阅读说明：本技术 推力箔片轴承、箔片轴承单元、涡轮机械以及箔片 (Thrust foil bearing, foil bearing unit, turbo machine, and foil ) 是由 原田和庆 吉野真人 冈本实树 于 2020-02-26 设计创作，主要内容包括：各箔片(22)具有：顶部箔片部(22a),其具有轴承面(S)；以及背部箔片部(22b),其设置于顶部箔片部(22a)的上游侧,并重叠配置在相邻的箔片(22)的顶部箔片部(22a)的背后(与轴承面(S)相反的一侧)。相邻的箔片(22)彼此的重合部(P)的内径端所占的角度(E)比重合部(P)的外径端所占的角度(D)小。(Each foil (22) has: a top foil portion (22a) having a bearing surface (S); and a back foil piece part (22b) which is arranged on the upstream side of the top foil piece part (22a) and is overlapped and arranged on the back (the side opposite to the bearing surface (S)) of the top foil piece part (22a) of the adjacent foil piece (22). The angle (E) occupied by the inner diameter ends of the overlapping portions (P) of adjacent foil pieces (22) is smaller than the angle (D) occupied by the outer diameter ends of the overlapping portions (P).)

1. A thrust foil bearing comprising a plurality of foils having bearing surfaces axially opposed to a rotating member, the plurality of foils being arranged in a line in a rotating direction of the rotating member,

each foil has:

a top foil sheet portion having the bearing surface; and

a back foil piece portion provided on an upstream side of the top foil piece portion and arranged to be overlapped on a top foil piece portion of an adjacent foil on a side opposite to the bearing surface,

the angle occupied by the inner diameter end of the overlapping portion of adjacent foils is smaller than the angle occupied by the outer diameter end of the overlapping portion.

2. The thrust foil bearing of claim 1,

an angle occupied by an inner diameter end of the main body portion composed of the top foil portion and the back foil portion in each foil is smaller than an angle occupied by an outer diameter end of the main body portion.

3. Thrust foil bearing according to claim 1 or 2,

the difference between the angle occupied by the inner diameter end of the overlapping portion and the angle occupied by the outer diameter end of the overlapping portion is 10 degrees or more.

4. A foil bearing unit, wherein,

the foil bearing unit having the thrust foil bearing of any one of claims 1 to 3 and the rotating member.

5. A turbo-machine, wherein,

the turbomachine has a foil bearing unit as claimed in claim 4.

6. A foil for a thrust foil bearing, wherein,

the foil has a main body portion including a top foil portion having a bearing surface axially opposed to the rotary member and a back foil portion provided upstream of the top foil portion and arranged on the opposite side of the top foil portion of the adjacent foil from the bearing surface,

an angle occupied by an inner diameter end of the main body portion is smaller than an angle occupied by an outer diameter end of the main body portion.

Technical Field

The present invention relates to a thrust foil bearing.

Background

A bearing for supporting a main shaft of a turbo machine such as a gas turbine or a turbocharger is required to be able to withstand a severe environment such as high-temperature and high-speed rotation. As a bearing suitable for use under such conditions, a foil bearing, which is one type of dynamic pressure bearing, is focused. The foil bearing has a bearing surface formed of a flexible film (foil) having low bending rigidity, and supports a load by allowing the bearing surface to flex (see, for example, patent documents 1 and 2 below).

Documents of the prior art

Patent document

Patent document 1: japanese laid-open patent publication No. 2004-108485

Patent document 2: japanese patent laid-open publication No. 2015-132309

Disclosure of Invention

Problems to be solved by the invention

Since the lubricant of the foil bearing is gas (air), the foil bearing has an advantage of low torque compared to a dynamic pressure bearing using oil as a lubricant. However, since the load capacity of the dynamic pressure bearing depends on the viscosity of the lubricant, the load capacity of a foil bearing using gas as the lubricant is inevitably smaller than that of a dynamic pressure bearing using oil as the lubricant. Therefore, in order to expand the application range of the foil bearing, it is necessary to further increase the load capacity.

Here, fig. 16 shows a conventional blade-type thrust foil bearing 120. In the thrust foil bearing 120, as shown in fig. 18, the foil pieces 122 having the shapes shown in fig. 17 are arranged to overlap each other while being shifted in phase. Of the foil pieces 122, a portion disposed behind (on the opposite side to the bearing surface) the adjacent foil piece 122 functions as a back foil piece portion 122b, and a portion overlapping the adjacent foil piece 122 functions as a top foil piece portion 122a having a bearing surface.

When the thrust collar 106 provided on the main shaft is rotated in the arrow direction of fig. 19, a bearing gap C 'is formed between the bearing surface S' provided on each foil 122 and the end surface of the thrust collar 106. At this time, since the top foil piece 122a of each foil piece 122 is caught by the back foil piece 122b of the adjacent foil piece 122, the bearing gap C' between the top foil piece 122a of each foil piece 122 and the thrust ring 106 becomes a wedge shape whose gap width gradually narrows toward the downstream side. By pressing the lubricant (air) into the small gap portion of the wedge-shaped bearing clearance C', the pressure of the lubricant is increased and the thrust ring 106 is supported in a non-contact manner.

The load capacity of the thrust foil bearing 120 as described above depends on the minimum width of the bearing gap C '(hereinafter, this width is referred to as "floating gap") h'. That is, theoretically, the smaller the floating gap h', the more the load capacity of the thrust foil bearing 120 increases. Therefore, in order to increase the load capacity of the thrust foil bearing 120, the levitation gap h' may be reduced as much as possible.

However, if the floating gap h' of the thrust foil bearing 120 is to be reduced, the following problem occurs. In forming the foil 122, as shown in fig. 20, the foil material 130 in a hollow disk shape is generally divided into a plurality of portions in the circumferential direction, and the entire circumferential region of the foil material 130 is used as the foil 122, thereby improving the material yield. In this case, as shown in fig. 17, the angle a 'occupied by the arc portion 122c provided at the outer diameter end of each foil 122 is equal to the angle B' occupied by the arc portion 122d provided at the inner diameter end, and as a result, the circumferential length of the arc portion 122c at the outer diameter end is longer than the circumferential length of the arc portion 122d at the inner diameter end.

If the foils 122 are overlapped while being shifted in phase, the circumferential pitch L1 'of the foils 122 becomes relatively large near the outer diameter ends of the foils 122 as shown in fig. 21, while the circumferential pitch L2' of the foils 122 becomes relatively small near the inner diameter ends of the foils 122 as shown in fig. 22. As a result, the rigidity of each foil 122 near the inner diameter end is higher than the rigidity near the outer diameter end, and therefore each foil 122 is less likely to flex and is likely to contact the thrust ring. In this case, since it is necessary to set the floating gap with reference to the inner diameter end of each foil piece, there is a problem that the floating gap cannot be sufficiently reduced.

Therefore, an object of the present invention is to reduce a floating gap and increase a load capacity in a blade type thrust foil bearing.

Means for solving the problems

In order to solve the above problem, the present invention provides a thrust foil bearing including a plurality of foils each having a bearing surface axially opposed to a rotating member, the plurality of foils being arranged in a row in a rotation direction of the rotating member, wherein each of the foils includes: a top foil sheet portion having the bearing surface; and a back foil piece portion provided on an upstream side of the top foil piece portion and arranged to be overlapped on a side of the top foil piece portion of the adjacent foil piece opposite to the bearing surface, wherein an angle occupied by an inner diameter end of an overlapped portion of the adjacent foil pieces is smaller than an angle occupied by an outer diameter end of the overlapped portion.

In the present invention, as described above, the angle occupied by the inner diameter end of the overlapping portion of the adjacent foil pieces (i.e., the region where the top foil piece portion of each foil piece is supported from the back (the side opposite to the bearing surface) by the back foil piece portion) is made smaller than the angle occupied by the outer diameter end of the overlapping portion. Accordingly, the rigidity of each foil piece in the vicinity of the inner diameter end is relatively reduced, so that the difference in rigidity between the vicinity of the outer diameter end and the vicinity of the inner diameter end of each foil piece is reduced, and the foil piece can be bent substantially uniformly over the entire surface, so that the floating gap can be set smaller.

In the thrust foil bearing described above, for example, the angle occupied by the inner diameter end of the main body portion including the top foil portion and the back foil portion in each foil piece is smaller than the angle occupied by the outer diameter end of the main body portion, whereby the angle occupied by the inner diameter end of the overlapping portion between the adjacent foil pieces can be smaller than the angle occupied by the outer diameter end of the overlapping portion.

In the thrust foil bearing, it is preferable that a difference between an angle occupied by an inner diameter end of an overlapping portion of adjacent foils and an angle occupied by an outer diameter end of the overlapping portion is 10 ° or more.

Effects of the invention

As described above, according to the present invention, in the blade type thrust foil bearing, the floating gap can be reduced to increase the load capacity.

Drawings

FIG. 1 is a schematic view of a gas turbine.

Fig. 2 is a sectional view showing a support structure of the main shaft of the gas turbine.

Fig. 3 is a sectional view of the thrust foil bearing assembled to the support structure.

Fig. 4 is a front view of the thrust foil bearing as viewed in the axial direction.

Fig. 5 is a front view of the foil of the thrust foil bearing.

Fig. 6 is a front view showing a state where a foil is formed from a foil raw material.

Fig. 7 is a front view showing a state where the foil pieces are overlapped.

Fig. 8 is a cross-sectional view taken along line X-X of fig. 4.

Fig. 9 is a cross-sectional view taken along line Y-Y of fig. 4.

Fig. 10 is a cross-sectional view taken along line Z-Z of fig. 4.

FIG. 11 is a front view of another embodiment of a foil.

Fig. 12 is a front view of a foil according to yet another embodiment.

Fig. 13 is a photograph (front view) showing the test results of the foil of the comparative example.

Fig. 14 is a photograph (front view) showing the test results of the foil of example 1.

Fig. 15 is a photograph (front view) showing the test results of the foil of example 2.

Fig. 16 is a front view of a conventional thrust foil bearing.

Fig. 17 is a front view of the foils of the thrust foil bearing of fig. 16.

Fig. 18 is a front view showing a state where the foils of fig. 17 are overlapped.

Fig. 19 is a cross-sectional view taken along line X '-X' of fig. 16.

Fig. 20 is a front view showing a state where the foil of fig. 17 is formed from a foil stock material.

Fig. 21 is a cross-sectional view taken along line Y '-Y' of fig. 16.

FIG. 22 is a cross-sectional view taken along line Z '-Z' of FIG. 16.

Detailed Description

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

Fig. 1 conceptually illustrates a structure of a gas turbine as one kind of a turbo machine. The gas turbine mainly has a turbine 1 and a compressor 2 formed with a blade row, 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, the turbine 1, and the compressor 2 constitute a rotor that is integrally rotatable. The air taken in from the intake port 7 is compressed by the compressor 2, heated by the regenerator 5, and sent to the combustor 4. The compressed air is mixed with fuel and burned, and the turbine 1 is rotated by high-temperature and high-pressure gas. The rotational force of the turbine 1 is transmitted to the generator 3 via the main shaft 6, and the generator 3 rotates to generate electric power, which is output via the inverter 8. Since the temperature of the gas after the turbine 1 is rotated is relatively high, the gas is sent to the regenerator 5 to exchange heat with the compressed air before combustion, and the heat of the gas after combustion is reused. The gas after the heat exchange in the regenerator 5 passes through the exhaust heat recovery device 9 and is discharged as an exhaust gas.

Fig. 2 shows an example of a rotor support structure in the gas turbine. In this support structure, radial bearings 10 are disposed at two locations in the axial direction, and thrust bearings 20, 20 are disposed on both sides in the axial direction of a thrust collar 6a provided on a main shaft 6. The main shaft 6 is supported by the radial bearing 10 and the thrust bearing 20 so as to be rotatable in both the radial direction and the thrust direction.

In this support structure, the region between the turbine 1 and the compressor 2 is adjacent to the turbine 1 that is rotated by the high-temperature and high-pressure gas, and therefore, a high-temperature atmosphere is formed. In this high-temperature atmosphere, since a lubricant composed of oil, grease, or the like is deteriorated and evaporated, it is difficult to apply a normal bearing (rolling bearing or the like) using such a lubricant. Therefore, as the bearings 10 and 20 used in such a support structure, an aerodynamic bearing is suitable, and a foil bearing is particularly suitable.

Hereinafter, a structure of a foil bearing (hereinafter, referred to as a "thrust foil bearing 20") suitable for the thrust bearing 20 for a gas turbine will be described with reference to the drawings.

As shown in fig. 3, the thrust foil bearing 20 includes a disc-shaped foil holder 21 and a plurality of foils 22 attached to an end face 21a of the foil holder 21. In the present embodiment, thrust foil bearings 20, 20 are provided on both sides of the thrust ring 6a in the axial direction. These thrust foil bearings 20, 20 have a structure that is axially symmetrical about the thrust collar 6 a. Hereinafter, the downstream side of the fluid in the flow direction with respect to the foil 22 when the main shaft 6 rotates is referred to as "downstream side", and the opposite side thereof is referred to as "upstream side".

The foil holder 21 is formed of metal, resin, or the like. The foil holder 21 has a hollow disk shape having an inner hole 21b into which the spindle 6 is inserted. A plurality of foils 22 are attached to one end face 21a of the foil holder 21. The other end face 21c of the foil retainer 21 is fixed to a casing of a device (gas turbine in the present embodiment) in which the thrust foil bearing 20 is assembled.

The foil 22 is made of a metal having high elasticity and good workability, for example, steel or a copper alloy. The foil 22 is formed of a thin metal plate (foil) having a thickness of about 20 to 200 μm. In the aerodynamic bearing using air as a fluid film as in the present embodiment, since oil does not exist in the atmosphere, it is preferable to form the foil 22 by using stainless steel or bronze.

As shown in fig. 4, the foils 22 are arranged in a circumferential direction with a phase shift. As shown in fig. 5, each foil piece 22 has a main body portion 22c including a top foil piece portion 22a and a back foil piece portion 22b, the top foil piece portion 22a has a bearing surface S, and the back foil piece portion 22b is provided continuously with the upstream side of the top foil piece portion 22 a. In the illustrated example, both the downstream end 22f (i.e., the downstream end of the top foil portion 22a) and the upstream end 22g (i.e., the upstream end of the back foil portion 22b) of the body 22c have a chevron shape with a radially intermediate portion protruding toward the downstream side. In the present embodiment, the downstream end 22f of the top foil piece 22a is different in shape from the upstream end 22g of the back foil piece 22 b. Each foil 22 is fixed to the foil holder 21 by an appropriate method, and for example, an upstream end portion 22g of the main body portion 22c is fixed to an end face 21a of the foil holder 21 by welding.

The foil 22 has an arc portion 22d at the outer diameter end of the main body portion 22c and an arc portion 22e at the inner diameter end of the main body portion 22 c. The circular arc portions 22d and 22e are both centered on the rotation center O of the main shaft 6. The angle B occupied by the arcuate portion 22e at the inner diameter end of the main body portion 22c is smaller than the angle a occupied by the arcuate portion 22d at the outer diameter end of the main body portion 22c, for example, by 10 ° or more. In the illustrated example, the outer diameter end and the inner diameter end of the downstream end 22f of the body 22c are arranged at the same phase (circumferential position), and the inner diameter end of the upstream end 22g of the body 22c is arranged downstream of the outer diameter end.

The foil 22 is formed by punching or electrical discharge machining a flat plate-like foil material (metal thin plate). In the present embodiment, as shown in fig. 6, 6 foils 22 are formed from a hollow disk-shaped foil material 30. At this time, the outer diameter ends of the downstream side end portion 22f and the upstream side end portion 22g of the adjacent foils 22 contact each other, and the inner diameter ends are separated from each other. In the illustrated example, the downstream end 22f and the upstream end 22g of the adjacent foils 22 are in contact with each other in a region on the outer diameter side of the apex provided at the center in the radial direction, and are separated from each other in a region on the inner diameter side of the apex. In fig. 6, the unnecessary portion 31 between the downstream end 22f and the upstream end 22g of the adjacent foil 22 in the foil material 30 is marked with scattering points. In the illustrated example, since 6 foils 22 are formed from the foil material 30, the angle a (see fig. 5) occupied by the arc portion 22d of the outer diameter end of each foil 22 is 60 °. On the other hand, the angle B occupied by the arc portion 22e of the inner diameter end of each foil 22 is smaller than 60 °, for example, 50 ° or less.

In a state where the above-described foil pieces 22 are attached to the foil piece holder 21, as shown in fig. 7 and 8, the bearing surface S of the top foil piece portion 22a provided on each foil piece 22 directly faces the thrust ring 6a in the axial direction, and the back foil piece portion 22b of the foil piece 22 adjacent to the downstream side is arranged behind (on the opposite side of) the top foil piece portion 22a of each foil piece 22. That is, the back foil piece 22b of each foil piece 22 is disposed between the top foil piece 22a of the foil piece 22 adjacent to the upstream side and the foil piece holder 21. In the present embodiment, since the angle B occupied by the arc portion 22E at the inner diameter end of each foil piece 22 is smaller than the angle a occupied by the arc portion 22D at the outer diameter end of each foil piece 22 (see fig. 5), the angle E occupied by the inner diameter end of the overlapping portion P (shown by a dotted line in fig. 7) of the adjacent foil pieces 22 is smaller than the angle D occupied by the outer diameter end of the overlapping portion P. In the illustrated example, the angles occupied by the inner diameter ends and the outer diameter ends of the top foil portions 22a having the bearing surfaces S in the respective foil pieces 22 are equal, and the angle occupied by the inner diameter ends of the back foil portions 22b disposed behind the adjacent foil pieces 22 is smaller than the angle occupied by the outer diameter ends.

When the main shaft 6 rotates in one circumferential direction (the direction of arrow R in fig. 8), a bearing gap C is formed between the bearing surface S of each foil 22 of the thrust foil bearing 20 and the end surface of the thrust ring 6 a. At this time, each foil 22 is bent while being lapped over the adjacent foil 22, and the bearing gap C becomes a wedge shape that becomes narrower toward the downstream side (in fig. 8, each foil 22 is simplified to be a flat plate shape). By pressing the air in the large clearance portion C1 of the wedge-shaped bearing clearance C into the small clearance portion C2, the pressure of the air film in the bearing clearance C is increased, and the main shaft 6 is supported by the pressure in the thrust direction in a non-contact manner. At this time, the foil 22 is elastically deformed in accordance with the operating conditions such as the load, the rotational speed of the spindle 6, and the ambient temperature, and the bearing clearance C is automatically adjusted to an appropriate width in accordance with the operating conditions. Therefore, even under severe conditions such as high-temperature and high-speed rotation, the bearing clearance C can be controlled to an optimum width, and the main shaft 6 can be stably supported.

At this time, since the circumferential pitch L2 (see fig. 10) near the inner diameter end of each foil piece 22 is smaller than the circumferential pitch L1 (see fig. 9) near the outer diameter end of each foil piece 22, the rigidity of the bearing surface S tends to be higher (that is, the bearing surface S is less likely to be displaced in the axial direction) near the inner diameter end of the foil piece 22 than near the outer diameter end.

In the present invention, as described above, the angle B occupied by the arc portion 22E at the inner diameter end of each foil piece 22 is made smaller than the angle a occupied by the arc portion 22D at the outer diameter end, so that the angle E occupied by the inner diameter end of the overlapping portion P of the adjacent foil pieces 22 is made smaller than the angle D occupied by the outer diameter end of the overlapping portion P. That is, the overlapping portions P of the adjacent foil pieces 22 are provided continuously in the circumferential direction near the outer diameter ends of the foil pieces 22 (see fig. 9), whereas the overlapping portions P of the adjacent foil pieces 22 are provided at intervals in the circumferential direction near the inner diameter ends of the foil pieces 22 (see fig. 10). In this way, by reducing the proportion of the region where the top foil piece portion 22a is supported by the back foil piece portion 22b in the vicinity of the inner diameter end of each foil piece 22, the rigidity of the bearing surface S in the vicinity of the inner diameter end of each foil piece 22 is reduced. As a result, the difference between the rigidity near the outer diameter end and the rigidity near the inner diameter end of each foil 22 is reduced, and therefore the entire region of each foil 22 in the radial direction can be bent substantially uniformly. This can further reduce the width of the small gap portion C2 of the bearing gap C (the floating gap h), and can increase the load capacity of the thrust foil bearing 20.

In the present embodiment, the angles occupied by the outer diameter end and the inner diameter end of the top foil portion 22a of each foil 22 are equal, and the angle occupied by the inner diameter end of the back foil portion 22b of each foil 22 is smaller than the angle occupied by the outer diameter end. In this case, the area of the top foil portion 22a, that is, the area of the bearing surface S does not change as compared with the conventional foil 122 shown in fig. 18, and therefore, a reduction in load capacity due to a reduction in the area of the bearing surface S can be avoided.

Further, since the bearing surface S of each foil piece 22 slides in contact with the end surface of the thrust ring 6a during low-speed rotation of the main shaft 6 immediately before stopping or immediately after starting, a low-friction coating such as a DLC film, an aluminum titanium nitride film, a tungsten disulfide film, or a molybdenum disulfide film may be formed on one or both of them. Further, during the rotation of the main shaft 6, minute sliding occurs between the foil pieces 22 and the foil retainer 21 and between the top foil piece portions 22a and the back foil piece portions 22b of the stacked foil pieces 22, and the vibration of the main shaft 6 can be damped by the frictional energy generated by the minute sliding. In order to adjust the frictional force generated by such minute sliding, the above-described low-friction coating may be formed on one or both of the surfaces that slide against each other.

The present invention is not limited to the above-described embodiments. For example, in the embodiment shown in fig. 11, the foil 22 is provided with a fixing portion 22h extending from the main body portion 22c to the outer diameter side. The foil 22 is fixed to the foil holder 21 by fixing the fixing portion 22h to the foil holder 21 by an appropriate method such as welding.

In the embodiment shown in fig. 12, the downstream end 22f and the upstream end 22g of the main body 22c of the foil 22 are linear. In the illustrated example, the entire region of the downstream end 22f is arranged at the same phase (circumferential position), and the inner diameter end of the upstream end 22g is arranged downstream of the outer diameter end. Thus, the angle B occupied by the inner diameter end of the body portion 22c is made smaller than the angle a occupied by the outer diameter end.

The thrust foil bearing 20 described above is not limited to a gas turbine, and can be applied to other turbo machines such as a supercharger and the like and applications for supporting other rotating shafts.

[ examples ] A method for producing a compound

In order to confirm the effect of the present invention, a foil (comparative example) having a difference of 0 ° between the angle B occupied by the inner diameter end and the angle a occupied by the outer diameter end of the main body, a foil (example 1) having an angle of 5 ° and a foil (example 2) having an angle of 10 ° were prepared, and the state of the foils after the track stop test of the thrust foil bearing provided with these foils was performed was observed. As a result, in the comparative example, as shown in fig. 13, a trace sliding with the thrust ring was provided in the vicinity of the inner diameter end of the top foil portion of each foil (the region surrounded by the broken line). On the other hand, in example 1, as shown in fig. 14, the number of slip marks of each foil piece was reduced as compared with the comparative example. In example 2, as shown in fig. 15, almost no slip marks were observed on each foil. From the above results, the following were confirmed: by making the angle B of the inner diameter end of each foil smaller than the angle a of the outer diameter end, even if the angle of the inner diameter end of the overlapping portion of adjacent foils is smaller than the angle of the outer diameter end, the contact of the inner diameter end of each foil with the thrust ring is alleviated. In particular, in example 2 in which the difference between the angle B of the inner diameter end and the angle a of the outer diameter end of each foil was set to 10 °, it was found that only the inner diameter ends of the foils were not in contact with each other, and the entire foils were uniformly bent. By suppressing the contact between the inner diameter end of the foil and the thrust ring in this way, the bearing gap (particularly the floating gap) can be further reduced, and the load capacity can be increased.

Description of the reference symbols

1: a turbine; 2: a compressor; 6: a main shaft; 6 a: a thrust ring; 10: a radial bearing; 20: a thrust foil bearing; 21: a foil retainer; 22: a foil; 22 a: a top foil sheet portion; 22 b: a back foil sheet portion; 22 c: a main body portion; 22 d: a circular arc portion (outer diameter end); 22 e: a circular arc portion (inner diameter end); 22 f: a downstream-side end portion; 22 g: an upstream-side end portion; 30: a foil stock; 31: an unnecessary portion; c: a bearing gap; o: a center of rotation; p: the overlapping part of the foil pieces; s: a bearing surface.