Centrifugal compressor

Abstract

This centrifugal compressor is provided with a rotary shaft, a compressor impeller fixed to the rotary shaft, and a flow path wall forming a scroll flow path around the compressor impeller. The flow path wall is provided with an outer peripheral wall portion disposed on an outer side in a radial direction of the rotary shaft, and an inner peripheral wall portion disposed on an inner side closer to the rotary shaft than the outer peripheral wall portion in the radial direction. The outer peripheral wall portion is provided with a thick portion having a wall thickness greater than that of the inner peripheral wall portion facing in the radial direction.

Description

centrifugal compressor

[0001] The present disclosure relates to centrifugal compressors.

[0002] Patent Document 1 discloses a centrifugal compressor equipped with a compressor cover. The compressor cover has a flow path wall of a scroll flow path. The flow path wall of the scroll flow path is formed by a plurality of pieces. Patent Document 1 discloses an outer fastening member and an inner fastening member for fastening the plurality of pieces. Patent Document 2 discloses a turbine wheel and a turbine housing, although it is not a centrifugal compressor. Furthermore, Patent Document 3 discloses a blower equipped with an impeller and a scroll, although it is not a centrifugal compressor.

[0003] JP 2012-211544 A International Publication No. 2015 / 188028 JP 2021-105385 A

[0004] To downsize a centrifugal compressor, it is necessary to reduce the outer diameter of the scroll passage. However, reducing the outer diameter of the scroll passage reduces the cross-sectional area of ​​the scroll passage, resulting in a decrease in compression efficiency. On the other hand, if the wall thickness of the scroll passage wall is reduced to maintain the cross-sectional area, the containment property may be impaired in the event of impeller damage.

[0005] The present disclosure describes a centrifugal compressor that can maintain containment in the scroll passage and ensure the necessary flow cross-sectional area for the scroll passage.

[0006] A centrifugal compressor according to one aspect of the present disclosure includes a rotating shaft, a compressor impeller fixed to the rotating shaft, and a flow path wall forming a scroll flow path around the compressor impeller. The flow path wall includes an outer circumferential wall portion disposed radially outward of the rotating shaft, and an inner circumferential wall portion disposed radially inward and closer to the rotating shaft than the outer circumferential wall portion. The outer circumferential wall portion includes a thick portion that is thicker than the radially opposing inner circumferential wall portion.

[0007] In the event of a compressor impeller failure, the outer peripheral wall portion located radially outward of the rotating shaft is most susceptible to damage. Conversely, the inner peripheral wall portion located radially inward is less susceptible to damage than the outer peripheral wall portion. Therefore, by providing a thick portion in the outer peripheral wall portion, the containment of a damaged compressor impeller can be maintained. On the other hand, the inner peripheral wall portion can be made thinner than the thick portion, which contributes to a more compact design than if the inner peripheral wall portion had a uniform thickness while maintaining the necessary cross-sectional area for the scroll passage. As a result, a centrifugal compressor can maintain the containment of the scroll passage and ensure the necessary cross-sectional area for the scroll passage.

[0008] In some embodiments, the flow path wall may include a connecting wall portion connecting the outer peripheral wall portion and the inner peripheral wall portion. The connecting wall portion may include a thickness change portion in which the thickness changes continuously from the thick portion to the inner peripheral wall portion. The connecting wall portion connects the outer peripheral wall portion and the inner peripheral wall portion. If the compressor impeller were to break, the impact on the connecting wall portion would gradually decrease from the thick portion to the inner peripheral wall portion. By providing a thickness change portion in which the thickness changes continuously from the thick portion to the inner peripheral wall portion, it is possible to set the wall thickness taking into account the magnitude of this impact.

[0009] In some embodiments, the scroll passage may further include a discharge pipe forming a discharge passage communicating with the scroll passage. The thick-walled portion may be located on the opposite side of the rotation axis from the discharge pipe. According to this embodiment, it is possible to maintain the containment of the portion of the scroll passage far from the discharge passage with respect to the rotation axis.

[0010] In some aspects, the compressor may further include a discharge pipe that forms a discharge passage communicating with the scroll passage and has a pipe axis extending tangentially to the scroll passage. The passage wall includes a first passage wall portion disposed upstream in the flow direction of the scroll passage and a second passage wall portion disposed downstream in the flow direction, in a cross section that includes the rotation axis of the compressor impeller and is cut along a plane parallel to the pipe axis. The thickened portion may be disposed in a passage region extending from the first passage wall portion to the second passage wall portion in the flow direction of the scroll passage. The passage region extending from the first passage wall portion to the second passage wall portion is susceptible to damage when the compressor impeller is damaged. According to this aspect, by providing the thickened portion in the passage region, sealability can be maintained in at least a portion of the passage region.

[0011] In some embodiments, the thickened portion can be provided over the entire flow path region, which allows the sealability to be maintained over the entire flow path region.

[0012] In some embodiments, the ratio of the thickness of the thickened portion provided throughout the flow path region to the thickness of the inner circumferential wall portion radially opposite the thickened portion can be constant, thereby maintaining substantially the same degree of sealability throughout the flow path region.

[0013] In some aspects, the compressor may further include a compressor housing that houses the compressor impeller and has a flow path wall, and a diffuser plate that is fixed to the compressor housing to form a diffuser flow path. The thickness of the diffuser plate may be thinner than the thickness of the thickened portion. If the compressor impeller is damaged, the impact on the diffuser plate is smaller than that on the outer peripheral wall portion. According to this aspect, by making the diffuser plate thinner than the thickness of the thickened portion, it is possible to reduce the size while maintaining the containment performance.

[0014] In some aspects, the thickness of the diffuser plate can be made thicker than the wall thickness of the inner circumferential wall portion radially opposite the thick portion.

[0015] In some embodiments, the compressor further includes a compressor housing that houses the compressor impeller and that includes a flow path wall, and a diffuser plate that is fixed to the compressor housing to form a diffuser flow path. The flow path wall may include a connecting wall portion that connects the outer circumferential wall portion and the inner circumferential wall portion and is disposed opposite the diffuser plate.

[0016] In some aspects, the connecting wall can include a portion that is thinner than the diffuser plate.

[0017] In some embodiments, the compressor housing includes a compressor impeller, the compressor housing including a scroll section having a flow passage wall, and a discharge pipe connected to the scroll section and forming a discharge passage communicating with the scroll flow passage. The outer peripheral wall section may have a thickened portion in an entire region along the scroll flow passage.

[0018] According to some aspects of the present disclosure, it is possible to maintain containment in the scroll passage and ensure the necessary flow passage cross-sectional area for the scroll passage.

[0019] Fig. 1 is a cross-sectional view showing a centrifugal compressor according to an embodiment of the present disclosure. Fig. 2 is a cross-sectional view taken along line II-II in Fig. 1. Fig. 3 is a perspective view of a compressor housing. Fig. 4 is a plan view of the compressor housing. Fig. 5 is a cross-sectional view taken along line VV in Fig. 4. Fig. 6 is a cross-sectional view taken along line VI-VI in Fig. 4.

[0020] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the description of the drawings, the same elements are designated by the same reference numerals, and duplicated descriptions will be omitted. In the following description, unless otherwise specified, the term "radial direction" is used based on the rotation axis 12 or the rotation axis X. The "radial direction" refers to, for example, the centrifugal direction relative to the rotation axis 12 or the rotation axis X.

[0021] A centrifugal compressor 1 according to one embodiment will be described with reference to Fig. 1 . The centrifugal compressor 1 is applied to an internal combustion engine of a vehicle or a ship, for example. The centrifugal compressor 1 is a type of rotary machine and includes a compressor 7. The centrifugal compressor 1 rotates a compressor impeller 8 through the interaction of a rotor section 13 and a stator section 14, compresses a gas such as air, and generates a compressed fluid such as compressed air. The rotor section 13 and the stator section 14 form a motor 5.

[0022] The centrifugal compressor 1 may be connected to a turbocharger (not shown) applied to an internal combustion engine of a vehicle or a ship, for example. In this case, the centrifugal compressor 1 sends compressed air to a compressor 7 of the turbocharger. By combining the centrifugal compressor 1 with the turbocharger, the centrifugal compressor 1 helps the turbocharger start up.

[0023] The centrifugal compressor 1 includes a rotating shaft 12 rotatably supported within a housing 2, and a compressor impeller 8 attached to the end of the rotating shaft 12. The housing 2 includes a motor housing 3 that houses a rotor section 13 and a stator section 14, and a compressor housing 6 that houses the compressor impeller 8. The compressor housing 6 is fixed to the end (left side in the figure) of the motor housing 3. The compressor housing 6 includes a suction pipe 9, a scroll section 10, and a discharge pipe 11 (see FIGS. 2 and 3 ). An inverter, an inverter housing, etc. may be provided outside the motor housing 3.

[0024] The motor housing 3 includes a cylindrical outer housing 31 that is open on one side, an inner housing 32 housed within the outer housing 31, and a lid 35 that closes the open end of the outer housing 31. The inner housing 32 includes a bearing support 17 that supports the bearing 20A, and the lid 35 includes a bearing support 18 that supports the bearing 20B.

[0025] The rotating shaft 12 is rotatably supported by bearings 20A and 20B. The rotation axis X of the rotating shaft 12 can be described as the rotation axis X of the compressor impeller 8. The rotor unit 13 is attached to the center of the rotating shaft 12. The stator unit 14 is disposed around the rotating shaft 12 and is fixed to the inner surface of the inner housing 32 so as to surround the rotor unit 13. When an alternating current is applied to the coil of the stator unit 14 via a conductor, the rotor unit 13 and the stator unit 14 interact with each other to rotate the rotating shaft 12 and the compressor impeller 8 together. As the compressor impeller 8 rotates, it draws in external air through the suction pipe 9, compresses the air through the scroll unit 10, and discharges it from the discharge pipe 11. The compressed air discharged from the discharge pipe 11 is supplied to the internal combustion engine.

[0026] As shown in FIGS. 2 and 4 , the scroll section 10 includes a flow passage wall 21 that forms a scroll flow passage F1 around the compressor impeller 8. The interior of the discharge pipe 11 is a discharge flow passage F2 that communicates with the scroll flow passage F1. The discharge flow passage F2 is connected to an inlet Fa (upstream end) and an outlet Fb (downstream end) of the scroll flow passage F1. The discharge pipe 11 extends linearly from the outlet Fb of the scroll flow passage F1 and has a linear pipe axis Xa. For example, the pipe axis Xa is a straight line that extends from the outlet Fb of the scroll flow passage F1 in a tangential direction of the scroll flow passage F1. The discharge pipe 11 may extend linearly from the outlet Fb of the scroll flow passage F1 and then curve midway. In the case of a curved discharge pipe 11, the pipe axis Xa also curves midway.

[0027] The scroll flow passage F1 is a flow passage that forms a substantially spiral shape from the inlet Fa to the outlet Fb, and the flow passage cross-sectional area gradually increases from the inlet Fa to the outlet Fb. The flow passage wall 21 includes an outer peripheral wall portion 22 disposed on the outer side in the radial direction D1 with respect to the scroll flow passage F1, and an inner peripheral wall portion 23 disposed on the inner side in the radial direction D1. The inner peripheral wall portion 23 is a wall portion that is closer to the rotation shaft 12 in the radial direction D1 than the outer peripheral wall portion 22. In the flow direction D2 of the scroll flow passage F1, the wall thickness Ta of the outer peripheral wall portion 22 is substantially constant, and the wall thickness Tb of the inner peripheral wall portion 23 is substantially constant.

[0028] 2, the flow direction D2 of the scroll flow passage F1 is clockwise. The inlet Fa of the scroll flow passage F1 is an upstream end in the flow direction D2, and the outlet Fb is a downstream end. The inlet Fa is provided with a tongue portion 6a.

[0029] For example, assuming that the flow direction D2 is the direction of rotation around the rotation axis X, the straight line connecting the rotation axis X and the tongue portion 6a is the inlet cross line L1. Also, the straight line that is perpendicular to the center line of the discharge flow path F2 and intersects with the rotation axis X is the outlet cross line L2. In this case, in the scroll flow path F1, the portion that intersects with the inlet cross line L1 is the inlet Fa, and the portion that intersects with the outlet cross line L2 is the outlet Fb.

[0030] Furthermore, assuming that the inlet intersecting line L1 is positioned at 0° in the rotational direction, the rotation angle of the inlet intersecting line L1 is 0°. For example, the straight line indicating a position rotated 300° in the rotational direction from the inlet intersecting line L1 is the outlet intersecting line L2. In this case, in the scroll flow path F1, the portion that intersects with the inlet intersecting line L1 is the inlet Fa, and the portion that intersects with the outlet intersecting line L2 is the outlet Fb.

[0031] For example, the scroll flow path F1 includes an inlet region FB including the inlet Fa, an outlet region FC including the outlet Fb, and a flow path region FA between the inlet region FB and the outlet region FC. For example, the inlet region FB can be defined as a region rotated 30° (30° rotation angle) from the inlet Fa in the rotational direction. The flow path region FA can be defined as a region rotated 210° (210° rotation angle) from the 30° rotational direction to the 210° rotational direction. The outlet region FC can be defined as a region rotated 210° from the 210° rotational direction to the outlet Fb. Note that the above rotation angles are merely examples, and the inlet region FB, the outlet region FC, and the flow path region FA can be defined by different rotation angles depending on the shape and dimensions of the scroll flow path F1. For example, the inlet region FB can be defined as a region rotated 20° from the inlet Fa to a region rotated 20°, the flow path region FA can be defined as a region rotated 30° from the 200° rotational direction to the outlet Fb, and the outlet region FC can be defined as a region rotated 200° from the 200° rotational direction to the outlet Fb.

[0032] The inlet region FB, outlet region FC, and flow path region FA can be described based on a reference plane Bs that includes the rotation axis X. For example, a plane that includes the rotation axis X and is parallel to the pipe axis Xa is assumed to be the reference plane Bs. The pipe axis Xa when assuming the reference plane Bs is a portion that extends linearly from the outlet Fb of the scroll flow path F1. If the pipe axis Xa is curved, this portion can be identified by ignoring the curved portion. The region from the inlet Fa to the reference plane Bs is the inlet region FB. The region from the outlet Fb to the reference plane Bs is the outlet region FC. The region located on the opposite side of the reference plane Bs from the discharge pipe 11 is the flow path region FA.

[0033] For example, Fig. 5 is a cross-sectional view of the compressor housing 6 cut along a reference plane Bs. In the cross section shown in Fig. 5, the scroll flow passage F1 is shown with two flow passage portions: a flow passage portion on the inlet Fa side, which is upstream of the flow direction D2, and a flow passage portion on the outlet Fb side, which is downstream of the flow direction D2. The flow passage wall 21 includes a first flow passage wall portion 21a that forms the flow passage portion on the inlet Fa side, and a second flow passage wall portion 21b that forms the flow passage portion on the outlet Fb side. The flow passage area FA (see Fig. 2) of the scroll flow passage F1 is the area from the first flow passage wall portion 21a to the second flow passage wall portion 21b.

[0034] As shown in Fig. 2, the outer peripheral wall portion 22 has a thick portion 22a having a wall thickness Ta that is thicker than that of the inner peripheral wall portion 23. The thick portion 22a is located at least on the opposite side of the discharge pipe 11 with respect to the rotary shaft 12. The thick portion 22a is provided, for example, in the flow path region FA. The thick portion 22a is a portion of the inner peripheral wall portion 23 where the wall thickness Ta is thicker than the wall thickness Tb of a portion of the inner peripheral wall portion 23 that is located opposite the thick portion 22a in the radial direction D1 (see Fig. 6). In the example shown in Fig. 2, the thick portion 22a is formed in the entire region along the scroll flow path F1.

[0035] For example, in the flow path region FA, the wall thickness Ta of the outer peripheral wall portion 22 is constant in the flow direction D2, and the wall thickness Tb of the inner peripheral wall portion 23 is constant in the flow direction D2. In other words, the wall thickness Ta of the outer peripheral wall portion 22 of the flow path region FA is thicker than the wall thickness Tb of the inner peripheral wall portion 23 throughout the entire flow direction.

[0036] For example, the ratio of the thickness of the thick portion 22a provided throughout the entire flow path area FA to the thickness of the inner circumferential wall portion 23 facing the thick portion 22a in the radial direction D1 is constant. The ratio of the wall thickness Ta of the thick portion 22a to the wall thickness Tb of the inner circumferential wall portion 23 can be, for example, 1.1 to 3.0 times. Furthermore, the ratio of the wall thickness Ta to the wall thickness Tb can be 1.3 to 2.0 times.

[0037] For example, the wall thickness Ta of the outer peripheral wall portion 22 may not be constant in the flow direction D2 but may vary partially. Furthermore, the wall thickness Tb of the inner peripheral wall portion 23 may not be constant in the flow direction D2 but may vary partially. In such an example, if the wall thickness Ta of a portion (target portion) of the outer peripheral wall portion 22 is thicker than the wall thickness Tb of a portion of the inner peripheral wall portion 23 facing it in the radial direction D1, the target portion of the outer peripheral wall portion 22 is the thick portion 22a. Furthermore, in such an example, if the wall thickness of an arbitrary portion (arbitrary portion) of the outer peripheral wall portion 22 is thicker than the wall thickness of a portion of the inner peripheral wall portion 23 facing it in the radial direction D1, the outer peripheral wall portion 22 has the thick portion 22a throughout the entire flow path region FA.

[0038] As shown in FIGS. 5 and 6 , the flow path wall 21 includes a connecting wall 24 connecting the outer peripheral wall 22 and the inner peripheral wall 23. The connecting wall 24 is disposed opposite the diffuser plate 51. The connecting wall 24 includes a thickness-changing portion 24a whose thickness continuously changes from the thick portion 22a of the outer peripheral wall 22 to the inner peripheral wall 23. For example, the thickness-changing portion 24a is provided so that the wall thickness gradually decreases from the thick portion 22a to the inner peripheral wall 23. For example, the thickness-changing portion 24a is thickest at an outer portion connected to the thick portion 22a and thinnest at an inner portion connected to the inner peripheral wall 23. For example, the outer portion of the thickness-changing portion 24a connected to the thick portion 22a is thicker than the wall thickness Tc (thickness) of the diffuser plate 51, and the inner portion connected to the inner peripheral wall 23 is thinner than the wall thickness Tc (thickness) of the diffuser plate 51.

[0039] The thick portion 22a is provided, for example, over the entire flow path area FA in the flow direction D2. The thickness change portion 24a is provided, for example, over the entire flow path area FA in the flow direction D2 so as to correspond to the thick portion 22a. Note that the thickness change portion 24a may be provided partially or in multiple portions in the flow direction D2.

[0040] A diffuser plate 51 that forms a diffuser flow path F3 is fixed to the compressor housing 6. The diffuser plate 51 forms the diffuser flow path F3 between itself and the compressor housing 6. The compressor housing 6 is formed with an impeller housing F4 that houses the compressor impeller 8 and a scroll flow path F1. The diffuser flow path F3 is provided to communicate between the impeller housing F4 and the scroll flow path F1. For example, the wall thickness Tc of the diffuser plate 51 is constant. However, the wall thickness Tc of the diffuser plate 51 does not have to be constant.

[0041] For example, the wall thickness Ta of the thick portion 22a of the outer peripheral wall portion 22 is thicker than the wall thickness Tc of the diffuser plate 51. The following explains the meaning of "wall thickness Ta is thicker than wall thickness Tc." When the wall thickness Ta of the thick portion 22a and the wall thickness Tc of the diffuser plate 51 are constant, this means that the thick portion 22a is thicker than the wall thickness Tc of the diffuser plate 51 over the entire region. When the wall thickness Ta of the thick portion 22a and the wall thickness Tc of the diffuser plate 51 are not constant, for example, by comparing the thickest portion of the wall thickness Ta of the thick portion 22a with the thickest portion of the wall thickness Tc of the diffuser plate 51, this means that the wall thickness Ta of the thick portion 22a is thicker than the wall thickness Tc of the diffuser plate 51.

[0042] For example, the wall thickness Tc of the diffuser plate 51 is thicker than the wall thickness Tb of the inner circumferential wall portion 23. When the wall thickness Tc of the diffuser plate 51 and the wall thickness Tb of the inner circumferential wall portion 23 are constant, this means that the diffuser plate 51 is thicker than the wall thickness Tb of the inner circumferential wall portion 23 over the entire region. When the wall thickness Tc of the diffuser plate 51 and the wall thickness Tb of the inner circumferential wall portion 23 are not constant, for example, by comparing the thickest portion of the wall thickness Tc of the diffuser plate 51 with the thinnest portion of the wall thickness Ta of the inner circumferential wall portion 23, this means that the wall thickness Tc of the diffuser plate 51 is thicker than the wall thickness Tb of the inner circumferential wall portion 23.

[0043] Next, the operation and effects of the centrifugal compressor 1 according to the embodiment will be described. Assuming that the compressor impeller 8 is damaged, the outer peripheral wall portion 22, which is located on the outer side in the radial direction D1 of the rotating shaft 12, is most susceptible to damage. Conversely, the inner peripheral wall portion 23, which is located on the inner side in the radial direction D1, is less susceptible to damage than the outer peripheral wall portion 22. The centrifugal compressor 1 includes the thick portion 22a in the outer peripheral wall portion 22, so that the outer peripheral wall portion 22 has sufficient strength to withstand the damage even if the compressor impeller 8 is damaged. As a result, the containment of the damaged compressor impeller 8 can be maintained. Meanwhile, the flow path cross-sectional area required for the scroll flow path F1 can be adjusted by adjusting the wall thickness Tb of the inner peripheral wall portion 23, which is thinner than the thick portion 22a. This contributes to a more compact design than when the inner peripheral wall portion 23 has a uniform thickness. As a result, the centrifugal compressor 1 makes it possible to maintain the containment of the scroll flow path F1 and ensure the flow path cross-sectional area required for the scroll flow path F1.

[0044] For example, the flow path wall 21 includes a connecting wall portion 24 that connects the outer peripheral wall portion 22 and the inner peripheral wall portion 23. The connecting wall portion 24 includes, for example, a thickness-changing portion 24a whose thickness changes continuously from the thick portion 22a to the inner peripheral wall portion 23. If the compressor impeller 8 were to be damaged, the effect on the connecting wall portion 24 would gradually decrease from the thick portion 22a to the inner peripheral wall portion 23. By providing the thickness-changing portion 24a whose thickness changes continuously from the thick portion 22a to the inner peripheral wall portion 23, it is possible to set the wall thickness taking into account the magnitude of this effect.

[0045] For example, the centrifugal compressor 1 includes a discharge pipe 11, and the thick portion 22a is disposed on the opposite side of the discharge pipe 11 with respect to the rotary shaft 12. As a result, in the scroll flow path F1, it is possible to maintain the containment performance of a portion far from the discharge flow path F2 with respect to the rotary shaft 12.

[0046] For example, the scroll flow passage F1 includes a first flow path wall 21a disposed upstream in the flow direction D2 of the scroll flow passage F1 and a second flow path wall 21b disposed downstream in the flow direction D2. The thick portion 22a is disposed in a flow path region FA extending from the first flow path wall 21a to the second flow path wall 21b in the flow direction D2 of the scroll flow passage F1. The flow path region FA extending from the first flow path wall 21a to the second flow path wall 21b is susceptible to damage when the compressor impeller 8 is damaged. By providing the thick portion 22a in the flow path region FA, it is possible to maintain the sealing performance in at least a portion of the flow path region FA.

[0047] For example, the thickened portion 22a can be provided over the entire flow path area FA, so that the sealing performance can be maintained over the entire flow path area FA.

[0048] For example, the ratio of the thickness of the thick portion 22 a provided throughout the flow path region FA to the thickness of the inner circumferential wall portion 23 facing the thick portion 22 a in the radial direction D1 can be constant, thereby maintaining substantially the same degree of sealing performance throughout the flow path region FA.

[0049] For example, the thickness of the diffuser plate 51 is thinner than the thickness of the thick portion 22a. If the compressor impeller 8 were to be damaged, the impact would be smaller on the diffuser plate 51 than on the outer peripheral wall portion 22. By making the diffuser plate 51 thinner than the thick portion 22a, it is possible to reduce the size while maintaining the containment performance.

[0050] The centrifugal compressor according to the present disclosure is not limited to the above-described examples, and various other modifications are possible. For example, the above-described examples may be combined with each other depending on the required purpose and effect. The thickened portion may be provided throughout the entire scroll flow path. The thickened portion may be provided in a part or multiple locations of the flow path region of the scroll flow path. The thickened portion may be provided in a location outside the flow path region of the scroll flow path, for example, in the inlet region or the outlet region.

[0051] X Rotation axis 1 Centrifugal compressor 6 Compressor housing 8 Compressor impeller 11 Discharge pipe 12 Rotation shaft 21 Flow path wall 21a First flow path wall portion 21b Second flow path wall portion 22 Outer peripheral wall portion 22a Thick portion 23 Inner peripheral wall portion 24 Connection wall portion 24a Thickness change portion 51 Diffuser plate Bs Reference plane F1 Scroll flow path FA Flow path area F2 Discharge flow path F3 Diffuser flow path Xa Pipe axis D1 Radial direction D2 Flow direction Ta Wall thickness of outer peripheral wall portion (thick portion) Tb Wall thickness of inner peripheral wall portion Tc Wall thickness of diffuser plate

Claims

1. A centrifugal compressor comprising: a rotating shaft; a compressor impeller fixed to the rotating shaft; and a flow passage wall forming a scroll flow passage around the compressor impeller, wherein the flow passage wall comprises: an outer peripheral wall portion arranged radially outward of the rotating shaft; and an inner peripheral wall portion arranged inward in the radial direction and closer to the rotating shaft than the outer peripheral wall portion, and the outer peripheral wall portion has a thick portion whose wall thickness is thicker than the inner peripheral wall portion facing it in the radial direction.

2. A centrifugal compressor as claimed in claim 1, wherein the flow path wall further comprises a connecting wall portion connecting the outer peripheral wall portion and the inner peripheral wall portion, and the connecting wall portion comprises a thickness changing portion whose thickness changes continuously from the thick portion to the inner peripheral wall portion.

3. The centrifugal compressor according to claim 1, further comprising a discharge pipe forming a discharge passage communicating with said scroll passage, said thick-walled portion being disposed on the opposite side of said discharge pipe with respect to said rotation axis.

4. A centrifugal compressor according to claim 1, further comprising a discharge pipe forming a discharge passage communicating with said scroll passage and having a pipe axis extending in a tangential direction of said scroll passage, wherein said passage wall includes the rotation axis of said compressor impeller and comprises a first passage wall portion arranged on the upstream side in the flow direction of said scroll passage and a second passage wall portion arranged on the downstream side in the flow direction, in a cross section cut by a plane that includes the rotation axis of said compressor impeller and is parallel to said pipe axis, and wherein said thick portion is arranged in a passage region extending from said first passage wall portion to said second passage wall portion in the flow direction of said scroll passage.

5. A centrifugal compressor according to claim 4, wherein said thickened portion is provided over the entire flow passage area.

6. A centrifugal compressor according to claim 5, wherein in said flow passage region, a ratio of a thickness of said thick portion to a thickness of said inner circumferential wall portion opposed to said thick portion in the radial direction is constant.

7. The centrifugal compressor according to claim 1, further comprising: a compressor housing that houses the compressor impeller and is provided with the flow passage wall; and a diffuser plate that is fixed to the compressor housing to form a diffuser flow passage, wherein the thickness of the diffuser plate is thinner than the thickness of the thick portion.

8. A centrifugal compressor according to claim 7, wherein the thickness of said diffuser plate is greater than the wall thickness of said inner circumferential wall portion opposed to said thick portion in the radial direction.

9. A centrifugal compressor according to claim 1, further comprising: a compressor housing that houses the compressor impeller and has the flow path wall; and a diffuser plate that is fixed to the compressor housing to form a diffuser flow path, wherein the flow path wall connects the outer circumferential wall portion and the inner circumferential wall portion and has a connecting wall portion disposed opposite to the diffuser plate.

10. A centrifugal compressor according to claim 9, wherein said connecting wall has a portion thinner than said diffuser plate.

11. A centrifugal compressor according to claim 1, comprising a compressor housing that accommodates the compressor impeller, the compressor housing comprising a scroll section having the flow passage wall, and a discharge pipe that is connected to the scroll section and forms a discharge passage communicating with the scroll flow passage, and the outer circumferential wall portion is provided with the thick portion over the entire area along the scroll flow passage.

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