JP2014085006A - Thrust bearing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thrust bearing capable of suppressing warp of a bearing surface (bearing plate), and thereby even in an initial step up to formation of a fluid lubricating film, capable of displaying excellent bearing load capacity according to a plan.SOLUTION: A thrust bearing 3 arranged opposite to a thrust collar 4 attached to a rotary shaft 1 includes an annular bearing plate 19 arranged opposite to the thrust collar 4 and a base part arranged opposite to a surface of the bearing plate 19, which is the opposite side surface of a surface opposite to the thrust collar 4, to support the bearing plate 19. In the bearing plate 19, a spiral groove for generating dynamic pressure is formed on a first surface opposite to the thrust color 4 and a spiral groove is formed on a second surface which is the opposite side surface of the first surface.

Description

  The present invention relates to a thrust bearing.

Conventionally, as a bearing for a high-speed rotating body, a thrust bearing is known that is disposed so as to face a thrust collar provided on a rotating shaft. Among such thrust bearings, a thrust dynamic pressure bearing that uses a dynamic pressure effect, for example, forms a spiral groove on the bearing surface and forms a fluid lubrication film between the thrust collar and the bearing surface, thereby providing the lubrication. The rotating shaft is supported through the membrane.
As such a thrust dynamic pressure bearing, in Patent Document 1, a bearing surface is formed of a flexible foil, for example, a metal thin plate having a thickness of about 100 μm, in order to absorb shaft vibration and shock, and the bearing surface is formed below the bearing surface. The one having a foil structure for flexibly supporting the bearing surface is disclosed.

In Patent Document 1, a foil (top foil) in which a spiral groove is formed on one surface (a surface facing the thrust collar) is used as a bearing surface (bearing plate). Etching grooves are also formed in each foil inserted under the bearing surface, and the foils are overlapped so that the grooves are alternated to function like a spring.
Therefore, in the bearing disclosed in Patent Document 1, since the bearing surface is flexible, the movement of the rotating shaft caused by vibration or impact, that is, the axial movement of the thrust collar and the vibration of the thrust collar (surface runout). ) Can be absorbed to some extent.

Japanese Patent Application Laid-Open No. 06-073437

  By the way, when groove processing is performed on one side of a thin metal plate, the balance of residual stresses on both sides of the plate is lost, and the metal plate is warped. That is, since compressive stress remains in the thin metal plate during the rolling process, if a groove is formed on one side, the processed surface side is released from the compressive stress, and a stress difference occurs between the back side where the residual stress remains, Warping occurs. Therefore, when the spiral groove is machined on one surface of the top foil that becomes the bearing surface (bearing plate), the top foil warps for the same reason.

  If this warpage is large, the gap between the thrust collar and the top foil becomes non-uniform, especially at the initial stage after the rotation of the rotating shaft until the fluid lubrication film is formed and the warp is flattened. The load capacity will not be demonstrated. If the warpage is larger, the warpage is not flattened even when the fluid lubricating film is formed. Therefore, in the worst case, the top foil may be kept in contact with the thrust collar and may be seized.

  The present invention has been made in view of the above circumstances, and an object thereof is to suppress warping of the bearing surface (bearing plate), and as a result, even at the initial stage until the fluid lubrication film is formed. It is an object of the present invention to provide a thrust bearing capable of exhibiting a good bearing load capability.

The thrust bearing of the present invention is a thrust bearing disposed to face a thrust collar provided on a rotating shaft,
An annular bearing plate disposed to face the thrust collar;
The bearing plate is disposed to face the surface opposite to the surface facing the thrust collar, and includes a base portion that supports the bearing plate,
In the bearing plate, a spiral groove for generating dynamic pressure is formed on a first surface facing the thrust collar, and a spiral groove is formed on a second surface opposite to the first surface. It is characterized by.

  According to this thrust bearing, the spiral groove for generating dynamic pressure is formed on the first surface of the bearing plate facing the thrust collar, and the spiral groove is formed on the second surface opposite to the first surface. Therefore, by forming spiral grooves not only on the first surface but also on the second surface, the difference in compressive stress remaining on both surfaces of the bearing plate is reduced, so that warpage due to the stress difference is caused in the bearing plate. Occurrence is suppressed.

In the thrust bearing, it is preferable that the spiral groove on the second surface is formed in the same shape as the spiral groove on the first surface.
In this way, the difference in compressive stress remaining on both surfaces of the bearing plate is almost eliminated, and therefore the occurrence of warpage is prevented.
Further, the thrust bearing is generally used by being disposed on both sides of the thrust collar, and in this case, the thrust collars having different directions on one side and the other side are used. That is, conventionally, different bearing plates are used on one side and the other side of the thrust collar. On the other hand, the bearing plate in this thrust bearing should be used on both the one side and the other side of the thrust collar with the same bearing plate by using the spiral groove on the first surface and the spiral groove on the second surface. Is possible. Therefore, it is possible to reduce the cost by enabling common parts.

In the thrust bearing, it is preferable that the spiral groove on the second surface is formed symmetrically with respect to the spiral groove on the first surface.
In this way, there is no difference in compressive stress remaining on both surfaces of the bearing plate, and therefore warpage is reliably prevented.
Further, the same bearing plate can be used for both the one side and the other side of the thrust collar, so that the parts can be shared and the cost can be reduced.
Further, the back side (second surface) of the land portion between the grooves formed on the first surface of the bearing plate is always a land portion, and therefore the land portion formed on the first surface corresponds to the land of the corresponding portion of the second surface. By being supported by the portion, the bearing plate is hardly bent. Thereby, the thrust bearing comes to exhibit a good load capacity as designed.

  In the thrust bearing, the spiral groove on the first surface is preferably a pump-in spiral groove.

  According to the thrust bearing of the present invention, the spiral groove is formed not only on the first surface but also on the second surface of the bearing plate, thereby reducing the difference in compressive stress remaining on both surfaces of the bearing plate. Therefore, the bearing load capacity as designed can be exhibited even at the initial stage until the fluid lubrication film is formed. Therefore, it is possible to reliably avoid the inconvenience that the bearing plate continues to contact the thrust collar and falls into seizure.

It is a schematic diagram which shows an example of the turbomachine to which the thrust bearing which concerns on this invention is applied. (A) is a sectional side view which shows schematic structure of 1st Embodiment of the thrust bearing which concerns on this invention, (b) is an AA arrow directional view of (a). It is a figure which shows schematic structure of a bearing foil (bearing plate), (a) is a top view which shows 1st surface (front surface), (b) is a side view, (c) is a plane which shows 2nd surface (back surface). FIG. It is a graph which shows distribution of the pressure (dynamic pressure) of a fluid lubricating film. It is a top view of the bearing surface which shows the modification of a spiral groove. (A) is side sectional drawing which shows schematic structure of 2nd Embodiment of the thrust bearing which concerns on this invention, (b) is an effect | action explanatory drawing of the thrust bearing shown to (a), (c) is shown to (a). It is a figure which shows the modification of the other thrust bearing. It is a top view of the bearing surface which shows the modification of a spiral groove.

Hereinafter, the thrust bearing of the present invention will be described in detail with reference to the drawings. In the following drawings, the scale of each member is appropriately changed to make each member a recognizable size.
FIG. 1 is a side view schematically showing an example of a turbo machine to which a thrust bearing of the present invention is applied. In FIG. 1, reference numeral 1 denotes a rotating shaft, 2 denotes an impeller provided at the tip of the rotating shaft, 3 Is a thrust bearing according to the present invention.

A thrust collar 4 is fixed to the rotary shaft 1 on the side where the impeller 2 is formed, and a thrust bearing 3 is disposed on the thrust collar 4 so as to sandwich the thrust collar 4.
The impeller 2 is disposed in a housing 5 on the stationary side, and has a tip clearance 6 between the impeller 2 and the housing 5.
The rotary shaft 1 is provided with a radial bearing 7 on the center side of the thrust collar 4.

  FIGS. 2A and 2B are views showing a first embodiment of a thrust bearing applied to the turbomachine having such a configuration, where FIG. 2A is a side sectional view, and FIG. It is an AA line arrow directional view. In addition, (a) is the figure seen by the cross section by the BB line of (b). The thrust bearing 3 </ b> A (3) of the first embodiment has bearing portions 30, 30 disposed on both sides of the thrust collar 4, and the bearing portions 30, 30 are integrated through a bearing spacer 31. It is a thing.

  The bearing portions 30 and 30 are formed in the same configuration as each other, and are disposed symmetrically with the thrust collar 4 interposed therebetween. These bearing portions 30 are annular (cylindrical) members disposed opposite to the disc-shaped thrust collar 4 fixed to the rotating shaft 1, and are provided in a state of being extrapolated to the rotating shaft 1. . The bearing portion 30 includes a bearing layer 8 disposed to face the thrust collar 4, and a base plate 9 disposed to face a surface of the bearing layer 8 opposite to the surface facing the thrust collar 4. , And an annular spring (elastic support portion) 10 disposed between the bearing layer 8 and the base plate 9.

  In the present embodiment, the bearing layer 8 is formed by overlapping three bearing foils 19, 20, and 21. The three bearing foils 19, 20, and 21 are all made of a metal and an annular plate having a through hole 8 a for inserting the rotating shaft 1. Of these bearing foils 19, 20, and 21, the bearing foil 19 on the thrust collar 4 side functions as a bearing plate in the present invention, and has a thickness of, for example, about 0.2 mm. ) To (c), spiral grooves 11 (16) are formed on both the front and back surfaces. 3A is a plan view showing the first surface (surface) 19a of the bearing foil 19, FIG. 3B is a side view of the bearing foil 19, and FIG. 3C is a second view of the bearing foil 19. As shown in FIG. It is a top view which shows the surface (back surface) 19b.

  As shown in FIGS. 2 (b) and 3 (a), the bearing foil 19 has a dynamic pressure generating spiral on a surface facing the thrust collar 4, that is, a first surface (surface) 19a serving as a bearing surface. The groove 11 is formed with a depth of about 30 to 40 μm. The spiral groove 11 is a well-known pump-in type, in which a number of spiral grooves (spiral grooves) 11a are arranged at equal intervals along the circumferential direction. All are formed with the same inflow angle. However, in the spiral groove in the present invention, the spiral grooves do not necessarily have the same inflow angle. For example, the spiral grooves are different in some spiral grooves, or are different in one spiral groove. Even if it is a spiral groove for dynamic pressure generation like this, it shall be a pump-in type spiral groove for dynamic pressure generation in the present invention.

  The spiral groove 11a is formed to extend from the outer peripheral end of the first surface 19a to an annular land 11b provided around the through hole 8a. The land 11b has an outer surface at a relatively high position (outside position) with respect to the bottom surface of the spiral groove 11a. A land (not shown) is also formed between the spiral grooves 11a and 11a.

  With such a configuration, when the thrust collar 4 rotates, the spiral groove 11 (spiral groove 11a) causes the fluid around the bearing to be drawn from the outer peripheral side of the first surface 19a to the inner peripheral side along the spiral groove 11a. As a result, a fluid lubricating film is formed between the thrust collar 4 and the first surface 19a. In addition, the fluid drawn in by the spiral groove 11 (spiral groove 11a) is impeded by the land 11b and the flow thereof is blocked, so that the dynamic pressure is maintained. Get higher. That is, the fluid lubricating film formed by the spiral groove 11 (spiral groove 11a) has a pressure distribution that is higher on the inner peripheral side than on the outer peripheral side of the first surface 19a.

  FIG. 4 is a graph showing the distribution of pressure (dynamic pressure) of such a fluid lubricating film. The horizontal axis in FIG. 4 indicates the distance (position) [r] in the radial direction from the center on the first surface 19a shown in FIG. 2B (the longer it goes to the right), and the vertical axis indicates fluid lubrication. The pressure (dynamic pressure) [P] of the film is shown (the higher the value goes to the upper side). Also, (1) in the graph of FIG. 4 shows the pressure at the inner peripheral edge of the land 11b in FIG. 2 (b), (2) shows the pressure at the outer peripheral edge of the land 11b, and (3) The pressure at the outer peripheral edge of the first surface 19a is shown.

As shown in FIG. 4, within the range from the outer peripheral edge (3) of the first surface 19a to the outer peripheral edge (2) of the land 11b, the pressure of the fluid lubricating film (from the outer peripheral side to the inner peripheral side) (Dynamic pressure) is continuously increased. Further, even when viewed from the entire first surface 19a, the pressure (dynamic pressure) of the fluid lubricating film is highest at the outer peripheral edge (2) of the land 11b, that is, the inner peripheral end of the region where the spiral groove 11 is formed. Yes.
In the present invention, an expression showing the relationship between the radial distance [r] and the fluid lubricating film pressure [P] shown in such a graph (FIG. 4) is defined as P (r).

  Further, as shown in FIG. 3C, the bearing foil 19 has a spiral groove 16 formed on the second surface (back surface) 19b. The spiral groove 16 faces the opposite side of the thrust collar 4, that is, the bearing foil 20 in FIG. 2, so that it does not function for generating dynamic pressure and is a dummy groove. In this embodiment, as shown in FIGS. 3A and 3C, the spiral groove 16 has the same shape as the spiral groove 11 of the first surface 19a and is formed symmetrically with the spiral groove 11. Yes. That is, the spiral groove 11 on the first surface 19a and the spiral groove 16 on the second surface 19b are not only the same in shape and number of the spiral grooves 11a but also in the same phase, only in the direction. Are formed opposite to each other.

  These spiral grooves 11 and 16 are formed by etching the base material (metal foil). Therefore, the etching process on the first surface 19a and the etching process on the second surface 19b can be performed under the same conditions by using, for example, the same mask in reverse, thereby facilitating process management. it can. Since the spiral grooves 11 and 16 having the same shape are formed on the first surface 19a and the second surface 19b in this way, the bearing foil 19 has no difference in compressive stress remaining on both surfaces. Yes. Accordingly, the bearing foil 19 is a flat thin plate without warping, unlike a conventional bearing plate in which a spiral groove is formed only on one surface. That is, the occurrence of warpage is reliably prevented.

  Further, the bearing foil 19 may be a bearing foil 19 disposed on the upper side (one side) of the thrust collar 4 in FIG. 2A or a bearing foil 19 disposed on the lower side (the other side). It can be used.

  That is, on the one side and the other side of the thrust collar 4, those having different directions are used so that the direction of the spiral groove is plane-symmetric. Therefore, conventionally, different bearing plates are used on one side and the other side of the thrust collar 4. On the other hand, the bearing foil 19 of the present embodiment is used by, for example, properly using the first surface 19a so as to face the thrust collar 4 on one side and the second surface 19b so as to face the thrust collar 4 on the other side. The same bearing foil 19 can be used on both one side and the other side of the thrust collar 4. That is, it can be used by making the second surface 19b function as the first surface on the other side.

  Further, in the bearing foil 19, the spiral groove 11a formed on the first surface 19a is formed symmetrically with the spiral groove 11 of the first surface 19a and the spiral groove 16 of the second surface 19b. The back side (second surface 19b) of the land portion between 11a is always the same land portion. Therefore, the land portion formed on the first surface 19a is supported by the land portion corresponding to the second surface 19b during the operation of the thrust bearing 3A (3), so that the bearing foil 19 is hardly bent.

  Further, as shown in FIG. 2B, the bearing foil 19 is formed with a plurality of holding pieces 12 extending from the outer peripheral edge at the outer peripheral portion thereof. In the present embodiment, the holding pieces 12 are formed at positions that divide the circumference of the bearing foil 19 into four equal parts, and thus a total of four holding pieces 12 are formed. These holding pieces 12 are arranged in a notch 32 formed in the bearing spacer 31, whereby the bearing foil 19 is held by the bearing spacer 31. The depth of the notch 32 is sufficiently deeper than the thickness of the holding piece 12, and the width is formed wider than the width of the holding piece 12.

  With this configuration, the holding piece 12 can be displaced in the depth direction in the notch 32 and can also be displaced in the width direction (the circumferential direction of the bearing spacer 31). Yes. The portion where the holding piece 12 is formed is slightly smaller than the entire circumference of the bearing foil 19, and in many portions where the holding piece 12 is not formed, the bearing foil 19 is not supported by the bearing spacer 31. That is, there is no support point.

  The bearing foils 20 and 21 that form the bearing layer 8 other than the bearing foil 19 are formed in the same shape and the same dimensions as the bearing foil 19. However, unlike the bearing foil 19, these bearing foils 20 and 21 are not formed with spiral grooves on the first and second surfaces thereof, and are merely thin circular plates. The bearing foils 20 and 21 are each formed to have a thickness of about 0.2 mm to 0.6 mm.

  As shown in FIG. 2 (a), the base plate 9 is a metal annular plate (substantially cylindrical) having a through hole 9 a for inserting the rotary shaft 1, and a thrust collar in the bearing layer 8. It is arranged so as to face the surface opposite to the 4 side. The base plate 9 is fixed to the bearing spacer 31 with a bolt 33 via an annular spring 10, and is further fixed to a casing 35 of the turbomachine with the bolt 33. In this embodiment, as shown in FIG. 2B, eight bolt holes 34 are formed in the bearing spacer 31, and therefore the thrust bearing 3 </ b> A (3) of the present embodiment has a casing formed by eight bolts 33. 35 is fixed.

  In the base plate 9, a protruding portion 13 is formed on the inner peripheral portion of the surface facing the bearing layer 8 with a predetermined gap therebetween. The protrusion 13 is formed in a cylindrical shape, and is half the diameter of the land 11b from the position corresponding to the inner peripheral edge of the land 11b of the bearing foil 19 shown in FIG. It is formed to have a width (thickness) up to a certain position. Further, the front end face is arranged with respect to the bearing layer 8 so that the predetermined gap is 20 to 30 μm, and is fixed to the bearing spacer 31.

  Further, the outer peripheral portion of the base plate 9 also protrudes in a cylindrical shape, and this protruding cylindrical portion is a fixed portion 14 that is connected and fixed to the bearing spacer 31 via the annular spring 10. . That is, a bolt hole (not shown) through which the bolt 33 is inserted is formed in the fixing portion 14, and the fixing portion 14 (base plate 9) is fixed to the bearing spacer 31 by the bolt 33. It is fixed to the casing 35. Further, the fixed portion 14 is formed at a lower height than the protruding portion 13, whereby the annular spring 10 is sandwiched between the fixed portion 14 and the bearing spacer 31. ing. And since the fixing | fixed part 14 was formed in the outer peripheral part in this way, and the protrusion part 13 was formed in the inner peripheral part, the relative recessed part is formed in the base plate 9 in the center part.

  The annular spring 10 is made of metal and has an annular plate shape, and a bolt hole (not shown) through which the bolt 33 is inserted is formed on the outer peripheral portion thereof. Thereby, as described above, the annular spring 10 is sandwiched between the fixing portion 14 of the base plate 9 and the bearing spacer 31 and is fixed to the bearing spacer 31 by the bolt 33 and also fixed to the casing 35. ing. The annular spring 10 is formed with a thickness of about 1 mm, for example, and an annular thick portion 15 is formed on the inner peripheral side thereof.

  The thick portion 15 is formed so as to project symmetrically on both the front and back surfaces of the annular spring 10, and in particular, the convex portion formed on the surface of the bearing layer 8 facing the bearing foil 21 is a bearing foil. It abuts on 21 (bearing layer 8) and supports it. Since the thick portion 15 is formed so as to protrude on both the front and back surfaces of the annular spring 10, the annular spring 10 is less likely to warp. In addition, although the protrusion height of the thick part 15 can be changed by design, it is formed to about 50 μm, for example.

  The annular spring 10 having such a thick portion 15 is arranged on the inner peripheral side thereof, that is, on the thick portion 15 side in the concave portion of the base plate 9, so that the inner peripheral side is in the concave portion. The bearing layer 8 and the base plate 9 can be elastically deformed, that is, can be displaced. Thus, the annular spring 10 is an elastic support portion that elastically supports the central portion in the radial direction of the bearing layer 8 with the thick portion 15. The annular spring 10 and the base plate 9 form a base portion of the present invention.

  Here, the radial central portion of the bearing layer 8 does not mean only the central position in the radial direction of the bearing layer 8, that is, the central point (line) position, and the central point (line) position and its position. It means the range including the neighborhood. Specifically, a weighted average position of the bearing layer 8 is employed as such a radial center part, and in this embodiment, the annular spring 10 is disposed so that the thick part 15 abuts on this position. ing.

  The weighted average position of the bearing layer 8, that is, the position Rc at which the thick portion 15 is brought into contact with and supported by the bearing layer 8 (bearing foil 21) is obtained by the following equation. However, Rc is a distance (radius) from the center of the bearing layer 8 (bearing foil 21).

Rc = [2π∫rP (r) rdr] / [2π∫P (r) rdr] [Formula]
In the above formula, P (r) is a formula showing the relationship between the radial distance [r] shown in FIG. 4 and the pressure [P] of the fluid lubricating film as described above. R is the distance (position) in the radial direction shown in FIG. 4, and P is the pressure (dynamic pressure) of the fluid lubricating film.
In the above formula, the denominator [2π∫P (r) rdr] represents the sum of loads acting on the bearing surface, and the numerator [2π∫rP (r) rdr] represents the sum of moments.
Note that the radial width of the thick portion 15 is determined by structural analysis so as not to concentrate stress, and is, for example, about 1/10 of the Rc.

  The bearing spacer 31 is made of metal and cylindrical as shown in FIGS. 2A and 2B, and its inner diameter is slightly larger than the outer diameter of the bearing layer 8 (outer diameter excluding the holding piece 12). Has been. As a result, the bearing spacer 31 accommodates the bearing layer 8 therein while allowing a certain amount of backlash in the surface direction of the bearing layer 8 to some extent. Further, as described above, the bearing spacer 31 holds the holding piece 12 of the bearing layer 8 in the notch portion 32, so that the holding piece 12 can be displaced in the depth direction of the notch portion 32. And it can also be displaced in the width direction (the circumferential direction of the bearing spacer 31).

  Here, as shown in FIG. 2A, the bearing layer 8 has a surface opposite to the thrust collar 4, that is, the back surface (second surface) of the bearing foil 21 supported by the annular spring 10. The holding piece 12 is urged toward the inner surface (bottom face) side of the notch 32, whereby the bearing foils 19, 20, 21 constituting the bearing layer 8 are held by the bearing spacer 31. At that time, the bearing layer 8 is arranged with a predetermined gap of about 20 to 30 μm with respect to the protruding portion 13 of the base plate 9 as described above. In addition, the bearing layer 8 is not supported by the bearing spacer 31 at a portion where the holding piece 12 is not formed, and therefore, the outer peripheral side has no support point. Accordingly, the outer peripheral side of the bearing layer 8 is a free end that is not substantially supported by the bearing spacer 31.

Next, the operation of the thrust bearing 3A (3) having such a configuration will be described.
When the rotary shaft 1 rotates at a high speed, a fluid lubricating film is formed by the dynamic pressure formed by the spiral groove 11 between the thrust collar 4 and the bearing surface (first surface 19a) of the bearing foil 19 of the bearing layer 8. As a result, the thrust bearing 3A (3) supports the thrust collar 4 through the formed fluid lubricating film.

At this time, since the bearing foil 19 is a flat thin plate without warping as described above, the bearing foil 19 is thrust even in the initial period from when the rotating shaft 1 starts to rotate until the fluid lubricating film is formed. There is no contact with the collar 4, so that the bearing load capacity as designed is exhibited even at the initial stage.
The dynamic pressure of the formed fluid lubrication film is high on the inner peripheral side of the thrust bearing 3A (3) and lower on the outer peripheral side as described above.

  Further, when a thrust load is applied to the rotary shaft 1, the thrust load is transmitted to the bearing layer 8 (bearing foil 19) through a fluid lubricating film formed between the thrust collar 4 and the first surface 19a. When the thrust load further increases, the bearing layer 8 starts to deform (move) in the axial direction while pushing the annular spring 10 that supports the bearing layer 8.

At that time, the bearing layer 8 is not supported on the inner peripheral side in the initial state, and on the other hand, the fluid film pressure on the inner peripheral side (dynamic pressure of the fluid lubricating film) is high. It will bend.
When the amount of bending reaches an amount corresponding to the gap with the protruding portion 13 of the base plate 9 and the inner peripheral side of the bearing layer 8 contacts the protruding portion 13, the inner peripheral side of the bearing layer 8 is bent (deformed). That is, the movement of the rotating shaft 1 (thrust collar 4) in the axial direction stops.

  When the thrust load further increases from this state, the annular spring 10 is further pushed in by the bearing layer 8, and the outer peripheral side of the bearing layer 8 starts to bend. When the outer peripheral side is bent, the outer peripheral side is bent outward so that the bearing layer 8 has a “C” shape in a side view, but the inner peripheral side contacts the protruding portion 13 of the base plate 9. Since they are in contact with each other, they are not displaced in the axial movement of the rotary shaft 1.

Accordingly, since the inner peripheral side where the high-pressure fluid lubricating film is generated is rigidly supported by contact with the base plate 9, the bending of the bearing layer 8 on the inner peripheral side is restricted and does not bend more than necessary. As a result, a desired dynamic pressure is likely to be generated in the fluid lubricating film even on the inner peripheral side, so that a decrease in the bearing load capacity of the bearing 3A (3) is suppressed.
In addition, since the center portion of the bearing layer 8 is supported by the annular spring 10, if the thickness of the bearing layer 8 is appropriately designed in advance, the first surface 19a of the bearing foil 19 serving as the bearing surface is the outer periphery. Only slightly tilted in the direction. Therefore, since local bending of the bearing foil 19 is difficult to occur, a reduction in load capacity is further suppressed.

  Further, the rotation shaft 1 may vibrate slightly from the center of rotation due to the unbalance of the rotation shaft, the influence of the external environment, the operating condition, and the like. The collar 4 may also vibrate slightly and run out of surface, resulting in an instantaneously tilted state. Moreover, it may be in a similar tilted state due to an impact. At that time, the bearing layer 8 is only supported by the annular spring 10 from the central portion to the outer peripheral portion thereof, and thus is deformed (inclined) along the thrust collar 4. Therefore, the thickness of the fluid lubricating film is not extremely narrowed and is kept constant, and thus it is difficult to break. Thereby, the inclination by the vibration of the thrust collar 4 etc. comes to be favorably absorbed by the bearing 3A (3).

Further, when the thrust collar 4 is tilted (surface runout), the plurality of bearing foils 19, 20, and 21 forming the bearing layer 8 rub against each other, so that the above-mentioned whirling vibration is better damped by the friction. Can be made.
Further, when the bearing layer 8 is deformed, sliding with the annular spring 10 occurs and energy is dissipated by friction, so that the movement (mainly tilting movement) of the rotating shaft due to vibration or impact can be attenuated.

  According to the thrust bearing 3A (3) of the present embodiment, the spiral groove is formed not only on the first surface 19a but also on the second surface 19b in the bearing foil 19 functioning as the bearing plate of the present invention. It is possible to reduce the difference in compressive stress remaining on both surfaces and eliminate the warp caused by the stress difference. Therefore, by providing the bearing foil 19 having no warp, the thrust bearing 3A (3) can exhibit a good bearing load capability as designed even at the initial stage until the fluid lubrication film is formed. Can do. Therefore, it is possible to surely avoid the inconvenience that the bearing foil 19 continues to contact the thrust collar 4 and falls into the seizure.

Further, the bearing foil 19 can be used on one side or the other side of the thrust collar 4 by properly using the spiral groove 11 on the first surface 19a and the spiral groove 16 on the second surface 19b. Therefore, it is possible to reduce the cost by making the parts common.
Further, the back side (second surface 19b) of the land portion between the spiral grooves 11a and 11a formed on the first surface (bearing surface) 19a of the bearing foil 19 is also necessarily the land portion, and thus formed on the first surface 19a. Since the land portion is supported by the land portion corresponding to the second surface 19b, the bearing foil 19 is less likely to bend. Thereby, the thrust bearing comes to exhibit a good load capacity as designed.

Further, in the thrust bearing 3A (3), even if a thrust load (static load) increases and the dynamic pressure increases, the movement of the bearing layer 8 toward the base plate 9 is restricted as described above. Therefore, the movement of the rotating shaft 1 in the axial direction is sufficiently limited. Therefore, for example, when this thrust bearing 3A (3) is applied to the rotating shaft 1 having the impeller 2 of the turbomachine, the impeller 2 moves in the axial direction, so that the impeller 2 is moved to the housing (stationary part) of the outer side ) The possibility of touching 5 is eliminated.
Further, on the inner peripheral side where the dynamic pressure of the fluid lubrication film is increased, the support state of the bearing layer 8 is rigidly switched by the protruding portion 13 when the dynamic pressure becomes higher than the set value. Since it does not bend much more than necessary, and therefore it is easy to generate a desired dynamic pressure on the inner peripheral side, a decrease in the bearing load capacity of the bearing 3A (3) is suppressed. Further, since the bearing layer 8 can be deformed so as to follow the inclination of the thrust collar 4, the inclination due to vibration (surface runout) of the thrust collar 4 can be absorbed better.
Further, since the bearing layer 8, the base plate 9, the annular spring 10, and the bearing spacer 31 are all made of metal, the bearing layer 8, the base plate 9, the annular spring 10, and the bearing spacer 31 can be applied to a rotating machine used in a high temperature environment. (3) can be applied to, for example, a supercharger.

  In the above-described embodiment, the spiral groove 16 on the second surface 19b of the bearing foil 19 functioning as the bearing plate in the present invention is formed in the same shape as the spiral groove 11 on the first surface 19a and symmetrical with the surface. For example, it may be formed by shifting the phase without making the plane symmetric only by using the same shape. Even in such a case, it is possible to eliminate warpage and to reduce the cost by making it possible to share parts.

  Further, the spiral groove of the second surface 19b may be formed by changing the shape and number of grooves, for example, without forming the same shape as the spiral groove 11 of the first surface 19a. In this case, the depth of the spiral groove on the second surface is the same as that of the spiral groove 11 on the first surface 19a, and the cutting amount at the time of forming the groove, that is, the volume of the entire groove, is set to It is preferable that the volume of the groove 11 is approximately the same. By doing in this way, the difference of the compressive stress between the 1st surface 19a and the 2nd surface 19b can be made small, and generation | occurrence | production of the curvature resulting from a stress difference can be suppressed.

  Moreover, about the spiral groove of the 1st surface 19a, the thing of a various form other than the form shown in FIG.2 (b) and FIG.3 (a) is employable. For example, as shown in FIG. 5, a first groove group 40A composed of a plurality of first spiral grooves 40 formed on the inner peripheral side of the first surface (bearing surface), and a first groove group 40A that is first. A pump-in type spiral groove 42 having a second groove group 41 </ b> A formed of a plurality of second spiral grooves 41 formed on the outer peripheral side of the surface and circulating in the same direction as the first spiral groove 40 is employed. be able to.

  On the first surface on which the spiral groove 42 is formed, an annular land portion 43 is formed on the inner circumferential side from the first groove group 40A, that is, on the side where fluid is drawn. In addition, a part of the first spiral grooves 40 in the first groove group 40A and a part of the second spiral grooves 41 in the second groove group 41A are at least one part and a partial communication portion that communicates with the other. 44 is continuous.

  In the bearing foil in which such spiral grooves 42 are formed, a part of the first spiral grooves 40 in the first groove group 40A and a part of the second spiral grooves 41 in the second groove group 41A are: Since it continues through the partial communication portion 44, a part of the lubricating fluid that has flowed along a part of the second spiral groove 41 in the second groove group 41 </ b> A on the outer peripheral side is partly connected portion 44. Is temporarily dammed, and a high membrane pressure is generated at the partial communication portion 44. Further, the remaining portion passes through the first spiral groove 40 in the first groove group 40A on the inner peripheral side, reaches the land portion 43 on the side where the lubricating fluid is drawn, and here also generates a high film pressure. Further, such a side flow that deviates from the main flow along the spiral grooves 41 and 40 becomes a flow in the circumferential direction and overcomes the lands 45 and 46 between the spiral grooves to generate a film pressure.

  From the above, the pressure (film pressure) of the lubricating film made of the lubricating fluid formed on the first surface is a film whose film pressure distribution is high at one place like the bearing foil 19 shown in FIG. Unlike the case of having a pressure (peak pressure), the pressure distribution is a distribution in which the film pressure is dispersed as a whole, and the maximum film pressure is also lower than the conventional pressure. Therefore, the fluid lubricating film is less likely to break and can be used without being seized up to a higher bearing load, and the margin for sudden load due to disturbance or the like can be increased.

  In the above embodiment, the bearing layer 8 is formed by superimposing the three bearing foils 19, 20, and 21, and the bearing foil 19 on the thrust collar 4 side functions as the bearing plate of the present invention. You may make it form the bearing board of this invention by a single foil, without overlapping foil. Further, the bearing layer may be formed by stacking two or four or more bearing foils.

  6A to 6C are views showing a second embodiment of a thrust bearing applied to the turbomachine shown in FIG. The thrust bearing 3B (3) of the second embodiment is disposed on the impeller 2 side in FIG. In this embodiment, the thrust bearing 3 disposed on the impeller 2 side in FIG. 1 is the same as the thrust bearing 3 disposed on the opposite side of the thrust collar 4 in FIG. 1, that is, on the radial bearing 7 side. It consists of the following.

  As shown in FIG. 6A, the thrust bearing 3B (3) is an annular (cylindrical) member disposed opposite to the disc-shaped thrust collar 4 fixed to the rotating shaft 1, and the rotating shaft 1 is provided by extrapolation. The thrust bearing 3B (3) is disposed to face a bearing layer 50 disposed to face the thrust collar 4, and to a surface of the bearing layer 50 opposite to the surface facing the thrust collar 4. And a base plate (base part) 51.

  In this embodiment, the bearing layer 50 is formed by laminating three foils 10, 11, 12, which are in the form of an annular thin plate, and are formed in an annular plate shape as a whole. It has a through hole 50a. The three foils are all formed in the same size and dimensions in the planar shape, and are a top foil 52, a first back foil 53, and a second back foil 54 in order from the thrust collar 4 side. .

  The top foil 52 functions as a bearing plate in the present invention. Like the bearing foil 19 shown in FIGS. 2 (b), 3 (a), and 3 (c), the top foil 52 is opposed to the thrust collar 4. A spiral groove (not shown) for generating dynamic pressure is formed on one surface (bearing surface) 52a, and a spiral groove (not shown) is also formed on the second surface 52b opposite to the first surface 52a. Therefore, the top foil 52 is a flat thin plate without warping. The spiral groove on the second surface 52b does not function for generating dynamic pressure as in the first embodiment. However, when the parts are made common so that the top foil (bearing plate) 52 can be used on one side or the other side of the thrust collar 4, as in the first embodiment, the first side is the second side. Two surfaces function as the first surface.

  The top foil 52 is made of, for example, an alloy such as stainless steel or Inconel (registered trademark), or a metal, and is a thin plate having a thickness of about 0.1 mm to 0.3 mm. Moreover, the 1st back foil 53 and the 2nd back foil 54 consist of metals, such as copper, and a damping alloy, and are thin plate-shaped things about 0.05 mm-0.1 mm in thickness. It should be noted that the first back foil 53 and the second back foil 54 may be coated on the surface to enhance the damping effect due to friction.

  The base plate 51 is in the shape of an annular plate (substantially cylindrical) having a through-hole 51a through which the rotary shaft 1 is inserted, and is heat resistant made of an alloy such as stainless steel or a metal. The second back foil 54 is disposed opposite to the second back foil 54. The base plate 51 is fixed to a casing or the like (not shown) with screws or the like, and is held in a fixed state.

  Further, the surface of the base plate 51 that faces the second back foil 54 is disposed on the outer peripheral side thereof, and is disposed on the inner peripheral side of the first surface portion 51b. And a second surface portion 51c. The recess 55 is formed continuously along the entire circumferential direction of the base plate 51. That is, the recess 55 is formed in an annular shape in plan view. Further, the recess 55 is formed so that the depth thereof continuously increases from the inner peripheral side toward the outer peripheral end in the radial direction of the base plate 51. Accordingly, the base plate 51 has a tapered surface formed by the recess 55, and the thickness thereof is continuously reduced from the inner peripheral side toward the outer peripheral end.

Further, the inner peripheral edge 55 a of the recess 55 is located on the outer peripheral side of the inner peripheral end 56 a of the surface on which the recess 55 is formed. Therefore, the second surface portion 51 c (between the inner peripheral end 56 a of the surface on which the concave portion 55 is formed and the end edge 55 a on the inner peripheral side of the concave portion 55) is a flat surface 56.
Under such a configuration, the bearing layer 50 is supported by the base plate 51 with the second back foil 54 normally contacting only the flat surface 56.

Here, the width of the first surface portion 51b (the length in the radial direction of the base plate 51) and the width of the second surface portion 51c (the radius of the base plate 51) on the surface of the base plate 51 facing the second back foil 54. The length in the direction is preferably designed as follows.
When giving priority to the bearing load capability of the thrust bearing 3B (3), the width (the length in the radial direction) of the flat surface 15 is increased.

  If priority is given to the followability of the bearing surface (first surface) 52a with respect to the thrust collar 4 and the damping effect is to be enhanced, the width (the length in the radial direction) of the flat surface 15 is reduced to reduce the bearing layer 50. To make it easier to tilt. In particular, when the followability of the bearing surface 52 a with respect to the thrust collar 4 is to be given the highest priority, the entire surface facing the second back foil 54 may be the recess 55 without forming the flat surface 56. Also in this case, since the inner peripheral end of the concave portion 55 (the inner peripheral end of the base plate 51) is not recessed from other portions in the concave portion 55, the bearing load capability is exhibited by the inner peripheral end.

  In the thrust bearing 3B (3) having such a configuration, when the rotary shaft 1 rotates at a high speed, the dynamic bearing formed by the spiral groove for generating dynamic pressure is formed between the thrust collar 4 and the bearing surface 52a of the bearing layer 50. A fluid lubrication film is formed by the pressure, whereby the thrust bearing 3B (3) supports the thrust collar 4 through the formed fluid lubrication film.

  At this time, since the top foil 52 is a flat thin plate without warping as described above, the top foil 52 is thrust even in the initial period from when the rotating shaft 1 starts to rotate until the fluid lubricating film is formed. There is no contact with the collar 4, so that the bearing load capacity as designed is exhibited even at the initial stage. The dynamic pressure of the formed fluid lubricating film is high on the inner peripheral side of the thrust bearing 3B (3) and low on the outer peripheral side.

  Further, the rotation shaft 1 may vibrate slightly from the center of rotation due to the unbalance of the rotation shaft, the influence of the external environment, the operating condition, and the like. The collar 4 also vibrates slightly and shakes the surface, and instantaneously tilts as shown in FIG.

At this time, in the thrust bearing 3B (3) of the present embodiment, the recess 55 is formed in the base plate 51, and the depth of the recess 55 is continuously increased from the inner peripheral side toward the outer peripheral end. Therefore, the bearing layer 50 is supported by the base plate 51 in which the recess 55 is formed, so that the dynamic pressure of the fluid lubrication film is higher on the inner peripheral side than on the outer peripheral side where the dynamic pressure is lower. Bending rigidity is high and functions as a relatively strong spring. That is, since the bearing layer 50 has a cantilever shape in which only the inner peripheral side is held by the base plate 51, the bearing layer 50 functions as a spring having a weak force on the outer peripheral side, whereas the force is exerted on the inner peripheral side. It functions as a strong spring.
Therefore, since the inner circumference side of the top foil 52 hardly bends, a desired dynamic pressure is generated in the fluid lubricating film on the inner circumference side, and the thrust bearing 3B (3) has a reduced bearing load capability. Is suppressed.

  Further, since the depth of the concave portion 55 is continuously increased from the inner peripheral side toward the outer peripheral end, the outer peripheral side of the bearing layer 50 is easily deformed to the base plate 51 side. 1 surface) 52a follows the thrust collar 4 well, and as shown on the left side of FIG. 6B, the fluid lubricating film between the thrust collar 4 and the bearing surface (first surface) 52a of the top foil 52 The thickness (the gap between the thrust collar 4 and the bearing surface 52a of the top foil 52) is kept constant, and the fluid lubricating film is difficult to break. That is, since the outer peripheral side is easily bent, the inclination of the thrust collar 4 can be easily followed.

  Further, a flat surface 56 is formed on the surface of the base plate 51 where the recess 55 is formed, and the bearing layer 50 is supported by the flat surface 56, so that the bearing layer 50 presses the flat surface 56. In this case, the bearing layer 50 will not be bent (bend). Therefore, for example, even if a thrust load (static load) increases, the flat surface 56 suppresses the bearing layer 50 from moving toward the base plate 51, so that the rotary shaft 1 moves in the axial direction. Be restricted.

  Furthermore, since the bearing layer 50 is configured by laminating the three foils 52, 53, 54, the rotating shaft 1 is inclined as shown in FIG. 6B due to unbalance or disturbance, for example. The bearing layer 50 that follows the whirling vibration via the thrust collar 4 acts to attenuate the whirling vibration by the friction of the laminated foils against each other.

  According to the thrust bearing 3B (3) of the present embodiment, similarly to the thrust bearing 3A (3) of the first embodiment, not only the first surface 52a but also the second surface 52b are formed on the top foil 52 that functions as a bearing plate. In addition, since the spiral groove is formed, the top foil 52 is not warped. Therefore, the thrust bearing 3B (3) has a good bearing load capacity as designed even at the initial stage until the fluid lubrication film is formed. To come out. Therefore, it is possible to surely avoid the inconvenience that the top foil 52 continues to contact the thrust collar 4 and falls into the seizure.

Further, the top foil 52 can be used on one side or the other side of the thrust collar 4 by properly using the spiral groove on the first surface 52a and the spiral groove on the second surface 52b. Can be shared, and cost reduction can be achieved.
Further, since the back side (second surface 52b) of the land portion between the spiral grooves formed on the first surface (bearing surface) 52a of the top foil 52 is also a land portion, the top foil 52 is difficult to bend. Thrust bearings will exhibit good load capacity as designed.

  Even if the thrust load (static load) increases, the bearing layer 50 is restrained from moving toward the base plate 51 as described above, so that the rotary shaft 1 is sufficiently moved in the axial direction. Limited. Therefore, when this thrust bearing 3 (3B) is applied to the rotating shaft 1 having the impeller 2 of the turbomachine as shown in FIG. 1, the rotating shaft 1 moves in the direction of the arrow in FIG. By doing so, there is no possibility that the impeller 3 comes into contact with the outer housing (stationary part) 5. Thereby, the tip clearance 6 between the tip of the impeller 3 and the housing 5 can be reduced, and the efficiency of the turbomachine can be increased.

Further, on the inner peripheral side where the dynamic pressure of the fluid lubricating film increases, the bearing layer 50 does not bend more than necessary, so that a desired dynamic pressure is likely to be generated at this portion, so that the bearing 3B (3). It is possible to suppress a decrease in bearing load capacity.
Further, since the recess 55 is formed in the base plate 51, the bearing layer 50 follows the tilt even if the thrust shaft vibrates so as to tilt and the thrust collar is tilted (surface runout). In this case, the friction generated between the foils 52, 53, and 54 constituting the bearing layer 50 acts so as to attenuate the whirling vibration of the rotating shaft 1, so that the bearing function is more stably exhibited. be able to.

In the embodiment, as shown in FIGS. 6A and 6B, the bottom surface of the recess 55 is a flat inclined surface. For example, the depth of the recess 55 is the inner peripheral side of the base plate 51. As long as it is formed so as to be continuously deeper from the outer periphery toward the outer peripheral end, it may be a curved surface curved as shown in FIG.
In the embodiment, the number of foils constituting the bearing layer 50 is three, but it may be one, two, or four or more.

The present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention.
For example, in the above embodiment, a pump-in spiral groove is used as a dynamic pressure generating spiral groove formed on the first surface of the bearing plate. Instead, as shown in FIG. 7, a pump-out spiral groove is used. 60 can also be adopted. In FIG. 7, reference numeral 61 denotes a bearing plate, 62 denotes a spiral groove, and 63 denotes an outermost peripheral land portion.

Even in this bearing plate 61, the second surface opposite to the first surface (bearing surface) 60a on which the pump-out spiral groove 60 is formed is preferably the same shape as the spiral groove 60 of the first surface 60a. More preferably, a plane-symmetric spiral groove is formed.
Such a bearing plate 61 can be used, for example, as a bearing foil (top foil) of Patent Document 1. That is, by using the bearing plate 61 according to the present invention as a bearing foil (top foil) in the thrust bearing of Patent Document 1, the thrust bearing of the present invention can be obtained.

DESCRIPTION OF SYMBOLS 1 ... Rotating shaft 3, 3A, 3B ... Thrust bearing, 4 ... Thrust collar, 8 ... Bearing layer, 9 ... Base plate (base part), 10 ... Ring spring (base part), 11 ... Spiral groove, 11a ... Spiral groove, 16 ... spiral groove, 19 ... bearing foil (bearing plate), 19a ... first surface, 19b ... second surface, 42 ... spiral groove, 50 ... bearing layer, 51 ... base plate (base portion), 52 ... top foil (bearing plate), 60 ... pump-out spiral groove, 60a ... bearing surface (first surface), 61 ... bearing plate

Claims (4)

A thrust bearing disposed opposite to a thrust collar provided on a rotating shaft,
An annular bearing plate disposed to face the thrust collar;
The bearing plate is disposed to face the surface opposite to the surface facing the thrust collar, and includes a base portion that supports the bearing plate,
In the bearing plate, a spiral groove for generating dynamic pressure is formed on a first surface facing the thrust collar, and a spiral groove is formed on a second surface opposite to the first surface. Thrust bearing characterized by.   2. The thrust bearing according to claim 1, wherein the spiral groove on the second surface is formed in the same shape as the spiral groove on the first surface.   2. The thrust bearing according to claim 1, wherein the spiral groove on the second surface is formed symmetrically with respect to the spiral groove on the first surface.   The thrust bearing according to any one of claims 1 to 3, wherein the spiral groove on the first surface is a pump-in spiral groove.

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