Foil bearing device

Abstract

In the present invention, a foil bearing device that rotatably supports a rotating shaft comprises an annular member having an insertion hole through which the rotating shaft is inserted, a top foil of arcuate cross section that is positioned between the inner peripheral surface of the annular member and the outer peripheral surface of the rotating shaft so as to surround the entire outer periphery of the rotating shaft, and a bump foil that supports the top foil from the outer peripheral side of the top foil and that is supported on the inner peripheral surface of the annular member. In a cross-section perpendicular to the center line of the top foil, the top foil includes a first region in which at least one through hole formed through the top foil has an angular position of 240 degrees or more and less than 360 degrees, and a second region in which the angular position at which there are no through holes formed through the top foil is equal to or greater than 0 degrees and less than 240 degrees, if 0 degrees is regarded to be the angular position of a virtual line extending upward in the direction of gravity from the center line of the top foil, the angular position increasing as the imaginary line rotates in the direction of rotation of the rotating shaft with the center line of the top foil as the center of rotation, and 360 degrees is regarded to be the angular position when the imaginary line has completed one rotation.

Description

【Technical Field】 【0001】 The present disclosure relates to a foil bearing device that rotatably supports a rotating shaft. 【Background Art】 【0002】 A foil bearing includes a top foil that forms a bearing surface for a rotating shaft of a turbo blower, a turbo compressor, etc., and a bump foil that elastically supports the top foil. When the rotating shaft rotates, a fluid film (air film) is formed between the bearing surface of the top foil and the rotating shaft, and the rotating shaft is rotatably supported through this air film. Such a foil bearing is effective particularly for a rotating shaft that rotates at high speed because an appropriate air film is automatically formed according to the rotation speed of the rotating shaft. 【0003】 In order to stably support the rotating shaft with an air film, it is necessary to appropriately maintain the pressure of the air film. For example, Patent Document 1 discloses a foil bearing device provided with a valve that forms a communication hole in the top foil and opens and closes this communication hole according to the pressure (dynamic pressure) of the air film. 【Prior Art Documents】 【Patent Documents】 【0004】 【Patent Document 1】 Japanese Unexamined Patent Application Publication No. 2021-046913 【Summary of the Invention】 【Problems to be Solved by the Invention】 【0005】 Incidentally, the air film includes a region (referred to as a reduced pressure region) where the air film expands as it moves downstream in the direction of rotation of the rotating shaft. In the reduced pressure region, the pressure of the air film becomes negative, and this negative pressure becomes an exciting force that causes the rotating shaft to vibrate, potentially reducing the vibration stability of the rotating shaft. However, Patent Document 1 opens a valve when the dynamic pressure of the air film becomes high outside the reduced pressure region, releasing the dynamic pressure to the outer circumference of the top foil, and does not suggest a solution to the problem of negative pressure being generated in the reduced pressure region. 【0006】 This disclosure has been made in view of the above-mentioned problems and aims to provide a foil bearing device that can improve the vibration stability of a rotating shaft. [Means for solving the problem] 【0007】 To achieve the above objective, the foil bearing device according to the present disclosure is a foil bearing device for rotatably supporting a rotating shaft, comprising: an annular member having an insertion hole through which the rotating shaft is inserted; a top foil with a circular arc cross-section arranged between the inner circumferential surface of the annular member and the outer circumferential surface of the rotating shaft to surround the entire outer circumference of the rotating shaft; and a bump foil supporting the top foil from the outer circumferential side of the top foil, the bump foil being supported on the inner circumferential surface of the annular member, wherein in a cross-section perpendicular to the center line of the top foil, If we define the angular position of a virtual line extending upward in the direction of gravity from the center line as 0 degrees, and the angular position increases as the virtual line rotates in the direction of rotation of the rotation axis with the center line of the top foil as the rotation center, and the angular position when the virtual line has completed one rotation as 360 degrees, then the top foil includes a first region in which the angular position is 240 degrees or more and less than 360 degrees and in which at least one through hole penetrating the top foil is formed, and a second region in which the angular position is 0 degrees or more and less than 240 degrees and in which no through hole penetrating the top foil is formed. [Effects of the Invention] 【0008】 The foil bearing device of this disclosure can improve the vibration stability of the rotating shaft. [Brief explanation of the drawing] 【0009】 [Figure 1] This diagram schematically shows the configuration of an electric compressor equipped with a foil bearing device according to several embodiments. [Figure 2] This is a schematic cross-sectional view showing the configuration of a foil bearing device according to one embodiment. [Figure 3] This is an unfolded view of the inner circumferential surface of the top foil according to one embodiment. [Figure 4] This figure shows an example of the state in which the rotation axis shown in Figure 2 is rotating. [Figure 5] This graph shows the relationship between the angular position corresponding to Figure 4 and the pressure of the air film. [Figure 6] This is an unfolded view of the inner surface of the top foil according to another embodiment. [Figure 7] This is an unfolded view of the inner circumferential surface of the top foil according to yet another embodiment. [Figure 8] This diagram schematically shows the configuration of the top foil according to yet another embodiment. [Modes for carrying out the invention] 【0010】 Hereinafter, a foil bearing device according to an embodiment of the present disclosure will be described with reference to the drawings. Such an embodiment represents one aspect of the present disclosure and is not limiting, and can be modified at will within the scope of the technical idea of ​​the present disclosure. 【0011】 Figure 1 is a schematic diagram showing the configuration of an electric compressor 100 equipped with a foil bearing device 1 according to several embodiments. As illustrated in Figure 1, the electric compressor 100 includes a rotating shaft 102, an electric motor 104 that rotates the rotating shaft 102, an impeller 106 that compresses fluid by rotating integrally with the rotating shaft 102, a housing 108 that houses the electric motor 104 and the impeller 106, and a foil bearing device 1. 【0012】 The foil bearing device 1 rotatably supports the rotating shaft 102. The foil bearing device 1 supports the rotating shaft 102 in contact with it until the rotational speed of the rotating shaft 102 reaches the levitation speed that causes the rotating shaft 102 to levitate. When the rotational speed of the rotating shaft 102 reaches the levitation speed, the foil bearing device 1 supports the rotating shaft 102 in a non-contact state via a fluid film (hereinafter referred to as air film A) formed between the inner circumferential surface 5 (bearing surface) of the top foil 4 and the outer circumferential surface 110 of the rotating shaft 102. 【0013】 While this disclosure exemplifies the application of the foil bearing device 1 to an electric compressor 100, the devices to which the foil bearing device 1 is applied are not limited to the electric compressor 100. The foil bearing device 1 according to this disclosure is applicable to rotating devices having a rotating shaft 102, in particular rotating devices having a rotating shaft 102 capable of high-speed rotation. For example, rotating devices include turbochargers and turbo blowers. 【0014】 <Foil bearing device> (composition) The configuration of a foil bearing device 1 according to one embodiment will be described. Figure 2 is a schematic cross-sectional view showing the configuration of a foil bearing device 1 according to one embodiment, and the foil bearing device 1 is viewed in a direction perpendicular to the axial direction of the rotation shaft 102 (hereinafter referred to as the axial direction D1). As illustrated in Figure 2, the foil bearing device 1 includes an annular member 2, a top foil 4, and a bump foil 6. 【0015】 The annular member 2 has an insertion hole 3 through which the rotation shaft 102 is inserted. In one embodiment, the annular member 2 has a cylindrical shape, and the inner diameter of the annular member 2 is larger than the outer diameter of the rotation shaft 102. In some embodiments, the housing 108 of the electric compressor 100 described above includes the annular member 2. In this case, the annular member 2 is a part of the housing 108. 【0016】 The top foil 4 has an arc shape and is disposed so as to surround the entire outer circumference of the rotation shaft 102 between the inner circumferential surface 7 of the annular member 2 and the outer circumferential surface 110 of the rotation shaft 102. The top foil 4 is formed, for example, by bending a flexible metal plate material made of stainless steel into a cylindrical shape. In the form illustrated in FIG. 2, one end portion 10 in the circumferential direction D2 (hereinafter referred to as "circumferential direction D2") of the top foil 4 is bent outward in the radial direction D3 (hereinafter referred to as "radial direction D3") of the top foil 4. The top foil 4 is disposed inside the annular member 2 in a state where one end portion 10 in the circumferential direction D2 is held by the annular member 2. The other end portion 12 of the top foil 4 in the circumferential direction D2 is slightly separated from the one end portion 10 in the circumferential direction D2. In the form illustrated in FIG. 2, the top foil 4 is formed of a single metal plate material, and since the air film A does not flow out to the outside of the top foil 4 except through the through hole 8 described later, it is easy to obtain the effects described later, but the present disclosure is not limited to this form. Although not shown, in some embodiments, the foil bearing device 1 includes a plurality of top foils 4 that are separate from each other and are continuously arranged along the circumferential direction D2. 【0017】 In the present disclosure, the circumferential direction D2 is the circumferential direction centered on the center line O1 of the top foil 4. In the plane of FIG. 2, the direction from the other end portion 12 to the one end portion 10 of the top foil 4 (the counterclockwise direction) is taken as one side of the circumferential direction D2, and the direction from the one end portion 10 to the other end portion 12 of the top foil 4 (the clockwise direction) is taken as the other side of the circumferential direction D2. The radial direction D3 is a direction perpendicular to the center line O1, the direction approaching the center line O1 is taken as the inside of the radial direction D3, and the direction away from the center line O1 is taken as the outside of the radial direction D3. 【0018】 The bump foil 6 has an arc shape and is arranged to surround the entire outer periphery of the top foil 4. This bump foil 6 is supported by the inner peripheral surface 7 of the annular member 2. The bump foil 6 is formed, for example, by bending a flexible metal plate made of stainless steel into a cylindrical shape. In the form illustrated in FIG. 2, the bump foil 6 extends over the entire circumferential direction D2 and is in contact with the inner peripheral surface 7 of the annular member 2. The bump foil 6 is configured such that one end portion 10 of the top foil 4 passes therethrough. Although not shown, in some embodiments, the foil bearing device 1 includes a plurality of bump foils 6 that are separate from each other and are continuously arranged along the circumferential direction D2. 【0019】 The bump foil 6 includes a plurality of bump portions 14 that project toward the top foil 4 and at least a part of which abuts against the top foil 4. Each of the plurality of bump portions 14 projects in a direction away from the inner peripheral surface 7 of the annular member 2 (that is, inward in the radial direction D3) and is curved in an arc shape. The top of each of the plurality of bump portions 14 abuts against the top foil 4. Each of the plurality of bump portions 14 is arranged at intervals along the circumferential direction D2, and the bump foil 6 has a waveform. Such a bump foil 6 is configured to elastically support the top foil 4. 【0020】 As shown in FIG. 2, in a cross-sectional view of the foil bearing device 1 cut in a direction orthogonal to the axial direction D1 of the rotating shaft 102, the angular position θ of a virtual line L extending upward from the center line O1 of the top foil 4 in the direction of gravity D4 is defined as 0 degrees. This angular position θ increases as the virtual line L rotates in the other side (counterclockwise) of the circumferential direction D2, which is the rotation direction of the rotating shaft 102, with the center line O1 of the top foil 4 as the rotation center, and the angular position θ when the virtual line L makes one rotation is defined as 360 degrees. In the form illustrated in FIG. 2, the other end portion 12 of the top foil 4 is located at an angular position θ of 350 degrees or more and less than 360 degrees. 【0021】 Figure 3 is an unfolded view of the inner circumferential surface 5 of a top foil 4 according to one embodiment. As shown in Figure 3, the top foil 4 includes a first region R1 with an angular position θ of 240 degrees or more and less than 360 degrees, and a second region R2 with an angular position θ of 0 degrees or more and less than 240 degrees. In the first region R1, the top foil 4 has a plurality of through holes 8 that penetrate the top foil 4. On the other hand, in the second region R2, the top foil 4 does not have any through holes 8 that penetrate the top foil 4. 【0022】 In the embodiment illustrated in Figure 3, the multiple through holes 8 include a first through hole 8A(8) and a second through hole 8B(8) in a first region R1, with an angular position θ different from that of the first through hole 8A. In other words, each of the first through hole 8A and the second through hole 8B is arranged along the circumferential direction D2. Each of the first through hole 8A and the second through hole 8B overlaps with each other in the axial direction D1, at least in part. The multiple through holes 8 further include a third through hole 8C(8) located in the circumferential direction D2, on the opposite side of the second through hole 8B from the first through hole 8A. Each of the first through hole 8A, the second through hole 8B, and the third through hole 8C has a circular shape with the same diameter. 【0023】 In the embodiment illustrated in Figure 3, the plurality of through holes 8 include a first through hole 8A and a first axial through hole 8D(8) arranged along the axial direction D1 in a first region R1. Each of the first through hole 8A and the first axial through hole 8D overlaps with each other in the circumferential direction D2 at least in part. The plurality of through holes 8 further includes a second axial through hole 8E(8) arranged on the opposite side of the first through hole 8A in the axial direction D1, with the first axial through hole 8D in between. Each of the first through hole 8A, the first axial through hole 8D, and the second axial through hole 8E has a circular shape with the same diameter as each other. 【0024】 (Effects / Actions) The operation and effects of a foil bearing device 1 according to one embodiment will be described. Figure 4 is a diagram showing an example of the state in which the rotating shaft 102 shown in Figure 2 is rotating, and the rotating shaft 102 is rotating at a rotational speed greater than or equal to the levitation rotational speed. 【0025】 As shown in Figure 4, the foil bearing device 1 supports the rotating shaft 102 in a non-contact manner via an air film A. The rotating shaft 102 tends to fall due to its own weight. Also, as the rotating shaft 102 rotates, it approaches the portion of the inner circumferential surface 5 of the top foil 4 where the angular position θ is 180 degrees or more. In other words, in the plane of Figure 4, the rotating shaft 102 moves to the right due to rotation. Therefore, in the example shown in Figure 4, the air film A is thinnest at an angular position θ of 210 degrees. The air film A becomes thinner as the angular position θ moves from 0 degrees to 210 degrees, and thickens as the angular position θ moves from 210 degrees to 360 degrees (the thickness of the air film A is increased). 【0026】 Figure 5 is a graph showing the relationship between the angular position θ corresponding to Figure 4 and the pressure of the air film A. In Figure 5, the horizontal axis represents the angular position θ, and the vertical axis represents the pressure of the air film A. The pressure of the air film A in Figure 5 is shown as gauge pressure, with 0 Pa being the value when the pressure of the air film A is equal to the surrounding pressure (atmospheric pressure). A value less than 0 Pa is considered negative pressure, and a value of 0 Pa or greater is considered positive pressure. In Figure 5, the pressure of the air film A when the foil bearing device 1 according to one embodiment supports the rotating shaft 102 is denoted as P1 and shown by a solid line. Also, the pressure of the air film A when multiple through holes 8 are not formed in the first region R1 of the top foil 4 (comparative example) is denoted as P2 and shown by a dotted line. 【0027】 As shown in Figure 4, when the rotating shaft 102 is rotating, in the first region R1 where the angular position θ is between 240 degrees and 360 degrees, the air film A becomes thinner and the pressure of the air film A decreases as the angular position θ increases. Therefore, as shown in Figure 5, in the first region R1, there is a risk that the pressure of the air film A will become negative. This negative pressure then becomes an excitation force that causes the rotating shaft 102 to vibrate, reducing the vibration stability of the rotating shaft 102. 【0028】 According to one embodiment, since the top foil 4 has multiple through holes 8 formed in the first region R1, even if the pressure of the air film A becomes negative, air on the outer circumference of the top foil 4 flows into the air film A through the multiple through holes 8, suppressing the air film A pressure from becoming negative. In other words, as shown in Figure 5, it prevents the pressure of the air film A from falling below 0 Pa. Therefore, it is possible to suppress an increase in the excitation force and improve the vibration stability of the rotating shaft 102. 【0029】 However, if through holes 8 are formed around the entire circumference of the top foil 4, the pressure of the air film A supporting the rotating shaft 102 will decrease, thinning the air film A and potentially causing the rotating shaft 102 to come into contact with the top foil 4. According to one embodiment, since the top foil 4 does not have through holes 8 in the second region R2, the decrease in the pressure of the air film A is suppressed, and contact between the rotating shaft 102 and the top foil 4 can be suppressed. In particular, as shown in Figure 5, the air film A in the second region R2 is often at a positive pressure of 0 Pa or more, unlike the air film A in the first region R1. Therefore, there is no need to allow air to flow into the air film A in the second region R2 through the through holes 8. Rather, the absence of through holes 8 in the second region R2 of the top foil 4 prevents the air film A in the second region R2 from flowing out to the outer circumference of the top foil 4 through the through holes 8. As a result, it is possible to secure a pressure in the air film A that is suitable for supporting the rotating shaft 102. More specifically, the pressure of the air film A at an angular position θ of 210 degrees can be maintained at a high positive pressure, thereby stably supporting the rotation axis 102. 【0030】 The pressure of the air film A varies depending on the angular position θ, as shown in Figure 5. According to one embodiment, the vibration stability of the rotating shaft 102 can be further improved by arranging the first through-hole 8A, the second through-hole 8B, and the third through-hole 8C to correspond to the angular position θ. The first through-hole 8A, the second through-hole 8B, and the third through-hole 8C may have different diameters from each other, and may have shapes other than circular, such as a rectangular shape. 【0031】 The pressure of the air film A may vary depending on the axial direction D1. According to one embodiment, the vibration stability of the rotating shaft 102 can be further improved by arranging the first through-hole 8A, the first axial through-hole 8D, and the second axial through-hole 8E to correspond to the magnitude of the pressure of the air film A in the axial direction D1. The first through-hole 8A, the first axial through-hole 8D, and the second axial through-hole 8E may have different diameters from each other, and may have shapes other than circular, such as rectangular shapes. 【0032】 In some embodiments, the foil bearing device 1 has its shape and position determined based on the weight of the rotating shaft 102 and the rated rotational speed of the rotating shaft 102 (i.e., the magnitude of the negative pressure). In some embodiments, the foil bearing device 1 has its density and number determined based on the weight of the rotating shaft 102 and the rated rotational speed of the rotating shaft 102. 【0033】 In some embodiments, multiple through holes 8 are formed in the portion of the first region R1 of the top foil 4 where the angular position θ is between 240 degrees and less than 300 degrees. In this case, through holes 8 do not need to be formed in the portion of the top foil 4 where the angular position θ is between 300 degrees and less than 360 degrees. With such a configuration, when the top foil 4 is configured to close the gap between one end 10 and the other end 12, the strength of each end 10 and the other end 12 can be maintained. 【0034】 In some embodiments, the multiple through holes 8 include large-diameter holes and small-diameter holes that are smaller in diameter than the large-diameter holes, arranged along the axial direction D1. In an unfolded view of the inner circumferential surface 5 of the top foil 4, the distance from the large-diameter holes to a virtual straight line passing through the center of the axial direction D1 of the top foil 4 is shorter than that from the small-diameter holes. In the first region R1, the absolute value of negative pressure in the air film A may be large towards the center in the axial direction D1. With such a configuration, the negative pressure on the central side of the air film A can be effectively suppressed or eliminated. 【0035】 In one embodiment, the top foil 4 had a plurality of circular through holes 8, but the disclosure is not limited to this embodiment. Figure 6 is an unfolded view of the inner circumferential surface 5 of the top foil 4 according to another embodiment. Figure 7 is an unfolded view of the inner circumferential surface 5 of the top foil 4 according to yet another embodiment. Figure 8 is a schematic diagram showing the configuration of the top foil 4 according to yet another embodiment. 【0036】 In another embodiment, as illustrated in Figure 6, the top foil 4 has a through hole 8. This through hole 8 includes a slit 20(8) having an axial notch 22 and a pair of rotational notches 24A, 24B. 【0037】 The axial notch 22 is cut out in a straight line along the axial direction D1. Each of the pair of rotational notches 24A and 24B is cut out in a straight line from the axial notch 22 toward one side of the circumferential direction D2, which is the upstream side in the rotational direction. Each of the pair of rotational notches 24A and 24B is aligned with each other along the axial direction D1. Each of the pair of rotational notches 24A and 24B overlaps with each other in the axial direction D1, at least in part. Each of the pair of rotational notches 24A and 24B faces each other. The slit 20 has a U-shape that protrudes toward the other side of the circumferential direction D2. 【0038】 In the embodiment illustrated in Figure 6, one end 4a of the top foil 4 in the axial direction D1 is defined as the 0% position relative to the length of the top foil 4 in the axial direction D1. The position increases from one end 4a to the other end 4b of the top foil 4, with the other end 4b being defined as the 100% position relative to the length of the top foil 4 in the axial direction D1. The axial notch 22 has one end 22a located in the range greater than 0% and less than 10%, and the other end 22b located in the range greater than 90% and less than 100%. One of the pair of rotational notches 24A is cut out from one end 22a of the axial notch 22 toward one side in the circumferential direction D2. The other of the pair of rotational notches 24B is cut out from the other end 22b of the axial notch 22 toward one side in the circumferential direction D2. 【0039】 According to the embodiment illustrated in Figure 6, the formation of a U-shaped slit 20 allows the suction portion 4c of the top foil 4 surrounded by the slit 20 to be drawn toward the rotation axis 102 when the pressure of the air film A becomes negative, thereby making the thickness of the air film A nearly uniform (a parallel gap can be formed). Therefore, as the angular position θ increases, the decrease in the pressure of the air film A due to the expansion of the air film A is suppressed, and the pressure of the air film A becoming negative can be suppressed. 【0040】 In the embodiment illustrated in Figure 6, the slit 20 has one end 22a located in a range greater than 0% and less than 10%, and the other end 22b located in a range greater than 90% and less than 100%. Therefore, the suction portion 4c of the top foil 4 is made longer in the axial direction D1, and it is possible to suppress the pressure of the air film A becoming negative over the entire or a large portion of the axial direction D1. 【0041】 In the embodiment illustrated in Figure 6, the slit 20 had a U-shape, but this disclosure is not limited to this embodiment. The slit 20 can have any configuration as long as the suction portion 4c is formed. For example, one of the pair of rotational notches 24A is cut out from between one end 22a and the other end 22b of the axial notch 22 toward one side in the circumferential direction D2. 【0042】 In yet another embodiment, as illustrated in Figure 7, the through hole 8 includes a rectangular elongated hole 30(8) that extends along the axial direction D1. The elongated hole 30 has one end 30a located in a range greater than 0% and less than 10% of the length of the axial direction D1 of the top foil 4 described above, and the other end 30b located in a range greater than 90% and less than 100%. As illustrated in Figure 8, the elongated hole 30 and the vertices 15 of the bump portion 14 overlap each other in the circumferential direction D2 (the rotation direction of the rotation axis 102). The vertices 15 of the bump portion 14 overlap each other with the center 31 of the elongated hole 30 in the circumferential direction D2. The length of the elongated hole 30 in the circumferential direction D2 is shorter than that of the bump portion 14. 【0043】 According to the embodiments illustrated in Figures 7 and 8, even if the pressure of the air film A becomes negative, air can be allowed to flow into the negative-pressure air film A through the elongated holes 30, thereby preventing the pressure of the air film A from becoming negative. Furthermore, when the pressure of the air film A becomes greater than positive pressure, the elongated holes 30 are blocked by the bump portion 14, suppressing the outflow of the air film A. As a result, a pressure of the air film A greater than positive pressure can be maintained. 【0044】 In the embodiment illustrated in Figure 7, the elongated hole 30 has one end 30a located in a range greater than 0% and less than 10%, and the other end 30b located in a range greater than 90% and less than 100%. Therefore, it is possible to suppress the pressure of the air film A from becoming negative over the entire or most of the axial direction D1. 【0045】 In addition, the embodiments described above described cases in which only a plurality of circular through holes 8A to 8E (as illustrated in Figure 3), a U-shaped slit 20 (as illustrated in Figure 6), and an elongated hole 30 are formed in the top foil 4. In some embodiments, at least two of the circular through holes 8A, slit 20, and elongated hole 30 are formed in the top foil 4. 【0046】 The contents described in each of the above embodiments can be understood, for example, as follows: 【0047】 [1] The foil bearing device (1) relating to this disclosure is A foil bearing device that rotatably supports a rotating shaft (102), An annular member (2) having an insertion hole (3) through which the rotating shaft is inserted, Between the inner circumferential surface (7) of the annular member and the outer circumferential surface (110) of the rotating shaft, a top foil (4) with a circular arc cross-section is arranged to surround the entire outer circumference of the rotating shaft, A bump foil that supports the top foil from the outer circumferential side of the top foil, comprising a bump foil (6) supported on the inner circumferential surface of the annular member, In a cross-sectional view taken in a direction perpendicular to the axial direction (D1) of the rotation axis, the angular position (θ) of a virtual line (L) extending upward from the center line (O1) of the top foil in the direction of gravity (D4) is defined as 0 degrees, and the angular position increases as the virtual line rotates in the rotation direction of the rotation axis with the center line of the top foil as the rotation center, and the angular position when the virtual line completes one rotation is defined as 360 degrees. The top foil includes a first region (R1) having an angular position of 240 degrees or more and less than 360 degrees in which at least one through hole (8) penetrating the top foil is formed, and a second region (R2) having an angular position of 0 degrees or more and less than 240 degrees in which no through hole penetrating the top foil is formed. 【0048】 When the rotating shaft is rotating, in the first region where the angular position is between 240 degrees and less than 360 degrees, the gap between the top foil and the rotating shaft increases as the angular position increases. As a result, the pressure of the fluid film (air film) formed between the top foil and the rotating shaft decreases, and there is a risk that it will become negative pressure. This negative pressure becomes an excitation force that causes the rotating shaft to vibrate, reducing the vibration stability of the rotating shaft. According to the configuration described in [1] above, since the top foil has through holes formed in the first region, even if the pressure of the fluid film becomes negative, fluid (air) on the outer circumference of the top foil flows into the fluid film through the through holes, suppressing the fluid film pressure from becoming negative. As a result, it is possible to suppress an increase in the excitation force and improve the vibration stability of the rotating shaft. 【0049】 However, if through holes are formed around the entire circumference of the top foil, the pressure of the fluid film supporting the rotating shaft will decrease, thinning the fluid film and potentially causing the rotating shaft to come into contact with the top foil. According to the configuration described in [1] above, since no through holes are formed in the second region of the top foil, the decrease in the pressure of the fluid film can be suppressed, and contact between the rotating shaft and the top foil can be suppressed. In particular, the fluid film in the second region is often under positive pressure, unlike the fluid film in the first region. Therefore, there is no need to introduce fluid into the fluid film in the second region through the through holes. Rather, the absence of through holes in the second region of the top foil prevents the fluid film in the second region from flowing out to the outer circumference of the top foil through the through holes. As a result, it is possible to secure a fluid film pressure that can suitably support the rotating shaft. 【0050】 [2] In some embodiments, in the configuration described in [1] above, The at least one through hole includes a plurality of through holes (8A, 8D, 8E) arranged in the first region along the axial direction of the rotation axis. 【0051】 The pressure of the fluid film may vary in magnitude depending on the axial direction. According to the configuration described in [2] above, multiple through holes can be arranged to correspond to the magnitude of the pressure in the axial direction of the fluid film, thereby further improving the vibration stability of the rotating shaft. 【0052】 [3] In some embodiments, in the configuration described in [1] or [2] above, The at least one through hole includes, in the first region, a first through hole (8A) and a second through hole (8B) which is at a different angular position from the first through hole. 【0053】 The pressure of the fluid film varies depending on the angular position. According to the configuration described in [3] above, the first and second through-holes can be positioned to correspond to the angular position, further improving the vibration stability of the rotating shaft. 【0054】 [4] In some embodiments, in the configuration described in any one of [1] to [3] above, The at least one through hole includes a slit (20) having an axial notch (22) cut out along the axial direction of the rotation axis, and a pair of rotational notches (24A, 24B) cut out from the axial notch toward the upstream side in the rotation direction and aligned along the axial direction. 【0055】 According to the configuration described in [4] above, when the pressure of the fluid film becomes negative, the portion of the top foil surrounded by the slits is drawn toward the axis of rotation, making the size of the gap between this portion of the top foil and the axis of rotation equal or nearly equal. As a result, the decrease in the pressure of the fluid film due to the gap increasing as the angular position increases can be suppressed, and the fluid film pressure can be prevented from becoming negative. 【0056】 [5] In some embodiments, in the configuration described in [4] above, If we define one end (4a) of the top foil in the axial direction as the 0% position relative to the axial length of the top foil, and the position increases from the one end to the other end (4b) of the top foil, with the other end being defined as the 100% position relative to the axial length of the top foil, The axial cutout portion has one end (22a) located in a range greater than 0% and less than 10%, and the other end (22b) located in a range greater than 90% and less than 100%. One of the pair of rotational notches (24A) is cut out from one end of the axial notch toward the upstream side in the rotational direction, The other (24B) of the pair of rotational notches is cut out toward the upstream side in the rotational direction from the other end of the axial notch. 【0057】 According to the configuration described in [5] above, it is possible to suppress the pressure of the fluid film from becoming negative over the entire or most of the axial direction. 【0058】 [6] In some embodiments, in the configuration described in any one of [1] to [5] above, The bump foil includes a bump portion (14) that protrudes toward the top foil, Each of the at least one through hole and the apex (15) of the bump portion overlaps with each other in the rotational direction of the rotation axis. 【0059】 According to the configuration described in [6] above, even if the pressure of the fluid film becomes negative, fluid (air) can be introduced into the negative-pressure fluid film through the through-holes, preventing the fluid film pressure from becoming negative. Furthermore, when the pressure of the fluid film becomes greater than the positive pressure, the through-holes can be blocked by the bump section, ensuring that the fluid film pressure is greater than the positive pressure. [Explanation of Symbols] 【0060】 1. Foil bearing device 2. Annular member 3. Through hole 4 Top foil 4a One end of the top foil 4b The other end of the top foil 5. Inner surface of the top foil 6 Bump Foil 7. Inner circumferential surface of the annular member 8 Through holes 8A First through hole 8B Second through hole 14. Bump section 15 vertices 20 slits 22 Axial cutout 22a One end of the axial cutout 22b One end of the axial cutout 24A One of a pair of rotational notches 24B The other of the pair of rotational notches 30 long hole 100 Electric Compressor 102 Rotation axis 104 Electric Motor 106 Impeller 108 Housing 110 Outer surface of the rotating shaft A air membrane D1 Axial direction D2 Circumferential direction D3 radial direction D4 Gravity direction L virtual line O1 center line R1 1st area R2 2nd area

Claims

[Claim 1] A foil bearing device that rotatably supports a rotating shaft, An annular member having an insertion hole through which the rotating shaft is inserted, Between the inner circumferential surface of the annular member and the outer circumferential surface of the rotating shaft, a top foil with a circular arc cross-section is arranged to surround the entire outer circumference of the rotating shaft, A bump foil that supports the top foil from the outer circumferential side of the top foil, comprising a bump foil supported on the inner circumferential surface of the annular member, In a cross-section perpendicular to the axis of rotation, the angular position of a virtual line extending upward in the direction of gravity from the center line of the top foil is defined as 0 degrees. The angular position increases as the virtual line rotates in the direction of rotation of the rotation axis with the center line of the top foil as the rotation center, and the angular position when the virtual line completes one rotation is defined as 360 degrees. The top foil includes a first region having an angular position of 240 degrees or more and less than 360 degrees in which at least one through hole penetrating the top foil is formed, and a second region having an angular position of 0 degrees or more and less than 240 degrees in which no through hole penetrating the top foil is formed. Foil bearing device. [Claim 2] The at least one through hole includes a plurality of through holes arranged in the first region along the axial direction of the rotation axis, The foil bearing device according to claim 1. [Claim 3] The at least one through hole includes, in the first region, a first through hole and a second through hole having a different angular position from the first through hole. The foil bearing device according to claim 1 or 2. [Claim 4] The at least one through hole includes an axial notch cut out along the axial direction of the rotation axis, and a slit having a pair of rotational notches cut out from the axial notch toward the upstream side in the rotational direction and aligned along the axial direction. The foil bearing device according to claim 1 or 2. [Claim 5] If we define one end of the top foil in the axial direction as the 0% position relative to the axial length of the top foil, and the position increases from the one end to the other end of the top foil, with the other end being defined as the 100% position relative to the axial length of the top foil, The axial cutout portion is located in a range greater than 0% and less than 10% at one end, and in a range greater than 90% and less than 100% at the other end. One of the pair of rotational notches is cut out from one end of the axial notch toward the upstream side in the rotational direction, The other of the pair of rotational notches is cut out toward the upstream side in the rotational direction from the other end of the axial notch. The foil bearing device according to claim 4. [Claim 6] The bump foil includes a bump portion that protrudes toward the top foil, Each of the at least one through hole and the apex of the bump portion overlaps with each other in the rotational direction of the rotation axis. The foil bearing device according to claim 1 or 2.

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