COMPRESSOR WHEEL AND CENTRIFUGAL COMPRESSOR

Abstract

A compressor wheel comprises a hub and at least one blade provided on an outer surface of the hub, wherein a rear surface of the compressor wheel includes a flat section extending along a radial direction of the compressor wheel and located on a rear end of the compressor wheel in an axial direction with respect to an outer circumferential end of the rear surface, and an outer surface connecting the flat section and the outer circumferential end of the rear surface, and the outer surface has an axially recessed section recessed in the axial direction with respect to the outer circumferential end of the rear surface.

Description

Technical area

[0001] The present disclosure relates to a compressor wheel and a centrifugal compressor including the compressor wheel. State of the art

[0002] In the prior art, as a technique for improving the performance of an engine (internal combustion engine) such as an automobile engine, a turbocharger (supercharger) is widely used, which compresses intake air sucked by the engine to increase the density and supplies the intake air containing a large amount of oxygen to the engine.

[0003] The turbocharger includes, for example, a centrifugal compressor provided on one end of the rotating shaft and a turbine provided on the other end of the rotating shaft. The turbocharger is configured to rotate a turbine rotor using energy from exhaust gas discharged from an engine, rotate a compressor wheel of a centrifugal compressor, which rotates in conjunction with the rotation of the turbine rotor, to compress the intake air, and supply the compressed air to the engine.

[0004] The compressor wheel described above includes a back surface configured with a flat portion extending along a radial direction of the compressor wheel, at least a portion of which contacts another member, such as a sleeve, and an outer side surface connecting the flat portion and an outer peripheral end of the back surface. In a general compressor wheel, the outer side surface has a large distance from the flat portion in the axial direction of the compressor wheel and a small inclination as the outer side surface extends outward in the radial direction of the compressor wheel (see, for example, PTL 1). Citation listPatent literature

[0005] [PTL 1] International Publication No. WO2019 / 130405 Summary of the inventionTechnical problem

[0006] The blade profile shape of the compressor wheel plays an important role in compressing the intake air delivered to the engine; however, the blade profile shape is limited by the stress generated at the compressor wheel during rotation of the compressor wheel. With the back surface shape of the above-mentioned compressor wheel, there is a case where it is not possible to reduce the stress generated at the compressor wheel during rotation of the compressor wheel to a stress range required to prevent an influence on noise generated during rotation of the compressor wheel. Furthermore, with the back surface shape of the above-mentioned compressor wheel, the moment of inertia of the compressor wheel tends to be large, and thus, there are concerns that the transient response characteristics of the centrifugal compressor or the turbocharger incorporating the centrifugal compressor will deteriorate.

[0007] In view of the above circumstances, an object of at least one embodiment of the present disclosure is to provide a compressor wheel and a centrifugal compressor capable of reducing a stress generated at the compressor wheel during rotation of the compressor wheel and reducing an inertia moment of the compressor wheel. Solution to the problem

[0008] A compressor wheel according to at least one embodiment of the present disclosure comprises: a hub; and at least one blade provided on an outer surface of the hub, where a back surface of the compressor wheel contains: a flat portion extending along a radial direction of the compressor wheel and located on a rear end side of the compressor wheel in an axial direction with respect to an outer peripheral end of the rear surface, and an outer side surface connecting the flat portion and the outer peripheral end of the back surface, and the outer side surface has an axially recessed portion recessed toward a front end side in the axial direction with respect to the outer peripheral end of the rear surface.

[0009] The centrifugal compressor according to at least one embodiment of the present disclosure includes the compressor wheel. Advantageous effects of the invention

[0010] According to at least one embodiment of the present disclosure, a compressor wheel and a centrifugal compressor are provided that are capable of reducing a stress generated at the compressor wheel during rotation of the compressor wheel and reducing a moment of inertia of the compressor wheel. Brief Description of the Drawings Fig. 1 is a schematic cross-sectional view along an axis of a supercharger including a centrifugal compressor according to an embodiment. Fig. 2 is a schematic cross-sectional view of a vicinity of a compressor wheel along an axis of a centrifugal compressor according to the embodiment. Fig. 3 is a schematic cross-sectional view of a vicinity of a compressor wheel along an axis of a centrifugal compressor according to a comparative example. Fig. 4 is a schematic cross-sectional view along an axis of the compressor wheel according to the embodiment. Fig. 5 is a schematic cross-sectional view taken along an axis of the compressor wheel according to the embodiment. Description of embodiments

[0011] Some embodiments of the present disclosure will be described below with reference to the accompanying drawings. However, the sizes, materials, shapes, and relative arrangements of components described as the embodiments or illustrated in the drawings are not intended to limit the scope of the present disclosure and are merely examples for describing the present disclosure. (supercharger, centrifugal compressor)

[0012] Fig. 1 is a schematic cross-sectional view along an axis LA of a supercharger 10 including a centrifugal compressor 1 according to an embodiment. The centrifugal compressor 1 according to the present disclosure may be mounted, for example, in a supercharger (turbocharger) 10 for a car, a ship, or an industrial application (for example, for land-based power generation). In each of the following embodiments, the centrifugal compressor 1 mounted in the supercharger (turbocharger) 10 is described as an example, but the centrifugal compressor 1 according to the present disclosure is not limited to the centrifugal compressor mounted in the supercharger 10. Furthermore, the operating fluid of the centrifugal compressor 1 need not be limited to air.That is, the centrifugal compressor 1 of the present disclosure only needs to be able to compress the operating fluid by mechanical power (for example, rotational force), and may be configured as a single centrifugal compressor 1 or may be configured to be combined with a mechanism or device other than the turbine 11.

[0013] As in Fig. 1, according to some embodiments, the supercharger 10 is configured to be driven by energy from exhaust gas discharged from an engine (internal combustion engine, not shown) and to compress a fluid (e.g., air). The supercharger 10 includes a turbine 11 driven by the exhaust gas discharged from the engine, and a centrifugal compressor 1 coaxially connected to the turbine 11, which supplies air compressed by rotation to the engine.

[0014] The turbine 11 includes a turbine rotor 12 and a turbine housing 13 configured to receive the turbine rotor 12 in a rotatable manner. The centrifugal compressor 1 includes a compressor wheel (impeller) 2 and a compressor housing 14 configured to receive the compressor wheel 2 in a rotatable manner.

[0015] As in Fig. 1, the supercharger 10 further includes a rotating shaft 15 to which the compressor wheel 2 is connected at one end and to which the turbine rotor 12 is connected at the other end, and a bearing 16 configured to rotatably support the rotating shaft 15 between the turbine wheel 2 and the turbine rotor 12. Furthermore, the supercharger 10 may further include a bearing housing 17 disposed between the compressor housing 14 and the turbine housing 13 and configured to receive the bearing 16.

[0016] The turbine 11 is configured to rotate the turbine rotor 12 using energy from the exhaust gas discharged from the engine. Since the compressor wheel 2 is coaxially connected to the turbine rotor 12 via the rotating shaft 15, the compressor wheel 2 is driven to rotate about the LA axis in conjunction with the rotation of the turbine rotor 12. The centrifugal compressor 1 is configured to rotate and drive the compressor wheel 2 about the LA axis to draw air (air supply, gas) into the compressor housing 14, compress the air, and deliver the compressed air to the engine. The compressed air delivered by the centrifugal compressor 1 to the engine is supplied for combustion in the engine. The exhaust gas generated by the combustion in the engine is delivered from the engine to the turbine 11 to rotate the turbine rotor 12.

[0017] Hereinafter, a direction in which the axis LA of the compressor wheel 2 extends is defined as an axial direction of the compressor wheel 2 (centrifugal compressor 1), a direction perpendicular to the axis LA is defined as a radial direction of the compressor wheel 2 (centrifugal compressor 1), and a circumferential direction around the axis LA is defined as a circumferential direction of the compressor wheel 2 (centrifugal compressor 1). In the axial direction of the compressor wheel 2, a side on which the outer surface 22 of the hub 21 is located with respect to the rear surface 3 of the compressor wheel 2 is defined as a front end side, and a side opposite to the front end side is defined as a rear end side. (turbine rotor)

[0018] The turbine rotor 12 includes a hub 121 having a substantially truncated conical shape and a plurality of turbine blades 122 provided on an outer surface of the hub 121. Since the hub 121 is connected to one end side of the rotating shaft 15, the turbine rotor 12 is provided 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 outside in the radial direction of the turbine rotor 12 to the front side of the turbine rotor 12 along the axial direction of the turbine rotor 12. (turbine casing)

[0019] In the turbine housing 13, a turbine scroll flow path 131 for guiding the exhaust gas discharged from the engine to the turbine rotor 12 and an exhaust gas discharge flow path 132 for discharging the exhaust gas that has passed through the turbine rotor 12 to the outside of the turbine housing 13 are formed. The turbine scroll flow path 131 is provided in a radial direction on an outer side of the turbine rotor 12 and consists of a spiral flow path extending along a circumferential direction of the turbine rotor 12. The exhaust gas discharge flow path 132 extends along the axial direction (extension direction of the axis LA) of the turbine rotor 12.

[0020] The exhaust gas discharged from the engine is guided to the turbine rotor 12 through the turbine scroll flow path 131, and the turbine rotor 12 is driven to rotate. The exhaust gas that drives the turbine rotor 12 to rotate is discharged to the outside of the turbine housing 13 through the exhaust discharge flow path 132. (compressor wheel)

[0021] The compressor wheel 2 includes a hub 21 having a substantially truncated conical shape and a plurality of compressor blades 23 provided on an outer surface 22 of the hub 21. Each of the plurality of compressor blades 23 protrudes from the outer surface 22 of the hub 21 and is spaced apart from each other in a circumferential direction around the axis LA. A gap (clearance) is formed between the tip-side end (tip) 24 of the plurality of compressor blades 23 and the shroud surface 141 curved to convexly face the tip-side end 24. That is, the compressor wheel 2 does not include an annular member covering the tip-side end 24. The plurality of compressor blades 23 may include a plurality of long blades 23A and a plurality of short blades 23B formed to be shorter than the long blades 23A in the axial direction of the compressor wheel 2.

[0022] The compressor wheel 2 is provided so that it is rotatable about the axis LA integrally with the rotating shaft 15, since the hub 21 is connected to one end of the rotating shaft 15. The compressor wheel 2 is configured to guide the air introduced along the axial direction of the compressor wheel 2 toward the outside of the compressor wheel 2 in the radial direction. In the illustrated embodiment, the compressor wheel 2 is made of a metal material (specifically, aluminum or an aluminum alloy). (compressor housing)

[0023] The compressor housing 14 has the above-described shell surface 141. A gas introduction flow path 142, a diffuser flow path 143, and a scroll flow path 144 are formed in the compressor housing 14.

[0024] The gas introduction flow path 142 is a flow path that sucks air (gas) from the outside of the compressor housing 14 and guides the intake air to the compressor impeller 2. The gas introduction flow path 142 is provided on one side (tip end side) of the compressor impeller 2 in the axial direction of the compressor impeller 2 and extends along the axial direction of the compressor impeller 2. By rotating and driving the compressor impeller 2, air is sucked into the gas introduction flow path 142 from the outside of the compressor housing 14, and the intake air flows through the gas introduction flow path 142 and is guided to the compressor impeller 2.

[0025] The scroll flow path 144 is provided on the outside of the compressor wheel 2 in the radial direction and consists of a spiral flow path extending along the circumferential direction of the compressor wheel 2. The diffuser flow path 143 is a flow path for guiding the air that has passed through the compressor wheel 2 and been compressed by the compressor wheel 2 to the scroll flow path 144. The diffuser flow path 143 is provided between the scroll flow path 144 and the compressor wheel 2 in the radial direction of the compressor wheel 2, and a downstream end portion (outer peripheral end portion) thereof communicates with the scroll flow path 144. The compressed air (compressed gas) compressed by the compressor wheel 2 flows into the diffuser flow path 143 and flows in the diffuser flow path 143 to the outside in the radial direction of the compressor wheel 2 so as to be guided to the scroll flow path 144.

[0026] Fig. Fig. 2 is a schematic cross-sectional view of the vicinity of the compressor wheel 2 along the axis LA of the centrifugal compressor 1 according to the embodiment. As shown in Fig. 2, the compressor wheel 2 has a front end surface 25, which is an end surface on the front end side of the hub 21 in the axial direction, and a rear surface 3, which is an end surface on the rear end side of the hub 21 in the axial direction. The front end surface 25 extends along the radial direction of the compressor wheel 2. The rear surface 3 includes a flat portion 4 extending along the radial direction of the compressor wheel 2, and an outer side surface 5 connecting the flat portion 4 and an outer peripheral end 31 of the rear surface 3. The outer side surface 5 has no portion protruding toward the rear end side in the axial direction with respect to the flat portion 4. The flat portion 4 includes a flat surface 40 extending in at least a part of the compressor wheel 2 in the circumferential direction along the radial direction of the compressor wheel 2.The flat surface 40 is not limited to a flat surface having no unevenness at all, and may have unevenness due to a tolerance or machining accuracy during the formation of the flat surface 40. The flat portion 4 is a groove portion provided on the flat surface 40 and may include an arcuate or annular groove portion (not shown) extending along the circumferential direction of the compressor wheel 2. Furthermore, the flat portion 4 may include at least one radial groove portion (not shown), which is a groove portion provided on the flat surface 40 and extending along the radial direction of the compressor wheel 2.

[0027] At the Fig. In the embodiment shown in Figure 2, a through hole 26 is formed in the compressor wheel 2, extending from the front end surface 25 to the flat portion 4 along the axial direction of the compressor wheel 2, and into which the rotary shaft 15 is inserted. The centrifugal compressor 1 includes a contact portion 18 that comes into contact with the flat portion 4 of the compressor wheel 2, and a locking member 19 that is locked to the rotary shaft 15 on the front end side of the compressor wheel 2 and clamps the compressor wheel 2 between the contact portion 18 and the locking member 19.

[0028] The contact portion 18 is a part of a member other than the compressor wheel 2, protrudes to an outer side in a radial direction with respect to the through hole 26, and comes into contact with at least a part of the flat portion 4. In the illustrated embodiment, the centrifugal compressor 1 includes a tubular sleeve 18A into which the rotary shaft 15 is inserted, and the contact portion 18 includes an end surface of the sleeve 18A on the front end side that comes into contact with at least a part of the flat portion 4. The sleeve 18A is prevented from moving to the rear end side in the axial direction of the compressor wheel 2 by the other members, such as the rotary shaft 15. The contact portion 18 may be a part of the rotary shaft 15.

[0029] At the Fig. In the embodiment shown in Fig. 2, the locking member 19 includes an annular nut member having a screw portion 191 formed on the inner surface, the screw portion 191 being screwed into a screw portion 151 formed on the outer surface of the rotating shaft 15 on the front end side of the compressor wheel 2. In a state where the contact portion 18 is in contact with the flat portion 4, by screwing the screw portion 191 into the screw portion 151, the compressor wheel 2 can be inserted between the contact portion 18 and the locking member 19. Accordingly, the compressor wheel 2 is connected to the rotating shaft 15. (Axially recessed section)

[0030] Fig. 3 is a schematic cross-sectional view of the vicinity of the compressor wheel 02 along the axis LA of the centrifugal compressor 01 according to the comparative example. Fig. 4 is a schematic cross-sectional view along the axis LA of the compressor wheel 2 (2A) according to the embodiment. Fig. 5 is a schematic cross-sectional view along the axis LA of the compressor wheel 2 (2B) according to the embodiment. As shown in Fig. 2, Fig. 4 and Fig. As shown in FIG. 5, the compressor wheel 2 of the centrifugal compressor 1 according to some embodiments includes an axially recessed portion 6 in which the outer side surface 5 is recessed from the outer peripheral end 31 of the rear surface 3 in the axial direction toward the front end side (front end surface 25 side) of the compressor wheel 2. The axially recessed portion 6 means a portion of the outer side surface 5 located on the front end side with respect to the outer peripheral end 31 of the rear surface 3 in the axial direction of the compressor wheel 2. (Centrifugal compressor according to comparison example)

[0031] The compressor wheel 02 of the centrifugal compressor 01 according to the comparative example differs from the compressor wheel 2 according to the present disclosure in that the outer side surface 05 connecting the flat portion 4 and the outer peripheral end 31 of the rear surface 3 has the Fig. 3. Along the radial direction of the compressor wheel 02 toward the outside, as the distance between the outer side surface 05 and the flat portion 4 of the compressor wheel 02 increases in the axial direction, the inclination becomes moderate.

[0032] According to the above configuration, the compressor wheel 2 having the axially recessed portion 6 can reduce the mass around the area where the axially recessed portion 6 is formed, compared to the compressor wheel 2 not having the axially recessed portion 6, and can reduce the centrifugal force applied to the compressor wheel 2 in the axial direction area where the axially recessed portion 6 is formed (the area between the flat portion 4 and the outer peripheral end 31 of the rear surface 3 in the axial direction). Accordingly, it is possible to reduce the stress at the bore portion (in the vicinity of the through hole 26 of the hub 21) of the compressor wheel 2 during rotation of the compressor wheel 2.Furthermore, since the compressor wheel 2 having the axially recessed portion 6 has a mass reduced around a region where the axially recessed portion 6 is formed, compared to the compressor wheel 2 not having the axially recessed portion 6, the moment of inertia (inertia) of the compressor wheel 2 is reduced. Therefore, the transient response characteristics of the centrifugal compressor 1 or the supercharger (turbocharger) 10 including the centrifugal compressor 1 are improved. (shape of outer surface)

[0033] In some embodiments, as in Fig. 4 and Fig. 5, the above-described outer side surface 5 has at least one arc portion 5A extending in an arc shape in a cross section along the axis LA of the compressor wheel 2, and at least one linear portion 5B extending in a linear shape in a cross section along the axis LA.

[0034] According to the above configuration, the outer side surface 5 includes at least one arcuate portion 5A and at least one linear portion 5B, and thus the outer side surface 5 can have a smooth shape. By making the outer side surface 5 have a smooth shape, it is possible to effectively reduce the stress on the bore portion of the compressor wheel 2 during rotation of the compressor wheel 2.

[0035] In some embodiments, as in Fig. 4 and Fig. 5, the at least one arcuate portion 5A described above includes at least a first arcuate portion 51 and a second arcuate portion 52. The at least one linear portion 5B described above includes at least a first linear portion 53. In other words, the outer side surface 5 described above includes at least the first arcuate portion 51, the second arcuate portion 52, and the first linear portion 53.

[0036] In the first arc portion 51, a rear end 511 is connected to the outer peripheral end 41 of the flat portion 4, and a front end 512 is located on a front end side of the compressor wheel 2 in the axial direction with respect to the rear end 511. In the second arc portion 52, an inner peripheral end 521 is connected to the front end 512 of the first arc portion 51 and extends from the inner peripheral end 521 to the outside in the radial direction. In the first linear portion 53, an inner peripheral end 531 is connected to an outer peripheral end 522 of the second arc portion 52, and the first linear portion 53 extends in a linear shape from the inner peripheral end 531 to the outside in the radial direction.

[0037] At the Fig. In the embodiment shown in Figure 4, the first arc portion 51 has a recess shape toward the front end side in the axial direction of the compressor wheel 2, and the distance from the axis LA of the compressor wheel 2 in the radial direction increases toward the front end side in the axial direction of the compressor wheel 2. The front end 512 is located on the outside of the rear end 511 in the radial direction of the compressor wheel 2.

[0038] At the Fig. In the embodiment shown in Figure 5, the first arc portion 51 has a recess shape toward the inner side in the radial direction of the compressor wheel 2, and a distance from the axis LA of the compressor wheel 2 in the radial direction decreases toward the front end side of the compressor wheel 2 along the axial direction. The front end 512 is located on the inner side of the rear end 511 in the radial direction of the compressor wheel 2.

[0039] The second arc portion 52 has a recessed shape toward the front end side of the compressor wheel 2 in the axial direction. Fig. 4 and Fig. 5, the outer peripheral end 522 is located on the front end side in the axial direction of the compressor wheel 2 with respect to the inner peripheral end 521.

[0040] According to the above configuration, the outer side surface 5 includes at least the first arc portion 51, the second arc portion 52, and the first linear portion 53. Therefore, the outer side surface 5 can have a smooth shape with a relatively low complexity without a discontinuous point. By making the outer side surface 5 have a smooth shape, it is possible to effectively reduce the stress at the bore portion of the compressor wheel 2 during rotation of the compressor wheel 2. Moreover, since the outer side surface 5 includes at least the first arc portion 51, the second arc portion 52, and the first linear portion 53, the back surface portion of the compressor wheel 2 where the outer side surface 5 is formed can ensure sufficient strength.Moreover, with the above configuration, since the outer side surface 5 includes the first arc portion 51, the second arc portion 52, and the first linear portion 53, it is possible to suppress the vibration characteristics of the compressor blade 23 from being changed due to the operation of the centrifugal compressor 1 or the supercharger 10 including the centrifugal compressor 1.

[0041] At the Fig. 4 and Fig. 5, the at least one linear portion 5B described above further includes a second linear portion 54 extending from the outer peripheral end 31 of the back surface 3 toward the inner side in the radial direction in a linear shape. The second linear portion 54 extends along a direction intersecting the axis LA (perpendicular thereto in the example shown in the drawing). The at least one arc portion 5A described above further includes a third arc portion 55 connecting the outer peripheral end 532 of the first linear portion 53 and the inner peripheral end 541 of the second linear portion 54.In other words, the above-described outer side surface 5 includes a first arc portion 51, a second arc portion 52, a first linear portion 53, a third arc portion 55, and a second linear portion 54 in this order from the inner side in the radial direction of the compressor wheel 2. The first arc portion 51, the second arc portion 52, the first linear portion 53, the third arc portion 55, and the second linear portion 54 each have an annular surface extending along the circumferential direction around the axis LA. (Front end of axially recessed section)

[0042] In some embodiments, at least one of the first arc portion 51 and the second arc portion 52 includes a leading end 50 located in the axially recessed portion 6 closest to the leading end side in the axial direction. According to the above configuration, with the leading end 50 provided in the first arc portion 51 or the second arc portion 52 having no discontinuous point, it is possible to suppress stress concentration in the vicinity of the leading end 50 during rotation of the compressor wheel 2. As a result, it is possible to effectively reduce the stress at the bore portion of the compressor wheel 2 during rotation of the compressor wheel 2.

[0043] At the Fig. 4 and Fig. 5, the second arcuate portion 52 and the first linear portion 53 form at least a part of the axially recessed portion 6. As shown in Fig. 4 and Fig. As shown in FIG. 5, a virtual plane passing through the outer peripheral end 31 of the rear surface 3 and perpendicular to the axis LA is defined as PL1, and an intersection point of the first arc portion 51 or the second arc portion 52 with the virtual plane PL1 is defined as P1. The axially recessed portion 6 is formed between the intersection point P1 and the inner peripheral end 541 of the second linear portion 54 on the outer side surface 5.

[0044] At the Fig. 4 and Fig. 5, the second arc portion 52 includes the front end 50 of the axially recessed portion 6. In the second arc portion 52, in a 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 increases toward the outside in the axial direction of the compressor wheel 2 along the radial direction of the compressor wheel 2. In the second arc portion 52, in a range from the front end 50 to the outer peripheral end 522, the distance between the second arc portion 52 and the flat portion 4 decreases toward the outside in the axial direction of the compressor wheel 2 along the radial direction of the compressor wheel 2. (Radius of curvature of first arc section and second arc section)

[0045] In some embodiments, as in Fig. 4, the radius of curvature R1 of the first arc portion 51 is smaller than the radius of curvature R2 of the second arc portion 52. In the illustrated embodiment, in a case where a distance (radial distance) from the axis LA of the compressor wheel 2 to the outer peripheral end 31 of the back surface 3 is defined as D1, the radius of curvature R1 is configured to satisfy a condition of 0.075 × D1 ≤ R1 ≤ 0.15 × D1. Moreover, the radius of curvature R2 is configured to satisfy a condition of 0.45 × D1 ≤ R2 ≤ 0.55 × D1.

[0046] According to the above configuration, by setting the radius of curvature R1 of the first arc portion 51, where the rear end 511 is connected to the flat portion 4, to be relatively small, the stress applied to the flat portion 4 during rotation of the compressor wheel 2 can be reduced. Moreover, by setting the radius of curvature R2 of the second arc portion 52, which connects the first arc portion 51 and the first linear portion 53, to be relatively large, the first arc portion 51, the second arc portion 52, and the first linear portion 53 of the outer side surface 5 can be formed into a smooth shape. (Inclination of first linear section)

[0047] In some embodiments, as in Fig. 4 and Fig. 5, the above-described first linear portion 53 is inclined such that the inner peripheral end 531 is located on the front end side in the axial direction with respect to the outer peripheral end 532. As shown in Fig. As shown in Figure 4, an angle (shorter side angle) between the above-mentioned virtual plane PL1 and the first linear portion 53 is defined as θ. In the illustrated embodiment, the compressor wheel 2 is configured to satisfy the condition of 5° ≤ θ ≤ 10°.

[0048] According to the above configuration, by making the first linear portion 53 have an inclined shape such that the inner peripheral end 531 of the first linear portion 53 is located on the front end side with respect to the outer peripheral end 532, it is easy to make the radius of curvature R2 of the second arc portion 52 connected to the inner peripheral end 531 of the first linear portion 53 relatively large. Accordingly, the second arc portion 52 and the first linear portion 53 of the outer side surface 5 can be smoothly connected to each other. (Radial position from front end)

[0049] In some embodiments, as in Fig. 4, in a case where a distance (radial distance) from the axis LA of the compressor wheel 2 to the outer peripheral end 31 of the back surface 3 is defined as D1 and a distance (radial distance) from the axis LA to the front end 50 located closest to the front end side in the axial direction in the axially recessed portion 6 is defined as D2, the compressor wheel 2 is configured to satisfy a condition of D2 ≥ 0.5D1.

[0050] According to the above configuration, the larger the distance D2, the greater the effect of reducing the moment of inertia of the compressor wheel 2 by the axially recessed portion 6. By configuring the compressor wheel 2 to satisfy the condition of D2 ≥ 0.5D1, the moment of inertia of the compressor wheel 2 can be effectively reduced, and thus the transient response characteristics of the centrifugal compressor 1 or the supercharger (turbocharger 10) including the centrifugal compressor 1 are improved. Furthermore, in several other embodiments, as shown in Fig. 5, the compressor wheel 2 may not be configured to meet the condition of D2 ≥ 0.5D1. (Axial position of outer peripheral end of back surface)

[0051] In some embodiments, as in Fig. 2, in a case where a distance (axial distance) from an end surface (front end surface) 25 on a front end side of the compressor wheel 2 in the axial direction to the flat portion 4 is defined as L1 and a distance (axial distance) from an outer peripheral end 31 of the rear surface 3 to the flat portion 4 in the axial direction of the compressor wheel 2 is defined as L2, the compressor wheel 2 is configured to satisfy a condition of L2 ≥ 0.1L1.

[0052] According to the above configuration, the larger the distance L2, the smaller the stress applied to the flat portion 4 during rotation of the compressor wheel 2. By configuring the compressor wheel 2 to satisfy the condition of L2 ≥ 0.1L1, the stress on the flat portion 4 during rotation of the compressor wheel 2 can be effectively reduced. (Radial recessed section)

[0053] In some embodiments, as shown in Fig. 5, an outer side surface 5 of the compressor wheel 2 (2B) has a radially recessed portion 7 recessed inward from an outer peripheral end 41 of the flat portion 4 in the radial direction of the compressor wheel 2. The radially recessed portion 7 means a portion of the outer side surface 5 located on the inner side of the compressor wheel 2 with respect to the outer peripheral end 41 of the flat portion 4 in the radial direction.

[0054] At the Fig. 5, the first arc portion 51 includes an inner end located closest to the inner side in the radial direction in the radially recessed portion 7. The first arc portion 51 and the second arc portion 52 constitute at least a part of the radially recessed portion 7. A virtual plane extending parallel to the axis LA and passing the outer peripheral end 41 of the flat portion 4 is defined as PL2, and an intersection point of the second arc portion 52 with the virtual plane PL2 is defined as P2. The radially recessed portion 7 is formed between the intersection point P2 on the outer side surface 5 and the outer peripheral end 41 of the flat portion 4. Both the axially recessed portion 6 and the radially recessed portion 7 are formed between the intersection point P1 and the intersection point P2 on the outer side surface 5.

[0055] According to the above configuration, the compressor wheel 2B having the radially recessed portion 7 can reduce the mass around the region where the radially recessed portion 7 is formed, compared to the compressor wheel 2A not having the radially recessed portion 7, and can reduce the centrifugal force of the compressor wheel 2B in the axial direction region where the radially recessed portion 7 is formed. Accordingly, it is possible to reduce the stress at the bore portion (in the vicinity of the through hole 26 of the hub 21) of the compressor wheel 2B during rotation of the compressor wheel 2B.

[0056] As in Fig.1, the centrifugal compressor 1 according to some embodiments includes the above-mentioned compressor wheel 2. In this case, by providing the axially recessed portion 6 and the radially recessed portion 7 in the compressor wheel 2, the stress generated in the compressor wheel 2 during rotation of the compressor wheel 2 can be reduced, and the moment of inertia of the compressor wheel 2 can be reduced.

[0057] In the present specification, an expression representing a relative or absolute arrangement such as "in a certain direction", "along a certain direction", "parallel", "perpendicular", "center", "concentric" or "coaxial" does not strictly represent only such an arrangement, but also a tolerance or a state relatively shifted by an angle or a distance, as far as the same function can be obtained.

[0058] For example, expressions that represent things being in a same state, such as "identical," "equal," and "homogeneous," represent not only strictly a same state, but also a state in which a difference exists with a tolerance or to such an extent that the same function can be obtained.

[0059] Moreover, in the present specification, a term representing a shape such as a quadrangular shape or a cylindrical shape represents not only a shape such as a quadrangular shape or a cylindrical shape in a geometrically strict sense, but also a shape including an uneven portion, a chamfer portion, and the like within a range where the same effect can be obtained.

[0060] Furthermore, in this specification, expressions such as “provided with,” “containing,” or “having” a component are not exclusive expressions that exclude the presence of other components.

[0061] The present disclosure is not limited to the above-described embodiments, and also includes a form in which modifications are added to the above-described embodiments or a form in which the embodiments are combined with each other as appropriate.

[0062] For example, contents described in some of the embodiments described above are understood as follows.

[0063] 1) A compressor wheel (2) according to at least one embodiment of the present disclosure comprises: a hub (21); and at least one blade (compressor blade 23) provided on an outer surface (22) of the hub (21), wherein a rear surface (3) of the compressor wheel (2) contains: a flat portion (4) extending along a radial direction of the compressor wheel (2) and located on a rear end side of the compressor wheel (2) in an axial direction with respect to an outer peripheral end (31) of the rear surface (3), and an outer side surface (5) connecting the flat portion (4) and the outer peripheral end (31) of the rear surface (3), and the outer side surface (5) has an axially recessed portion (6) which is recessed toward a front end side in the axial direction with respect to the outer peripheral end (31) of the rear surface (3).

[0064] According to the configuration of the above 1), the compressor wheel (2) having the axially recessed portion (6) can reduce the mass around the region where the axially recessed portion (6) is formed, compared to the compressor wheel (02) not having the axially recessed portion (6), and can reduce the centrifugal force with respect to the compressor wheel (2) in the axial direction region where the axially recessed portion (6) is formed. As a result, it is possible to reduce the stress at the bore portion (in the vicinity of the through hole 26 of the hub 21) of the compressor wheel (2) during rotation of the compressor wheel (2).Furthermore, in the compressor wheel (2) having the axially recessed portion (6), compared to the compressor wheel (02) not having the axially recessed portion (6), the mass around the area where the axially recessed portion (6) is formed is reduced, so that the moment of inertia (inertia) of the compressor wheel (2) is reduced. Therefore, the transient response characteristics of the centrifugal compressor (1) or the turbocharger (10) including the centrifugal compressor (1) are improved.

[0065] 2) In some embodiments, the compressor wheel (2) according to 1), the outer surface (5): at least one arc section (5A) extending in a cross-section along an axis (LA) of the compressor wheel (2) in an arc shape, and at least one linear portion (5B) extending in a linear shape in a cross-section along the axis (LA).

[0066] According to the configuration of 2) above, the outer side surface (5) includes at least one arc portion (5A) and at least one linear portion (5B), so that the outer side surface (5) can have a smooth shape. By making the outer side surface (5) have a smooth shape, it is possible to effectively reduce the stress on the bore portion of the compressor wheel (2) during rotation of the compressor wheel (2).

[0067] 3) In some embodiments, the compressor wheel (2) according to 2), the at least one arc section (5A) at least: a first arc portion (51) of which a rear end (511) is connected to the flat portion (4) and a front end (512) is located on the front end side with respect to the rear end (511) in the axial direction, and a second arc portion (52) of which an inner peripheral end (521) is connected to the front end (512) of the first arc portion (51) and which extends outwardly from the inner peripheral end (521) in the radial direction, and the at least one linear portion (5B) includes at least: a first linear portion (53) of which an inner peripheral end (531) is connected to an outer peripheral end (522) of the second arc portion (52) and which extends in a linear shape outward from the inner peripheral end (531) in the radial direction.

[0068] According to the configuration of the above 3), the outer side surface (5) includes the first arc portion (51), the second arc portion (52), and the first linear portion (53). Therefore, the outer side surface (5) can have a smooth shape with relatively low complexity and no discontinuous points. By making the outer side surface (5) have a smooth shape, it is possible to effectively reduce the stress on the bore portion of the compressor wheel (2) during rotation of the compressor wheel (2). Moreover, the outer side surface (5) includes the first arc portion (51), the second arc portion (52), and the first linear portion (53), so that the back surface portion of the compressor wheel (2) where the outer side surface (5) is formed can ensure sufficient strength.Moreover, with the configuration of 3) described above, the outer side surface (5) includes the first arc portion (51), the second arc portion (52), and the first linear portion (53), so that it is possible to suppress the vibration characteristics of the blade (compressor blade 23) from changing due to the operation of the centrifugal compressor (1) or the supercharger (10) including the centrifugal compressor (1).

[0069] 4) In some embodiments, the compressor wheel (2) according to 3), at least one of the first arc section (51) and the second arc section (52): a front end (50) located closest to the front end side in the axial direction in the axially recessed portion (6).

[0070] According to the configuration of 4) above, since the front end (50) is provided in the first arc portion (51) or the second arc portion (52) that does not have a discontinuous point, it is possible to suppress stress concentration at the front end (50) during rotation of the compressor wheel (2). As a result, it is possible to effectively reduce the stress at the bore portion of the compressor wheel (2) during rotation of the compressor wheel (2).

[0071] 5) In some embodiments, the compressor wheel (2) according to 3) or 4), a radius of curvature (R1) of the first arc section (51) is smaller than a radius of curvature (R2) of the second arc section (52).

[0072] According to the configuration of the above 5), the radius of curvature (R1) of the first arc portion (51) where the rear end (511) is connected to the flat portion (4) is set to be relatively small, so that it is possible to reduce the stress on the flat portion (4) during rotation of the compressor wheel (2). Moreover, by setting the radius of curvature (R2) of the second arc portion (52) connecting the first arc portion (51) and the first linear portion (53) to be relatively large, the first arc portion (51), the second arc portion (52), and the first linear portion (53) of the outer side surface (5) can be formed in a smooth shape.

[0073] 6) In some embodiments, the compressor wheel (2) according to one of 3) to 5), the first linear portion (53) is inclined such that the inner peripheral end (531) is located on the front end side in the axial direction with respect to the outer peripheral end (532).

[0074] According to the configuration of the above 6), since the first linear portion (53) is provided in the inclined shape such that the inner peripheral end (531) of the first linear portion (53) is located on the front end side with respect to the outer peripheral end (532), it is easy to make the radius of curvature (R2) of the second arc portion (52) connected to the inner peripheral end (531) of the first linear portion (53) relatively large. Accordingly, the second arc portion (52) and the first linear portion (53) of the outer side surface (5) can be smoothly connected to each other.

[0075] 7) In some embodiments, the compressor wheel (2) according to one of 1) to 6), in a case where a distance from an axis (LA) of the compressor wheel (2) to the outer peripheral end (31) of the back surface (3) is defined as D1 and a distance from the axis (LA) to a front end (50) located closest to the front end side in the axial direction in the axially recessed portion (6) is defined as D2, the compressor wheel (2) is configured to satisfy a condition of D2 ≥ 0.5D1.

[0076] According to the configuration of the above 7), the effect of reducing the moment of inertia of the compressor wheel (2) by the axially recessed portion (6) is increased as the distance D2 is larger. By configuring the compressor wheel (2) to satisfy the condition of D2 ≥ 0.5D1, the moment of inertia of the compressor wheel (2) can be effectively reduced, and thus the transient response characteristics of the centrifugal compressor (1) or the turbocharger (10) including the centrifugal compressor (1) are improved.

[0077] 8) In some embodiments, the compressor wheel (2) according to one of 1) to 7), in a case where a distance from an end surface (25) on the front end side to the flat portion (4) of the compressor wheel (2) in the axial direction is defined as L1 and a distance from the outer peripheral end (31) of the rear surface (3) to the flat portion (4) in the axial direction is defined as L2, the compressor wheel (2) is configured to satisfy a condition of L2 ≥ 0.1L1.

[0078] According to the configuration of 8 above, the tension applied to the flat portion (4) during rotation of the compressor wheel (2) can be reduced as the distance L2 is larger. By configuring the compressor wheel (2) to satisfy the condition of L2 ≥ 0.1L1, the tension on the flat portion (4) during rotation of the compressor wheel (2) can be effectively reduced.

[0079] 9) In some embodiments, in the compressor wheel (2) according to any one of 1) to 8), the outer side surface (5) has a radially recessed portion (7) which is recessed inward in the radial direction of the compressor wheel (2) with respect to an outer peripheral end (41) of the flat portion (4).

[0080] According to the configuration of the above 9), the compressor wheel (2B) having the radially recessed portion (7) can reduce the mass around the region where the radially recessed portion (7) is formed, compared to the compressor wheel (2A) not having the radially recessed portion (7), and can reduce the centrifugal force of the compressor wheel (2B) in the axial direction region where the radially recessed portion (7) is formed. As a result, it is possible to reduce the stress at the bore portion (in the vicinity of the through hole 26 of the hub 21) of the compressor wheel (2B) during rotation of the compressor wheel (2B).

[0081] 10) A centrifugal compressor (1) according to at least one embodiment of the present disclosure comprises the compressor wheel (2) according to one of 1) to 9).

[0082] According to the configuration of the above 10), since the axially recessed portion (6) or the radially recessed portion (7) is provided in the compressor wheel (2), the stress generated in the compressor wheel (2) during rotation of the compressor wheel (2) can be reduced, and the moment of inertia of the compressor wheel (2) can be reduced. List of reference symbols 1.01 centrifugal compressor 2.02 compressor wheel 21 Hub 23 Compressor blade 3 Back surface 4 flat section 5.05 outer surface 6 axially recessed section 7 radially recessed section 10 chargers 11 Turbine 12 Turbine rotor 13 Turbine housing 14 Compressor housing 15 Rotating shaft 16 warehouses 17 Bearing housing 18 Contact section 18A sleeve 19 Locking element 21 Hub 22 exterior surface 23 Compressor blade 23A long shovel 23B short shovel 24 tip end 25 front end face 26 through hole 31 Outer circumference end 40 flat surface 121 Hub 122 turbine blade 131 Screw flow path 132 Exhaust gas discharge flow path 141 sheathing area 142 Gas introduction flow path 143 Diffuser flow path 144 Screw flow path La Axis QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] WO 2019 / 130405

[0005]

Claims

[1] Compressor wheel, comprising: a hub; and at least one blade provided on an outer surface of the hub, where a back surface of the compressor wheel contains: a flat portion extending along a radial direction of the compressor wheel and located on a rear end side of the compressor wheel in an axial direction with respect to an outer peripheral end of the rear surface, and an outer side surface connecting the flat portion and the outer peripheral end of the back surface, and the outer side surface has an axially recessed portion recessed toward a front end side in the axial direction with respect to the outer peripheral end of the rear surface. [2] The compressor wheel of claim 1, wherein the outer side surface includes: at least one arc portion extending in a cross-section along an axis of the compressor wheel in an arc shape, and at least one linear portion extending in a linear shape in a cross-section along the axis. [3] The compressor wheel of claim 2, wherein the at least one arc portion includes at least: a first arc portion of which a rear end is connected to the flat portion and a front end is located on the front end side with respect to the rear end in the axial direction, and a second arc portion having an inner peripheral end connected to the front end of the first arc portion and extending outwardly from the inner peripheral end in the radial direction, and including at least one linear portion at least: a first linear portion having an inner peripheral end connected to an outer peripheral end of the second arc portion and extending in a linear shape outward from the inner peripheral end in the radial direction. [4] The compressor wheel according to claim 3, wherein at least one of the first arc portion and the second arc portion includes: a front end located closest to the front end side in the axial direction in the axially recessed portion. [5] The compressor wheel according to claim 3 or 4, wherein a radius of curvature of the first arc portion is smaller than a radius of curvature of the second arc portion. [6] The compressor wheel according to claim 3, wherein the first linear portion is inclined so that the inner peripheral end is located on the front end side in the axial direction with respect to the outer peripheral end. [7] The compressor wheel according to any one of claims 1 to 4 and 6, wherein in a case where a distance from an axis of the compressor wheel to the outer peripheral end of the back surface is defined as D1 and a distance from the axis to a front end closest to the front end side in the axial direction in the axially recessed portion is defined as D2, the compressor wheel is configured to satisfy a condition of D2 ≥ 0.5D1. [8] The compressor wheel according to any one of claims 1 to 4 and 6, wherein in a case where a distance from an end surface on the front end side to the flat portion of the compressor wheel in the axial direction is defined as L1 and a distance from the outer peripheral end of the rear surface to the flat portion in the axial direction is defined as L2, the compressor wheel is configured to satisfy a condition of L2 ≥ 0.1L1. [9] The compressor wheel according to any one of claims 1 to 4 and 6, wherein the outer side surface has a radially recessed portion recessed inward in the radial direction of the compressor wheel with respect to an outer peripheral end of the flat portion. [10] Centrifugal compressor comprising the compressor wheel according to any one of claims 1 to 4 and 6.

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