Compressor impeller and centrifugal compressor

Abstract

A compressor impeller provided with a hub and at least one blade provided on the outer surface of the hub, the rear surface of the compressor impeller including: a flat portion extending in the radial direction of the compressor impeller, the flat portion being positioned further toward the rear end side in the axial direction of the compressor impeller than the outer peripheral end of the rear surface; and an outer side surface connecting the flat portion and an outer peripheral end of the back surface, the outer side surface having an axial recess recessed toward a distal end side in the axial direction than the outer peripheral end of the back surface.

Description

Technical Field

[0001] The present invention relates to a compressor impeller and a centrifugal compressor having the compressor impeller. Background Art

[0002] Conventionally, as a technology for increasing the output of engines (internal combustion engines) such as automobile engines, a turbocharger (supercharger) is often used, which compresses the intake air sucked into the engine, increases its density, and supplies the intake air containing a large amount of oxygen to the engine.

[0003] The turbocharger, for example, includes a centrifugal compressor disposed on one end of a rotating shaft and a turbine disposed on the other end of the rotating shaft. The turbine rotor is rotated by the energy of the exhaust gas from the engine, and the compressor impeller of the centrifugal compressor rotates in conjunction with the rotation of the turbine rotor to compress the intake air and supply it to the engine.

[0004] The compressor impeller has: a flat portion extending in the radial direction of the compressor impeller and at least a portion of which abuts against other components such as a sleeve; and a back surface, which is composed of an outer surface connecting the flat portion and the outer peripheral end of the back surface. In a general compressor impeller, the distance between the outer surface and the flat portion in the axial direction of the compressor impeller increases as it moves toward the outer side in the radial direction of the compressor impeller, and the inclination becomes gentler (for example, refer to Patent Document 1).

[0005] Previous technical literature

[0006] Patent Literature

[0007] Patent Document 1: International Publication No. 2019-130405 Summary of the invention

[0008] Technical issues to be solved by the invention

[0009] The blade shape of the compressor impeller plays an important role in the compression of the intake air sent to the engine, but the above-mentioned blade shape is limited by the stress generated in the compressor impeller when the compressor impeller rotates. In the above-mentioned back shape of the compressor impeller, it is sometimes impossible to reduce the stress generated in the compressor impeller when the compressor impeller rotates to the stress range required to prevent the influence on the noise generated when the compressor impeller rotates. In addition, in the above-mentioned back shape of the compressor impeller, since the moment of inertia of the compressor impeller tends to increase, it is possible to deteriorate the transient response characteristics of the centrifugal compressor or the turbocharger equipped with the centrifugal compressor.

[0010] In view of the above, an object of at least one embodiment of the present invention is to provide a compressor impeller and a centrifugal compressor, wherein the compressor impeller can reduce stress generated in the compressor impeller when the compressor impeller rotates and can reduce the moment of inertia of the compressor impeller.

[0011] Means for solving technical problems

[0012] A compressor impeller according to at least one embodiment of the present invention includes:

[0013] A hub and at least one blade disposed on an outer surface of the hub,

[0014] The back side of the compressor impeller comprises:

[0015] a flat portion extending in the radial direction of the compressor impeller, the flat portion being located closer to the rear end side in the axial direction of the compressor impeller than the outer peripheral end of the back surface; and

[0016] an outer side surface, connecting the flat portion and the outer peripheral end of the back surface,

[0017] The outer side surface has an axial recessed portion that is recessed toward a front end side in the axial direction relative to the outer peripheral end of the rear surface.

[0018] A centrifugal compressor according to at least one embodiment of the present invention comprises:

[0019] The compressor impeller.

[0020] Effects of the Invention

[0021] According to at least one embodiment of the present invention, a compressor impeller and a centrifugal compressor are provided, wherein the compressor impeller can reduce stress generated in the compressor impeller when the compressor impeller rotates and can reduce the moment of inertia of the compressor impeller. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a schematic cross-sectional view along the axis of a supercharger including a centrifugal compressor according to an embodiment.

[0023] Figure 2 This is a schematic cross-sectional view of the vicinity of a compressor impeller along the axis of a centrifugal compressor according to one embodiment.

[0024] Figure 3 It is a schematic cross-sectional view of the vicinity of a compressor impeller along the axis of a centrifugal compressor according to a comparative example.

[0025] Figure 4 This is a schematic cross-sectional view along the axis of a compressor impeller according to one embodiment.

[0026] Figure 5 This is a schematic cross-sectional view along the axis of a compressor impeller according to one embodiment. DETAILED DESCRIPTION

[0027] Hereinafter, several embodiments of the present invention will be described with reference to the accompanying drawings. The dimensions, materials, shapes, relative arrangements, etc. of the components described in the embodiments or shown in the accompanying drawings are not intended to limit the scope of the present invention, but are merely illustrative examples.

[0028] (supercharger, centrifugal compressor)

[0029] Figure 1 It is a schematic cross-sectional view along the axis LA of a supercharger 10 of a centrifugal compressor 1 involved in one embodiment. The centrifugal compressor 1 involved in the present invention can be mounted on a supercharger (turbocharger) 10 for automobiles, ships or industrial use (for example, for land power generation). In the following embodiments, the centrifugal compressor 1 mounted on the supercharger (turbocharger) 10 is used as an example for description, but the centrifugal compressor 1 involved in the present invention is not limited to the case of being mounted on the supercharger 10. In addition, the working fluid of the centrifugal compressor 1 does not need to be limited to air. That is, as long as the centrifugal compressor 1 of the present invention can compress the working fluid by mechanical power (for example, rotational force), it can be composed of the centrifugal compressor 1 alone, or it can be composed of a mechanism or device other than the turbine 11.

[0030] like Figure 1 As shown, the supercharger 10 involved in several embodiments is configured to be driven by the energy of the exhaust gas of an engine (internal combustion engine) not shown in the figure, and compress a fluid (for example, air). The supercharger 10 includes: a turbine 11 driven by the exhaust gas of the above-mentioned engine; and a centrifugal compressor 1 coaxially connected to the turbine 11, for supplying the compressed air while rotating to the above-mentioned engine.

[0031] The turbine 11 includes a turbine rotor 12 and a turbine housing 13 configured to rotatably accommodate the turbine rotor 12. The centrifugal compressor 1 includes a compressor impeller (impeller) 2 and a compressor housing 14 configured to rotatably accommodate the compressor impeller 2.

[0032] like Figure 1 As shown, the supercharger 10 further includes: a rotating shaft 15, the compressor impeller 2 is connected to one end side, and the turbine rotor 12 is connected to the other end side; and

[0033] The bearing 16 is configured to rotatably support the rotary shaft 15 between the compressor impeller 2 and the turbine rotor 12. The supercharger 10 may further include a bearing housing 17 that is disposed between the compressor housing 14 and the turbine housing 13 and that is configured to accommodate the bearing 16.

[0034] The turbine 11 is configured to rotate the turbine rotor 12 by the energy of the exhaust gas from the above-mentioned engine. The compressor impeller 2 is coaxially connected to the turbine rotor 12 via the rotating shaft 15, and is therefore driven to rotate around the axis LA of the compressor impeller 2 in conjunction with the rotation of the turbine rotor 12. The centrifugal compressor 1 is configured to suck air (supply air, gas) into the interior of the compressor housing 14 by driving the compressor impeller 2 to rotate around the axis LA, compress the air, and deliver the compressed air to the above-mentioned engine. The compressed air delivered from the centrifugal compressor 1 to the above-mentioned engine will be supplied to the combustion in the above-mentioned engine. The exhaust gas generated by the combustion in the above-mentioned engine is delivered from the above-mentioned engine to the turbine 11 to rotate the turbine rotor 12.

[0035] Hereinafter, the direction in which the axis LA of the compressor impeller 2 extends is defined as the axial direction of the compressor impeller 2 (centrifugal compressor 1), the direction orthogonal to the axis LA is defined as the radial direction of the compressor impeller 2 (centrifugal compressor 1), and the circumferential direction around the axis LA is defined as the circumferential direction of the compressor impeller 2 (centrifugal compressor 1). In the axial direction of the compressor impeller 2, with respect to the back surface 3 of the compressor impeller 2, the side where the outer surface 22 of the hub 21 is located is defined as the front end side, and the side opposite to the front end side is defined as the rear end side.

[0036] (Turbine rotor)

[0037] The turbine rotor 12 includes a hub 121 having a substantially truncated cone shape and a plurality of turbine blades 122 provided on the outer surface of the hub 121. Since the hub 121 is connected to one end of the rotating shaft 15, the turbine rotor 12 is provided so as to be rotatable integrally with the rotating shaft 15 about the axis LA. The turbine rotor 12 is configured to guide the exhaust gas introduced from the outer side in the radial direction of the turbine rotor 12 toward the front side of the turbine rotor 12 along the axial direction of the turbine rotor 12.

[0038] (Turbine housing)

[0039] The turbine housing 13 is provided with a turbine vortex flow path 131 for guiding the exhaust gas from the engine to the turbine rotor 12, and an exhaust gas discharge flow path 132 for discharging the exhaust gas passing through the turbine rotor 12 to the outside of the turbine housing 13. The turbine vortex flow path 131 is composed of a vortex-shaped flow path provided on the radially outer side of the turbine rotor 12 and extending in the circumferential direction of the turbine rotor 12. The exhaust gas discharge flow path 132 extends in the axial direction of the turbine rotor 12 (the extension direction of the axis LA).

[0040] The exhaust gas from the engine is introduced to the turbine rotor 12 via the turbine scroll flow path 131 to rotate the turbine rotor 12. The exhaust gas that rotates the turbine rotor 12 is discharged to the outside of the turbine housing 13 via the exhaust gas discharge flow path 132.

[0041] (Compressor impeller)

[0042] The compressor impeller 2 includes a hub 21 having a substantially truncated cone shape and a plurality of compressor blades 23 disposed on an outer surface 22 of the hub 21. The plurality of compressor blades 23 protrude from the outer surface 22 of the hub 21, respectively, and are arranged at intervals from each other in the circumferential direction around the axis LA. A gap (interval) is formed between the blade side ends (front ends) 24 of the plurality of compressor blades 23 and the shroud surface 141 that is convexly curved in a manner opposite to the blade side ends 24. That is, the compressor impeller 2 does not include an annular component covering the blade side ends 24. The plurality of compressor blades 23 may include a plurality of long blades 23A and a plurality of short blades 23B that are formed shorter than the long blades 23A in the axial direction of the compressor impeller 2.

[0043] Since the hub 21 is connected to one end of the rotating shaft 15, the compressor impeller 2 is provided so as to be rotatable integrally with the rotating shaft 15 about the axis LA. The compressor impeller 2 is configured to guide the air introduced in the axial direction of the compressor impeller 2 to the radially outer side of the compressor impeller 2. In the illustrated embodiment, the compressor impeller 2 is formed of a metal material (specifically, aluminum or an aluminum alloy).

[0044] (Compressor housing)

[0045] The compressor housing 14 has the above-mentioned shroud surface 141. The compressor housing 14 is formed with a gas introduction flow path 142, a diffuser flow path 143, and a scroll flow path 144.

[0046] The gas introduction flow path 142 is a flow path for taking in air (gas) from the outside of the compressor housing 14 and guiding the taken-in air to the compressor impeller 2. The gas introduction flow path 142 is provided on one side (front end side) of the compressor impeller 2 in the axial direction of the compressor impeller 2, and extends in the axial direction of the compressor impeller 2. By driving the compressor impeller 2 to rotate, air is taken in from the outside of the compressor housing 14 to the gas introduction flow path 142, and the taken-in air flows in the gas introduction flow path 142 and is guided to the compressor impeller 2.

[0047] The vortex flow path 144 is arranged on the radially outer side of the compressor impeller 2, and is composed of a vortex-shaped flow path extending in the circumferential direction of the compressor impeller 2. The diffuser flow path 143 is a flow path for guiding the air that passes through the compressor impeller 2 and is compressed by the compressor impeller 2 to the vortex flow path 144. The diffuser flow path 143 is arranged between the vortex flow path 144 and the compressor impeller 2 in the radial direction of the compressor impeller 2, and its downstream end (outer peripheral end) is connected to the vortex flow path 144. The compressed air (compressed gas) compressed by the compressor impeller 2 flows into the diffuser flow path 143, so that the diffuser flow path 143 flows toward the radially outer side of the compressor impeller 2 and is guided to the vortex flow path 144.

[0048] Figure 2 1 is a schematic cross-sectional view of the vicinity of the compressor impeller 2 along the axis LA of the centrifugal compressor 1 according to one embodiment. Figure 2 As shown, the compressor impeller 2 has a front end face 25 and a back face 3, wherein the front end face 25 is an end face on the front end side of the hub 21 in the axial direction, and the back face 3 is an end face on the rear end side of the hub 21 in the axial direction. The front end face 25 extends in the radial direction of the compressor impeller 2. The back face 3 includes a flat portion 4 and an outer side face 5, wherein the flat portion 4 extends in the radial direction of the compressor impeller 2, and the outer side face 5 connects the flat portion 4 and the outer peripheral end 31 of the back face 3. The outer side face 5 does not have a portion protruding further to the rear end side in the axial direction than the flat portion 4. The flat portion 4 includes a flat surface 40, which extends in the radial direction of the compressor impeller 2 in at least a portion in the circumferential direction of the compressor impeller 2. In addition, the flat surface 40 is not limited to a flat surface without any unevenness, and may have unevenness caused by tolerance or processing accuracy when forming the flat surface 40. The flat portion 4 may include an arc-shaped or annular groove portion (not shown), which is provided on the flat surface 40 and extends in the circumferential direction of the compressor impeller 2. Furthermore, the flat portion 4 may include at least one radial groove (not shown) provided on the flat surface 40 and extending in the radial direction of the compressor impeller 2 .

[0049] exist Figure 2 In the illustrated embodiment, a through hole 26 is formed in the compressor impeller 2, the through hole 26 extending from the front end surface 25 to the flat portion 4 in the axial direction of the compressor impeller 2, and the rotating shaft 15 is inserted therethrough. The centrifugal compressor 1 includes: an abutment portion 18 abutting against the flat portion 4 of the compressor impeller 2; and a locking member 19 locked to the rotating shaft 15 at a position closer to the front end side than the compressor impeller 2, and the locking member 19 clamps the compressor impeller 2 between the abutment portion 18 and the locking member 19.

[0050] The abutment portion 18 is a part of a component other than the compressor impeller 2, protrudes radially outward from the through hole 26, and abuts against at least a portion of the flat portion 4. In the illustrated embodiment, the centrifugal compressor 1 includes a cylindrical sleeve 18A through which the rotating shaft 15 is inserted, and the abutment portion 18 includes an end surface on the front end side of the sleeve 18A abutting against at least a portion of the flat portion 4. The sleeve 18A suppresses the compressor impeller 2 from moving toward the rear end side in the axial direction through other components such as the rotating shaft 15. In addition, the abutment portion 18 may also be a part of the rotating shaft 15.

[0051] exist Figure 2 In the illustrated embodiment, the locking member 19 includes an annular nut member having a threaded portion 191 formed therein, and the threaded portion 191 is screwed with a threaded portion 151 formed on the outer surface of the rotary shaft 15 on the front end side of the compressor impeller 2. With respect to the compressor impeller 2, the threaded portion 191 is screwed with the threaded portion 151 in a state where the abutment portion 18 is abutted against the flat portion 4, so that the compressor impeller 2 is clamped between the abutment portion 18 and the locking member 19. Thus, the compressor impeller 2 is connected to the rotary shaft 15.

[0052] (Axial recess)

[0053] Figure 3 It is a schematic cross-sectional view of the vicinity of the compressor impeller 02 along the axis LA of the centrifugal compressor 01 according to the comparative example. Figure 4 This is a schematic cross-sectional view along the axis LA of the compressor impeller 2 ( 2A) according to one embodiment. Figure 5 2 is a schematic cross-sectional view along the axis LA of the compressor impeller 2 (2B) according to one embodiment. Figure 2 , Figure 4 , Figure 5 As shown, the compressor impeller 2 of the centrifugal compressor 1 according to some embodiments has an axial recess 6 which is recessed toward the outer side surface 5 closer to the front end side (front end surface 25 side) of the compressor impeller 2 in the axial direction than the outer peripheral end 31 of the back surface 3. The axial recess 6 indicates a portion of the outer side surface 5 which is located closer to the front end side of the compressor impeller 2 in the axial direction than the outer peripheral end 31 of the back surface 3.

[0054] (Centrifugal compressor according to comparative example)

[0055] like Figure 3 As shown, the compressor impeller 02 of the centrifugal compressor 01 involved in the comparative example does not have the axial recessed portion 6 on the outer side surface 05 connecting the flat portion 4 and the outer peripheral end 31 of the back surface 3, which is different from the compressor impeller 2 involved in the present invention. As the outer side surface 05 is toward the radially outer side of the compressor impeller 02, the distance between the outer side surface 05 and the axial flat portion 4 of the compressor impeller 02 increases, and the inclination becomes gentle.

[0056] According to the above-mentioned structure, the compressor impeller 2 having the axial recess 6 can reduce the mass of the area where the axial recess 6 is formed, compared with the compressor impeller 02 without the axial recess 6, and can reduce the centrifugal force acting on the compressor impeller 2 in the axial range (the range between the flat portion 4 in the axial direction and the outer peripheral end 31 of the back surface 3) where the axial recess 6 is formed. As a result, the stress acting on the hole portion (near the through hole 26 of the hub 21) of the compressor impeller 2 when the compressor impeller 2 rotates can be reduced. In addition, the compressor impeller 2 having the axial recess 6 reduces the mass of the area where the axial recess 6 is formed, compared with the compressor impeller 02 without the axial recess 6, and the moment of inertia (inertia) of the compressor impeller 2 is reduced, so that the transient response characteristics of the centrifugal compressor 1 or the supercharger (turbocharger) 10 equipped with the centrifugal compressor 1 are improved.

[0057] (Shape of the outer surface)

[0058] In several embodiments, such as Figure 4 and Figure 5 As shown, the outer side surface 5 includes: at least one arc portion 5A extending in an arc shape in a cross section along the axis LA of the compressor impeller 2; and at least one straight portion 5B extending in a straight shape in a cross section along the axis LA.

[0059] According to the above structure, the outer side surface 5 includes at least one arc portion 5A and at least one straight portion 5B, so that the outer side surface 5 can be set to a smooth shape. By setting the outer side surface 5 to a smooth shape, the stress acting on the above-mentioned hole portion of the compressor impeller 2 when the compressor impeller 2 rotates can be effectively reduced.

[0060] In several embodiments, such as Figure 4 and Figure 5 As shown, the at least one arc portion 5A includes at least a first arc portion 51 and a second arc portion 52. The at least one straight portion 5B includes at least a first straight portion 53. In other words, the outer side surface 5 includes at least a first arc portion 51, a second arc portion 52 and a first straight portion 53.

[0061] The rear end 511 of the first arc portion 51 is connected to the outer peripheral end 41 of the flat portion 4, and the front end 512 is located closer to the front end side of the compressor impeller 2 in the axial direction than the rear end 511. The inner peripheral end 521 of the second arc portion 52 is connected to the front end 512 of the first arc portion 51, and extends radially outward from the inner peripheral end 521. In the first straight portion 53, the inner peripheral end 531 is connected to the outer peripheral end 522 of the second arc portion 52, and extends radially outward from the inner peripheral end 531 in a straight shape.

[0062] exist Figure 4 In the illustrated embodiment, the first arc portion 51 has a concave shape that is recessed toward the front end side in the axial direction of the compressor impeller 2, and the distance from the axis LA of the compressor impeller 2 in the radial direction increases toward the front end side in the axial direction of the compressor impeller 2. The front end 512 is located at a position closer to the outside of the compressor impeller 2 in the radial direction than the rear end 511.

[0063] exist Figure 5 In the illustrated embodiment, the first arc portion 51 has a concave shape toward the inner side in the radial direction of the compressor impeller 2, and the radial distance from the axis LA of the compressor impeller 2 decreases toward the front end side in the axial direction of the compressor impeller 2. The front end 512 is located at a position closer to the inner side of the compressor impeller 2 in the radial direction than the rear end 511.

[0064] The second arc portion 52 has a concave shape toward the front end side in the axial direction of the compressor impeller 2. Figure 4 , Figure 5 In the illustrated embodiment, the outer peripheral end 522 is located closer to the front end side in the axial direction of the compressor impeller 2 than the inner peripheral end 521 .

[0065] According to the above structure, the outer side surface 5 includes at least the first arc portion 51, the second arc portion 52 and the first straight portion 53, thereby the outer side surface 5 can be set to a smooth shape with relatively low complexity and no discontinuity. By setting the outer side surface 5 to a smooth shape, the stress acting on the above-mentioned hole portion of the compressor impeller 2 when the compressor impeller 2 rotates can be effectively reduced. In addition, the outer side surface 5 includes at least the first arc portion 51, the second arc portion 52 and the first straight portion 53, thereby the back portion of the outer side surface 5 of the compressor impeller 2 can ensure sufficient strength. In addition, according to the above structure, the outer side surface 5 includes the first arc portion 51, the second arc portion 52 and the first straight portion 53, thereby the vibration characteristics of the compressor blade 23 can be suppressed from changing with the operation of the centrifugal compressor 1 or the supercharger 10 equipped with the centrifugal compressor 1.

[0066] In addition, Figure 4 and Figure 5In the illustrated embodiment, the at least one straight portion 5B further includes a second straight portion 54 extending in a straight line from the outer peripheral end 31 of the back surface 3 to the inner side in the radial direction. The second straight portion 54 extends in a direction intersecting (orthogonal to) the axis LA. The at least one arc portion 5A further includes a third arc portion 55 connecting the outer peripheral end 532 of the first straight portion 53 and the inner peripheral end 541 of the second straight portion 54. In other words, the outer side surface 5 includes the first arc portion 51, the second arc portion 52, the first straight portion 53, the third arc portion 55 and the second straight portion 54 in order from the inner side in the radial direction of the compressor impeller 2. The first arc portion 51, the second arc portion 52, the first straight portion 53, the third arc portion 55 and the second straight portion 54 each have an annular surface extending in the circumferential direction of the axis LA.

[0067] (Front end of the axial recess)

[0068] In some embodiments, at least one of the first arc portion 51 or the second arc portion 52 includes a front end 50 located at the most front end side in the axial direction in the axial recess 6. According to the above structure, the front end 50 is provided in the first arc portion 51 or the second arc portion 52 without a discontinuous point, thereby suppressing the stress concentration near the front end 50 when the compressor impeller 2 rotates. As a result, the stress acting on the above hole portion of the compressor impeller 2 when the compressor impeller 2 rotates can be effectively reduced.

[0069] exist Figure 4 and Figure 5 In the embodiment shown, the second arc portion 52 and the first straight portion 53 form at least a portion of the axial recess 6. Figure 4 and Figure 5 As shown, an imaginary plane perpendicular to the axis LA and passing through the outer peripheral end 31 of the back surface 3 is set as PL1, and an intersection point with the imaginary plane PL1 of the first arc portion 51 or the second arc portion 52 is set as P1. The axial recess 6 is formed between the intersection point P1 and the inner peripheral end 541 of the second straight line portion 54 in the outer side surface 5.

[0070] exist Figure 4 and Figure 5 In the illustrated embodiment, the second arc portion 52 includes the front end 50 of the axial recess 6. The second arc portion 52 is arranged such that the distance between the second arc portion 52 and the flat portion 4 in the axial direction of the compressor impeller 2 increases as it moves toward the radially outer side of the compressor impeller 2 in the range from the inner peripheral end 521 to the front end 50. The distance between the second arc portion 52 and the flat portion 4 in the axial direction of the compressor impeller 2 decreases as it moves toward the radially outer side of the compressor impeller 2 in the range from the front end 50 to the outer peripheral end 522.

[0071] (Radius of curvature of the first arc and the second arc)

[0072] In several embodiments, such as Figure 4 As shown, the curvature radius R1 of the first arc portion 51 is smaller than the curvature radius R2 of the second arc portion 52. In the illustrated embodiment, when the distance (radial distance) from the axis LA of the compressor impeller 2 to the outer peripheral end 31 of the back surface 3 is defined as D1, the curvature radius R1 is configured to satisfy the condition of 0.075×D1≤R1≤0.15×D1. In addition, the curvature radius R2 is configured to satisfy the condition of 0.45×D1≤R2≤0.55×D1.

[0073] According to the above-mentioned structure, by setting the curvature radius R1 of the first arc portion 51 connecting the rear end 511 and the flat portion 4 to a relatively small value, the stress acting on the flat portion 4 can be reduced when the compressor impeller 2 rotates. In addition, by setting the curvature radius R2 of the second arc portion 52 connecting the first arc portion 51 and the first straight portion 53 to a relatively large value, the first arc portion 51, the second arc portion 52 and the first straight portion 53 of the outer side surface 5 can be set to a smooth shape.

[0074] (Inclination of the first straight line portion)

[0075] In several embodiments, such as Figure 4 and Figure 5 As shown in FIG. 1 , the first straight portion 53 is inclined so that the inner peripheral end 531 is located closer to the front end side in the axial direction than the outer peripheral end 532. Figure 4 As shown, an angle (smaller angle) formed between the virtual plane PL1 and the first straight line portion 53 is defined as θ. In the illustrated embodiment, the compressor impeller 2 is configured to satisfy the condition of 5°≤θ≤10°.

[0076] According to the above-mentioned structure, the first straight portion 53 is set to an inclined shape so that the inner peripheral end 531 of the first straight portion 53 is located closer to the front end side than the outer peripheral end 532, thereby making it easy to set the curvature radius R2 of the second arc portion 52 connected to the inner peripheral end 531 of the first straight portion 53 to a relatively large value. As a result, the second arc portion 52 and the first straight portion 53 of the outer side surface 5 can be smoothly connected.

[0077] (Radial position of the front end)

[0078] In several embodiments, such as Figure 4 As shown, when the distance (radial distance) from the axis LA of the compressor impeller 2 to the outer peripheral end 31 of the back side 3 is defined as D1, and the distance (radial distance) from the axis LA to the front end 50 located at the axially most front end side in the axial recess 6 is defined as D2, the compressor impeller 2 is constructed to satisfy the condition of D2≥0.5D1.

[0079] According to the above structure, the larger the distance D2 is, the greater the effect of reducing the moment of inertia of the compressor impeller 2 based on the axial recess 6 is. By configuring the compressor impeller 2 to satisfy the condition of D2 ≥ 0.5D1, the moment of inertia of the compressor impeller 2 can be effectively reduced, thereby improving the transient response characteristics of the centrifugal compressor 1 or the supercharger (turbocharger) 10 having the centrifugal compressor 1. In addition, in other embodiments, such as Figure 5 As shown, the compressor impeller 2 may not be configured to satisfy the condition D2 ≥ 0.5D1.

[0080] (Axial position of the outer peripheral end of the back side)

[0081] In several embodiments, such as Figure 2 As shown, when the distance (axial distance) from the end face (front end face) 25 on the front end side of the compressor impeller 2 in the axial direction to the flat portion 4 is defined as L1, and the distance (axial distance) from the outer peripheral end 31 of the back face 3 of the compressor impeller 2 in the axial direction to the flat portion 4 is defined as L2, the compressor impeller 2 is configured to satisfy the condition of L2≥0.1L1.

[0082] According to the above configuration, the greater the distance L2, the less stress applied to the flat portion 4 when the compressor impeller 2 rotates. By configuring the compressor impeller 2 to satisfy the condition of L2 ≥ 0.1L1, the stress applied to the flat portion 4 when the compressor impeller 2 rotates can be effectively reduced.

[0083] (Radial recess)

[0084] In several embodiments, such as Figure 5 As shown, the outer side surface 5 of the compressor impeller 2 (2B) has a radial recess 7 that is recessed toward the inner side in the radial direction of the compressor impeller 2 relative to the outer peripheral end 41 of the flat portion 4. The radial recess 7 indicates a portion of the outer side surface 5 that is located at the inner side in the radial direction of the compressor impeller 2 relative to the outer peripheral end 41 of the flat portion 4.

[0085] exist Figure 5 In the illustrated embodiment, the first arc portion 51 includes an inner square end, which is located at the radially innermost position in the radial recess 7. The first arc portion 51 and the second arc portion 52 form at least a portion of the radial recess 7. An imaginary plane extending parallel to the axis LA and passing through the outer peripheral end 41 of the flat portion 4 is set as PL2, and an intersection with the imaginary plane PL2 of the second arc portion 52 is set as P2. The radial recess 7 is formed between the intersection point P2 in the outer side surface 5 and the outer peripheral end 41 of the flat portion 4. Both the axial recess 6 and the radial recess 7 are formed between the intersection point P1 and the intersection point P2 in the outer side surface 5.

[0086] According to the above-mentioned structure, the compressor impeller 2B having the radial recessed portion 7 can reduce the mass of the region where the radial recessed portion 7 is formed, compared with the compressor impeller 2A not having the radial recessed portion 7, and can reduce the centrifugal force acting on the compressor impeller 2B in the axial range where the radial recessed portion 7 is formed. As a result, the stress acting on the hole portion (near the through hole 26 of the hub 21) of the compressor impeller 2B when the compressor impeller 2B rotates can be reduced.

[0087] like Figure 1 As shown, the centrifugal compressor 1 according to several embodiments includes the above-mentioned compressor impeller 2. In this case, by providing the axial recess 6 or the radial recess 7 on the compressor impeller 2, the stress generated on the compressor impeller 2 when the compressor impeller 2 rotates can be reduced, thereby reducing the moment of inertia of the compressor impeller 2.

[0088] In this specification, expressions such as "in a certain direction", "along a certain direction", "parallel", "orthogonal", "center", "concentric" or "coaxial" that indicate relative or absolute configuration not only indicate such configuration in a strict sense, but also indicate a state of relative displacement at an angle or distance with a tolerance or a degree that the same function can be obtained.

[0089] For example, expressions such as “same”, “equal” and “homogeneous” that indicate that things are in the same state not only indicate the same state in a strict sense, but also indicate a state in which there is a tolerance or a difference in the degree to which the same function can be obtained.

[0090] Furthermore, in this specification, expressions indicating shapes such as a quadrilateral or a cylinder not only indicate shapes such as a quadrilateral or a cylinder in a strict geometric sense, but also indicate shapes including concave-convex portions or chamfered portions within a range that can obtain the same effect.

[0091] Furthermore, in the present specification, expressions such as “having”, “including” or “having” a constituent element are not exclusive expressions excluding the presence of other constituent elements.

[0092] The present invention is not limited to the above-described embodiments, and includes modified embodiments of the above-described embodiments or embodiments in which these embodiments are appropriately combined.

[0093] The contents described in the above-mentioned several embodiments can be understood, for example, as follows.

[0094] 1) A compressor impeller 2 according to at least one embodiment of the present invention includes:

[0095] A hub 21 and at least one blade (compressor blade 23) disposed on an outer surface 22 of the hub 21,

[0096] The back side 3 of the compressor impeller 2 comprises:

[0097] a flat portion 4 extending in the radial direction of the compressor impeller 2, the flat portion 4 being located closer to the rear end side in the axial direction of the compressor impeller 2 than the outer peripheral end 31 of the back surface 3; and

[0098] The outer side surface 5 connects the flat portion 4 and the outer peripheral end 31 of the back surface 3,

[0099] The outer side surface 5 has an axial recessed portion 6 that is recessed toward the front end side in the axial direction relative to the outer peripheral end 31 of the rear surface 3 .

[0100] According to the structure 1) above, the compressor impeller 2 having the axial recess 6 can reduce the mass of the region where the axial recess 6 is formed, compared with the compressor impeller 02 not having the axial recess 6, and can reduce the centrifugal force acting on the compressor impeller 2 in the axial range where the axial recess 6 is formed. As a result, the stress acting on the hole portion (near the through hole 26 of the hub 21) of the compressor impeller 2 when the compressor impeller 2 rotates can be reduced. In addition, the compressor impeller 2 having the axial recess 6 reduces the mass of the region where the axial recess 6 is formed, compared with the compressor impeller 02 not having the axial recess 6, and the moment of inertia (inertia) of the compressor impeller 2 is reduced, so that the transient response characteristics of the centrifugal compressor 1 or the turbocharger 10 equipped with the centrifugal compressor 1 are improved.

[0101] 2) In several embodiments, according to the compressor impeller 2 described in 1) above, wherein:

[0102] The outer side 5 comprises:

[0103] at least one arc portion 5A extending in an arc shape in a cross section along the axis LA of the compressor impeller 2; and

[0104] At least one straight portion 5B extends in a straight line in a cross section along the axis LA.

[0105] According to the structure of 2) above, the outer side surface 5 includes at least one arc portion 5A and at least one straight portion 5B, so that the outer side surface 5 can be set to a smooth shape. By setting the outer side surface 5 to a smooth shape, the stress acting on the above-mentioned hole portion of the compressor impeller 2 when the compressor impeller 2 rotates can be effectively reduced.

[0106] 3) In several embodiments, according to the compressor impeller 2 described in 2) above, wherein:

[0107] The at least one arc portion 5A comprises:

[0108] The first arc portion 51 has a rear end 511 connected to the flat portion 4 and a front end 512 located closer to the front end side in the axial direction than the rear end 511; and

[0109] The second arc portion 52 has an inner peripheral end 521 connected to the front end 512 of the first arc portion 51 and extends from the inner peripheral end 521 toward the outside in the radial direction.

[0110] The at least one straight portion 5B comprises at least:

[0111] The first straight portion 53 has an inner peripheral end 531 connected to the outer peripheral end 522 of the second arc portion 52 , and extends linearly from the inner peripheral end 531 toward the outside in the radial direction.

[0112] According to the structure of 3) above, the outer side surface 5 includes at least the first arc portion 51, the second arc portion 52 and the first straight portion 53, thereby making it possible to set the outer side surface 5 to a smooth shape with relatively low complexity and no discontinuity. By setting the outer side surface 5 to a smooth shape, the stress acting on the above-mentioned hole portion of the compressor impeller 2 when the compressor impeller 2 rotates can be effectively reduced. In addition, the outer side surface 5 includes at least the first arc portion 51, the second arc portion 52 and the first straight portion 53, thereby ensuring that the back portion of the outer side surface 5 formed with the compressor impeller 2 has sufficient strength. In addition, according to the structure of 3) above, the outer side surface 5 includes the first arc portion 51, the second arc portion 52 and the first straight portion 53, thereby suppressing the vibration characteristics of the blade (compressor blade 23) from changing with the operation of the centrifugal compressor 1 or the supercharger 10 equipped with the centrifugal compressor 1.

[0113] 4) In several embodiments, according to the compressor impeller 2 described in 3) above, wherein:

[0114] At least one of the first arc portion 51 or the second arc portion 52 includes:

[0115] The front end 50 is located closest to the front end side in the axial direction in the axial recess 6 .

[0116] According to the structure of 4), by providing the front end 50 on the first arc portion 51 or the second arc portion 52 without a discontinuous point, it is possible to suppress the stress concentration on the front end 50 when the compressor impeller 2 rotates. As a result, the stress acting on the hole portion of the compressor impeller 2 when the compressor impeller 2 rotates can be effectively reduced.

[0117] 5) In some embodiments, according to the compressor impeller 2 described in 3) or 4) above, wherein:

[0118] The curvature radius R1 of the first arc portion 51 is smaller than the curvature radius R2 of the second arc portion 52 .

[0119] According to the structure of 5) above, by setting the radius of curvature R1 of the first arc portion 51 connecting the rear end 511 and the flat portion 4 to a relatively small value, the stress acting on the flat portion 4 can be reduced when the compressor impeller 2 rotates. In addition, by setting the radius of curvature R2 of the second arc portion 52 connecting the first arc portion 51 and the first straight portion 53 to a relatively large value, the first arc portion 51, the second arc portion 52 and the first straight portion 53 of the outer side surface 5 can be set to a smooth shape.

[0120] 6) In some embodiments, according to the compressor impeller 2 described in any one of 3) to 5),

[0121] The first straight portion 53 is inclined so that the inner peripheral end 531 is located closer to the front end side in the axial direction than the outer peripheral end 532 .

[0122] According to the structure of 6) above, the first straight portion 53 is set to an inclined shape so that the inner peripheral end 531 of the first straight portion 53 is located closer to the front end side than the outer peripheral end 532, thereby making it easy to set the curvature radius R2 of the second arc portion 52 connected to the inner peripheral end 531 of the first straight portion 53 to a relatively large value. As a result, the second arc portion 52 and the first straight portion 53 of the outer side surface 5 can be smoothly connected.

[0123] 7) In some embodiments, according to the compressor impeller 2 described in any one of 1) to 6), wherein:

[0124] When the distance from the axis LA of the compressor impeller 2 to the outer peripheral end 31 of the back side 3 is defined as D1, and the distance from the axis LA to the front end 50 located closest to the front end side in the axial direction in the axial recess 6 is defined as D2, the compressor impeller 2 is constructed to satisfy the condition of D2≥0.5D1.

[0125] According to the structure of 7) above, the larger the distance D2 is, the greater the effect of reducing the moment of inertia of the compressor impeller 2 based on the axial recess 6. By configuring the compressor impeller 2 to satisfy the condition of D2 ≥ 0.5D1, the moment of inertia of the compressor impeller 2 can be effectively reduced, thereby improving the transient response characteristics of the centrifugal compressor 1 or the turbocharger 10 having the centrifugal compressor 1.

[0126] 8) In some embodiments, according to the compressor impeller 2 described in any one of 1) to 7), wherein:

[0127] When the distance from the end face 25 on the front end side of the compressor impeller 2 in the axial direction to the flat portion 4 is defined as L1, and the distance from the outer peripheral end 31 of the back side 3 in the axial direction to the flat portion 4 is defined as L2, the compressor impeller 2 is configured to satisfy the condition of L2≥0.1L1.

[0128] According to the structure of 8), the greater the distance L2 is, the more the stress acting on the flat portion 4 can be reduced when the compressor impeller 2 rotates. By configuring the compressor impeller 2 to satisfy the condition of L2 ≥ 0.1L1, the stress acting on the flat portion 4 when the compressor impeller 2 rotates can be effectively reduced.

[0129] 9) In some embodiments, according to the compressor impeller 2 described in any one of 1) to 8),

[0130] The outer surface 5 has a radial recessed portion 7 that is recessed toward the inner side in the radial direction of the compressor impeller 2 relative to the outer peripheral end 41 of the flat portion 4 .

[0131] According to the structure of 9) above, the compressor impeller 2B having the radial recess 7 can reduce the mass of the region where the radial recess 7 is formed, compared with the compressor impeller 2A not having the radial recess 7, and can reduce the centrifugal force acting on the compressor impeller 2B in the axial range where the radial recess 7 is formed. As a result, the stress acting on the hole portion (near the through hole 26 of the hub 21) of the compressor impeller 2B when the compressor impeller 2B rotates can be reduced.

[0132] 10) A centrifugal compressor 1 according to at least one embodiment of the present invention includes:

[0133] The compressor impeller 2 according to any one of 1) to 9) above.

[0134] According to the configuration of 10), by providing the axial recess 6 or the radial recess 7 on the compressor impeller 2 , stress generated on the compressor impeller 2 when the compressor impeller 2 rotates can be reduced, thereby reducing the moment of inertia of the compressor impeller 2 .

[0135] Explanation of symbols

[0136] 1.01-centrifugal compressor, 2.02-compressor impeller, 21-hub, 23-compressor blade, 3-back side, 4-flat portion, 5.05-outer side, 6-axial recess, 7-radial recess, 10-supercharger, 11-turbine, 12-turbine rotor, 13-turbine housing, 14-compressor housing, 15-rotating shaft, 16-bearing, 17-bearing housing, 18-abutment portion, 18A-sleeve, 19-locking member, 21-hub, 22-outer surface, 23-compressor blades, 23A-long blades, 23B-short blades, 24-blade side ends, 25-front end faces, 26-through holes, 31-outer peripheral ends, 40-flat surfaces, 121-hub, 122-turbine blades, 131-vortex flow paths, 132-exhaust gas discharge flow paths, 141-shield surfaces, 142-gas inlet flow paths, 143-diffuser flow paths, 144-vortex flow paths, LA-axis lines.

Claims

1. A compressor impeller comprising a hub and at least one blade disposed on an outer surface of the hub, The back side of the compressor impeller comprises: a flat portion extending in the radial direction of the compressor impeller, the flat portion being located closer to the rear end side in the axial direction of the compressor impeller than the outer peripheral end of the back surface; and an outer side surface, connecting the flat portion and the outer peripheral end of the back surface, The outer side surface has an axial recessed portion that is recessed toward a front end side in the axial direction relative to the outer peripheral end of the rear surface.

2. The compressor impeller according to claim 1, wherein: The outer side comprises: at least one arc portion extending in an arc shape in a cross section along the axis of the compressor impeller; and At least one straight portion extends in a straight line in a cross section along the axis.

3. The compressor impeller according to claim 2, wherein: The at least one arc portion comprises at least: a first arc portion, the rear end of which is connected to the flat portion, and the front end of which is located closer to the front end in the axial direction than the rear end; and The second arc portion has an inner peripheral end connected to the front end of the first arc portion and extends from the inner peripheral end toward the outer side in the radial direction. The at least one straight line portion comprises at least: The first straight portion has an inner peripheral end connected to the outer peripheral end of the second arc portion and extends linearly from the inner peripheral end toward the outer side in the radial direction.

4. The compressor impeller according to claim 3, wherein: At least one of the first arc portion or the second arc portion includes: The front end is located at a position closest to the front end side in the axial direction in the axial direction in the axial recess.

5. The compressor impeller according to claim 3 or 4, wherein: The curvature radius of the first arc portion is smaller than the curvature radius of the second arc portion.

6. The compressor impeller according to claim 3, wherein: The first straight portion is inclined so that the inner peripheral end is located closer to the front end side in the axial direction than the outer peripheral end.

7. The compressor impeller according to any one of claims 1 to 4 and 6, wherein: When the distance from the axis of the compressor impeller to the outer peripheral end of the back side is defined as D1, and the distance from the axis to the front end located closest to the front end side in the axial direction in the axial recess is defined as D2, the compressor impeller is constructed to satisfy the condition of D2≥0.5D1.

8. The compressor impeller according to any one of claims 1 to 4 and 6, wherein: When the distance from the end face on the front end side of the compressor impeller in the axial direction to the flat portion is defined as L1, and the distance from the outer peripheral end of the back side in the axial direction to the flat portion is defined as L2, the compressor impeller is configured to satisfy the condition of L2≥0.1L1.

9. The compressor impeller according to any one of claims 1 to 4 and 6, wherein: The outer side surface has a radial recessed portion that is recessed toward the inside in the radial direction of the compressor impeller relative to an outer peripheral end of the flat portion. 10 . A centrifugal compressor comprising the compressor impeller according to claim 1 .

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