JPS58160619A - Structure of gas bearing - Google Patents

Abstract

PURPOSE:To secure high speed stability of a bearing by engaging ridge engagement parts of a foil of almost cup-like section with engagement grooves on the inner periphery of a bearing case and having a foil piece to overlap an adjacent foil. CONSTITUTION:The plural number of engagement grooves 11 are formed at appropriate intervals along the peripheral direction on the inner peripheral surface of a bearing case 8. On the other hand, after forming ridge engagement part 13 in the central part of a foil 12, the foil 12 of almost cup-like section is formed with a spring-like and arc-shaped foil piece 15 arranged on its both sides. The engagement part 13 of the foil is engaged with engagement groove 11 of the bearing case 8 so that foil pieces 15a, 15b cover a shaft 9 along the peripheral direction. The foil pieces overlap each other in such a manner as a foil piece 15a on the rotating direction side of the shaft is closer to the shaft core than a foil piece 15b on the contrary side of the rotating direction of a neighboring foil.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a novel gas bearing structure, and more particularly to a high-performance gas bearing structure capable of stably supporting a high-speed rotating body by polymerizing spring elements.

Generally, gas has a lower viscosity than oil, so the gas bearing structure is widely used in high-speed turbo machines such as turbo compressors, turbo expanders, and turbo chargers, or refrigerators, and has a large gain. It is known that in order to improve the performance of gas bearings, it is sufficient to reduce the bearing gap, which is the gap between the bearing and the shaft, but there is a physical limit to this.

FIG. 1 is a diagram illustrating a conventional foil bearing. 1st
The foil bearing shown in the figure is disclosed in U.S. Pat. No. 3,382,014, and includes a foil 3 which has one end engaged with the inner peripheral surface of the bearing case 1 and whose other end extends in the direction of rotation of the shaft 2 so as to partially surround the shaft 2. A plurality of foils (eight in the illustrated example) are provided, and the tip of each foil 3 is configured to come into contact with the adjacent foil 3. Therefore, Coulomb friction at the contact point X between the foils damps the fluctuations in the gas film force caused by the vibration of the shaft 2, stabilizing the shaft rotation, and has a relatively excellent performance and track record as a foil bearing. ing.

However, it has the following drawbacks.

(1) High-speed stability is lacking because the damping element is mainly caused by Coulomb friction at the contact point between the foils.

(2) The foil at the contact point is likely to be worn and damaged, and therefore there is a problem in durability.

(3) The starting torque is large because the foil initially tightens the shaft.

Therefore, in view of the shortcomings in the conventional gas bearing structure, the present inventor has devised the present invention in order to effectively solve this problem.

The purpose of the present invention is to improve the high-speed stability of shaft rotation as much as possible, to withstand a wide range of environmental temperatures, to reduce the number of parts and reduce the size, and to facilitate mass production and reduce costs. , to provide a gas bearing structure that can be easily disassembled.

In order to achieve this object, the present invention is as follows. It is composed of

That is, a plurality of engagement grooves are formed at appropriate intervals along the circumferential direction of the inner circumferential surface of the journal or thrust bearing that supports the load of the shaft. On the other hand, the foil is curved over its entire length in the central width direction to form an engaging part of the protrusion, and by forming this engaging part, each of the foils, which are divided into two parts on both sides with the retaining part as a border, becomes a spring. A foil having a substantially cup-shaped cross section is formed as a circular arc-shaped foil piece or a flat foil piece. The retaining portion of the foil is engaged with each engagement groove on the inner circumferential surface of the bearing case, and the foil piece is disposed so as to cover the shaft along the circumferential direction. The foil pieces of the foils arranged in this way are overlapped with each other so that the foil pieces on the rotational side of the shaft are closer to the axis center than the foil pieces on the opposite rotational side of the adjacent foil, and Fluctuations in the gas film force in the radial direction are absorbed by the spring action of the foil pieces, as well as the squeezing action and Coulomb friction that occur when they separate from each other. Further, since appropriate gaps are formed between the overlapping coil pieces and between the foil pieces and the inner circumferential surface of the bearing case, there is a damping effect. This structure improves the high-speed stability of the journal or thrust shaft.

Further, in the above configuration, the inner circumferential surface of the bearing case is formed into a conical shape, and the foil is divided along the conical surface to form a conical split shape to fit the conical shape, thereby forming a conical foil gas bearing. Since the gas film pressure at each part is different between the large-diameter side and the small-diameter side, the rigidity of this cone-shaped foil piece is made to gradually decrease from the large-diameter side to the small-diameter side. The thickness of the piece is varied or slits are provided to stably support both radial and axial ρ loads, thereby improving the high-speed stability of the shaft supported by the conical bearing.

Hereinafter, a preferred embodiment of the gas bearing structure according to the present invention will be described with reference to the accompanying drawings.

2, 5, and 6 are examples of the gas journal bearing of the present invention, and FIGS. 3 and 4 are perspective views of foils that are constituent elements of the gas journal bearing in FIG. 2. . Moreover, FIGS. 7 and 8 are diagrams showing an embodiment applied to a thrust bearing.

In FIG. 2, reference numeral 8 denotes a journal bearing case that supports the load in the radial direction of the shaft 9, and the inner circumferential surface 1 of the bearing case
A plurality of engagement grooves 1 are arranged at appropriate intervals along the circumferential direction of the
1 is formed in the axial direction. Here, a case is illustrated in which four engaging grooves 11 are formed as dovetail grooves.

As shown in FIGS. 3 and 4, the foil 12 that is engaged with the retaining groove 11 is a rectangular plate spring with a uniform thickness that is curved across its center width direction. A retaining part 13 is formed so as to engage with the groove 11, and the foil pieces 15a and 15b extending on both sides of the formed engaging part 13 are made into the same arcuate surface, and are processed and formed into a substantially cup-shaped cross section. It is something. The shape is not symmetrical, and one foil piece 15a is somewhat longer than the other foil piece 15b, which will be described later.
This is to increase the area of polymerization between 5 molecules. The foil 12 shown in FIG. 4 has an inclined side 16 on the upright portion of one foil piece 15a to weaken the rigidity and enhance the formation of a gas film.

The foil 12 is made of spring steel subjected to wear-resistant surface treatment, such as Teflon coating or ceramic plasma coating.

As shown in FIG. 2, the foil 12 processed and formed as described above has the foil piece 15a on the side of the rotational direction ω of the shaft 90 adjacent to the foil piece 120 and the foil piece 15 on the opposite side of the rotational direction.
The foil pieces 15 are overlapped with each other so that the b-side also comes to the axial center side. Therefore, when the foil piece 15 is viewed from the axis side along the rotational direction ω, the seams 17 due to the overlap with each of the foil pieces 15 do not appear on the front surface, but are all hidden on the back surface. Further, as shown in the figure, since the longer foil piece 15a is oriented toward the rotation direction and the shorter foil piece 15b is oriented toward the counter-rotation direction, the foil pieces 15 can be overlapped at different levels as described above. This allows the polymerization area to be increased, and in particular, in this example, all of the shorter foil pieces 15b are polymerized.

The inner diameter of the journal bearing case 8 is the diameter of the shaft 9 and the foil 12.
The shaft 9 is machined to be slightly larger than the sum of four times the plate thickness, and when inserting the shaft 9 into such a journal bearing, as shown in FIG.
The a1 foil piece 15a and the foil piece 15b and the foil piece 15b and the inner peripheral surface 1o of the bearing case are configured to slightly contact each other and have gaps A, B, and C, respectively.

The journal bearing shown in FIG. 5 has a circular engagement groove 21 formed on the inner circumferential surface of the bearing case 18.
1, the engaging portion 23 of the foil 22 is also formed into a circular curve. Further, in the journal bearing shown in FIG. 6, as shown in FIG. 6, one foil piece 25a extends from the circular retaining part 26 on the inner peripheral surface of the bearing case 24, while the other foil piece 25a The foil piece 25b is once extended along one foil piece 25a, overlapped, then folded back and then extended in the opposite direction, which is completely asymmetrically formed.

By forming this asymmetrically, the foil piece 2
5 increases the bearing area surrounding the shaft 27 by maintaining a uniform gap A, and also increases the overlapping area of the foil pieces 25 to improve performance.

FIG. 7 and FIG. 8 are diagrams showing an embodiment in which the present invention is applied to a thrust gas bearing.

As shown, a foil 33 is disposed between the thrust bearing case 28 and a collar 29 fixed to the shaft.

The upper surface of this bearing case 28 is mountain-shaped, and its edges are formed radially in the radial direction. The grooves between the adjacent support pieces 3o are formed as dovetail grooves 31, and the engagement portion 34 of the foil 33 having the fan-shaped planar foil piece 32 is engaged with the engagement groove 31. Adjacent foil pieces 32 are assembled so as to overlap each other on the support piece 3o. The essential structural difference from the journal bearing is the gap CK between the foil piece 32 and the support piece 30. In journal bearings, the purpose of the caving gap is mainly for the squeezing action described later, whereas in thrust bearings, the gap C serves as a linear fulcrum in the radial direction by the support piece 3o, and the foil piece 32 The polymerization mainly plays a pivot role as an elastic surface tailing pad bearing, promoting the formation of a wedge-shaped gas film oriented in the direction of rotation in the gap A between the collar 29 and the foil piece 32, increasing the load capacity of the shaft. DESCRIPTION OF THE PREFERRED EMBODIMENTS The operation of the present invention having the above structure will be described using FIG. 2 as an example.

In the figure, when the shaft 9 rotates in the direction of the arrow ω, the gas in the space 35 in the retaining portion 13 is drawn in due to the viscosity of the gas, and the gas is trapped in the gap A between the shaft 9 and the 7-year-old coil piece 15a. Pressure is generated due to viscosity-based effects.

The foil piece 15a overlaps with the foil piece 15b and has a spring function, but there is no void as described above. The generated pressure of A! I'J
They are displaced radially outward to fit together, forming a gap Ai/c gas film. Thus, the foil piece 7.5a and the shaft 9
The air gap A formed by this becomes a lubricating gas film for the gas bearing, and gas film pressure is generated in each air gap A to balance the four radial forces acting on the shaft. However, when a fluctuating external force is applied to the shaft 9, the features of this bearing are exhibited, and if it relies only on the action of the foil, the spring element, or Coulomb friction, the fluctuating external force cannot be sufficiently damped. Yes, high speed stability is not very good.

Therefore, in the present invention, as described above, the shaft 9 and the foil piece 1
5. Air gap A with foil piece 15. and foil piece 15b
empty @B and foil piece 15b and bearing case inner peripheral surface 1
By forming gaps C with 0, these gaps A when the axis 9 is varied.

The gas present in B and C is pushed out from the gap by the squeezing action, and the external force due to shaft fluctuation is absorbed by the amount of gas pushed out, thereby attenuating the fluctuation. Therefore, as in the journal bearing shown in FIG. 6, the foil piece 25. The larger the overlapping area between the foil piece 25b and the foil piece 25b, the larger the squeezing action area and the larger the amount of gas to be pushed out, so that the damping effect can be increased. The same thing can also be said by increasing the number of empty layers, in other words, by increasing the number of overlapping foil pieces.

On the other hand, the fact that the debris is pushed out through the gaps A, B, and C means that the gas film pressure existing in the gaps becomes large, and the gas film pressure in the gaps on the opposite side of the axis 9 from the side of displacement becomes small. Therefore, the shaft 9 is pushed in the opposite direction by the gap gas film pressure on the displacement side to correct the displacement of the shaft shaft. This correction is
Since the gas film pressure increases in proportion to the void area, the larger the overlapping area of the foil pieces 15, the more effectively the overlapping process will be performed.

In addition to the damping effect of the above-mentioned squeeze action, the spring action of the foil piece can also exert damping property by independently acting together with the force in the radial direction. At this time, the foil piece 15 is further displaced outward to match this force by approximately 9 degrees, and pinches the gaps B and C, thereby further promoting the squeezing action. When the foil piece 15 is displaced, Coulomb friction is generated due to slight contact between the three spaces B and c, and this generated Coulomb friction also has a damping effect on the shaft fluctuation. .

In this way, when a fluctuating external force acts on the shaft 9, there is a damping effect due to the squeezing action of the gas existing in the gaps A, B, and C, Coulomb friction damping due to the foil pieces 15a and 15b, and polymerization of the foil pieces 15. Due to its elasticity, a stable gas film is formed on the bearing surface and a vibration damping effect is achieved.
This makes it possible to achieve high-speed stabilization of the shaft-bearing system. Such effects are the same for the thrust bearing structures shown in FIGS. 7 and 8.

9 to 11 show an embodiment in which the present invention is applied to a conical gas bearing, and FIGS. 12 to 15 show various embodiments of foils that are the constituent elements thereof.

In FIGS. 9 to 11, 36 is a conical inner peripheral surface 3.
7 and is configured to support the radial and axial loads of a conically constructed shaft 38. Inner peripheral surface 3 of this conical bearing case 36
8, a plurality of circular engagement grooves 39 are formed in the axial direction at appropriate intervals along the circumferential direction of the inner peripheral surface.

The foil 40 is attached to a conical shaft 38 as shown in FIG.
In order to fit this, it has a conical split shape in which the conical surface is divided in the axial direction along the circumferential direction, and has an engaging part 41 that is curved in the direction of the solid axis. Springy 7
It has a total of 42 pieces. The foil 40 is assembled so that its engaging portion 41 is engaged with the engaging groove 39 and the foil pieces 42 overlap with adjacent foil pieces 42 to cover the shaft 38 along the circumferential direction. The overlapping order of the foil pieces 42 is as follows: the foil pieces 42 on the rotational direction ω side of the shaft 38
2 are always placed on top of each other so that they are always on the axis side.

The effects of the above structure include the damping effect due to the squeezing action of the gas existing in the gaps A, B, and C, as well as the couloid/friction damping provided by the foil pieces 42, as well as the overlapping of the foil pieces 42, similar to the journal bearings or thrust bearings described above. Spring!
As a result, a stable gas film on the bearing surface is formed in the gap A, exhibiting a vibration damping effect, and achieving high-speed stabilization of the bearing system within 3 days.

However, in order to fully demonstrate the above-mentioned function, an appropriate rigidity of the foil 40 or foil piece 42 must be selected in accordance with the gas film pressure generated in the bearing portion, which is the gap A between the shaft 38 and the foil piece 42. This is very important. As is well known, the magnitude of the pressure generated in the gas film is proportional to the relative speed (circumferential speed), and in a conical bearing like this bearing, the large diameter R+ side and the small diameter R2 side of the conical shaft 38 Therefore, even when rotating at the same rotation speed, there will be a difference in the gas film pressure generated. In other words, the small diameter R2 side is the large diameter R2 side.
The gas film pressure is smaller than that on the I side. Therefore,
Corresponding to this, it is necessary to appropriately select the foil stiffness. From this, in the foil 40 shown in FIG. 12, which is a plate spring with uniform plate thickness simply formed into a conical split shape,
This results in a drawback that the rigidity of the foil piece 42 on the small diameter side is rather greater than that on the large diameter side.

So, as a foil to avoid this drawback! Three embodiments are shown in FIGS. 13 to 15.

The foil 43 shown in FIG. 13 changes the thickness of the foil 43 or foil piece 44 along the axial direction so that the foil thickness tl on the large diameter side and the foil thickness t2 on the small diameter side continuously decrease. This allows the foil stiffness to correspond to the gas film pressure.

The second embodiment shown in FIG. 14 has a structure in which a plurality of cut-out slits 46 of appropriate length are provided in a part of the foil piece 45 in a direction perpendicular to the axis.

The foil piece 45 provided with this slit 46 is not the foil piece 45° on the side that is closer to the axis when overlapped with the foil piece 45 of the adjacent foil 47, but the foil piece 45 on the opposite side that backs up this. It is mainly provided on the small diameter side of the foil piece 45b, and a plurality of slits 46
The length increases toward the small diameter side. In this way, the stiffness of the foils on the small diameter side of the assembled foil bearing is prevented from becoming excessively large.

The third embodiment shown in FIG. 15 has a structure in which, in addition to the embodiment shown in FIG.
8, the foil piece 45 is partially divided into a plurality of pieces (five pieces in the case of the figure), so that appropriate foil rigidity can be obtained depending on the cone diameter. Although not shown, contrary to the case shown in FIG. 14, the foil piece 45 on the opposite side is closer to the axis. A similar effect can be expected when the slit 48 shown in FIG. 15 is provided.

Furthermore, unlike the above embodiments, instead of using a single foil, a plurality of short length divided foils with different thicknesses and different diameters are manufactured, and these divided foils are sequentially engaged with the engagement grooves. It is also possible to provide the same function as the structure shown in FIG. 15 by incorporating the same.

As described above, the present invention exhibits the following excellent effects.

(1) By forming an appropriate gap between each overlapped foil piece and the bearing surface, there is a double or triple squeeze damping effect, and the shaft-bearing system of the journal bearing or thrust shaft is stabilized at high speed. It is also possible to reduce the starting torque.

(2) By polymerizing adjacent foil pieces, a double spring action is activated, which equalizes the deformation of the foil pieces, stabilizes the gas film on the bearing surface, and increases load capacity. . In addition, Coulomb friction damping is also added due to the contact of the foil pieces, which is a secondary effect, and further stabilization of shaft fluctuations can be achieved.

(3) Since the foil piece forms an elastic bearing surface,
Less damage from intrusion of foreign objects than rigid tailing pads.

(4) Since the bearing surface has elasticity, the damping effect against shaft fluctuations has little effect on dimensional changes due to contraction or expansion of the shaft and bearing due to temperature changes, and the applicable temperature range is wide.

(5) Assembly is easy because the foil can be incorporated into the bearing surface simply by engaging the engaging portion with the engaging groove. .

(6) By making the inner circumferential surface of the bearing case conical and the foil having a conical split shape, a single bearing functions as both a journal and a thrust bearing, resulting in a high-speed shaft-bearing system. Stabilization can be achieved.

(7) In addition, by having both functions with a single bearing, the number of component parts and mechanical loss are reduced, and the rigidity of the shaft can be increased, making it possible to increase the critical speed.

(8) By decreasing the rigidity of the cone-shaped foil piece from the large diameter side to the small diameter side, the deformation of the foil piece can be equalized, the gas film on the conical bearing surface can be stabilized, and the load capacity can be increased. High performance can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a conventional gas bearing structure, FIG. 2 is a cross-sectional view of a journal gas bearing structure showing an application example of the gas bearing structure of the present invention, and FIGS. 3 and 4 are FIG. Perspective view of the foil that is an element of the journal gas bearing structure of
6 and 6 are cross-sectional views showing modified examples of the journal gas bearing structure, FIG. 7 is a perspective view of a thrust bearing showing another application example of the gas bearing structure of the present invention, and FIG. 8 is a collar shaft added. The developed side view of FIG. 7 and FIGS. 9 to 11 show a conical gas bearing structure showing another application example of the gas bearing structure of the present invention. A sectional view and a bottom view, FIG. 12 is a perspective view of a foil prototype that is an element of the conical gas bearing structure, and FIGS. 13 to 15 are perspective views showing specific foil forms. In the figure, 8 is a journal bearing case, 9 is a shaft, 10 is an inner peripheral surface of the bearing case, 11 is an engagement groove, 12 is a foil, 1
3 is an engaging portion, 15a, 15b are foil pieces, 18 is a journal bearing case, 19 is an inner peripheral surface of the bearing case, 21 is an engaging groove, 22 is a foil, 23 is an engaging portion, 24 is a journal bearing case, 25a , 25b is a foil piece, 26 is an engagement groove, 27 is a shaft, 28 is a thrust bearing case, 29 is a collar, 31 is an engagement groove, 32 is a foil piece, 33 is a foil, 34 is an engagement part 1, and 36 is a A conical bearing case, 37 is an inner peripheral surface of the bearing case, 38 is a conical shaft, 39 is an engagement groove,
40 is a foil, 41 is an engaging portion, 42 is a foil piece, 4
3 is a foil, 44 is a foil piece, 45a and 45b are foil pieces, 46 is a notch-shaped slit, 47 is a foil, 4B is a notch-shaped slit, A, B and C are voids, ω
is the direction of rotation. Patent Applicant Ishikawajima Harima Heavy Industries Co., Ltd. Representative Patent Attorney Nobuo Kinutani Figure 5 Figure 6 Figure 7 Figure 8

Claims (2)

[Claims] (1) Foil in which multiple retaining grooves are formed at appropriate intervals along the circumferential direction of the inner peripheral surface of the bearing case that supports the load of the shaft, and foil pieces are formed on both sides. An engaging portion is provided in the center of the shaft, and the engaging portion is engaged with the retaining groove so that the foil piece covers the shaft along the circumferential direction, and the foil piece on the rotational direction side of the shaft is arranged such that the foil piece covers the shaft along the circumferential direction. The foil pieces are overlapped with each other so that they are closer to the axis than the foil pieces on the opposite side of the rotation direction of the adjacent foils, and an appropriate gap is created between each of the overlapped foil pieces and the inner peripheral surface of the bearing case. A gas bearing structure characterized in that the shaft is formed to stabilize the shaft at high speed. (2) Foil in which multiple engagement grooves are formed at appropriate intervals along the circumferential direction of the inner circumferential surface of the bearing case that supports the load of the shaft, and foil pieces are formed on both sides. A retaining part is provided in the center of the shaft, and this guide part is engaged with the retaining groove, and the foil pieces are arranged so as to cover the shaft along the circumferential direction, and the foil pieces on the rotational direction side of the shaft are adjacent to each other. The foil pieces were overlapped with each other so that they were closer to the axis than the foil pieces on the opposite side of the rotation direction, and an appropriate gap was formed between each of the overlapped foil pieces and the inner peripheral surface of the bearing case. In the gas bearing structure, the inner circumferential surface of the bearing case is formed into a conical shape, and the foil is formed into a conical split shape in which the conical surface is divided along the circumferential direction in order to match the inner circumferential surface of the conical bearing case; A gas shaft bearing structure characterized in that the rigidity of the conically split foil piece is gradually decreased from the large diameter side to the small diameter side.