Radial bearing

Abstract

To provide a radial bearing with a simple structure and excellent load capacity. [Solution] The housing is cylindrical, and the top foil is positioned inside the housing and has a bearing surface facing the rotating member. Between the inner circumferential surface of the housing and the top foil, there is an axial groove which is a groove extending in the axial direction, a pad foil which covers at least a part of the axial groove so as to straddle the circumferential direction, and a support foil which has a pressing portion that presses the pad foil toward the axial groove.

Description

Technical Field

[0001] The present disclosure relates to a radial bearing.

Background Art

[0002] Foil-type radial bearings are disclosed in, for example, Patent Document 1 and Patent Document 2. The radial bearing described in Patent Document 1 is a bump-type radial bearing among others. On the other hand, the radial bearing described in Patent Document 2 is a leaf-type radial bearing.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0004] The bump-type foil bearing represented by Patent Document 1 needs to have the bump foil in a wave shape, and since the structure is complex, it is difficult to ensure the manufacturing cost issues such as the design of the bump (wave) and the need for pressing and bending in the manufacturing of the bump, and the manufacturing stability. In addition, the leaf-type foil bearing represented by Patent Document 2 eliminates the complexity of the bump type, but has a tendency that the rigidity and the damping performance against the shaft runout are lower than those of the bump type, and the applicable range of the load capacity (allowable load) is narrow.

[0005] Therefore, an object of the present disclosure is to provide a radial bearing having a simple structure and excellent load capacity.

Means for Solving the Problems

[0006] The present invention discloses a radial bearing comprising a cylindrical housing, a top foil disposed inside the housing and having a bearing surface facing a rotating member, and between the inner circumferential surface of the housing and the top foil, an axial groove which is a groove extending in the axial direction, a pad foil which covers at least a portion of the axial groove so as to straddle the circumferential direction, and a support foil which has a pressing portion that presses the pad foil toward the axial groove.

[0007] The axial groove may be formed in the housing.

[0008] The axial groove may be formed by a foil having grooves.

[0009] Multiple axial grooves and pressing portions are arranged with spacing in the circumferential direction, and the support foil may be configured to include circumferentially extending connecting portions that connect the multiple pressing portions.

[0010] The device may be configured to have circumferential grooves extending in the circumferential direction at positions corresponding to the connecting portion.

[0011] The circumferential grooves and connecting portions are provided at both ends in the axial direction of the radial bearing, and the pad foil is also positioned to cover the circumferential grooves. The groove width of the circumferential grooves may be configured to be greater than the width of the connecting portions.

[0012] The circumferential ends of the axial groove may be curved into an arc shape. [Effects of the Invention]

[0013] According to this disclosure, by combining the various components, it is possible to create a radial bearing that does not require the foil to have a complex structure such as a corrugated shape, and that can withstand large loads. [Brief explanation of the drawing]

[0014] [Figure 1] Figure 1 is a front view of the radial bearing 10. [Figure 2]Figure 2 is an exploded perspective view of the radial bearing 10. [Figure 3] Figure 3 is an enlarged view of a part of Figure 1. [Figure 4] Figure 4 is a view showing a part of the axial end face of the radial bearing 10. [Figure 5] Figure 5 is a view showing another part of the axial end face of the radial bearing 10. [Figure 6] Figure 6 is a perspective view of the housing 12. [Figure 7] Figure 7 is a view for explaining the arrangement of the pad foil 20. [Figure 8] Figure 8 is a perspective view of the support foil 26. [Figure 9] Figure 9 is a view for explaining the arrangement of the support foil 26. [Figure 10] Figure 10 is a view for explaining a scene where the rotating shaft 36 is arranged in the radial bearing 10. [Figure 11] Figure 11 is a view for explaining Modification 1-1. [Figure 12] Figure 12 is a view for explaining Modification 1-2. [Figure 13] Figure 13 is a front view of the radial bearing 50. [Figure 14] Figure 14 is an exploded perspective view of the radial bearing 50. [Figure 15] Figure 15 is an enlarged view of a part of Figure 13. [Figure 16] Figure 16 is a view showing a part of the axial end face of the radial bearing 50. [Figure 17] Figure 17 is a view showing another part of the axial end face of the radial bearing 50. [Figure 18] Figure 18 is a perspective view of the housing 52. [Figure 19] Figure 19 is a perspective view of the support foil 66. [Figure 20] Figure 20 is a view for explaining Modification 2-!

BEST MODE FOR CARRYING OUT THE INVENTION

[0015] An example of the radial bearing of this disclosure is its application to an oil-less hydrodynamic bearing. Such a bearing can be applied to various types of aircraft, vehicles that travel on land, ships that navigate at sea, and other transport equipment, as well as various devices and equipment other than transport equipment. It can be applied to bearings in equipment that is exposed to harsh environments such as high temperatures and high rotational speeds, such as turbochargers and macro gas turbines, and will be effective in these applications. The following will provide examples of the forms.

[0016] 1. Form 1 Figures 1 to 5 illustrate the radial bearing 10 according to form 1. Figure 1 is a front view of the radial bearing 10 (viewed from the direction of the straight arrow, with axis A (see Figure 2) in the direction of the back / front of the paper), and Figure 2 is an exploded perspective view. Figure 3 is an enlarged view of the part indicated by B in Figure 1. Although Figure 3 is not a cross-section, hatching is added to make the differences in materials easier to understand. Figure 4 is an end view of the part cut along the line indicated by CC in Figure 1. Figure 5 is an end view of the part cut along the line indicated by DD in Figure 1. As can be seen from these figures, the radical bearing 10 in this embodiment has a housing 12, a pad foil 20, a support foil 26, and a top foil 32. The components and their arrangement will be described below. The pad foil 20, support foil 26, and top foil 32 are arranged in layers along the inner surface of the cylindrical housing 12, starting from the inner surface side.

[0017] 1.1. Housing The housing 12 is the main body of the radical bearing 10, forming the external appearance of the radical bearing, and housing the various components inside it in a predetermined arrangement. Therefore, the housing 12 is cylindrical. The materials used to construct the housing 12 are not limited and can be considered in the same way as known radial bearing housings, such as steel or bronze.

[0018] Furthermore, in this embodiment, grooves are formed on the inner surface of the housing 12. Figure 6 shows the housing 12 extracted from Figure 2 and enlarged. As can be seen from Figures 1 to 6, in this embodiment, the housing 12 has an axial groove 14 and a circumferential groove 16.

[0019] [Axial groove] The axial groove 14 is a groove provided on the inner surface of the cylindrical housing 12, parallel to the axis of the cylinder, and extends from one end to the other in the axial direction of the housing 12. However, in this embodiment, it is divided by a circumferential groove 16 into a first axial groove 14a on the one end and a second axial groove on the other end.

[0020] In this embodiment, the axial groove 14 has a shape when viewed from a direction perpendicular to the axis (the shape seen in Figures 1 and 3), and is a concave shape that is curved in an arc. However, this shape may be an arc or a curved shape, but is not limited to these, and may be a square, a triangle, or other shape. Furthermore, when viewed from the viewpoints shown in Figures 1 and 3, it is preferable that both ends of the axial groove 14 have curved contact portions 14c that are convex toward the axial side of the cylinder and have a relatively large radius R, where they connect to the non-grooved portion. As will be explained later, this increases the contact area between the pad foil 20 and the inner surface of the housing 12, thereby improving friction damping when the pad foil 20 deforms. Although not limited to this, it is preferable that the surface be an arc of a circle with a radius of 1 mm or more. Furthermore, the contact portion 14c may be configured to have a greater surface roughness than the portion between adjacent axial grooves 14 (14a, 14b) in the circumferential direction (the portion that is not a groove). There are no particular limitations on the method for increasing the surface roughness, but examples include electrical discharge machining, filing, and coating with a high coefficient of friction. There are no particular limitations on the specific surface roughness of the contact portion 14c, but it is preferable that the calculated average roughness Ra (JIS B 0601-2001, ISO 4287-1997) in the direction indicated by arrow III in Figure 3 is 1.6 μm or more.

[0021] Multiple axial grooves 14 are provided at predetermined intervals along the inner surface of the housing 12. As can be seen from Figures 1 and 3, the axial grooves 14 are provided at positions corresponding to the pressing portions 30 (30a, 30b) of the support foil 26, as will be described later. Therefore, the number of axial grooves 14 should be determined according to the number of pressing portions 30 (30a, 30b). It is preferable that one axial groove 14 is provided for each pressing portion 30 (30a, 30b). The specific number of axial grooves 14 can be determined according to the required performance of the radial bearing 10. From the viewpoint of obtaining stable rotation of the shaft, it is preferable that the multiple axial grooves 14 be provided in an odd number at equal intervals. Furthermore, as can be seen from Figure 3, the groove width of the axial groove 14 is formed to be larger than the pressing portion 30 (30a, 30b) of the support foil 26, which will be described later. The depth of the axial groove 14 should be formed so as to be able to accommodate the moved portion of the pad foil 20 that has been deformed by the pressure, as will be explained later.

[0022] [Circumferential groove] The circumferential groove 16 is a groove provided on the inner surface of the cylindrical housing 12 so as to extend in the circumferential direction of the cylinder, and extends to complete a full circle around the housing 12.

[0023] In this embodiment, the circumferential groove 16 has a rectangular concave shape when viewed from a direction perpendicular to the direction in which the groove extends (the shape seen in Figures 4 and 5). However, this shape is not limited to this, and it may be arc-shaped, curved, or triangular or other shapes.

[0024] In this embodiment, the circumferential groove 16 is formed in the center of the inner circumferential surface of the housing 12, between one end and the other in the axial direction. This position corresponds to the position of the connecting portion 28 of the support foil 26, which will be described later. Furthermore, as can be seen from Figure 4, the groove width of the circumferential groove 16 is formed to be larger than the connecting portion 28 of the support foil 26, which will be described later. The depth of the circumferential groove 16 should be formed so as to be able to accommodate the portion of the connecting portion 28 of the support foil 26 that has been deformed by being pressed.

[0025] 1.2. Pad Foil The pad foil 20 is a member formed by creating an annular shape from a strip-shaped thin plate. The pad foil 20 is positioned to overlap the axial groove 14 of the housing 12 and is an annular thin plate extending along the circumferential direction of the inner surface of the housing 12. In this embodiment, as described above, the axial groove 14 is divided on both sides in the axial direction and is provided with a first axial groove 14a and a second axial groove 14b. Accordingly, the pad foil 20 also has a first pad foil 22 and a second pad foil 24 arranged with an interval in the axial direction.

[0026] The materials constituting the pad foil 20 (first pad foil 22, second pad foil 24) can be any known material and are not particularly limited, but materials with good spring properties are preferred. Among these, metals, such as steel or copper alloys, can be used from the viewpoint of processability. In the case of an oil-less hydrodynamic bearing as in this embodiment, air is used as the fluid film and oil is not provided for rust prevention. Therefore, from the viewpoint of rust prevention, it is preferable to use stainless steel or bronze. The thickness of the pad foil 20 is not particularly limited, but it can be approximately 20 μm to 200 μm.

[0027] Such pad foils 20 (first pad foil 22 and second pad foil 24 in this embodiment) are arranged to extend along the circumferential direction inside the housing 12 in a state in which a strip-shaped thin plate is rolled into an annular shape. Figure 7 shows a partial perspective view of the pad foils 20 arranged inside the housing 12. As can be seen from Figures 3, 4, and 7, the pad foils 20 extend along the inner circumference of the housing 12, with the first pad foil 22 positioned to overlap the first axial groove 14a, and the second pad foil 24 extends along the inner circumference of the housing 12 to overlap the second axial groove 14b. Here, the pad foils 20 are arranged so as not to overlap the circumferential groove 16.

[0028] The pad foil 20 is made of a strip-shaped thin plate arranged in a ring and placed inside the housing 12, but the ends of the strip may or may not be joined together. The pad foil 20 can be fixed to the housing 12 by means of partial welding, interlocking recesses and protrusions, etc., although the means are not particularly limited.

[0029] 1.3. Support Foil The support foil 26 is a component that locally presses the pad foil 20, causing it to elastically deform in that area. Figure 8 shows an enlarged view of the support foil 26 extracted from Figure 2.

[0030] The support foil 26 has a connecting portion 28 formed from a strip of thin sheet metal in an annular shape, and a pressing portion 30 of thin sheet metal extending axially from the connecting portion 28. The support foil 26 is laminated on the inside of the pad foil 20 (on the opposite side from the housing 12).

[0031] The connecting portion 28 is located inside the pad foil 20, along the circumferential groove 16, and is a thin, annular plate extending along the circumferential direction of the inner surface of the housing 12. The pressing portion 30 is a thin plate member provided so as to extend axially from the connecting portion 28. The connecting portion 30 is positioned in a location corresponding to the axial groove 14 of the housing 12. Therefore, multiple pressing portions 30 are provided at predetermined intervals along the direction in which the connecting portion 28 extends. In this embodiment, as described above, the axial groove 14 is divided into two sides in the axial direction and is provided with a first axial groove 14a and a second axial groove 14b. Accordingly, the pressing portion 30 extends from each of the axial sides of the connecting portion 28. Specifically, a pressing portion 30a corresponding to the first axial groove 14a and a pressing portion 30b corresponding to the second axial groove 14b are provided.

[0032] As can be seen in Figures 4 and 5, the width of the connecting portion 28 (the size in the direction perpendicular to the extension direction) is formed to be smaller than the groove width of the circumferential groove 16. Also, as can be seen in Figure 3, the width of the pressing portion 30 is formed to be smaller than the width of the axial groove 14.

[0033] The material constituting the support foil 26 can be considered in the same way as the pad foil 20. Furthermore, in the support foil 26, the connecting portion 28 and the pressing portion 30 may be formed integrally. This allows for easy manufacturing by punching or other processes.

[0034] Such a support foil 26 is positioned to extend along the inside of the pad foil 20 in an annular, rolled-up shape. Figure 9 shows a partial perspective view in which the support foil 26 is positioned inside the housing 12 and the pad foil 20. As can be seen in Figures 3, 4, and 9, the support foil 26 is positioned along the circumferential groove 16 such that the connecting portion 28 covers the circumferential groove 16 of the housing 12 that appears between the first pad foil 22 and the second pad foil 24. On the other hand, the pressing portion 30 is positioned on either side of the pad foil 20, corresponding to the axial groove 14.

[0035] The connecting portion 28 of the support foil 26 is made up of strip-shaped thin plates arranged in a ring shape, but the ends of the strips may or may not be joined together. The support foil 26 can be fixed into the housing 12 by means of partial welding, interlocking recesses and protrusions, etc., although the means are not particularly limited.

[0036] 1.4. Top foil The top foil 32 is a component formed by creating an annular shape from a strip-shaped thin plate. The top foil 32 is positioned to overlap the support foil 32 and is an annular thin plate extending along the circumferential direction of the inner surface of the support foil 32. The top foil 32 has an inner circumferential surface that forms the inner circumferential surface (bearing surface) of the radial bearing 10, and a rotating member (for example, a rotating shaft) is inserted inside the area enclosed by the top foil 32. As can be seen from Figures 4 and 5, the width (axial size) of the top foil 32 is such that it covers from one end to the other of the housing 12.

[0037] The material that makes up the top foil 32 can be considered in the same way as the pad foil 20.

[0038] The top foil 32 is made of a strip-shaped thin plate arranged in a ring and placed inside the housing 12, but the ends of the strip may or may not be joined together. The top foil 32 can be fixed to the housing 12 by means of partial welding, interlocking recesses and protrusions, etc., although the means are not particularly limited.

[0039] 1.5. Effects, etc. As shown in Figure 10, the radial bearing 10 functions as a bearing when a rotating shaft 36, which is a rotating member, is inserted inside the top foil 32. As is well known, radial bearings are bearings that support loads and vibrations applied radially to the shaft in rotating machinery. Among them, hydrodynamic bearings have a wedge shape with a flow path that tapers downstream due to the eccentricity that occurs between the shaft and the bearing, and generate dynamic pressure when a working fluid that rotates along with the shaft is supplied, forming a fluid film that functions as a lubricant and supports the load.

[0040] A structural problem with radially supporting a rotating shaft is that at high rotational speeds, centrifugal force and heat generated by frictional losses increase the radius of the rotating shaft, reducing the clearance between the rotating shaft and the bearing, thus negatively affecting the operating limit speed of the rotating shaft. In contrast, foil bearings, including those described in Patent Documents 1 and 2, maintain a constant clearance even at high rotational speeds by providing structural elasticity, allowing the foil to flex and enabling operation over a wide rotational range. In contrast, conventional foil bearings, such as those described in Patent Documents 1 and 2, have the problems of structural complexity and performance limitations mentioned above.

[0041] In contrast, with the radial bearing of this embodiment, the hydrodynamic effect of the wedge shape formed by the rotating shaft and the bearing causes the pressure received through the working fluid film to be transmitted as a load to the support foil 26 via the top foil 32. This load causes the pad foil 20 to deform toward the axial groove 14 (for example, arrow IIIa in Figure 3), thereby forming a double-ended support beam structure (see Figure 3) consisting of the elastic support foil 26, pad foil 20, and axial groove 14. This provides the aforementioned structural elasticity, and even in the high-speed rotation range, the flexing of the foil maintains a constant clearance, enabling operation over a wide rotation range.

[0042] In addition, in this embodiment of the radial bearing 10, at least in the end-supported beam structure portion, all foils have a simple cylindrical shape (for example, they do not have a shape that deforms in a wave-like manner in the thickness direction, such as a bump), and since it does not involve complex manufacturing processes, the manufacturing accuracy depends directly on the thickness accuracy of the material, resulting in low manufacturing costs and ensuring high manufacturing stability.

[0043] Furthermore, in foil-type radial hydrodynamic bearings, energy dissipation occurs mainly through friction between multiple foils and friction between the foils and the housing, which dampens fluctuations in the thickness of the fluid lubrication film, suppresses vibrations of the rotating shaft, and enables stable rotation against vibration. Therefore, the parameters that determine the damping performance of the bearing are the structure (sliding structure) that converts the radial vibration energy received from the rotating shaft via the top foil into sliding motion between the foils, and the coefficient of friction of the sliding surfaces. In contrast, as shown in Figure 3, by forming a contact portion 14c that is R-shaped rather than an edge, the contact area with the axial groove 14 increases when a load is applied and the pad foil 20 deforms. This generates friction through the movement indicated by arrow IIIb in Figure 3, thereby improving friction damping.

[0044] 1.6. Variations As explained above, the support foil 26 transmits the load via the top foil 32, and the pad foil 20 deforms toward the axial groove 14 due to the load, thereby forming a double-ended support beam structure (see Figure 3) consisting of the elastic support foil 26, pad foil 20, and axial groove 14. This disclosure is not limited to this, and it is sufficient if a double-ended support structure can be formed. Other forms are described below as modifications. Here, the specific form differs in each example (described below), but they produce the same effect as the radial bearing 10. The diagrams used to explain the modifications below show each radial bearing viewed from the inner side, with the inner surface spread out in a planar manner, illustrating the relationships between the components. For clarity, the top foil is omitted from the diagram.

[0045] [Variation 1-1] Figure 11 is a diagram illustrating modified example 1-1. In this modified example 1-1 as well, an axial groove 14 and a circumferential groove 16 are formed on the inner surface of the housing 12, and the pad foil 20, support foil 26, and top foil 32 are stacked therein in that order. In this modified example, there is one pad foil 20, positioned in the center between one end and the other in the axial direction on the inner surface of the housing 12. The support foil 26 has one connecting portion 28 provided on the axial end side and a pressing portion 30 extending from the other end in the axial direction of the connecting portion 28 to the other end in the axial direction. In this embodiment as well, multiple pressing portions 30 are arranged at intervals. As described above, the axial groove 14 of the housing 12 is provided at a position corresponding to the pressing portion 30, and the circumferential groove 16 is provided at a position corresponding to the connecting portion 28. Figure 11 illustrates an example where the connecting portion 28 is provided on one end in the axial direction, but conversely, the connecting portion 28 and the circumferential groove 16 may be provided on the other end in the axial direction.

[0046] [Variation 1-2] Figure 12 is a diagram illustrating Modification 1-2. In this Modification 1-2, the axial groove 14 is formed using a different component instead of the housing 12. Specifically, it is as follows: In this example, neither axial grooves nor circumferential grooves are formed on the inner surface of the housing 12, and the inner surface of the housing 12 is a flat surface. In this example, the inner surface of the housing 12 includes an axial groove forming foil 40, a pad foil 20, a support foil 26, and a top foil 32.

[0047] The axial groove-forming foil 40 has one connecting portion 42 provided on one end in the axial direction and a support portion 44 extending from the other end in the axial direction of the connecting portion 42 to the other end in the axial direction. The shape of the axial groove-forming foil 40 can be considered such that the connecting portion 42 is similar to the connecting portion 28 described in the above-mentioned modified example 1 (see Figure 11), and the support portion 44 is similar to the pressing portion 30 described in the above-mentioned modified example 1. As a result, a groove is formed between adjacent support portions 44, which becomes the axial groove 14. As described above, the pad foil 20 is a thin, strip-shaped plate, but as can be seen in Figure 12, it is arranged with multiple support portions 44 spanning it, so that the pad foil 20 is supported at both ends by the support portions 44 and positioned to cover the axial groove 14. The support foil 26 has a connecting portion 28 provided on the other end in the axial direction, and a pressing portion 30 extending from one end in the axial direction of the connecting portion 28 to the other end in the axial direction. The pressing portion 30 is superimposed on the pad foil 20 and is positioned to correspond to the axial groove 14. This configuration eliminates the need to form axial grooves and circumferential grooves in the housing.

[0048] In the modified example 1-2 shown in Figure 12, the axial groove-forming foil 40 has a connecting portion 42 only on one axial end of the support portion 44, but a further connecting portion 42 may also be provided on the other axial end of the support portion 44. In the modified example 1-2 shown in Figure 12, the support foil 26 is provided with a connecting portion 28 only on the other end in the axial direction of the pressing portion 30, but a further connecting portion 28 may also be provided on the one end in the axial direction of the pressing portion 30.

[0049] 2. Form 2 Figures 13 to 17 illustrate the radial bearing 50 according to form 2. Figure 13 is a front view of the radial bearing 50 (viewed from the direction of the straight arrow, with axis E (see Figure 14) in the direction of the back / front of the paper), and Figure 14 is an exploded perspective view. Figure 15 is a cross-sectional view of the radial bearing 50 at the axial center of the part indicated by F in Figure 13. Figure 16 is an end view of the part cut by the line indicated by GG in Figure 13. Figure 17 is an end view of the part cut by the line indicated by HH in Figure 13. As can be seen from these figures, the radical bearing 50 in this embodiment has a housing 52, a pad foil 60, a support foil 66, and a top foil 72. The components and their arrangement will be described below. The pad foil 60, support foil 66, and top foil 72 are arranged in layers along the inner surface of the cylindrical housing 52, starting from the inner surface side.

[0050] 2.1 Housing The housing 52 is the main body of the radical bearing 50, forming the external appearance of the radical bearing and housing the various components inside it in a predetermined arrangement. Therefore, the housing 52 is cylindrical. The materials used to construct the housing 52 are not limited and can be considered in the same way as those used for housings of known radial bearings, such as steel or bronze.

[0051] Furthermore, in this embodiment, grooves are formed on the inner surface of the housing 52. Figure 18 shows the housing 52 extracted from Figure 14 and enlarged. As can be seen from Figures 13 to 18, in this embodiment, the housing 52 has an axial groove 54 and a circumferential groove 56.

[0052] [Axial groove] The axial groove 54 is a groove provided on the inner surface of the cylindrical housing 52, parallel to the axis of the cylinder, and extends from one end to the other in the axial direction of the housing 52.

[0053] In this embodiment, the axial groove 54 has a rectangular shape when viewed from a direction perpendicular to the axis E (the shape seen in Figures 13 and 15). However, this shape is not limited to this; it may also be arc-shaped, curved, or other shapes such as a triangle.

[0054] Multiple axial grooves 54 are provided at predetermined intervals along the inner surface of the housing 52. As can be seen from Figures 13 and 15, the axial grooves 54 are provided at positions corresponding to the pressing portions 70 of the support foil 66, as will be described later. Therefore, the number of axial grooves 54 should be determined according to the number of pressing portions 70. It is preferable that one axial groove 54 is provided for each pressing portion 70. The specific number of axial grooves 54 can be determined according to the required performance of the radial bearing 50. From the viewpoint of obtaining stable rotation of the shaft, it is preferable that the multiple axial grooves 14 are provided in an odd number at equal intervals. Furthermore, as can be seen from Figure 15, the width of the axial groove 54 is formed to be larger than the pressing portion 70 of the support foil 66, which will be described later. The depth of the axial groove 54 should be such that it can accommodate the moved portion of the pad foil 60 that has been deformed by being pressed, as will be explained later.

[0055] [Circumferential groove] The circumferential groove 56 is a groove provided on the inner surface of the cylindrical housing 52 so as to extend in the circumferential direction of the cylinder, and extends around the housing 52 in a circular motion.

[0056] In this embodiment, the circumferential grooves 56 are formed on the inner circumferential surface of the housing 52 at both the axial end and the other end. These positions correspond to the positions of the connecting portion 68 of the support foil 66, which will be described later. Furthermore, as can be seen from Figure 16, the groove width of the circumferential groove 56 is formed to be larger than the connecting portion 68 of the support foil 66, which will be described later.

[0057] 2.2. Pad Foil The pad foil 60 is a component formed by creating an annular shape from a strip-shaped thin plate. The pad foil 20 is a thin annular plate that is arranged to cover the inner circumferential surface of the housing 12 and to overlap the axial groove 54 and the circumferential groove 56.

[0058] The materials used to make up the pad foil 60 can be any known material and are not particularly limited, but materials with good spring properties are preferred. Among these, metals such as steel or copper alloys can be used from the viewpoint of processability. In the case of an oil-less hydrodynamic bearing as in this embodiment, air is used as the fluid film and oil is not provided for rust prevention. Therefore, from the viewpoint of rust prevention, it is preferable to use stainless steel or bronze. The thickness of the pad foil 60 is not particularly limited, but it can be approximately 20 μm to 200 μm.

[0059] The pad foil 60 is made of a strip-shaped thin plate that is formed into a ring and placed inside the housing 52, but the ends of the strip may or may not be joined together. The pad foil 60 can be fixed to the housing 52 by means of partial welding, interlocking recesses and protrusions, etc., although the means are not particularly limited.

[0060] 2.3. Support Foil The support foil 66 is a component that locally presses the pad foil 60, causing it to elastically deform in that area. Figure 19 shows an enlarged view of the support foil 66 extracted from Figure 14.

[0061] The support foil 66 has two connecting portions 68 formed from strip-shaped thin plates in an annular shape, and a pressing portion 70 made of a thin plate that extends axially across the two connecting portions 28. The support foil 66 is laminated on the inside of the pad foil 60 (on the opposite side from the housing 52).

[0062] The connecting portion 68 is positioned inside the pad foil 60, along each of the two circumferential grooves 56, and is a thin, annular plate extending along the circumferential direction of the inner surface of the housing 52, sandwiching the pad foil 60. Therefore, the connecting portion 68 is positioned at both the axial end and the other end of the radial bearing 50. The pressing portion 70 is a thin plate member that extends axially across the two connecting portions 68. The pressing portion 70 is positioned in a location corresponding to the axial groove 54 of the housing 52. Therefore, multiple pressing portions 70 are provided at predetermined intervals along the direction in which the connecting portions 68 extend.

[0063] As can be seen in Figure 16, the width of the connecting portion 68 (the size in the direction perpendicular to the extending direction) is formed to be smaller than the groove width of the circumferential groove 56. Also, as can be seen in Figure 15, the width of the pressing portion 70 is formed to be smaller than the width of the axial groove 54.

[0064] The material that makes up the support foil 66 can be considered in the same way as the pad foil 70. Furthermore, in the support foil 66, the connecting portion 68 and the pressing portion 70 may be formed integrally. This allows for easy manufacturing by punching or other processes.

[0065] Such support foils 66 are positioned to extend along the inside of the pad foil 60 in a ring-shaped manner. As can be seen from Figures 15 to 17, the support foil 66 has a connecting portion 58 that is positioned along the circumferential groove 56 of the housing 52, sandwiching the pad foil 60. On the other hand, the pressing portion 70 is positioned on either side of the pad foil 60, corresponding to the axial groove 54.

[0066] The connecting portion 68 of the support foil 66 is made up of strip-shaped thin plates arranged in a ring shape, but the ends of the strips may or may not be joined together. The support foil 66 can be fixed into the housing 52 by means of partial welding, interlocking recesses and protrusions, etc., although the means are not particularly limited.

[0067] 2.4. Top foil Top foil 72 can be considered in the same way as top foil 32.

[0068] 2.5. Effects, etc. The radial bearing 50 described above functions as a bearing when a rotating shaft, which is a rotating member, is inserted inside the top foil 72. As is well known, radial bearings are bearings that support loads and vibrations applied radially to a rotating shaft in rotating machinery. Among them, hydrodynamic bearings have a wedge shape with a flow path that tapers downstream due to the eccentricity that occurs between the rotating shaft and the bearing, and generate dynamic pressure when a working fluid that rotates in conjunction with the rotating shaft is supplied, forming a fluid film that functions as a lubricant and supports the load.

[0069] A structural problem with radially supporting a rotating shaft is that at high rotational speeds, centrifugal force and heat generated by frictional losses increase the shaft radius, reducing the clearance between the shaft and the bearing, which significantly negatively impacts the operating limit speed of the rotating shaft. In contrast, foil bearings, including those described in Patent Documents 1 and 2, maintain a constant clearance even at high rotational speeds by providing structural elasticity, allowing the foil to flex and enabling operation over a wide rotational range. Conventional foil bearings, such as those described in Patent Documents 1 and 2, have the problems of structural complexity and performance limitations mentioned above.

[0070] In contrast, with the radial bearing of this embodiment, the hydrodynamic effect of the wedge shape formed by the rotating shaft and the bearing causes the pressure received through the working fluid film to be transmitted as a load to the support foil 66 via the top foil 72. This load causes the pad foil 60 to deform toward the axial groove 54 (arrow XV in Figure 15), forming a double-ended support beam structure (see Figure 15) consisting of the elastic support foil 66, pad foil 60, and axial groove 54. This provides the structural elasticity described above, and even in the high-speed range, the foil flexes to maintain a constant clearance, enabling operation over a wide range of rotations.

[0071] In addition, in this embodiment of the radial bearing 50, at least in the end-supported beam structure portion, all foils have a simple cylindrical shape (for example, they do not have a shape that deforms in a wave-like manner in the thickness direction, such as a bump), and since it does not involve complex manufacturing processes, the manufacturing accuracy depends directly on the thickness accuracy of the material, resulting in low manufacturing costs and ensuring high manufacturing stability.

[0072] Furthermore, in this embodiment, when viewing the radial bearing 50 in cross-section as shown in Figure 16, a connecting portion 68 exists between the pad foil 60 and the top foil 72 at positions J, which are both ends in the axial direction, but not at position K, which is near the center in the axial direction (at position K, there are places where the support foil 66 does not exist between the top foil 72 and the pad foil 60). Therefore, the rigidity of the foil laminated structure can be increased at position J. As a result, when the top foil 72 is subjected to force from the rotating shaft, the amount of elastic deformation at part J can be kept to a minimum. This suppresses the escape of gas from the formed gas film, allowing for stable gas film formation and further improvement of load capacity.

[0073] 2.6. Variations As explained above, the support foil 66 transmits the load via the top foil 72, and the pad foil 60 deforms toward the axial groove 54 due to the load, thereby forming a double-ended support beam structure (see Figure 15) consisting of the elastic support foil 66, pad foil 60, and axial groove 54. This disclosure is not limited to this, and it is sufficient if a double-ended support structure can be formed. Other forms are described below as modifications. Here, the specific form differs in each example (described below), but they produce the same effect as the radial bearing 50. The diagrams used to explain the modifications below show each radial bearing viewed from the inner side, with the inner surface spread out in a planar manner, illustrating the relationships between the components. For clarity, the top foil is omitted from the diagram.

[0074] [Variation 2-1] Figure 20 is a diagram illustrating modified example 2-1. In this modified example 2-1 as well, the pad foil 60, support foil 66, and top foil 72 are laminated on the inner surface of the housing 52 in this order. However, in this modified example, the support foil 66 is formed from two separate members, with the first support foil 66a positioned at one end in the axial direction and the second support foil 66b positioned at the other end in the axial direction. The first support foil 66a has a connecting portion 68a that extends circumferentially at one end in the axial direction, and is equipped with multiple pressing portions 70a that extend from the connecting portion 68a to the other end in the axial direction and are arranged circumferentially. The second support foil 66b has a connecting portion 68b that extends circumferentially at the other end in the axial direction, and is equipped with multiple pressing portions 70b that extend from the connecting portion 68b to one end in the axial direction and are arranged in the circumferential direction. The pressing portions 70a and 70b are arranged alternately in the circumferential direction, thereby forming axial grooves 54 between them.

[0075] [Modification 2-2] Up to this point, we have described examples in which both the pad foil 60 and the support foil 66 form an annular shape with a single component in the circumferential direction. However, at least one of the pad foil 60 and the support foil 66 may be divided in the circumferential direction, and these divisions may be arranged in the circumferential direction to form an annular shape. [Explanation of symbols]

[0076] 10, 50…Radial bearing, 12, 52…Housing, 14, 54…Axial groove, 16, 56…Circumferential groove, 20, 60…Pad foil, 26, 66…Support foil, 28, 68…Connecting section, 30, 70…Pressing section, 32, 72…Top foil

Claims

1. The housing is cylindrical, The housing has a top foil positioned inside the housing and having a bearing surface facing the rotating member, Between the inner circumferential surface of the housing and the top foil, An axial groove is a groove that extends in the axial direction, A pad foil covering at least a portion of the axial groove so as to span the circumferential direction, The system comprises a support foil having a pressing portion that presses the pad foil toward the axial groove, Radial bearing.

2. The radial bearing according to claim 1, wherein the axial groove is formed in the housing.

3. The radial bearing according to claim 1, wherein the axial groove is formed by a foil having a groove.

4. The axial grooves and pressing portions are arranged in a plurality with spacing in the circumferential direction. The radial bearing according to any one of claims 1 to 3, wherein the support foil comprises a circumferentially extending connecting portion that connects a plurality of the pressing portions.

5. The radial bearing according to claim 4, having a circumferential groove extending in the circumferential direction at a position corresponding to the connecting portion.

6. The circumferential groove and the connecting portion are provided at both ends of the radial bearing in the axial direction, The pad foil is also positioned to cover the circumferential groove, The groove width of the circumferential groove is greater than the width of the connecting portion. The radial bearing according to claim 5.

7. The radial bearing according to any one of claims 1 to 3, wherein both circumferential ends of the axial groove are curved in an arc shape.

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