Centrifugal compressor and turbocharger

A centrifugal compressor includes: a housing including an intake flow path; a compressor impeller arranged in the intake flow path and including a plurality of blades; an accommodation chamber formed upstream of the blades in a flow of intake air in the housing; a movable member arranged in the accommodation chamber and movable to a protruding position where the movable member protrudes into the intake flow path and to a retracted position where the movable member is retracted from the intake flow path; and one or more grooves formed over an inner circumferential surface and a side face closer to the blades in the movable member.

BACKGROUND ART

Technical Field

The present disclosure relates to a centrifugal compressor and a turbocharger.

A centrifugal compressor includes a compressor housing in which an intake flow path is formed. A compressor impeller is arranged in the intake flow path. When an air flow rate into the compressor impeller decreases, air compressed by the compressor impeller flows backward in the intake flow path, a phenomenon known as surging.

Patent Literature 1 discloses a centrifugal compressor comprising a throttling mechanism in a compressor housing. The throttling mechanism includes a movable member. The movable member is configured to be movable to a protruding position where the movable member protrudes into an intake flow path and to a retracted position where the movable member is retracted from the intake flow path. The throttling mechanism reduces a cross-sectional area of the intake flow path by causing the movable member to protrude into the intake flow path. When the movable member protrudes into the intake flow path, air flowing backward in the intake flow path is blocked by the movable member. By blocking the air flowing backward in the intake flow path, surging is curbed.

CITATION LIST

Patent Literature

SUMMARY

Technical Problem

The air flowing backward in the intake flow path includes a swirl component caused by the rotation of the compressor impeller. When the air flowing backward in the intake flow path is blocked by the movable member as described in Patent Literature 1, the swirl component of the air flowing backward disturbs a flow near a leading edge of the compressor impeller, which may generate noise that may be considered as aerodynamic noise.

The purpose of the present disclosure is to provide a centrifugal compressor and a turbocharger that can reduce noise.

Solution to Problem

In order to solve the above problem, a centrifugal compressor according to one aspect of the present disclosure includes: a housing including an intake flow path; a compressor impeller arranged in the intake flow path and including a plurality of blades; an accommodation chamber formed upstream of the blades in a flow of intake air in the housing; a movable member arranged in the accommodation chamber and movable to a protruding position where the movable member protrudes into the intake flow path and to a retracted position where the movable member is retracted from the intake flow path; and one or more grooves formed over an inner circumferential surface and a side face closer to the blades in the movable member.

The groove may include a plurality of spherical grooves arranged in a circumferential direction of the compressor impeller.

The groove may include a plurality of arc-shaped circumferential grooves arranged in a circumferential direction of the compressor impeller.

The plurality of grooves may be formed spaced apart from each other in the circumferential direction.

The plurality of grooves may be formed at unequal intervals in the circumferential direction.

In order to solve the above problem, a turbocharger of the present disclosure includes the centrifugal compressor described above.

Effects of Disclosure

According to the present disclosure, noise can be reduced.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. Specific dimensions, materials, and numerical values described in the embodiments are merely examples for a better understanding, and do not limit the present disclosure unless otherwise specified. In this specification and the drawings, duplicate explanations are omitted for elements having substantially the same functions and configurations by assigning the same reference sign. Furthermore, elements not directly related to the present disclosure are omitted from the figures.

First Embodiment

FIG.1is a schematic cross-sectional view of a turbocharger TC according to the first embodiment. A direction indicated by arrow L inFIG.1is described as the left side of the turbocharger TC. A direction indicated by arrow R shown inFIG.1is described as the right side of the turbocharger TC. In the turbocharger TC, a part including a compressor housing100(described later) functions as a centrifugal compressor CC. Hereinafter, the centrifugal compressor CC is described as being driven by a turbine impeller8(described later). However, the centrifugal compressor CC is not limited thereto, and may be driven by an engine (not shown) or by an electric motor (motor, not shown). As such, the centrifugal compressor CC may be incorporated into a device other than the turbocharger TC, or may be a stand-alone unit.

As shown inFIG.1, the turbocharger TC comprises a turbocharger body1. The turbocharger body1includes a bearing housing2, a turbine housing4, a compressor housing (housing)100, and a link mechanism200. Details of the link mechanism200will be described later. The turbine housing4is connected to the left side of the bearing housing2by fastening bolts3. The compressor housing100is connected to the right side of the bearing housing2by fastening bolts5.

An accommodation hole2ais formed in the bearing housing2. The accommodation hole2apasses through the bearing housing2in the left-to-right direction of the turbocharger TC. A bearing6is arranged in the accommodation hole2a. InFIG.1, a full floating bearing is shown as an example of the bearing6. However, the bearing6may be any other radial bearing, such as a semi-floating bearing or a rolling bearing. A part of a shaft7is arranged in the accommodation hole2a. The shaft7is rotatably supported by the bearing6. A turbine impeller8is provided at a left end of the shaft7. The turbine impeller8is rotatably housed in the turbine housing4. A compressor impeller9is provided at a right end of shaft7. In the present disclosure, a rotational axis direction, a radial direction, and a circumferential direction of the shaft7, the turbine impeller8, and the compressor impeller9may simply be referred to as the rotational axis direction, the radial direction, and the circumferential direction, respectively. The compressor impeller9is rotatably housed in the compressor housing100. The compressor impeller9includes a plurality of long blades9aand a plurality of short blades9bformed on an outer circumference surface of a hub. The plurality of long blades9aand short blades9bare formed alternately spaced apart from each other in the circumferential direction. The plurality of long blades9aand short blades9bare formed at equal intervals in the circumferential direction. A leading edge LE of the long blade9ais positioned spaced apart from the bearing housing2with respect to a leading edge LE of the short blade9b. In other words, the leading edge LE of the short blade9bis positioned closer to the bearing housing2with respect to the leading edge LE of the long blade9a. In the present embodiment, the compressor impeller9includes the long blades9aand the short blades9b. However, the compressor impeller9is not limited thereto, and may include only one of the long blades9aand the short blades9b.

An inlet10is formed in the compressor housing100. The inlet10opens to the right side of the turbocharger TC. The inlet10is connected to an air cleaner (not shown). A diffuser flow path11is formed between the bearing housing2and the compressor housing100. The diffuser flow path11pressurizes air. The diffuser flow path11is formed in an annular shape from a radially inner side to an outer side. The diffuser flow path11is connected to the intake flow path10via the compressor impeller9at a radially inner part.

A compressor scroll flow path12is formed in the compressor housing100. For example, the compressor scroll flow path12is located radially outside the compressor impeller9. The compressor scroll flow path12is connected to an intake port of an engine (not shown) and the diffuser flow path11. As the compressor impeller9rotates, air is sucked into the compressor housing100from the inlet10. The sucked air is pressurized and accelerated while passing through the blades of the compressor impeller9. The pressurized and accelerated air is further pressurized in the diffuser flow path11and the compressor scroll flow path12. The pressurized air flows out from an outlet (not shown) and is directed to the intake port of the engine.

As such, the turbocharger TC comprises the centrifugal compressor (compressor) CC that pressurizes fluid with using centrifugal force. The centrifugal compressor CC includes the compressor housing100, the compressor impeller9, and the link mechanism200described later.

An outlet13is formed in the turbine housing4. The outlet13opens to the left side of the turbocharger TC. The outlet13is connected to an exhaust gas purifier (not shown). A connecting flow path14and a turbine scroll flow path15are formed in the turbine housing4. The turbine scroll flow path15is located radially outside the turbine impeller8. The connecting flow path14is located between the turbine impeller8and the turbine scroll flow path15.

The turbine scroll flow path15is connected to a gas inlet (not shown). Exhaust gas discharged from an exhaust manifold of the engine (not shown) is directed to the gas inlet. The connecting flow path14connects the turbine scroll flow path15to the outlet13. The exhaust gas directed from the gas inlet to the turbine scroll flow path is directed to the outlet13through the connecting flow path14and blades of the turbine impeller8. The exhaust gas rotates the turbine impeller8when passing therethrough.

A rotational force of the turbine impeller8is transmitted to the compressor impeller9via the shaft7. As described above, air is pressurized by the rotational force of the compressor impeller9and directed to the intake port of the engine.

FIG.2is an extracted view of a part enclosed by dashed lines inFIG.1. As shown inFIG.2, the compressor housing100includes a first housing member110and a second housing member120. The first housing member110is located on the right side (a side spaced apart from the bearing housing2) inFIG.2with respect to the second housing member120. The second housing member120is connected to the bearing housing2. The first housing member110is connected to the second housing member120in the rotational axis direction.

The first housing member110has a substantially cylindrical shape. A through hole111is formed in the first housing member110. The first housing member110includes an end face112on a side adjacent (connected) to the second housing member120. The first housing member110also includes an end face113on a side spaced apart from the second housing member120. The inlet10is formed on the end face113. The through hole111extends from the end face112to the end face113(inlet10) along the rotational axis direction. In other words, the through hole111passes through the housing member110in the rotational axis direction. The through hole111includes the inlet10on the end face113.

The through hole111includes a parallel portion111aand a tapered portion111b. The parallel portion111ais located closer to the end face113with respect to the tapered portion111b. An inner diameter of the parallel portion111ais substantially constant over the rotational axis direction. The tapered portion111bis located closer to the end face112with respect to the parallel portion111a. The tapered portion111bis continuous with the parallel portion111a. An inner diameter at the continuous part of the tapered portion111bis substantially equal to the inner diameter of the parallel portion111a. The inner diameter of the tapered portion111bdecreases as it is spaced apart from the parallel portion111a(as approaching the end face112).

A notch112ais formed on the end face112. The notch112ais recessed from the end face112toward the end face113. The notch112ais formed at an outer periphery of the end face112. For example, the notch112ahas a substantially annular shape when seen from the rotational axis direction.

An accommodation chamber AC is formed on the end face112. The accommodation chamber AC is formed in the first housing member110so as to be closer to the inlet10with respect to the leading edge LE of the long blade9aof the compressor impeller9. The accommodation chamber AC includes an accommodation groove112b, bearing holes112d, and an accommodation hole115(seeFIG.3), which will be described later.

The accommodation groove112bis formed on the end face112. The accommodation groove112bis located between the notch112aand the through hole111. The accommodation groove112bis recessed from the end face112toward the end face113. For example, the accommodation groove112bhas a substantially annular shape when seen from the rotational axis direction. The accommodation groove112bis connected to the through hole111at a radially inner part.

The bearing holes112dare formed on a wall surface112cparallel to the end face113in the accommodation groove112b. The bearing holes112dextend from the wall surface112ctoward the end face113in the rotational axis direction. Two bearing holes112dare provided so as to be spaced apart from each other in the rotational direction. The two bearing holes112dare arranged spaced apart from each other by 180 degrees in the rotational direction.

A through hole121is formed in the second housing member120. The second housing member120includes an end face122on a side adjacent (connected) to the first housing member110. Furthermore, the second housing member120includes an end face123on a side spaced apart from the first housing member110(side connected to the bearing housing2). The through hole121extends from the end face122to the end face123along the rotational axis direction. In other words, the through hole121passes through the second housing member120in the rotational axis direction.

An inner diameter of the through hole121at an end closer to the end face122is substantially equal to the inner diameter of the through hole111at an end closer to the end face112. A shroud portion121ais formed on an inner wall of the through hole121. The shroud portion121afaces the compressor impeller9from a radially outer side. An outer diameter of the compressor impeller9increases as it is spaced apart from the leading edge LE of the long blade9aof the compressor impeller9in the rotational axis direction. An inner diameter of the shroud portion121aincreases as it is spaced apart from the end face122(as approaching the end face123).

An accommodation groove122ais formed in the end face122. The accommodation groove122ais recessed from the end face122toward the end face123. For example, the accommodation groove122ahas a substantially annular shape when seen from the rotational axis direction. The first housing member110is inserted into the accommodation groove122a. The end face112of the first housing member110contacts a wall surface122bparallel to the end face123in the accommodation groove122a. The accommodation chamber AC is formed between the first housing member110(wall surface112c) and the second housing member120(wall surface122b).

The through hole111of the first housing member110and the through hole121of the second housing member120form an intake flow path130. As such, the intake flow path130is formed in the compressor housing100. The intake flow path130is connected from the air cleaner (not shown) to the diffuser flow path11via the inlet10. A side closer to the air cleaner (inlet10) of the intake flow path130is referred to as an upstream side in a flow of intake air, and a side closer to the diffuser flow path11of the intake flow path130is referred to as a downstream side in the flow of the intake air.

The compressor impeller9is arranged in the intake flow path130. The cross-sectional shape of the intake flow path130(through holes111and121) perpendicular to the rotational axis direction is, for example, circular around the rotational axis of the compressor impeller9. However, the cross-sectional shape of the intake flow path130is not limited thereto, and may be, for example, elliptical.

A seal (not shown) is arranged in the notch112aof the first housing member110. The seal curbs a flow rate of air flowing in a gap between the first housing member110and the second housing member120. However, the notch112aand the seal are not essential.

FIG.3is an exploded perspective view of components included in the link mechanism200. InFIG.3, only the first housing member110of the compressor housing100is shown. As shown inFIG.3, the link mechanism200includes the first housing member110, a first movable member210, a second movable member220, a connecting member230, and a rod240. Hereinafter, the first movable member210and the second movable member220are also collectively referred to as movable members210and220. The link mechanism200is arranged closer to the inlet10(upstream side) of the intake flow path130with respect to the compressor impeller9in the rotational axis direction.

The first movable member210is arranged in the accommodation groove112b(accommodation chamber AC). Specifically, the first movable member210is arranged between the wall surface112cof the accommodation groove112band the wall surface122bof the accommodation groove122a(seeFIG.2) in the rotational axis direction. The first movable member210includes an opposing surface S1facing the wall surface112cof the accommodation groove112b, an opposing surface S2facing the wall surface122bof the accommodation groove122a, and an inner circumferential surface S3. In the first movable member210, the opposing surface S2is a side face closer to the blades9aand9bof the compressor impeller9. The first movable member210includes a body B1. The body B1includes a curved portion211and an arm212.

The curved portion211extends in the circumferential direction. The curved portion211has a substantially semi-arc shape. One end face211aand the other end face211bof the curved portion211in the circumferential direction extend parallel to the radial direction and the rotational axis direction. However, the one end face211aand the other end face211bmay be inclined with respect to the radial direction and the rotational axis direction.

The arm212is provided on the one end face211aof the curved portion211. The arm212extends radially outward from an outer circumferential surface211cof the curved portion211. Furthermore, the arm212extends in a direction inclined with respect to the radial direction (toward the second movable member220).

The second movable member220is arranged in the accommodation groove112b(accommodation chamber AC). Specifically, the second movable member220is arranged between the wall surface112cof the accommodation groove112band the wall surface122bof the accommodation groove122a(seeFIG.2) in the rotational axis direction. The second movable member220includes an opposing surface S1facing the wall surface112cof the accommodation groove112b, an opposing surface S2facing the wall surface122bof the accommodation groove122a, and an inner circumferential surface S3. In the second movable member220, the opposing surface S2is a side face closer to the blades9aand9bof the compressor impeller9. The second movable member220includes a body B2. The body B2includes a curved portion221and an arm222.

The curved portion221extends in the circumferential direction. The curved portion221has a substantially semi-arc shape. One end face221aand the other end face221bof the curved portion221in the circumferential direction extend parallel to the radial direction and the rotational axis direction. However, the one end face221aand the other end face221bmay be inclined with respect to the radial direction and the rotational axis direction.

The arm222is provided on the one end face221aof the curved portion221. The arm222extends radially outward from an outer circumferential surface221cof the curved portion221. Furthermore, the arm222extends in a direction inclined with respect to the radial direction (toward the first movable member210).

The curved portion211faces the curved portion221across the center of rotation of the compressor impeller9(intake flow path130). The one end face211aof the curved portion211circumferentially faces the other end face221bof the curved portion221. The other end face211bof the curved portion211circumferentially faces the one end face221aof the curved portion221. The first movable member210and the second movable member220are configured so that the curved portions211and221are movable in the radial direction, as described later in detail.

FIG.4is a schematic perspective view of the movable members210and220according to the first embodiment. As shown inFIG.4, one or more grooves300are formed on the movable members210and220. The grooves300are formed on the movable member210and220at an inner circumferential edge of the opposing surface S2closer to the blades9aand9bof the compressor impeller9. The grooves300are formed over the inner circumferential surface S3and the opposing surface S2in the movable members210and220.

The grooves300of the first embodiment include a plurality of spherical grooves300aarranged in the circumferential direction. The plurality of spherical grooves300aare formed next to each other in the circumferential direction. The plurality of spherical grooves300ahave the same size as each other. However, the plurality of spherical grooves300ais not limited thereto, and may have different sizes and different shapes from each other.

The plurality of spherical grooves300aof the first embodiment are formed at equal intervals in the circumferential direction. Protrusions302are formed between the plurality of spherical grooves300a. The protrusions302are formed adjacent to the grooves300ain the circumferential direction. The protrusions302partition off the plurality of spherical grooves300ain the circumferential direction.

A radially inward end face of the protrusion302is flush with the inner circumferential surface S3. Furthermore, an end face of the protrusion302closer to the blades9aand9bof the compressor impeller9is flush with the opposing surface S2. However, the radially inward end face of the protrusion302is not limited thereto, and may project radially inward with respect to the inner circumferential surface S3, or may be recessed radially outward with respect to the inner circumferential surface S3. Furthermore, the end face of the protrusion302closer to the blades9aand9bof the compressor impeller9may project in a direction toward the blades9aand9bwith respect to the opposing surface S2, or may be recessed in a direction spaced apart from the blades9aand9bwith respect to the opposing surface S2.

In the first embodiment, the example in which the plurality of spherical grooves300aand the plurality of protrusions302are provided on the movable members210and220is described. However, the movable members210and220may be provided with a single spherical groove300aand protrusion302. The movable members210and220may only be provided with at least one groove300aand protrusion302. Thus, for example, only one spherical groove300amay be formed in the movable members210and220. In this case, the single groove300amay only be formed on one of the first movable member210and the second movable member220, or may be formed over both the first movable member210and the second movable member220.

FIG.5shows the inner circumferential surface S3of the movable members210and220seen from a radially inner side inFIG.4. As shown inFIG.5, since the plurality of spherical grooves300aare formed in the inner circumferential surface S3, arc ends310having an arc shape are formed so as to face a direction toward the blades9aand9bof the compressor impeller9. The arc end310has a shape that is inclined in the circumferential direction RD with respect to the rotational axis direction R1.

Returning toFIG.3, the connecting member230connects with the first movable member210and the second movable member220. The connecting member230is located closer to the inlet10with respect to the first movable member210and the second movable member220. The connecting member230has a substantially arc shape. A first bearing hole231is formed at one end and a second bearing hole232is formed at the other end of the connecting member230in the circumferential direction. In the connecting member230, the first bearing hole231and the second bearing hole232are opened on the end face233closer to the first movable member210and the second movable member220. The first bearing hole231and the second bearing hole232extend in the rotational axis direction. In the present embodiment, the first bearing hole231and the second bearing hole232are non-through holes. However, the first bearing hole231and the second bearing hole232may pass through the connecting member230in the rotational axis direction.

A rod connector234is formed in the connecting member230between the first bearing hole231and the second bearing hole232. In the connecting member230, the rod connector234is formed on the end face235opposite to the first movable member210and the second movable member220. The rod connector234protrudes from the end face235in the rotational axis direction. The rod connector234has, for example, a substantially cylindrical shape.

The rod240has a substantially cylindrical shape. A flat portion241is formed at one end of the rod240, and a connecting portion243is formed at the other end. The flat portion241extends in a plane direction that is substantially perpendicular to the rotational axis direction. A bearing hole242is opened on the flat portion241. The bearing hole242extends in the rotational axis direction. The connecting portion243includes a connecting hole243a. The connecting portion243(connecting hole243a) is connected to an actuator described later. The bearing hole242may be, for example, an elongated hole whose length in the direction perpendicular to the rotational axis direction and an axial direction of the rod240(left-to-right direction inFIG.7, described below) is longer than a length in the axial direction of the rod240.

A rod large diameter portion244and two rod small diameter portions245are formed between the flat portion241and the connecting portion243in the rod240. The rod large diameter portion244is located between the two rod small diameter portions245. Between the two rod small diameter portions245, the rod small diameter portion245closer to the flat portion241connects the rod large diameter portion244to the flat portion241. Between the two rod small diameter portions245, the rod small diameter portion245closer to the connection portion243connects the rod large diameter portion244to the connecting portion243. An outer diameter of the rod large diameter portion244is larger than outer diameters of the two rod small diameter portions245.

An insertion hole114is formed in the first housing member110. One end114aof the insertion hole114opens to the outside of the first housing member110. The insertion hole114extends, for example, in a plane direction perpendicular to the rotational axis direction. The insertion hole114is located radially outside the through hole111(intake flow path130). A side including the flat portion241of the rod240is inserted into the insertion hole114. The rod large diameter portion244is guided by an inner wall of the insertion hole114. The rod240is prevented from moving except in the central axial direction of the insertion hole114(the central axial direction of the rod240).

An accommodation hole115is formed in the first housing member110. The accommodation hole115is opened on the wall surface112cof the accommodation groove112b. The accommodation hole115is recessed from the wall surface112ctoward the inlet10. The accommodation hole115is located spaced apart from the inlet10(closer to the second housing member120) with respect to the insertion hole114. The accommodation hole115has a substantially arc shape when seen from the rotational axis direction. The accommodation hole115extends longer than the connecting member230in the circumferential direction. The accommodation hole115is circumferentially spaced apart from the bearing holes112d.

A communication hole116is formed in the first housing member110. The communication hole116connects the insertion hole114to the accommodation hole115. The communication hole116is formed substantially in the middle of the accommodation hole115in the circumferential direction. The communication hole116is, for example, an elongated hole extending substantially parallel to the extending direction of the insertion hole114. In the communication hole116, a width in the longitudinal direction (extending direction) is greater than a width in the lateral direction (direction perpendicular to the extending direction). A width of the insertion hole114in the lateral direction is greater than an outer diameter of the rod connector234of the connecting member230.

The connecting member230is accommodated in the accommodation hole115(accommodation chamber AC). As such, the first movable member210, the second movable member220, and the connecting member230are arranged in the accommodation chamber AC formed in the first housing member110. The accommodation hole115is circumferentially longer and radially larger than the connecting member230. Accordingly, the connecting member230is allowed to move within the accommodation hole115in the plane direction perpendicular to the rotational axis direction.

The rod connector234is inserted through the communication hole116into the insertion hole114. The flat portion241of the rod240is inserted into the insertion hole114. The bearing hole242of the flat portion241faces the communication hole116. The rod connector234is inserted into (connected to) the bearing hole242. The rod connector234is supported by the bearing hole242.

FIG.6is a cross-sectional view taken along line VI-VI inFIG.2. As shown inFIG.6, the plurality of spherical grooves300aare formed on the opposing surfaces S2of the movable members210and220, thereby forming arc ends320having an arc shape in radially inner parts. The arc ends320have a shape that is inclined with respect to the radial direction R2in the circumferential direction RD.

As shown in dashed lines inFIG.6, the first movable member210includes a connecting shaft213and a rotational shaft214. In the first movable member210, the connecting shaft213and the rotational shaft214protrude in the rotational axis direction from the opposing surface S1(seeFIG.2) that faces the wall surface112c. The connecting shaft213and the rotational shaft214extend toward the back side of the paper inFIG.5. The rotational shaft214extends parallel to the connecting shaft213. The connecting shaft213and rotational shaft214have a substantially cylindrical shape.

An outer diameter of the connecting shaft213is smaller than an inner diameter of the first bearing hole231of the connecting member230. The connecting shaft213is inserted into the first bearing hole231. The connecting shaft213is rotatably supported by the first bearing hole231. An outer diameter of the rotational shaft214is smaller than an inner diameter of the bearing hole112dof the first housing member110. The rotational shaft214is inserted into the bearing hole112don the vertically upper side (closer to the rod240) of the two bearing holes112d. The rotational shaft214is rotatably supported by the bearing hole112d. The rotational shaft214connects the first movable member210to the wall surface112cthat faces the first movable member210in the rotational axis direction.

The second movable member220includes a connecting shaft223and a rotational shaft224. In the second movable member220, the connecting shaft223and the rotational shaft224protrude in the rotational axis direction from the opposing surface S1(seeFIG.2) that faces the wall surface112c. The connecting shaft223and the rotational shaft224extend toward the back side of the paper inFIG.4. The rotational shaft224extends parallel to the connecting shaft223. The connecting shaft223and the rotational shaft224have a substantially cylindrical shape.

An outer diameter of the connecting shaft223is smaller than an inner diameter of the second bearing hole232of the connecting member230. The connecting shaft223is inserted into the second bearing hole232. The connecting shaft223is rotatably supported by the second bearing hole232. An outer diameter of the rotational shaft224is smaller than an inner diameter of the bearing hole112dof the first housing member110. The rotational shaft224is inserted into the bearing hole112don the vertically lower side (spaced apart from the rod240) of the two bearing holes112d. The rotational shaft224is rotatably supported by the bearing hole112d. The rotational shaft224connects the second movable member220to the wall surface112cthat faces the second movable member220in the rotational axis direction.

As described above, the link mechanism200includes a four-bar linkage. The four links (nodes) are the first movable member210, the second movable member220, the first housing portion110, and the connecting portion230. Since the link mechanism200includes the four-bar linkage, it is a limited chain, has one degree of freedom, and is easy to control.

FIG.7is a first illustration of an operation of the link mechanism200. In the followingFIGS.7,8and9, the link mechanism200is seen from the inlet10. As shown inFIG.7, one end of a drive shaft251of an actuator250is connected to the connecting portion243of the rod240.

In the arrangement shown inFIG.7, the first movable member210and the second movable member220are in contact with each other. In this situation, as shown inFIGS.2and6, a protruding portion215that is a radially inner part of the first movable member210protrudes (is exposed) into the intake flow path130. A protruding portion225that is a radially inner part of the second movable member220protrudes (is exposed) into the intake flow path130. The positions of the first movable member210and the second movable member220in this situation are referred to as a protruding position (or a throttling position). As shown inFIG.2, inner surfaces of the protruding portions215and225are the inner circumferential surfaces S3. As such, the protruding portions215and225include the inner circumferential surfaces S3.

As shown inFIG.7, in the protruding position, ends215aand215bof the protruding portion215in the circumferential direction and ends225aand225bof the protruding portion225in the circumferential direction contact each other. The protruding portions215and225form an annular hole260. An inner diameter of the annular hole260is smaller than the inner diameter of the intake flow path130at a position where the protruding portions215and225protrude. For example, the inner diameter of the annular hole260is smaller than the inner diameter of the intake flow path130at any positions.

FIG.8is a second illustration of the operation of the link mechanism200.FIG.9is a third illustration of the operation of the link mechanism200. The actuator250linearly moves the rod240in a direction that intersects the rotational axis direction (up-and-down direction inFIGS.8and9). The rod240moves upward from the position shown inFIG.7. With regard to an amount of movement from the arrangement shown inFIG.7, the arrangement shown inFIG.9is larger than the arrangement shown inFIG.8.

As the rod240moves, the connecting member230moves upward inFIGS.8and9via the rod connector234. In this situation, the connecting member230is allowed to rotate around the rod connector234. Furthermore, there is a slight play between the inner diameter of the bearing hole242of the rod240and the outer diameter of the rod connector234. Accordingly, the connecting member230is allowed to slightly move in the plane direction perpendicular to the rotational axis direction.

As described above, the link mechanism200is the four-bar linkage. The connecting member230, the first movable member210, and the second movable member220exhibit a behavior of one degree of freedom with respect to the first housing member110. Specifically, the connecting member230slightly moves in the left-to-right direction while slightly rotating counterclockwise inFIGS.8and9within the allowable range described above.

The rotational shaft214of the first movable member210is supported by the first housing member110. The rotational shaft214is prevented from moving in the plane direction perpendicular to the rotational axis direction. The connecting shaft213is supported by the connecting member230. Since the connecting member230is allowed to move, the connecting shaft213is movable in the plane direction perpendicular to the rotational axis direction. As a result, as the connecting member230moves, the first movable member210rotates in a clockwise direction inFIGS.8and9around the rotational shaft214.

Similarly, the rotational shaft224of the second movable member220is supported by the first housing member110. The rotational shaft224is prevented from moving in the plane direction perpendicular to the rotational axis direction. The connecting shaft223is supported by the connecting member230. Since the connecting shaft223is allowed to move, the connecting shaft223is movable in the plane direction perpendicular to the rotational axis direction. As a result, as the connecting member230moves, the second movable member220rotates in a clockwise direction inFIGS.8and9around the rotational shaft224.

As such, the first movable member210and the second movable member220move in directions spaced apart from each other in the order ofFIG.8toFIG.9. The protruding portions215and225move to a radially outer side (retracted position) with respect to the protruding position. In the retracted position, for example, the protruding portions215and225are flush with an inner wall of the intake flow path130or are located radially outside the inner wall of the intake flow path130. When moving from the retracted position to the protruding position, the first movable member210and the second movable member220approach and contact each other in the order ofFIG.9toFIG.7. As such, the first movable member210and the second movable member220switch between the protruding position and the retracted position according to rotational angles around the rotational shafts214and224.

As described above, the first movable member210and the second movable member220are movable to the protruding position where they protrude into the intake flow path130, and a retracted position where they are retracted from the intake flow path130. In the present embodiment, the first movable member210and the second movable member220move in the radial direction. However, the first movable member210and the second movable member220are not limited thereto, and may rotate around the rotational axis (in the circumferential direction) of the compressor impeller9. For example, the first movable member210and the second movable member220may be shutter blades having two or more blades.

The first movable member210and the second movable member220do not protrude into the intake flow path130when in the retracted position, thus reducing pressure loss of intake gas (air) flowing in the intake flow path130.

Furthermore, as shown inFIG.2, in the first movable member210and the second movable member220, the protruding portions215and225are arranged in the intake flow path130in the protruding position. When the first movable member210and the second movable member220are in the protruding position, the cross-sectional area of the intake flow path130decreases.

As a flow rate of air flowing into the compressor impeller9decreases, air compressed by the compressor impeller9may flow backward (i.e., the air flows from the downstream side to the upstream side) in the intake flow path130.

As shown inFIG.2, when the first movable member210and the second movable member220are in the protruding position, the protruding portions215and225are located radially inside with respect to the radially outermost end of the leading edge LE of the long blade9aof the compressor impeller9. As a result, the air flowing backward in the intake flow path130is blocked by the protruding portions215and225. Accordingly, the first movable member210and the second movable member220can curb the backflow of air in the intake flow path130.

In addition, since the cross-sectional area of the intake flow path130decreases, velocity of the air flowing into the compressor impeller9increases. As a result, occurrence of surging in the centrifugal compressor CC can be curbed. In other words, the centrifugal compressor CC of the present embodiment can expand its operational area to a smaller flow rate area by maintaining the first movable member210and the second movable member220in the protruding position.

As such, the first movable member210and the second movable member220are configured as throttles that throttle the intake flow path130. In other words, in the present embodiment, the link mechanism200is configured as a throttling mechanism that throttles the intake flow path130. The first movable member210and the second movable member220can change the cross-sectional area of the intake flow path130when the link mechanism200is driven.

The air flowing backward in the intake flow path130includes a swirling flow component caused by the rotation of the compressor impeller9. When the air flowing backward in the intake flow path130is blocked by the movable members210and220, the swirling flow component of the air flowing backward disturbs the flow near the leading edge LE of the long blade9aof the compressor impeller9, and noise that may be considered as aerodynamic noise may be generated.

Accordingly, in the present embodiment, the grooves300are formed in the movable members210and220. The grooves300are formed over the inner circumferential surface S3and the opposing surface S2of the movable members210and220. In the movable members210and220, the opposing surface S2is the side face closer to the blades9aand9bof the compressor impeller9. As such, by forming the grooves300on the opposing surface S2, the air flowing backward in the intake flow path130enters the grooves300and collides with the protrusions302in the circumferential direction, thereby reducing the swirling flow component.

When the grooves300are only formed on the opposing surface S2, i.e., when a radially inner side of the groove300is provided with material and closed thereby, the air flowing backward in the intake flow path130is less likely to flow into the grooves300. In the present embodiment, the grooves300are formed over the opposing surface S2and the inner circumferential surface S3, so that the radially inner side of the grooves300are opened without material. Since the radially inner side of the grooves300are opened, the air flowing backward is likely to flow into the grooves300, compared to the case in which the grooves300are only formed on the opposing surface S2. As a result, the swirl component of the air flowing backward can be effectively reduced.

Furthermore, the grooves300form the arc ends310on the inner circumferential surface S3at positions closer to the blades9aand9bof the compressor impeller9. The arc ends310have a shape that is inclined with respect to the rotational axis direction R1in the circumferential direction RD. The arc ends310allow the air flowing backward to flow smoothly into and out of the grooves300, thereby reducing the pressure loss.

Furthermore, the grooves300form the arc ends320on the opposing surface S2at the radially inner part. The arc ends320have a shape that is inclined with respect to the radial direction R2in the circumferential direction RD. The arc ends320allow the air flowing backward to flow smoothly into and out of the grooves300, thereby reducing the pressure loss.

In addition, since the grooves300have a spherical shape, the number of corners can be reduced, compared to the case having a rectangular shape. Accordingly, the grooves300having a spherical shape can reduce the swirl flow component more smoothly, compared to the case in which the groove300has a rectangular shape, for example.

Second Embodiment

FIG.10is a schematic perspective view of movable members1210and1220according to the second embodiment. Components that are substantially equivalent to those of the centrifugal compressor CC of the above embodiment will be assigned with the same reference signs, and descriptions thereof will be omitted. The movable members1210and1220of the second embodiment differ from the movable members210and220of the first embodiment in the shape of the grooves400.

As shown inFIG.10, one or more grooves400are formed on the movable members1210and1220. The grooves400are formed over the inner circumferential surface S3and the opposing surface S2of the movable members1210and1220.

The grooves400of the second embodiment include a plurality of arc-shaped circumferential grooves400aarranged in the circumferential direction. The plurality of arc-shaped circumferential grooves400aextend in the circumferential direction. The circumferential grooves400aare circumferentially longer than the spherical grooves300aof the first embodiment. The plurality of arc-shaped circumferential grooves400aare formed next to each other in the circumferential direction. The plurality of arc-shaped circumferential grooves400ahave the same size as each other. However, the plurality of arc-shaped circumferential grooves400aare not limited thereto, and may have different sizes and different shapes from each other.

The plurality of arc-shaped circumferential grooves400aof the second embodiment are formed at equal intervals in the circumferential direction. Protrusions402are formed between the plurality of arc-shaped circumferential grooves400a. The protrusions402are formed adjacent to the circumferential grooves400ain the circumferential direction. The protrusions402partition off the plurality of arc-shaped circumferential grooves400ain the circumferential direction.

In the second embodiment, the example in which the plurality of arc-shaped circumferential grooves400aand protrusions402are provided on the movable members1210and1220is described. However, the movable members1210and1220may be provided with a single arc-shaped circumferential groove400aand protrusion402. The movable members1210and1220may only be provided with at least one circumferential groove400aand protrusion402. Accordingly, for example, only one arc-shaped circumferential groove400amay be formed in the movable members1210and1220. In this case, the single circumferential groove400amay only be formed on one of the first movable member1210and the second movable member1220, or may be formed over both the first movable member1210and the second movable member1220.

According to the second embodiment, the number of grooves400and protrusions402can be reduced compared to the first embodiment by extending the grooves400in a circumferential arc. As the number of collisions between the protrusions402and the air flowing backward increases, the pressure loss increases and the compressor efficiency decreases. Therefore, by reducing the number of protrusions402, the decrease in compressor efficiency can be curbed compared to the first embodiment.

Third Embodiment

FIG.11is a schematic perspective view of movable members2210and2220according to the third embodiment. Components that are substantially equivalent to those of the centrifugal compressor CC of the above embodiment will be assigned with the same reference signs, and descriptions thereof will be omitted. The movable members2210and2220of the third embodiment differ from the movable members210and220of the first embodiment and the movable members1210and1220of the second embodiment in the shape of the grooves500.

As shown inFIG.11, one or more grooves500are formed on the movable members2210and2220. The grooves500are formed over the inner circumferential surface S3and the opposing surface S2in the movable member2210and2220.

The grooves500of the third embodiment include a plurality of arc-shaped circumferential grooves500aarranged in the circumferential direction. The plurality of arc-shaped circumferential grooves500aextend in the circumferential direction. The circumferential grooves500aare circumferentially longer than the spherical grooves300aof the first embodiment. Furthermore, the plurality of arc-shaped circumferential grooves500aare spaced apart from each other in the circumferential direction. The plurality of arc-shaped circumferential grooves500ahave the same size as each other. However, the plurality of arc-shaped circumferential grooves500aare not limited thereto, and may have different sizes and different shapes from each other.

The plurality of arc-shaped circumferential grooves500aof the third embodiment are formed at equal intervals in the circumferential direction. Protrusions502are formed between the plurality of arc-shaped circumferential grooves500a. The protrusions502are formed adjacent to the circumferential grooves500ain the circumferential direction. The protrusions502partition off the plurality of arc-shaped circumferential grooves500ain the circumferential direction.

In the third embodiment, the example in which the plurality of arc-shaped circumferential grooves500aand protrusions502are provided in the movable members2210and2220is described. However, the movable members2210and2220may be provided with a single arc-shaped circumferential groove500aand protrusion502. The movable members2210and2220may only be provided with at least one circumferential groove500aand protrusion502. Accordingly, for example, only one arc-shaped circumferential groove500amay be formed in the movable members2210and2220. In this case, the single circumferential groove500amay only be formed on one of the first movable member2210and the second movable member2220, or may be formed over both the first movable member2210and the second movable member2220.

According to the third embodiment, the number of grooves500and protrusions502formed in the movable members2210and2220can be adjusted by forming the plurality of circumferential grooves500aspaced apart from each other in the circumferential direction. As the number of collisions between the protrusions502and the air flowing backward increases, the pressure loss increases and the compressor efficiency decreases. Therefore, by adjusting the number of protrusions502, the compressor efficiency can be adjusted.

Fourth Embodiment

FIG.12is a schematic perspective view of movable members3210and3220according to the fourth embodiment. Components that are substantially equivalent to those of the centrifugal compressor CC of the above embodiment will be assigned with the same reference signs, and descriptions thereof will be omitted. The movable members3210and3220of the fourth embodiment differ from the movable members210and220of the first embodiment, the movable members1210and1220of the second embodiment, and the movable members2210and2220of the third embodiment in the shape of the grooves600.

As shown inFIG.12, one or more grooves600are formed on the movable members3210and3220. The grooves600are formed over the inner circumferential surface S3and the opposing surface S2in the movable members3210and3220.

The grooves600of the fourth embodiment include a plurality of spherical grooves600aarranged in the circumferential direction. In the fourth embodiment, the plurality of spherical grooves600aare only formed on the second movable member3220. However, the plurality of spherical grooves600aare not limited thereto, and may be formed only on the first movable member3210or on both the first movable member3210and the second movable member3220.

The plurality of spherical grooves600aare spaced apart from each other in the circumferential direction. The plurality of spherical grooves600ahave the same size as each other. The plurality of spherical grooves600ahave the same size as those of the spherical grooves300aof the first embodiment, for example. However, the plurality of spherical grooves600aare not limited thereto, and may have different sizes from the spherical grooves300aof the first embodiment. Furthermore, the plurality of spherical grooves600amay also have different sizes and different shapes from each other.

The plurality of spherical grooves600aof the fourth embodiment are formed at unequal intervals in the circumferential direction. Protrusions602are formed between the plurality of spherical grooves600a. The protrusions602are formed adjacent to the grooves600ain the circumferential direction. The protrusions602partition off the plurality of spherical grooves600ain the circumferential direction.

In the fourth embodiment, the example in which the plurality of spherical grooves600aand protrusions602are provided in the movable members3210and3220is described. However, the movable members3210and3220may be provided with a single spherical groove600aand protrusion602. The movable members3210and3220may only be provided with at least one groove600aand protrusion602. Accordingly, for example, only one spherical groove600amay be formed in the movable member3210and3220. In this case, the single groove600amay only be formed on one of the first movable member3210and the second movable member3220, or may be formed over both the first movable member3210and the second movable member3220.

According to the fourth embodiment, by arranging the plurality of grooves600at unequal intervals in the circumferential direction, vibration induction of the compressor impeller9caused by the collision between the protrusions602and the air flowing backward can be reduced.

Although the embodiments of the present disclosure have been described above with reference to the accompanying drawings, the present disclosure is not limited thereto. It is obvious that a person skilled in the art can conceive of various examples of variations or modifications within the scope of the claims, which are also understood to belong to the technical scope of the present disclosure.