JP6541946B2 - Foil bearing and foil provided thereto - Google Patents

Description

  The present invention relates to a foil bearing.

  Foil bearings have attracted attention as bearings for supporting the main shaft of turbomachines such as gas turbines and turbochargers. A foil bearing constitutes a bearing surface with a thin film (foil) having low rigidity and flexibility for bending, and supports a load by allowing deflection of the bearing surface. During rotation of the shaft, a fluid film (for example, an air film) is formed between the outer peripheral surface of the shaft and the bearing surface of the foil, and the shaft is supported in a noncontact manner. In this case, the flexibility of the foil automatically forms an appropriate bearing gap according to the operating conditions such as the rotational speed and load of the shaft, ambient temperature, etc., resulting in excellent stability and general air dynamic pressure. It can be used at high speed compared to bearings.

  For example, Patent Document 1 below shows a so-called multi-arc type foil bearing in which both circumferential ends of a plurality of foils are held in contact with each other on the inner peripheral surface of a cylindrical foil holder. In this foil bearing, the effect of damping the vibration of the shaft is obtained by micro-sliding between each foil and the foil holder during rotation of the shaft.

JP 2014-119094 A

  However, even with the above foil bearings, the vibration damping effect of the shaft may not be sufficient.

  Therefore, the problem to be solved by the present invention is to further enhance the vibration damping effect of the shaft in the multi-arc type foil bearing.

  In order to solve the above problems, the present invention comprises a foil holder and a plurality of foils attached to the inner circumferential surface of the foil holder, and the circumferential ends of each foil are held in contact with the foil holder A plurality of first regions and second regions axially adjacent to each of the foils, wherein a part of the boundaries between the two regions is divided and another part of the boundaries between the two regions is connected Provide a bearing.

  Thus, the rigidity of each foil is reduced by dividing a part of the boundary between the first region and the second region of each foil. As a result, the freedom of deformation of each foil is increased, and each foil is easily deformed, so that the amount of sliding between each foil and the foil holder is increased, and a high damping effect is exerted against unstable vibration of the shaft. be able to. On the other hand, in the above-described foil bearing, the first region and the second region of each foil are not completely separated, and the other portion (region other than the divided portion) of the boundary between the two regions is connected. As a result, even when a load is generated only in one of the regions of each foil, for example, as when a vibration in the conical mode occurs in the shaft, the load is also transmitted to the other region through the connecting portion to deform and slide. By moving, a higher vibration damping effect can be obtained than when two completely separated foils are arranged in a double row.

  The above-mentioned foil bearing is provided on a top foil portion having a bearing surface and one circumferential end side of the top foil portion in each of the first area and the second area of each foil, and the inner peripheral surface of the foil holder And an under-foil portion provided on the other end side in the circumferential direction of the top foil portion and disposed between an adjacent foil and the inner circumferential surface of the foil holder. It is preferable to provide.

  Further, in the above-described foil bearing, the insertion portions provided in the first area and the second area of each foil are connected to each other, and the top foil parts and the under foil parts of both areas are circumferentially extended all over The division reduces the rigidity of the top foil portion and the under foil portion and makes them easy to slide on the inner peripheral surface of the foil holder, thereby enhancing the vibration suppression effect.

  In addition, the above-mentioned foil bearing gradually narrows the axial width toward one circumferential side at the other circumferential end of the under foil portion provided in the first area and the second area of each foil. A notch can be provided. As a result, a step is formed along the notched portion on the top foil portion of the adjacent foil overlapped on the inner circumferential side of the under-foiled portion of each foil, and the step causes the fluid to flow along the axis of each notched portion Collected in the center of the direction, the pressure of the fluid is increased to improve the bearing rigidity.

  As described above, according to the foil bearing of the present invention, the vibration damping effect of the shaft in the multi-arc type foil bearing can be enhanced.

It is a figure which shows the structure of a gas turbine notionally. It is sectional drawing which shows the support structure of the rotor in the said gas turbine. FIG. 5 is a cross-sectional view of a foil bearing according to an embodiment of the present invention incorporated into the support structure. It is a top view of the foil provided in the above-mentioned foil bearing. It is a top view which shows the state which connected the several foil. FIG. 4 is an enlarged cross-sectional view of the foil bearing of FIG. 3; It is a top view which shows the other example of a foil.

  FIG. 1 conceptually shows the configuration of a gas turbine which is a type of turbomachine. This gas turbine mainly includes a turbine 1 and a compressor 2 forming a cascade, a generator 3, a combustor 4 and a regenerator 5. The turbine 1, the compressor 2, and the generator 3 are provided with a common main shaft 6 extending in the horizontal direction, and the main shaft 6 and the turbine 1 and the compressor 2 constitute an integrally rotatable rotor. The air taken in from the air inlet 7 is compressed by the compressor 2, heated by the regenerator 5, and fed to the combustor 4. The compressed air is mixed with fuel and burned, and the turbine 1 is rotated by the high temperature, high pressure gas. The rotational force of the turbine 1 is transmitted to the generator 3 via the main shaft 6 to generate electricity as the generator 3 rotates, and this electric power is output via the inverter 8. Since the gas after rotating the turbine 1 is at a relatively high temperature, this gas is sent to the regenerator 5 to exchange heat with the compressed air before combustion to reheat the heat of the gas after combustion. Use The gas whose heat exchange has been completed by the regenerator 5 is discharged as exhaust gas after passing through the exhaust heat recovery device 9.

  FIG. 2 shows an example of the support structure of the rotor in the gas turbine. In this support structure, the radial bearings 10 are disposed at two places in the axial direction, and the thrust bearings 20, 20 are disposed on both sides in the axial direction of the flange portion 6 b provided on the main shaft 6. The main shaft 6 is rotatably supported in the radial direction and in both thrust directions by the radial bearing 10 and the thrust bearing 20.

  In this support structure, the area between the turbine 1 and the compressor 2 is a high temperature atmosphere because it is adjacent to the turbine 1 rotated with a high temperature, high pressure gas. In this high-temperature atmosphere, since a lubricant composed of a lubricant and grease is degraded and evaporated, it is difficult to apply a normal bearing (rolling bearing or the like) using such a lubricant. Therefore, air dynamic bearings, in particular foil bearings, are suitable as the bearings 10, 20 used in this type of support structure.

  Hereinafter, the configuration of the foil bearing 10 compatible with the radial bearing for the gas turbine will be described based on the drawings.

  As shown in FIG. 3, the foil bearing 10 has a cylindrical (cylindrical in the illustrated example) foil holder 11 and a plurality of (three in the illustrated example) foils 12 attached to the inner peripheral surface of the foil holder 11. Have. The outer peripheral surface of the foil holder 11 is fixed to the inner peripheral surface 31 of the housing 30 of the gas turbine.

  The foil holder 11 is formed of, for example, a metal such as a sintered metal or a molten material. The illustrated foil holder 11 has a cylindrical inner peripheral surface 11 a and an outer peripheral surface 11 b. The axial direction groove | channel 11c as a recessed part is formed in the multiple places (3 places in the example of illustration) spaced apart to the circumferential direction among the internal peripheral surfaces 11a. Both axial ends of each axial groove 11 c are open to the end face of the foil holder 11.

  The foil 12 is formed by pressing or electric discharge machining on a metal foil which is rich in elasticity and has good workability, such as a steel material or a copper alloy and having a thickness of about 20 μm to 200 μm. In the case of an air dynamic bearing using air as a fluid film as in the present embodiment, it is preferable to use stainless steel or bronze metal foil as no lubricating oil exists in the atmosphere.

  Each foil 12 consists of the 1st area | region 12a and the 2nd area | region 12b which were arranged in axial direction, as shown in FIG.

  The first region 12a includes a top foil portion 12a1 having a bearing surface, an insertion portion 12a2 provided on one circumferential end of the top foil portion 12a1, and an under provided on the other circumferential end of the top foil portion 12a1. And a foil portion 12a3. In the example of illustration, the insertion part 12a2 is provided in the axial direction both ends of the circumferential direction one end part of the top foil part 12a1. The under foil portion 12a3 is provided with a notch 12a4 whose axial width is gradually narrowed toward one circumferential end. In the illustrated example, the notch 12a4 is formed in a substantially arc shape. Besides, the notch 12a4 may be substantially V-shaped by bending a straight line at the center in the axial direction. In the circumferential direction one end of the top foil portion 12a1, a minute notch 12a5 in the circumferential direction is provided at a position close to the insertion portion 12a2. At the boundary between the top foil portion 12a1 and the under foil portion 12a3, an axial slit 12a6 into which the insertion portion 12a2 of the adjacent foil 12 is inserted is formed. In the illustrated example, slits 12a6 are formed at both axial ends of the boundary between the top foil portion 12a1 and the under foil portion 12a3.

  The second region 12b has a shape similar to that of the first region 12a, and has a top foil portion 12b1, an insertion portion 12b2, an under foil portion 12b3, a notch portion 12b4, a notch 12b5, a slit 12b6, etc. Omitted).

  In each foil, a part of the boundary between the first area 12a and the second area 12b is divided, and the other part of the boundary between both areas 12a and 12b is connected. For example, of the two regions 12a and 12b, regions having no bearing surface (the insertion portions 12a2 and 12b2 and the under foil portions 12a3 and 12b3) are connected to each other and a region having a bearing surface (top foil portions 12a1 and 12b1 ) Are divided all over the circumferential direction. In the present embodiment, the insertion portions 12a2 and 12b2 of the two regions 12a and 12b are connected to each other, and between the top foil portions 12a1 and 12b1 of the two regions 12a and 12b and between the underfoil portions 12a3 and 12b3. A circumferential slit 12c is formed to divide the entire circumferential direction.

  As shown in FIG. 5, the three foils 12 can be temporarily assembled in a tubular shape by inserting the insertion portions 12a2 and 12b2 of the respective foils 12 into the slits 12a6 and 12b6 of the adjacent foils. By inserting this temporary assembly into the inner periphery of the foil holder 11, the foil bearing 10 is assembled. Specifically, inserting the temporary assembly of the three foils 12 into the inner periphery of the foil holder 11, while inserting the insertion portions 12a2 and 12b2 of the respective foils 12 into the axial grooves 11c of the foil holder 11, one end side in the axial direction Plug in from As described above, the three foils 12 are attached to the inner circumferential surface 11 a of the foil holder 11 in the circumferential direction.

  With the three foils 12 assembled to the foil holder 11, both circumferential ends of each foil 12 are held in contact with the foil holder 11. In the example of illustration, the circumferential direction both ends of each foil 12 are distribute | arranged to the back (outer diameter side) of the adjacent foil 12, respectively. Specifically, the insertion portions 12a2 and 12b2 provided at one circumferential end of each foil 12 are inserted into the axial grooves 11c of the inner circumferential surface 11a of the foil holder 11 via the slits 12a6 and 12b6 of the adjacent foils 12, respectively. Inserted. On the other hand, the under foil portions 12a3 and 12b3 provided at the other circumferential end of each foil 12 are disposed between the top foil portions 12a1 and 12b1 of the adjacent foil 12 and the inner circumferential surface 11a of the foil holder 11 The top foil portions 12a1 and 12b1 of the foil 12 are supported from behind (see FIG. 6). Adjacent foils 12 engage with each other in the circumferential direction and are in tension with each other. As a result, the top foil portions 12a1 and 12b1 of the respective foils 12 project to the outer diameter side, and are curved in a shape along the inner peripheral surface 11a of the foil holder 11.

  When the main shaft 6 rotates in the direction of the arrow in FIG. 3, the air film in the radial bearing gap between the inner diameter surface (bearing surface) of the top foil portions 12a1 and 12b1 of each foil 12 of the foil bearing 10 and the outer peripheral surface 6a of the main shaft 6 Pressure is increased. As shown in FIG. 6, the area including the circumferential direction one end (end on the leading side in the rotational direction) of the top foil portions 12a1 and 12b1 runs on the underfoil portions 12a3 and 12b3 of the adjacent foils, so the bearing surface is And gradually approach the outer peripheral surface 6 a of the main shaft 6 toward the leading side in the rotational direction. Thus, a radial bearing gap gradually narrowed toward the leading side in the rotational direction is formed between the bearing surface of each foil 12 and the outer peripheral surface 6a of the main shaft 6, and air flows on the narrow side of the radial bearing gap. Pushed in. As a result, the pressure of the air film in the radial bearing gap is increased, and the main shaft 6 is supported in a non-contact manner in the radial direction by this pressure.

  At this time, due to the flexibility of the foil 12, the bearing surface of each foil 12 is arbitrarily deformed according to the operating conditions such as the load, the rotational speed of the main shaft 6, the ambient temperature, etc. Automatically adjusted to the appropriate width according to. Therefore, even under severe conditions such as high temperature and high speed rotation, the radial bearing gap can be managed to the optimum width, and the main shaft 6 can be supported stably. When the main shaft 6 is rotating, each foil 12 is pushed forward in the rotational direction by friction with fluid (air) flowing as the main shaft 6 rotates, and the axial groove 11 c of the foil holder 11 Butt against corner 11c1 of

  In the present embodiment, as shown in FIG. 4, the under foil portions 12a3 and 12b3 are provided with the notch portions 12a4 and 12b4, respectively, and the top foil portions 12a1 and 12b1 that ride on the under foil portions 12a4 and 12b4 are provided A step is formed. As a result, the fluid flowing along the top foil portions 12a1 and 12b1 flows along the steps and is collected at the axial center side, thereby enhancing the pressure improvement effect (see the arrow in FIG. 5).

  At this time, by providing minute notches 12a5 and 12b5 in the vicinity of the insertion portions 12a2 and 12b2 in one circumferential end of the top foil portions 12a1 and 12b1, the rigidity of this portion is reduced. As a result, the top foil portions 12a1 and 12b1 can be easily deformed along the notch portions 12a4 and 12b4 of the under foil portions 12a3 and 12b3 disposed behind the top foil portions 12a1 and 12b1.

  Also, each foil 12 is not completely fixed to the foil holder 11, and can be moved relative to the foil holder 11. Therefore, while the main shaft 6 is rotating, the foil 12 is pressed against the foil holder 11 by the influence of the air film formed in the radial bearing gap, and accordingly, each foil 12 and the foil holder 11, in particular, the top of each foil 12 Minute sliding occurs between the outer diameter surfaces of the foil portions 12a1 and 12b1 and the under foil portions 12a3 and 12b3 and the inner peripheral surface 11a of the foil holder 11. The vibration energy of the main shaft 6 can be damped by the frictional energy due to the minute sliding.

  In the present embodiment, as shown in FIG. 4, slits 12 c are provided at the boundary between the first region 12 a and the second region 12 b of each foil 12 to divide the two regions 12 a and 12 b. Stiffness decreases. Thereby, the freedom of deformation of the foil 12 is enhanced, the foil 12 is easily deformed, and the effect of damping the vibration of the main shaft 6 is enhanced. In particular, in the illustrated example, since the slits 12c are formed over the entire circumferential direction between the top foil portions 12a1 and 12b1 and the under foil portions 12a3 and 12b3 in surface contact with the inner peripheral surface 11a of the foil holder 11, vibration damping The effect is further enhanced.

  Moreover, in said foil bearing 10, area | regions (in the example of illustration, insertion part 12a2, 12b2) are connected among the boundaries of the 1st area | region 12a of each foil, and the 2nd area | region 12b. . Thus, even if, for example, vibration in the conical mode occurs in the main shaft 6 and a load is generated only in the first area 12a, the load is also transmitted to the second area 12b via the coupling portion, so only in the first area 12a Alternatively, the second region 12b can be deformed to slide on the foil holder 11, thereby further enhancing the vibration damping effect.

  At the time of low speed rotation immediately before the main shaft 6 stops or immediately after start-up, the bearing surface of each foil 12 and the outer peripheral surface of the main shaft 6 contact and slide, DLC film, titanium aluminum nitride on one or both of them A low friction film such as a ride film, a tungsten disulfide film, or a molybdenum disulfide film may be formed. Also, in order to adjust the frictional force due to micro-sliding between the foil 12 and the foil holder 11, one or both of these may be provided with the above-described low-friction coating.

  The present invention is not limited to the above embodiment. For example, the embodiment shown in FIG. 7 differs from the above embodiment in that the notches 12a4 and 12b4 are omitted. In this case, the other circumferential ends of the under foil portions 12 a 3 and 12 b 3 are in the form of a straight line extending in the axial direction.

  In the above embodiment, the first area 12a and the second area 12b are divided by the slits 12c having an axial width. However, the present invention is not limited to this. For example, both areas 12a and 12b can be You may divide by the cut which does not have axial width.

  Moreover, although the case where the circumferential direction width of the opening part of the groove | channel 11c formed in the internal peripheral surface 11a of the foil holder 11 was comparatively large was shown in the above embodiment, it does not restrict to this, For example, the inside of a foil holder A slit-like groove having a small circumferential width of the opening may be formed on the circumferential surface, and the end of the foil may be inserted into this groove.

  The application object of the foil bearing according to the present invention is not limited to the above-described gas turbine, and can also be used, for example, as a bearing that supports a rotor of a turbocharger (supercharger). In addition, the foil bearing according to the present invention can be widely used not only for gas turbines and turbomachines such as turbochargers, but also for bearings for vehicles and industrial equipment for which use of oil is limited.

  In addition, each foil bearing described above is an air dynamic bearing using air as a pressure generating fluid, but the invention is not limited to this, it is possible to use other gas as a pressure generating fluid, or water or oil Liquids such as can also be used.

10 foil bearing 11 foil holder 11 c axial groove (recess)
12 foil 12a first region 12b second region 12a1, 12b1 top foil portion 12a2, 12b2 insertion portion 12a3, 12b3 under foil portion 12a4, 12b4 notch portion 12a5, 12b5 notch 12a6, 12b6 slit 12c slit

Claims (3)

A foil bearing comprising: a foil holder; and a plurality of foils having a bearing surface and attached to an inner circumferential surface of the foil holder, wherein both circumferential ends of each foil are held in contact with the foil holder There,
Each foil is provided with a first area and a second area axially adjacent to each other, and the bearing surface is divided by dividing a part of the boundary of both areas, and the other part of the boundary of both areas is connected ,
The first region and the second region of each foil are respectively provided at the top foil portion having the bearing surface and at one circumferential end side of the top foil portion, and are provided at the inner circumferential surface of the foil holder And an under-foil portion provided continuously on the other end side in the circumferential direction of the top foil portion and disposed between an adjacent foil and an inner peripheral surface of the foil holder. ,
A foil bearing connecting the insertion portions of the first area and the second area of the respective foils, and dividing the top foil portions and the under foil portions over the entire circumferential direction . In the circumferential direction end of the under foil portion provided in the first region and the second region, to claim 1 having a gradually narrowed notched portion in the axial direction width toward the respective one circumferential direction Foil bearing as described. A foil which has a bearing surface and is attached with both circumferential ends in contact with the inner circumferential surface of the foil holder,
An axially adjacent first area and a second area are provided, and the bearing surface is divided by dividing a part of the boundary of both areas, and the other part of the boundary of both areas is connected ,
The first region and the second region are respectively provided on the top foil portion having the bearing surface and one end side in the circumferential direction of the top foil portion, and are inserted into the recess provided on the inner circumferential surface of the foil holder The plug-in portion and the under foil portion provided continuously on the other end side in the circumferential direction of the top foil portion and disposed between the adjacent foil and the inner circumferential surface of the foil holder,
A foil in which the insertion portions of the first region and the second region are connected to each other, and the top foil portions and the under foil portions are divided over the entire circumferential direction .

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