotor 2 is rotatably supported within the casing 102 via the tilting pad journal bearing 1 of this embodiment and a thrust bearing 103. The rotor 2 is driven to rotate by the operation of a driver (not shown). The centrifugal compressor 101 includes a suction port 104 for sucking in gas and a discharge port 105 for discharging compressed gas.

In the tilting pad journal bearing 1, thermal bending vibration is likely to occur if the oil film thickness between the rotor 2 and the pads 3 of the tilting pad journal bearing 1 becomes non-uniform in the axial direction. In the tilting pad journal bearing 1 of this embodiment, the pads 3 tilt (swing) in the axial direction, thereby keeping the oil film thickness uniform in the axial direction and preventing the occurrence of thermal bending vibration.
In other words, according to this embodiment, it is possible to provide a rotating machine equipped with a tilting pad type journal bearing 1 that suppresses the forces that destabilize the whirling vibration of the rotor 2 while easily suppressing unevenness in the bearing oil film in the axial direction, thereby preventing the occurrence of thermal bending vibration.

Second Embodiment
Next, a second embodiment of the present invention will be described, focusing on the differences from the tilting pad type journal bearing 1 of the first embodiment described above, and a description of common points will be omitted as appropriate.
FIG. 5 is an enlarged cross-sectional view of a main portion of a tilting pad journal bearing 1 according to a second embodiment of the present invention, taken along a line parallel to the central axis CL (see FIG. 4) of the rotor 2.

As shown in FIG. 5, the second embodiment includes a liner 4, an inner cleat 201, and an outer cleat 202, which are arranged between the pad 3 and the housing 7 in this order from the inside in the radial direction. The pad 3, the liner 4, and the inner cleat 201 are fastened together, for example, by bolts (not shown), to form a pad structure 203. The liner 4 can be omitted.

The outer surface 201a of the inner cleat 201 is provided with a single-axis pivot P3 that makes the outer surface 201a of the inner cleat 201 convex. The single-axis pivot P3 allows the pad 3 to tilt in the circumferential direction. On the other hand, the outer surface 202a of the outer cleat 202 is provided with a single-axis pivot P4 that makes the outer surface 202a of the outer cleat 202 convex. The single-axis pivot P4 allows the pad 3 to tilt in the axial direction.

In the second embodiment, as in the first embodiment, the radial position of the pad structure 203 is maintained by a groove 8 provided in the housing 7 and protrusions 9 provided on both axial sides of the inner cleat 201. The circumferential position is maintained by a pin 205 fixed to the housing 7 that penetrates the outer cleat 202 and is inserted into a hole 204 provided in the inner cleat 201. This allows the pad 3 to tilt (swing) not only in the circumferential direction but also in the axial direction, making it possible to keep the oil film thickness uniform in the axial direction and prevent the occurrence of thermal bending vibration.
Therefore, like the first embodiment, the second embodiment also makes it possible to provide a tilting pad type journal bearing 1 that suppresses the forces that destabilize the whirling vibration of the rotor 2, while simply suppressing unevenness in the bearing oil film in the axial direction, thereby preventing the occurrence of thermal bending vibration.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-mentioned embodiments and includes various modified examples. For example, the above-mentioned embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those having all of the configurations described. In addition, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

REFERENCE SIGNS LIST 1 tilting pad journal bearing 2 rotor 3 pad 3a outer surface 4 liner 4a outer surface 4b inner surface 5 cleat 5a outer surface 5b inner surface 7 housing 7b inner surface 13 end 14 groove 15 pin 16 hole CL central axis P1 1-axis pivot P2 1-axis pivot 101 centrifugal compressor 201 inner cleat 201a outer surface 202 outer cleat 202a outer surface P3 1-axis pivot P4 1-axis pivot

Claims (5)

a housing through which the rotor passes;
a plurality of tiltable pads disposed between the rotor and the housing;
two non-contacting surfaces present between an outer surface of the pad and an inner surface of the housing;
The two surfaces each have a single-axis pivot whose axis serving as a tilt center is oriented in a different direction from each other,
a liner, an inner cleat, and an outer cleat arranged between the pad and the housing in this order from the inside in the radial direction;
2. A tilting pad journal bearing comprising: a first cleat member and a second cleat member; a second cleat member and a second cleat member; the single pivot on the outer surface of the inner cleat allows the pad to tilt relative to a circumferential direction of the housing;
2. The tilting pad journal bearing of claim 1 , wherein the single pivot on the outer surface of the outer cleat allows the pad to tilt relative to an axial direction of the housing. a housing through which the rotor passes;
a plurality of tiltable pads disposed between the rotor and the housing;
two non-contacting surfaces present between an outer surface of the pad and an inner surface of the housing;
The two surfaces each have a single-axis pivot whose axis serving as a tilt center is oriented in a different direction from each other,
a liner and a cleat disposed between the pad and the housing in this order from the inside in a radial direction;
the two surfaces being any one of an inner surface of the liner, an outer surface of the liner, an inner surface of the cleat, and an outer surface of the cleat;
the two surfaces being an inner surface of the liner and an outer surface of the cleat;
the single axis pivot on the inner surface of the liner allows the pad to tilt relative to an axial direction of the housing;
the single pivot on the outer surface of the cleat allows the pad to tilt relative to a circumferential direction of the housing;
The pad has a concave shape that is concave toward the outside in the radial direction, and has grooves facing each other on both sides in the circumferential direction of the pad on the inner surface of the concave shape,
The liner has both end portions on both sides in the circumferential direction inserted into the grooves,
A tilting pad journal bearing, wherein the groove has a groove width that allows the liner to tilt within the groove. The liner and the cleat are fixed to each other,
the pad has a hole disposed in an outer surface of the pad;
4. A tilting pad journal bearing as claimed in claim 3 , wherein a pin fixed to said cleat or said liner is inserted into said hole. A rotary machine comprising: the tilting pad journal bearing according to any one of claims 1 to 4 ; and the rotor.

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