CENTRIFUGAL COMPRESSOR

Abstract

A centrifugal compressor includes a passage forming member being arranged in a rear side of an impeller fixed to a tip side of a rotor shaft, and forming a passage, together with a scroll member, and a casing member disposed adjacent to an opposite side of the passage forming member from the impeller along an axial direction. The passage forming member has a first protrusion, and the casing member has a second protrusion. The first protrusion and the second protrusion are fixed to each other by a bolt member inserted from an outside in a radial direction toward an inside in the radial direction.

Description

TECHNICAL FIELD

This disclosure relates to a centrifugal compressor.

BACKGROUND

A centrifugal compressor is known as a rotating machine, which is capable of compressing fluid by use of centrifugal force. Such a centrifugal compressor rotates an impeller attached to a rotor shaft to generate compressed fluid. The rotor shaft is rotatably supported by a bearing, and the impeller is fixed to at least one end side of the rotor shaft.

As for a rotor shaft having a cantilever structurer, an impeller is fixed to the rotor shaft in the tip side with respect to the position supported by a bearing, and the diameter of the impeller is larger than the diameter of the rotor shaft. Therefore, it is important to suppress the shaft vibration from occurring during rotation, and to prevent the impeller fixed to the rotor shaft from contacting with a peripheral member. In an example, Patent Document 1 discloses the configuration advantageous in suppressing shaft vibration, in which a nut for fixing an impeller to a rotor shaft is arranged inside the impeller so that the center of gravity of the rotor is shifted to a bearing.

CITATION LIST

Patent Literature

Patent Document 1: JP2011-52580A

SUMMARY

A downsized rotor is advantageous in suppressing the shaft vibration from occurring and in preventing the impeller from contacting with a peripheral component in the description above. Although, in Patent Document 1 described above, a nut is arranged inside an impeller so as to provide a shorter rotor, resulting in contributing to the suppression of the shaft vibration, there is room for further improvement.

At least one aspect of the present disclosure has been proposed in the light of the above-described circumstances. The present disclosure is to provide a centrifugal compressor capable of suppressing the rotor vibration from occurring in the rotor shaft during driving, and preventing the impeller fixed to the rotor shaft from contacting with a peripheral component.

A centrifugal compressor according to one aspect of the present disclosure and capable of coping with the above includes: a rotor shaft rotatably supported by a bearing; an impeller fixed to the rotor shaft in a tip side with respect to the bearing; a passage forming member being arranged in a rear side of the impeller, and forming a passage communicating with a scroll passage, together with a scroll member forming the scroll passage outside the impeller in a radial direction; and a casing member disposed adjacent to an opposite side of the passage forming member from the impeller along an axial direction. In the centrifugal compressor, the passage forming member has a first protrusion formed to protrude toward the casing member, the casing member has a second protrusion formed to protrude toward the passage forming member, and the first protrusion and the second protrusion are fixed to each other by a bolt member inserted from an outside in the radial direction to an inside in the radial direction.

At least one aspect of the present disclosure enables suppressing the vibration from occurring in the rotor shaft during driving, and further preventing the impeller fixed to the rotor shaft from contacting with a peripheral member.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a perspective view illustrating a schematic configuration of a centrifugal compressor according to one aspect of the present disclosure.

FIG. 2 is a cross-sectional configuration diagram of a vicinity of a turbo blower according to one aspect of the present disclosure.

FIG. 3 is a cross-sectional view at an A-A line shown in FIG. 2.

FIG. 4 is a cross-sectional view at a B-B line shown in FIG. 3.

FIG. 5 shows a modification of FIG. 3.

FIG. 6 shows another modification of FIG. 3.

FIG. 7 is a cross-sectional view at a D-D line shown in FIG. 6.

FIG. 8 shows another modification of FIG. 3.

FIG. 9 shows another modification of FIG. 4.

FIG. 10 is a cross-sectional configuration diagram of a vicinity of a turbo blower according to the reference art.

DETAILED DESCRIPTION

Some embodiments of the present invention will now be described below with reference to the drawings. However, the scope of the present invention is not limited to the embodiments described below. It is intended that sizes, materials, shapes, relative positions and the like of components described in the embodiments below are merely examples, and are not for limitation of the scope of the present invention.

FIG. 1 is a perspective view illustrating a schematic configuration of a centrifugal compressor 1 according to one aspect of the present disclosure. The centrifugal compressor 1 is a geared compressor (integrally geared compressor) in which a speed-increasing gear mechanism 2 speeds up power and transmits the power to a rotor 4 so as to compress fluid. The speed-increasing gear mechanism 2 has a main driving shaft 6 which accepts power from a power source (not shown), and a main driving gear 8 connected to the main driving shaft 6. The rotor 4 includes a driven gear 10 engaged with the main driving gear 8, a rotor shaft 12 connected to the driven gear 10, and an impeller 14A and an impeller 14B respectively provided at the tips of the rotor shaft 12.

When power is input from a power source to the speed-increasing gear mechanism 2 via the main driving shaft 6, the main driving gear 8 is rotated together with the main driving shaft 6. The rotation rotates the rotor 4 via the driven gear 10 engaged with the main driving gear 8. When the rotor 4 is rotated, the impellers 14A, 14B compress fluid by using the centrifugal force generated by the rotation of the rotor shaft 12.

It is noted that, in the description below, the extending direction of a rotation axis C of the rotor shaft 12 is called an axial direction; the direction of the circumference around the rotation axis C is called a circumferential direction; and the direction of the diameter of the circumference is called a radial direction. Moreover, the side close to the rotation axis C with respect to the radial direction is called an inside in the radial direction, and the side far from the rotation axis C with respect to the radial direction is called an outside in the radial direction.

The centrifugal compressor 1 has a gear casing 16 configured to accommodate the speed-increasing gear mechanism 2, and a turbo blower 18A and a turbo blower 18B respectively including the impellers 14A, 14B. The turbo blowers 18A, 18B are arranged respectively on the both sides in the axial direction with respect to the gear casing 16, so as to correspond to the impellers 14A, 14B.

The turbo blower 18A has an inlet passage 19 for taking in the fluid to be compressed from an upstream passage, and an outlet passage 15 for discharging the fluid after compression to the outside. The inlet passage 19 is communicated with an inlet pipe not shown and the outlet passage 15 is communicated with an outlet pipe not shown. As will be described below with reference to FIG. 2 and FIG. 10, the turbo blower 18A has, outside the impeller 14A in the radial direction, a discharge scroll 24 which forms the outlet passage 15 and which extends long in the radial direction to the outside of the gear casing 16.

The turbo blower 18B has the same configuration as the configuration of the turbo blower 18A described above, except that the position and orientation to be arranged are different. In the following description, the configuration of the turbo blower 18A is mainly described. Unless otherwise stated, the configuration of the turbo blower 18B is the same.

Reference Art

The internal configuration of the centrifugal compressor 1 is next described specifically. The reference art serving as a prior art is described first. FIG. 10 is a cross-sectional configuration diagram of the vicinity of the turbo blower 18A according to the reference art.

The turbo blower 18A includes an impeller casing body 20, and a passage forming member 22, together with the impeller casing body 20, forming the outer casing of the turbo blower 18A. The impeller 14A fixed to the tip of the rotor shaft 12 extending along the rotation axis C is accommodated in an internal space S defined by the impeller casing body 20 and the passage forming member 22. The impeller casing body 20 mainly surrounds the impeller 14A from the tip side (from the outside in the axial direction), and accommodates the discharge scroll 24. The passage forming member 22 is arranged in the rear side (inside in the axial direction) of the impeller 14A, and forms, together with the impeller casing body 20, a communication passage R communicating the internal space S and the discharge scroll 24.

The passage forming member 22 is fixed to the impeller casing body 20 outside the gear casing 16 in the radial direction, by a first bolt member 23 inserted along the axial direction. The first bolt member 23 is inserted into a first hole part 25 formed from the passage forming member 22 over to the impeller casing body 20, to fix the passage forming member 22 and the impeller casing body 20 to each other.

At least one set of the first bolt member 23 and the first hole part 25 is provided along the circumferential direction of the rotation axis C. In FIG. 10, a plurality of sets of the first bolt members 23 and the first hole parts 25 are provided, thereby improving the rigidity of the passage forming member 22 and the impeller casing body 20 fixed to each other.

The gear casing 16 accommodating the speed-increasing gear mechanism 2 is disposed on the opposite side from the impeller 14A along the axial direction with respect to the passage forming member 22. The gear casing 16 includes a gear casing body 16a, and a flange portion 16b which is disposed in the side of the passage forming member 22 with respect to the gear casing body 16a, and which faces the passage forming member 22 so as to be perpendicular to the rotation axis C. The flange portion 16b is fixed to the passage forming member 22 by a second bolt member 29 inserted along the axial direction.

The second bolt member 29 is inserted into a second hole part 30 formed from the flange portion 16b (gear casing 16) over to the passage forming member 22, to fix the passage forming member 22 and the flange portion 16b (gear casing 16) to each other. At least one set of such fixing structure including the second bolt member 29 and the second hole part 30 is provided along the circumferential direction of the rotation axis C. In the example shown in FIG. 10, a plurality of sets of the fixing structure including the second bolt members 29 and the second hole parts 30 are provided at equal intervals along the circumferential direction of the rotation axis C, to improve the rigidity.

The flange portion 16b has a disk shape substantially perpendicular to the rotation axis C, and includes an opening 31 having a substantially circular shape including the rotation axis C inside in the radial direction. In the opening 31, a sealing member 27 is arranged so as to rotatably support the rotor shaft 12 inside the impeller 14A in the axial direction, and to seal the internal space S from the outside. The flange portion 16b may be configured to be dividable into a plurality of pieces, whereby the sealing member 27 may be configured detachably.

The gear casing body 16a has a bearing 26 on the wall surface defining the outer casing of the turbo blower 18A. The bearing 26 rotatably supports the rotor shaft 12 inside the sealing member 27 in the axial direction. That is, the rotor shaft 12 is rotatably supported by the sealing member 27 of the flange portion 16b and by the bearing 26 of the gear casing body 16a, and the sealing member 27 and the bearing 26 are arranged respectively coaxially with the rotation axis C.

When the centrifugal compressor 1 is assembled, the second bolt member 29 shall be inserted into the second hole part 30 without any physical interference of the second bolt member 29 at the time of insertion. As for a gap M disposed along the rotation axis C between the flange portion 16b and the gear casing body 16a, such insertion requires the gap M to be ensured longer than the length in the axial direction of the second bolt member 29. The gap M as described above is required to be ensured by designing the rotor shaft 12 to be large in length due to the convenience of the assembly. The rotor shaft 12 designed large in length degrades the rotor build (in an example, a parameter in designing specified by D/L² becomes smaller, when a diameter and a length in the axial direction of the rotor shaft are denoted respectively by D and L). This may increase the risk of the shaft vibration occurring in the rotor 4 and/or the contact of the impeller 14A with a peripheral member. Several aspects to be described below are capable of suitably coping with the above.

It is noted that, in the aspects to be described below, the configurations corresponding to those in the reference art described above are denoted by the common reference signs, and the duplicate description will be appropriately omitted unless otherwise specified.

Embodiment

FIG. 2 is a cross-sectional configuration diagram of the vicinity of the turbo blower 18A according to one aspect of the present disclosure. FIG. 3 is a cross-sectional view at an A-A line shown in FIG. 2. FIG. 4 is a cross-sectional view at a B-B line shown in FIG. 3.

The passage forming member 22 has, on the side thereof facing the gear casing 16, a first protrusion 32 formed to protrude toward the gear casing 16. The gear casing 16 has, on the side thereof facing the passage forming member 22, a second protrusion 34 formed to protrude toward the passage forming member 22. The first protrusion 32 is arranged inside the second protrusion 34 in the radial direction, and the first protrusion 32 and the second protrusion 34 are arranged respectively coaxially with the rotation axis C. The first protrusion 32 and the second protrusion 34 are configured so that the outside face in the radial direction of the first protrusion 32 and the inside face in the radial direction of the second protrusion 34 are contacted with each other.

In the above-described arrangement where the first protrusion 32 is arranged inside the second protrusion 34 in the radial direction, the thermal expansion in the first protrusion 32 is greater than that in the second protrusion 34 when the turbo blower 18A is increased in temperature during the operation of the centrifugal compressor 1. As a result, the gap between the first protrusion 32 and the second protrusion 34 is decreased, thereby providing good sealing property.

The first protrusion 32 and the second protrusion 34 in contact with each other are fixed by a bolt member 36 inserted into a hole part 35 formed along the radial direction. The configuration allows the bolt member 36 to be inserted from the outside in the radial direction at the time of assembly. This eliminates the need for ensuring the gap M allowing the second bolt member 29 to be inserted as in the reference art described above by referring to FIG. 10. Accordingly, the rotor shaft 12 is enabled to be shortened in the axial direction (the corresponding gap can be reduced compared to the gap M shown in FIG. 10), thereby enabling to effectively suppress the risk of the shaft vibration occurring in the rotor 4 and/or the contact of the impeller 14A with a peripheral member.

The hole part 35 into which the bolt member 36 is inserted at the time of assembly is formed so as to be continuous from the second protrusion 34 over to the first protrusion 32 when the first protrusion 32 and the second protrusion 34 are in a predetermined positional relation shown in FIG. 3. In the example shown in FIG. 3, the hole part 35 penetrates through the second protrusion 34 located outside, from the outside in the radial direction toward the inside in the radial direction, and up to the inside of the first protrusion 32 located inside, from the outside in the radial direction. In such positional relation, the bolt member 36 is inserted into the hole part 35, thereby enabling to fix the relative positional relation between the first protrusion 32 and the second protrusion 34. That is, the hole part 35 and the bolt member 36 have the function of relative positioning of the first protrusion 32 and the second protrusion 34.

At least one set of such components of the hole part 35 and the bolt member 36 is provided along the circumferential direction around the rotation axis C. In the present embodiment, a plurality of sets of the hole parts 35 and the bolt members 36 are provided at equal intervals along the circumferential direction around the rotation axis C (when the upper direction in FIG. 3 is set as 0 degree, the sets of such components are respectively provided at the positions of 0 degree, 90 degrees, 180 degrees, and 270 degrees).

FIG. 5 shows a modification of FIG. 3. In the present modification, the first protrusion 32 and the second protrusion 34 in contact with each other include not only the fixing structure including the hole parts 35 and the bolt members 36 described above, but also additional fixing structure in which a pin member 38 is inserted into a pin hole part 37 along the radial direction. This configuration enables further improving the rigidity at the time when the first protrusion 32 and the second protrusion 34 are fixed to each other (in other words, the rigidity of the first protrusion 32 and the second protrusion 34 fixed to each other by the pin member 38 is improved in this way, thereby also enabling to provide sufficient strength even with fewer sets of the hole parts 35 and the bolt members 36 described above.

At least one set of the pin hole part 37 and the pin member 38 is provided along the circumferential direction around the rotation axis C. In the present embodiment, a plurality of sets of the pin hole parts 37 and the pin members 38 are provided at equal intervals along the circumferential direction around the rotation axis C (when the upper direction in FIG. 5 is set as 0 degree, the sets of the pin hole parts 37 and the pin members 38 are respectively arranged at the positions of 45 degrees, 135 degrees, 225 degrees, and 315 degrees).

FIG. 6 shows another modification of FIG. 3. FIG. 7 is a cross-sectional view at a D-D line shown in FIG. 6. In the present modification, at least one of the first protrusion 32 and the second protrusion 34 has a reinforcing rib 40. In FIG. 7, the reinforcing rib 40 is formed along the radial direction over both a radially outer surface 34a of the second protrusion 34 located outside the first protrusion 32 in the radial direction and a surface 34b of the gear casing 16 where the second protrusion 34 is disposed. This configuration enables to further improve the rigidity of the gear casing 16 where the second protrusion 34 is disposed.

FIG. 8 shows another modification of FIG. 3. In the present modification, the first protrusion 32 of the passage forming member 22 and the second protrusion 34 of the gear casing 16 are engaged with each other via a spline 42. The structure of connecting the first protrusion 32 and the second protrusion 34 enables to more effectively improve the rigidity in the circumferential direction.

FIG. 9 shows another modification of FIG. 4. In the present modification, the first protrusion 32 and the second protrusion 34 are engaged with each other in an inlay structure 44. In the example shown in FIG. 9, the passage forming member 22 has, outside the first protrusion 32 in the radial direction, a concave portion 44a allowing a convex portion 44b disposed at the tip of the second protrusion 34 to be engaged with. The adoption of the inlay structure 44 described above enables to accurately position the first protrusion 32 and the second protrusion 34 along the radial direction. The accurate positioning enables to coaxially and accurately align the sealing member 27 supported by the passage forming member 22 and the bearing 26 supported by the gear casing 16, thereby enabling to more effectively prevent the shaft vibration from occurring in the rotor 4 and/or the impeller 14A from contacting with a peripheral member.

Moreover, a known component is available as needed, instead of a component in the embodiment described above within the scope not deviating from the gist of the present disclosure. Some of the components described above may be combined as needed.

The contents described in the above respective embodiments are grasped, for example, as follows.

(1) A centrifugal compressor (for example, the centrifugal compressor 1 in the above described embodiments) according to one aspect of the present disclosure includes: a rotor shaft (for example, the rotor shaft 12 in the above described embodiments) rotatably supported by a bearing (for example, the bearing 26 in the above described embodiments); an impeller (for example, the impeller 14A or 14B in the above described embodiments) fixed to the rotor shaft in a tip side with respect to the bearing; a passage forming member (for example, the passage forming member 22 in the above described embodiments) being arranged in a rear side of the impeller, and forming a passage communicating with a scroll passage, together with a scroll member (for example, the impeller casing body 20 in the above described embodiments) forming the scroll passage outside the impeller in a radial direction; and a casing member (for example, the gear casing 16 in the above described embodiments) disposed adjacent to an opposite side of the passage forming member from the impeller along an axial direction. In the centrifugal compressor, the passage forming member has a first protrusion (for example, the first protrusion 32 in the above described embodiments) formed to protrude toward the casing member, the casing member has a second protrusion (for example, the second protrusion 34 in the above described embodiments) formed to protrude toward the passage forming member, and the first protrusion and the second protrusion are fixed to each other by a bolt member (for example, the bolt member 36 in the above described embodiments) inserted from an outside in the radial direction toward an inside in the radial direction.

According to the aspect of (1), the first protrusion of the passage forming member and the second protrusion of the casing member are fixed to each other by the bolt member. The bolt member is allowed to be inserted in the radial direction at the time of assembly, and this configuration eliminates the need for ensuring the gap allowing the bolt member to be inserted, between the casing member and the passage forming member. Accordingly, the rotor shaft is configured short in the axial direction, thereby enabling to effectively suppress the risk of the shaft vibration occurring in the rotor and/or the contact of the impeller with a peripheral member.

(2) In another aspect of the centrifugal compressor according to the aspect of (1), the first protrusion is arranged inside the second protrusion in the radial direction.

According to the aspect of (2), the first protrusion of the passage forming member and the second protrusion of the casing member under the state where the first protrusion is arranged inside the second protrusion in the radial direction are fixed by the bolt member. Accordingly, the thermal expansion in the first protrusion is greater than that in the second protrusion when the passage forming member is increased in temperature during the operation of the centrifugal compressor. As a result, the gap between the first protrusion and the second protrusion is decreased, thereby providing good sealing property.

(3) In another aspect of the centrifugal compressor according to the aspect of (1) or (2), a plurality of the bolt members are arranged along a circumferential direction of the rotor shaft.

According to the aspect of (3), the arrangement of the plurality of bolt members along the circumferential direction of the rotor shaft enables to effectively improve the rigidity of the fixing structure of the first protrusion and the second protrusion fixed by the bolt members.

(4) In another aspect of the centrifugal compressor according to any one aspect of (1) to (3), the first protrusion and the second protrusion are fixed to each other by a pin member (for example, the pin member 38 in the above described embodiment) inserted along the radial direction.

According to the aspect of (4), the pin member in addition to the bolt member fixes the first protrusion and the second protrusion, thereby providing further higher rigidity. Such a configuration additionally allowing the pin member to be inserted along the radial direction contributes to shorten the length in the axial direction of the rotor shaft, and thus enables to effectively suppress the risk of the shaft vibration occurring in the rotor and/or the contact of the impeller with a peripheral member. In this case, since the pin member is able to improve the rigidity of the first protrusion and the second protrusion fixed to each other, the number of the bolt members is able to be reduced.

(5) In another aspect of the centrifugal compressor according to any one aspect of (1) to (4), a reinforcing rib (for example, the reinforcing rib 40 in the above described embodiment) is formed along the radial direction, over both a radially outer surface of the second protrusion and a surface of the casing member.

According to the aspect of (5), the rigidity of the casing member provided with the second protrusion 34 is able to be improved further.

(6) In another aspect of the centrifugal compressor according to any one aspect of (1) to (5), the first protrusion and the second protrusion are engaged with each other via a spline (for example, the spline 42 in the above described embodiment).

According to the aspect of (6), the first protrusion and the second protrusion are engaged with each other via the spline, thereby enabling to provide higher rigidity, and further enabling to more effectively prevent the shaft vibration from occurring in the rotor and/or the impeller from contacting with a peripheral member.

(7) In another aspect of the centrifugal compressor according to any one aspect of (1) to (6), the first protrusion and the second protrusion are engaged with each other via an inlay structure (for example, the inlay structure 44 in the above described embodiment).

According to the aspect of (7), the first protrusion and the second protrusion are engaged with each other via the inlay structure, thereby enabling to provide higher rigidity, and further enabling to more effectively prevent the shaft vibration from occurring in the rotor and/or the impeller from contacting with a peripheral member.

(8) In another aspect of the centrifugal compressor according to any one aspect of (1) to (7), the passage forming member has a sealing member (for example, the sealing member 27 in the above described embodiments) configured to seal an internal space accommodating the impeller from an outside, and to rotatably support the rotor shaft.

According to the aspect of (8), the passage forming member is provided with the sealing member configured to seal the space accommodating the impeller from the outside. The sealing member needs to be arranged coaxially and accurately with the rotor shaft so as to rotatably support the rotor shaft. The bolt member inserted along the radial direction fixes the casing member and the passage forming member with high rigidity as described above, thereby enabling to realize the coaxial arrangement of the sealing member with high accuracy.

(9) In another aspect of the centrifugal compressor according to the aspect of (8), the casing member has a bearing (for example, the bearing 26 in the above described embodiments) configured to rotatably support the rotor shaft inside the sealing member in the axial direction.

According to the aspect of (9), the casing member is provided with the bearing configured to rotatably support the rotor shaft. The bearing needs to be arranged coaxially and accurately with the rotor shaft so as to rotatably support the rotor shaft. The bolt member inserted along the radial direction fixes the casing member and the passage forming member with high rigidity as described above, thereby enabling to realize the coaxial arrangement of the bearing with high accuracy.

(10) In another aspect of the centrifugal compressor according to any one aspect of (1) to (9), the casing member accommodates a speed-increasing gear mechanism (for example, the speed-increasing gear mechanism 2 in the above described embodiments) provided with the rotor shaft.

According to the aspect of (10), a geared compressor in which the casing member accommodates the speed-increasing gear mechanism is capable of suppressing the vibration from occurring in the rotor shaft during driving, and further capable of preventing the impeller fixed to the rotor shaft from contacting with a peripheral member.

Claims

1. A centrifugal compressor comprising:

a rotor shaft rotatably supported by a bearing;

an impeller fixed to the rotor shaft in a tip side with respect to the bearing;

a passage forming member arranged in a rear side of the impeller, the passage forming member forming, together with a scroll member forming a scroll passage outside the impeller in a radial direction, a passage communicating with the scroll passage; and

a casing member disposed adjacent to an opposite side of the passage forming member to the impeller along an axial direction, wherein

the passage forming member has a first protrusion formed to protrude toward the casing member,

the casing member has a second protrusion formed to protrude toward the passage forming member, and

the first protrusion and the second protrusion are fixed to each other by a bolt member inserted from an outside in the radial direction to an inside in the radial direction.

2. The centrifugal compressor according to claim 1, wherein

a plurality of the bolt members are disposed along a circumferential direction of the rotor shaft.

3. The centrifugal compressor according to claim 1, wherein

the first protrusion and the second protrusion are fixed to each other by a pin member inserted along the radial direction.

4. The centrifugal compressor according to claim 1, wherein

a reinforcing rib is formed along the radial direction, over both a radially outer surface of the second protrusion and a surface of the casing member.

5. The centrifugal compressor according to claim 1, wherein

the first protrusion and the second protrusion are engaged with each other via a spline.

6. The centrifugal compressor according to claim 1, wherein

the first protrusion and the second protrusion are engaged with each other via an inlay structure.

7. The centrifugal compressor according to claim 1, wherein

the passage forming member has a sealing member configured to seal an internal space accommodating the impeller from an outside, and to rotatably support the rotor shaft.

8. The centrifugal compressor according to claim 7, wherein

the casing member has a bearing configured to rotatably support the rotor shaft inside the sealing member in the axial direction.

9. The centrifugal compressor according to claim 1, wherein

the casing member accommodates a speed-increasing gear mechanism provided with the rotor shaft.

10. A centrifugal compressor comprising:

a rotor shaft rotatably supported by a bearing;

an impeller fixed to the rotor shaft in a tip side with respect to the bearing;

a passage forming member arranged in a rear side of the impeller, the passage forming member forming, together with a scroll member forming a scroll passage outside the impeller in a radial direction, a passage communicating with the scroll passage; and

a casing member disposed adjacent to an opposite side of the passage forming member to the impeller along an axial direction, wherein

the passage forming member has a first protrusion formed to protrude toward the casing member,

the casing member has a second protrusion formed to protrude toward the passage forming member,

the first protrusion and the second protrusion are fixed to each other by a bolt member inserted from an outside in the radial direction to an inside in the radial direction, and

the first protrusion is arranged inside the second protrusion in the radial direction.

11. The centrifugal compressor according to claim 10, wherein

a plurality of the bolt members are disposed along a circumferential direction of the rotor shaft.

12. The centrifugal compressor according to claim 10, wherein

the first protrusion and the second protrusion are fixed to each other by a pin member inserted along the radial direction.

13. The centrifugal compressor according to claim 10, wherein

a reinforcing rib is formed along the radial direction, over both a radially outer surface of the second protrusion and a surface of the casing member.

14. The centrifugal compressor according to claim 10, wherein

the first protrusion and the second protrusion are engaged with each other via a spline.

15. The centrifugal compressor according to claim 10, wherein

the first protrusion and the second protrusion are engaged with each other via an inlay structure.

16. The centrifugal compressor according to claim 10, wherein

the passage forming member has a sealing member configured to seal an internal space accommodating the impeller from an outside, and to rotatably support the rotor shaft.

17. The centrifugal compressor according to claim 16, wherein

the casing member has a bearing configured to rotatably support the rotor shaft inside the sealing member in the axial direction.

18. The centrifugal compressor according to claim 10, wherein

the casing member accommodates a speed-increasing gear mechanism provided with the rotor shaft.