IRON OF THE CENTRIFUGAL COMPRESSOR, CENTRIFUGAL COMPRESSOR AND TURBOCHARGER

Abstract

Impeller (5) of a centrifugal compressor (2), comprising: a hub (6); at least one airfoil section (7) erected on a hub surface (61) of the hub (6), wherein the at least one airfoil section has a trailing edge (28) configured such that the distance between the trailing edge (28) and an axis of the centrifugal compressor (2) increases with increasing distance from a rear surface (63) of the hub (6); and a first rounding (110) formed on a radially outer side of an outer circumferential surface (65) of a backplate section (67) forming a back surface section of the hub (6), wherein the first rounding (110) connects the outer circumferential surface and the trailing edge (28) of the at least one wing section, wherein at least part of the first rounding has a curved shape in which a center of curvature is located on the radially outer side of the outer circumferential surface (65) in a meridional cross-section of the impeller (5); and wherein one end edge of the curved shape is arranged on the side of the outer circumferential surface on the back plate section.

Description

TECHNICAL AREA

[0001] The present disclosure relates to an impeller of a centrifugal compressor, the centrifugal compressor and a turbocharger. BACKGROUND

[0002] For example, a turbocharger is known as a turbo device for improving the output of an engine by utilizing the energy of an exhaust gas expelled from the engine. The turbocharger drives a turbine wheel by means of the exhaust gas expelled from the engine, which in turn drives a compressor wheel that is coaxially connected to the turbine wheel to compress intake air and supply the compressed intake air to the engine (see, for example, patent document 1). Citation list for patent literature

[0003] Patent Document 1: JP2015-194091A US 2010 / 0322781A1 discloses an impeller with an axis of rotation, a radial direction, a backplate and a number of blades connected to the backplate along a connecting line. JP 2006-226 199 A discloses a centrifugal wheel in which several blades are radially mounted in a guide surface of a disk. A groove is formed between the guide surface of the disk and a blade side surface. US 2015 / 0125302A1 discloses an impeller for a hydroelectric power machine with a hub and a plurality of rotor blades attached to the hub around which a medium can flow through the hydroelectric power machine and which form a blade channel between two adjacent rotor blades with a blade channel length extending in the axial direction of the impeller. SUMMARY Technical Problem

[0004] In recent years, there has been a demand for high compression ratios in compressors, and to achieve these high compression ratios, a high peripheral speed of the compressor impeller is required. To increase the peripheral speed of the impeller, it is conceivable to modify the shape of the trailing edge of a wing section, in addition to increasing the impeller rotational speed. For example, in the centrifugal compressor disclosed in patent document 1 described above, part of the trailing edge of a wing is projected radially outward relative to a section with maximum diameter of an impeller hub, thereby increasing the peripheral speed at the trailing edge.However, simply projecting part of the trailing edge of the wing radially outwards relative to the section with maximum diameter of the wheel hub can lead to an increase in stress due to a centrifugal force acting on the wing section and a decrease in the natural frequency of the wing section.

[0005] In light of the above, it is an object of at least one embodiment of the present disclosure to increase the compression ratio of the centrifugal compressor while ensuring the durability of the centrifugal compressor. Solution to the problem

[0006] The aforementioned disadvantages are at least partially solved by the impeller of a centrifugal compressor according to claim 1. (1) An impeller of a centrifugal compressor according to at least one embodiment of the present disclosure comprises a hub, at least one airfoil section erected on a hub surface of the hub, wherein the at least one airfoil section has a trailing edge configured such that the distance between the trailing edge and an axis of the centrifugal compressor increases with increasing distance from a rear surface of the hub, and a first rounding formed on a radially outer side of an outer circumferential surface of a backplate section forming a rear surface section of the hub, wherein the first rounding connects the outer circumferential surface and the trailing edge of the at least one airfoil section. (2) A centrifugal compressor according to at least one embodiment of the present disclosure comprises the impeller of the centrifugal compressor as defined in (1) above and a compressor housing for receiving the impeller. (3) Turbocharger according to at least one embodiment of the present disclosure comprises the centrifugal compressor as defined in (2) above. Beneficial effects

[0007] According to at least one embodiment of the present disclosure, it is possible to increase the compression ratio of a centrifugal compressor while ensuring the durability of the centrifugal compressor. BRIEF DESCRIPTION OF THE DRAWINGS Fig. Figure 1 is a schematic cross-sectional view of a turbocharger according to some embodiments. Fig. Figure 2 is a schematic perspective view of a wheel according to one embodiment. Fig. Figure 3 is a schematic view showing a schematic meridional cross-section of the impeller according to one embodiment. Fig. Figure 4A is a view that schematically shows part of the impeller on an outer circumferential side when the impeller is viewed from a rear surface according to one embodiment. Fig. Figure 4B is a view that schematically shows part of the impeller on the outer circumferential side when the impeller is viewed from the rear surface according to another embodiment. Fig. Figure 5A is a schematic meridional cross-sectional view of the impeller according to one embodiment. Fig. Figure 5B is a schematic meridional cross-sectional view of the impeller according to another embodiment. Fig. Figure 6A is a schematic meridional cross-sectional view of the impeller according to one embodiment. Fig. Figure 6B is a schematic meridional cross-sectional view of the impeller according to another embodiment. Fig. Figure 7 is a schematic meridional cross-sectional view of the impeller according to one embodiment. Fig. Figure 8 is a schematic meridional cross-sectional view to describe another embodiment with respect to the shape of a first rounding. DETAILED DESCRIPTION

[0008] Embodiments of the present disclosure are described below with reference to the accompanying drawings. However, unless specifically identified, dimensions, materials, shapes, relative positions, and the like of components described or shown in the drawings as embodiments are intended to be interpreted as illustrative only and are not meant to limit the scope of the present disclosure.

[0009] For example, an expression of a relative or absolute arrangement, such as "in a direction", "along a direction", "parallel", "orthogonal", "centered", "concentric" and "coaxial", should not be interpreted as specifying only the arrangement in a strict literal sense, but also encompasses a state in which the arrangement is shifted relative to the other by a tolerance or by an angle or a distance, making it possible to achieve the same function.

[0010] For example, an expression of an equal state, such as "same", "equal" and "uniform", should not be interpreted as indicating only the state in which the feature is strictly equal, but also includes a state in which there is a tolerance or difference that can still achieve the same function.

[0011] Furthermore, for example, an expression for a shape, such as a rectangular shape or a tubular shape, should not be interpreted solely as the geometrically strict form, but also includes a shape with irregularities or chamfered corners within the area where the same effect can be achieved. On the other hand, the expressions "comprising," "containing," "exhibiting," "incorporating," and "forming" a single component are not exclusive expressions that exclude the presence of other individual components. (Overall configuration of turbocharger 1)

[0012] First, with reference to Fig. 1 a turbocharger is described which is equipped with a centrifugal compressor which includes an impeller according to some embodiments. Fig. Figure 1 is a schematic cross-sectional view of the turbocharger according to some embodiments. As shown in the figure, a turbocharger 1 is provided with a centrifugal compressor 2, which includes a compressor impeller 5. The turbocharger 1 includes a rotating shaft 4, a compressor impeller 5 (impeller 5) arranged at one end of the rotating shaft 4, a turbine impeller 8 arranged at another end of the rotating shaft 4, and a bearing 24 for rotatably mounting the rotating shaft 4. The bearing 24 is located in the axial direction of the rotating shaft 4 between the compressor impeller 5 and the turbine impeller 8. Although not specifically limited, the turbocharger 1, according to some embodiments, is a turbocharger that is mounted, for example, on an automobile engine or the like.

[0013] The compressor impeller 5 comprises a hub 6 and several airfoil sections 7, which are erected on a hub surface 61 of the hub 6. The turbine impeller 8 comprises a hub 11 and several airfoil sections 9, which are erected on a hub surface 11a of the hub 11. The rotating shaft 4, the compressor impeller 5, and the turbine impeller 8 have a common central axis AX.

[0014] Furthermore, the turbocharger 1 includes a compressor housing 10 for receiving the compressor impeller 5, a turbine housing 12 for surrounding the turbine impeller 8, and a bearing housing 14 located axially between the compressor housing 10 and the turbine housing 12 along the rotating shaft 4. The compressor housing 10 and the bearing housing 14, as well as the turbine housing 12 and the bearing housing 14, can each be fastened by screws (not shown).

[0015] The compressor housing 10 includes an air inlet 16, which opens axially outwards in an end section of the turbocharger 1, and forms an annular flow passage 18, which is located on the radially outer side of the compressor impeller 5.

[0016] Furthermore, the turbine housing 12 includes an exhaust outlet 20 which opens axially outwards in another end section of the turbocharger 1 and forms an annular flow passage 22 which is located on the radially outer side of the turbine wheel 8.

[0017] For example, turbocharger 1 with the configuration described above operates as follows.

[0018] Air flows through the air inlet 16 into the compressor impeller 5, and the air is compressed by the compressor impeller 5, which rotates with the shaft 4. The compressed air thus produced is temporarily expelled from the turbocharger 1 through the annular flow passage 18, which is formed on the radially outer side of the compressor impeller 5, and is supplied, for example, to an internal combustion engine (not shown).

[0019] In the internal combustion engine, fuel is burned with the compressed air described above, and this combustion reaction produces a combustion gas. The combustion gas flows into the turbine wheel 8 via the annular flow passage 22, which is formed on the radially outer side of the turbine wheel 8, as exhaust gas expelled from the internal combustion engine. The flow of the exhaust gas described above exerts a rotational force on the turbine wheel 8, thereby driving the rotating shaft 4. The exhaust gas, having completed its work in the turbine, is expelled from the turbocharger 1 via the exhaust outlet 20. (Regarding compressor impeller 5 (impeller 5))

[0020] Next, the compressor impeller 5 (impeller 5) will be described in more detail according to some embodiments.

[0021] Fig. Figure 2 is a schematic perspective view of the impeller according to one embodiment.

[0022] Fig. Figure 3 is a schematic view showing a schematic meridional cross-section of the impeller according to one embodiment. Since the basic configuration of the impeller 5 according to another embodiment, which will be described later, is the same as that of the impeller 5 according to one embodiment, in the following description the impeller 5 according to one embodiment and the impeller 5 according to another embodiment will be referred to as: Fig. 2 and Fig. 3 described.

[0023] As in Fig. 2 and Fig. As shown in Figure 3, in some embodiments of the impeller 5, each of the several airfoil sections 7 arranged around the hub 6 of the impeller 5 extends between a leading edge 26, located on an upstream side, and a trailing edge 28, located on an upstream side in the direction of flow of a fluid entering the impeller 5, and between a hub-side end 30 and a casing-side end (tip end) 32. The hub-side end 30 corresponds to a position of the airfoil section 7 that is connected to the hub 6. The casing-side end 32 is an end located opposite the hub-side end 30 and is adjacent to the compressor housing 10 (see Figure 3). Fig. 1).

[0024] In the impeller 5 according to some embodiments, the hub 6 includes a backplate of the impeller 5, that is, a backplate section that forms a back surface section of the hub 6. In the following description, the backplate section is also referred to as backplate section 67.

[0025] In the impeller 5 according to some embodiments, a surface on a rear surface side of the backplate section 67 is a rear surface 63 of the hub 6. The backplate section 67 has an outer circumferential surface 65, which is a radially outer surface of the backplate section 67.

[0026] In the impeller 5 according to some embodiments, each of the several airfoil sections 7 is inclined such that it tilts towards the side of a pressure surface 72. That is, each of the several airfoil sections 7 is designed such that it is gradually directed from the side of a suction surface 71 towards the side of the pressure surface 72, towards the casing-side end 32 from the hub-side end 30.

[0027] In the following description, when a direction of rotation of the impeller 5 is shown, it is represented by an arrow R.

[0028] Fig. Figure 4A is a view that schematically shows part of the impeller on an outer circumferential side when the impeller is viewed from a rear surface according to one embodiment.

[0029] Fig. Figure 4B is a view that schematically shows part of the impeller on the outer circumferential side when the impeller is viewed from the rear surface according to another embodiment.

[0030] As described above, each of the several wing sections 7 is inclined such that it tilts towards the side of the printing surface 72. However, in Fig. 4A and Fig. 4B For the sake of simplicity, wing section 7 is shown without reflecting the inclination of wing section 7 described above.

[0031] Fig. 5A is a schematic meridional cross-sectional view of the impeller according to an embodiment and shows a case in which the suction surface of the wing section is viewed from a first angular position C5a, which is an angular position of the backplate section in Fig. 4A is.

[0032] Fig. Figure 5B is a schematic meridional cross-sectional view of the impeller according to another embodiment and shows a case in which the suction surface of the wing section is viewed from a first angular position C5b, which is an angular position of the backplate section in Fig. 4B is.

[0033] Fig. 6A is a schematic meridional cross-sectional view of the impeller according to an embodiment and shows a case in which the suction surface of the wing section is viewed from a second angular position C6a, which is an angular position of the backplate section in Fig. 4A is.

[0034] Fig. Figure 6B is a schematic meridional cross-sectional view of the impeller according to another embodiment and shows a case in which the suction surface of the wing section is viewed from a second angular position C6b, which is an angular position of the backplate section in Fig. 4B is.

[0035] Fig. Figure 7 is a schematic meridional cross-sectional view of the impeller according to an embodiment and is a meridional cross-sectional view at a third angular position C7a, which represents an angular position of the backplate section in Fig. 4A is. A meridional cross-sectional view at a third angular position C7b, which is an angular position of the backplate section 67 in Fig. 4B is the same as the meridional cross-sectional view at the third angular position C7a, which is in Fig. 4A is shown, and thus other embodiments will also be described in the following description with reference to the meridional cross-sectional view of Fig. 7 described. A difference between the impeller 5 according to an embodiment described in Fig. 4A, Fig. 5A and Fig. 6A is shown, and the impeller 5 according to the other embodiment, which is shown in Fig. 4B, Fig. 5B and Fig. Figure 6B shows the main feature being the presence or absence of an intermediate blade rounding 105, which will be described later.

[0036] In the case of wheel 5 according to some embodiments, as in Fig. 4A, Fig. 4B, Fig. 5A, Fig. 5B, Fig. 6A, Fig. 6B and Fig. As shown in Figure 7, in order to improve the pressure ratio in the centrifugal compressor 2 by improving the circumferential speed at the trailing edge 28, the proximity of the trailing edge 28 of the airfoil section 7 is projected radially outwards from the outer circumferential surface 65 of the backplate section 67. More specifically, in the case of the impeller 5, according to some embodiments, as in Fig. 5A, Fig. 5B, Fig. 6A, Fig. 6B and Fig. As shown in Figure 7, each of the wing sections 7 has a trailing edge 28 configured such that the distance between the trailing edge 28 and the central axis (axis) AX of the centrifugal compressor 2 increases with increasing distance from the rear surface 63 of the hub 6. In the case of the impeller 5 according to some embodiments, as shown in Figure 7, the distance between the trailing edge 28 and the central axis (axis) AX of the centrifugal compressor 2 increases with increasing distance from the rear surface 63 of the hub 6. Fig. 5A, Fig. 5B, Fig. 6A, Fig. 6B and Fig. As shown in Figure 7, the trailing edge 28 is designed such that the distance between the trailing edge 28 and the axis AX (see Figure 7) is... Fig. 3) at a position of the back plate section 67, which is connected to the outer circumferential surface 65, is shortest and the distance between the rear edge 28 and the axis AX gradually increases towards a front surface side (a left side in the figure) along the axis AX.

[0037] In the following description, with respect to a direction along the axis AX of the wheel 5, a direction from the front edge 26 to the rear surface 63 is referred to as an axial rear surface side, or simply as a rear surface side, and a direction from the rear surface 63 to the front edge 26 is referred to as an axial front surface side, or simply as a front surface side.

[0038] In the case of wheel 5 according to some embodiments, as in Fig. 3, Fig. 4A, Fig. 4B, Fig. 5A, Fig. 5B, Fig. 6A, Fig. 6B and Fig. Figure 7 shows that, in order to increase the circumferential speed of the impeller 5, the entire trailing edge 28 is projected radially outwards from the outer circumferential surface 65 of the backplate section 67. Not the entire trailing edge 28, but a part of the trailing edge 28 can be projected radially outwards from the outer circumferential surface 65 of the backplate section 67.

[0039] If the trailing edge 28 of the wing section 7 is projected radially outward from the outer circumferential surface 65 of the backplate section 67, as in the wheel 5 according to some embodiments, the trailing edge 28 of the wing section 7 is separated from the hub surface 61, which can cause a decrease in the natural frequency of the wing section 7. Furthermore, if the trailing edge 28 of the wing section 7 is projected radially outward from the outer circumferential surface 65 of the backplate section 67, as in the wheel 5 according to some embodiments, a stress generated in the wing section 7 increases due to a centrifugal force acting on a section projected radially outward from the outer circumferential surface 65 of the backplate section 67, compared to a case without the section described above.

[0040] Thus, according to some embodiments, the impeller 5 includes the following configuration.

[0041] That is, as in Fig. 4A, Fig. 4B, Fig. 5A, Fig. 5B, Fig. 6A, Fig. 6B and Fig. As shown in Figure 7, the impeller 5, according to some embodiments, includes a first rounding 110 that connects the trailing edge 28 and the outer circumferential surface 65 of the backplate section 67. As shown in Fig. 4A, Fig. 4B, Fig. 5A, Fig. 5B, Fig. 6A, Fig. 6B and Fig. As shown in Figure 7, the first rounding 110 is formed, according to some embodiments, on a radially outer side of the outer circumferential surface 65 of the backplate section 67, which forms the back surface section of the hub 6. As shown in Fig. 5A, Fig. 5B, Fig. 6A, Fig. 6B and Fig. As shown in Figure 7, the first rounding 110, according to some embodiments, uniformly connects the trailing edge 28 and the outer circumferential surface 65 of the back plate section 67. Thus, in the meridional view, a section in which an angle suddenly changes does not occur in a connecting section 51 (see Figure 7). Fig. 3) between the rear edge 28 and the outer circumferential surface 65 of the back plate section 67.

[0042] In the impeller 5 according to some embodiments, the first radius 110 can be configured to connect the trailing edge 28 and the outer circumferential surface 65 of the back plate section 67 within a region that excludes a region that overlaps with at least a second radius 82 and a third radius 83, which will be described later, when the impeller 5 is viewed from the radially outer side.

[0043] The shape of the trailing edge 28 in a case without the first rounding 110 is defined by a double-dotted catenary line as a virtual trailing edge 28A in Fig. 5A, Fig. 5B, Fig. 6A and Fig. 6B, for example.

[0044] In the impeller 5 according to one embodiment, it is contacted as in Fig. 5A and Fig. 6A shows an end section of the virtual trailing edge 28A on the side of the hub 6 (back surface side) as a front surface side edge section of the outer circumferential surface 65 of the back plate section 67, that is, a radially outer edge section of the hub surface 61. Fig. 6A is a position of the outer circumferential surface 65, assuming that the first rounding 110 is not formed, represented by a double-dotted catenary 65B.

[0045] Furthermore, in the impeller 5 according to the other embodiment, as in Fig. 5B and Fig. 6B shows the end section of the virtual trailing edge 28A on the side of the hub 6 (back surface side) a front surface side edge section of a virtual outer circumferential surface 65A, which assumes that the intermediate blade rounding 105, which is described later, is not provided.

[0046] In the case of wheel 5 according to some embodiments, as in Fig. 4A, Fig. 4B, Fig. 5A, Fig. 5B, Fig. 6A, Fig. 6B and Fig. As shown in Figure 7, since the first rounding 110 connects the trailing edge 28 of the wing section 7 and the outer circumferential surface 65 of the backplate section 67, it is possible to improve the stiffness of the wing section 7 near the trailing edge 28. Thus, it is possible to suppress the decrease in the natural frequency of the wing section 7 while increasing the circumferential speed of the impeller. Furthermore, in the case of the impeller 5, according to some embodiments, as shown in Fig. 4A, Fig. 4B, Fig. 5A, Fig. 5B, Fig. 6A, Fig. 6B and Fig. As shown in Figure 7, since the first rounding 110 can bear some of the stress described above, it is possible to suppress the stress on the wing section 7 near the trailing edge 28. Therefore, with the impeller 5 according to some embodiments shown in Figure 7, it is possible to reduce the stress on the wing section 7 near the trailing edge 28. Fig. 4A, Fig. 4B, Fig. 5A, Fig. 5B, Fig. 6A, Fig. 6B and Fig. As shown in Figure 7, it is possible to ensure the durability of the impeller 5 while increasing its circumferential speed. Furthermore, with the impeller 5 according to some embodiments shown in Figure 7, it is possible to ensure the durability of the impeller 5 while increasing its circumferential speed. Fig. 4A, Fig. 4B, Fig. 5A, Fig. 5B, Fig. 6A, Fig. 6B and Fig. As shown in Figure 7, in a case where the impeller 5 is manufactured by machining, it is possible to mitigate the sudden change of the angle from the rear edge 28 to the outer circumferential surface 65 of the back plate section 67 by cutting from the rear edge 28 to the outer circumferential surface 65 of the back plate section 67, thereby facilitating processing.

[0047] In some embodiments, as in Fig. 4A and Fig. As shown in Figure 4B, the impeller 5 further includes the second fillet 82, which connects the hub surface 61 and the suction surface 71 of the wing section 7, and the third fillet 83, which connects the hub surface 61 and the pressure surface 72 of the wing section 7. The first fillet 110 includes a fillet section on a suction surface 102, which connects the second fillet 82 and the outer circumferential surface 65 of the backplate section 67, and a fillet section on a pressure surface 103, which connects the third fillet 83 and the outer circumferential surface 65 of the backplate section 67.

[0048] As described above, when the area near the trailing edge 28 of the wing section 7 is projected radially outward from the outer circumferential surface 65 of the backplate section 67, the stress generated in the wing section 7 increases due to the centrifugal force acting on the section projected radially outward from the outer circumferential surface 65 of the backplate section 67, compared to the case without the section described above. However, in some embodiments, as in Fig. 4A and Fig. As shown in Figure 4B, since the rounded section on a suction surface 102 and the rounded section on a pressure surface 103 can also carry some of the stress generated in the wing section 7, it is possible to further suppress the stress on the wing section 7 near the trailing edge 28. Furthermore, in some embodiments, as shown in Figure 4B, it is possible to further suppress the stress on the wing section 7 near the trailing edge 28. Fig. 4A and Fig. As shown in Figure 4B, since the first rounding 110 includes the rounding section on a suction surface 102 and the rounding section on a pressure surface 103, it is possible to further improve the stiffness of the wing section 7 near the trailing edge 28. Thus, it is possible to further suppress the decrease in the natural frequency of the wing section 7.

[0049] In some embodiments, as in Fig. 4A and Fig. As shown in Figure 4B, the circumferential length of the rounding section on a printing surface 103 is greater than the circumferential length of the rounding section on a suction surface 102.

[0050] In the case where the impeller 5 is manufactured by machining, if the airfoil section 7 is designed to be inclined towards the side of the pressure surface 72, it is easy to insert a tool used for cutting between the hub surface 61 and the suction surface 71 of the airfoil section 7, but it is difficult to insert the tool between the hub surface 61 and the pressure surface 72 of the airfoil section 7. Thus, despite attempts to reduce the thickness of the second fillet 82 and the third fillet 83 as much as possible, the third fillet 83 is more likely to remain thicker than the second fillet 82, and the circumferential length of the third fillet 83 is likely to be greater than that of the second fillet 82.Therefore, if the rounded section on a suction surface 102 and the rounded section on a pressure surface 103 are each formed according to the shapes of the second rounding 82 and the third rounding 83, the circumferential length of the rounded section on a pressure surface 103 is likely to be greater than the circumferential length of the rounded section on a suction surface 102. Conversely, making the circumferential length of the rounded section on a pressure surface 103 smaller than the circumferential length of the rounded section on a suction surface 102 requires time and effort for processing. Therefore, according to some embodiments, the processing is simplified. (Regarding the intermediate wing rounding 105)

[0051] In the impeller 5 according to some embodiments, for example, as in Fig. 4A and Fig. As shown in Figure 4B, the wing section 7 includes a first wing section 7A and a second wing section 7B adjacent to the first wing section 7A at an interval in the circumferential direction on the side of the suction surface 71 of the first wing section 7A. Then, as shown in Fig. 4B and Fig. As shown in Figure 5B, the impeller 5 according to the other embodiment further includes the intermediate wing rounding 105, which connects the rounding section on a suction surface 102, which is formed on the side of the suction surface 71 of the first wing section 7A, and the rounding section on a pressure surface 103, which is formed on the side of the pressure surface 72 of the second wing section 2B, on the outer circumferential side of the back plate section 67.

[0052] In a case where the impeller 5 is formed by cutting, if the outer circumference is cut while the impeller 5 is rotated about the axis AX, the intermediate wing radius 105 is also formed in the outer circumferential section of the backplate section 67 when the first radius 110 is formed. If the intermediate wing radius 105 is not provided, it is necessary to remove the intermediate wing radius 105 by cutting or the like, in the case where the intermediate wing radius 105 is formed as described above.

[0053] Therefore, with the wheel 5 according to the other embodiment, the wheel 5 is processed simply compared to the case without the intermediate wing rounding 105.

[0054] If the wheel 5 is formed by cutting work as described above, the intermediate surface rounding 105 does not project towards the side of the hub surface 61. (Regarding the shape of the first rounding 110)

[0055] The shape of the first rounding 110 is mainly determined with reference to Fig. 5A, Fig. 5B and Fig. 8 described. Fig. Figure 8 is a schematic meridional cross-sectional view to describe another embodiment with respect to the shape of the first rounding and shows a case in which the suction surface of the wing section is viewed from the first angular position C5a, which is the angular position of the backplate section in Fig. 4A is. Fig. 5A, Fig. 5B and Fig. Figure 8 each shows the area of ​​the first rounding 110 by means of an auxiliary line.

[0056] In some embodiments, as in Fig. 5A, Fig. 5B and Fig. As shown in Figure 8, at least part of the first rounding 110 has a curved shape, in which a center of curvature C is present on the radially outer side of the outer circumferential surface 65 in a meridional cross-section of the impeller 5. That is, for example, in the impeller 5 according to one embodiment as ... the first rounding 110 has a curved shape, in which a center of curvature C is present on the radially outer side of the outer circumferential surface 65 in a meridional cross-section of the impeller 5. Fig. 5A, Fig. 5B shows the first rounding 110, the curved shape from a first end surface 110a on the side of the trailing edge 28 to a second end surface 110b on the side of the outer circumferential surface 65 in the meridional cross-section of the impeller 5. In the Fig. 5A, Fig. In the embodiment shown in 5B, the first rounding 110 is formed along an arc AR1, which is centered on one center of curvature C in the meridional cross-section of the impeller 5. However, the curvature can change between the first end surface 110a and the second end surface 110b.

[0057] Furthermore, as in the Fig. In the embodiment shown in Figure 8, which will be described later, in the meridional cross-section of the impeller 5, the first rounding 110 includes a first curved section 111, a second curved section 113 and a straight section 115 from the first end surface 110a to the second end surface 110b, the curvature may be the same or may differ between the first curved section 111 and the second curved section 113.

[0058] Since at least part of the first rounding 110 has the curved shape in which the center of curvature C is located on the radially outer side of the outer circumferential surface 65 in the meridional cross-section of the impeller 5 compared to a case without the curved shape, a position of a radially outer surface 110s of the first rounding 110 is located on the radially inner side. That is, according to the in Fig. 5A, Fig. 5B and Fig. 8 embodiments shown, in the meridional cross-section of the impeller 5, for example in comparison to a case in which the first end surface 110a and the second end surface 110b are connected by a plane 190 which is defined by a long dashed double dotted straight line in Fig. As specified in 5A, the position of the radially outer surface 110s of the first fillet 110 is located on the radially inner side. Thus, compared to the case without the curved shape, as described above, it is possible to reduce the thickness of the first fillet and suppress the stress generated by the centrifugal force.

[0059] In some embodiments, as in Fig. As shown in Figure 8, at least part of the first rounding 110 can have a linear shape in the meridional cross-section of the impeller 5.

[0060] For example, in the Fig. In the embodiment shown in Figure 8, the first rounded section 110 comprises the first curved section 111, the second curved section 113, and the straight section 115. The first curved section 111 and the second curved section 113 each have a curved shape in which the center of curvature is located on the radially outer side of the outer circumferential surface 65 in the meridional cross-section of the impeller 5. The straight section 115 has a linear shape in the meridional cross-section of the impeller 5.

[0061] For example, in the Fig. In the embodiment shown in Figure 8, in the first rounding 110 in the first curved section 111, the first curved section 111, the straight section 115 and the second curved section 113 are arranged in the order from the side of the trailing edge 28 to the side of the outer circumferential surface 65. Fig.Figure 8 shows, by means of a double-dotted catenary, an assumed case in which a virtual arc AR2, in which the center of curvature is on the radially outer side of the outer circumferential surface 65, connects the first curved section 111 and the second curved section 113 in the meridional cross-section of the impeller 5.

[0062] Since at least part of the first rounding 110 has the linear shape in the meridional cross-section of the impeller 5, processing becomes simple when the impeller 5 is formed by cutting.

[0063] Since the centrifugal compressor 2 includes the impeller 5 according to some embodiments described above, it is possible to increase the compression ratio of the centrifugal compressor 2 while ensuring the durability of the centrifugal compressor 2.

[0064] Furthermore, since the turbocharger 1 includes the centrifugal compressor 2 described above according to some embodiments, it is possible to increase the compression ratio of the centrifugal compressor 2 while ensuring the durability of the centrifugal compressor 2.

[0065] The present disclosure is not limited to the embodiments described above and also includes an embodiment obtained by modifying the embodiments described above and an embodiment obtained by combining these embodiments as required.

[0066] For example, in some embodiments described above, the first rounding 110 is formed for each of all wing sections 7. However, the first rounding 110 can be formed for at least one wing section 7.

[0067] Furthermore, in some of the embodiments described above, the second end surface 110b of the first rounding 110 is located on the side of the outer circumferential surface 65 on the front surface side relative to the rear surface side edge section on the outer circumferential surface 65 of the rear plate section 67. However, the second end surface 110b of the first rounding 110 can be located on the side of the outer circumferential surface 65 in the rear surface side edge section on the outer circumferential surface 65 of the rear plate section 67.

[0068] The contents described in the above embodiments would be understood, for example, as follows.

[0069] (1) The impeller 5 of a centrifugal compressor 2 according to at least one embodiment of the present disclosure is the impeller 5 of the centrifugal compressor 2, that is, the compressor impeller 5, and comprises a hub 6, at least one airfoil section 7 erected on a hub surface 61 of the hub 6, and a first radius 110. The at least one airfoil section 7 has a trailing edge 28 configured such that the distance between the trailing edge 28 and an axis AX of the centrifugal compressor 2 increases with increasing distance from a rear surface 63 of the hub 6. The first radius 110 is formed on a radially outer side of an outer circumferential surface 65 of a backplate section 67, which forms a rear surface section of the hub 6. The first rounding 110 connects the outer circumferential surface 65 of the back plate section 67 and the trailing edge 28 of the at least one wing section 7.

[0070] As described above, in the case where the circumferential speed of the impeller 5 is to be increased by changing the shape of the trailing edge 28 of the airfoil section 7, simply projecting a part of the trailing edge 28 of the airfoil section 7 radially outwards from the section with maximum diameter of the hub 6 of the impeller 5 can lead to an increase in stress due to the centrifugal force acting on the airfoil section 7 and a decrease in the natural frequency of the airfoil section 7.

[0071] This means that if the area near the trailing edge 28 of the wing section 7 is projected radially outwards from the outer circumferential surface 65 of the backplate section 67, the area near the trailing edge 28 of the wing section 7 is separated from the hub surface 61, which can cause a decrease in the natural frequency of the wing section 7. However, with the configuration (1) above, since the first fillet 110 connects the trailing edge 28 of the wing section 7 and the outer circumferential surface 65 of the backplate section 67, it is possible to improve the stiffness of the wing section 7 near the trailing edge 28. Thus, it is possible to suppress the decrease in the natural frequency of the wing section 7 while increasing the circumferential speed of the impeller 5.

[0072] Furthermore, when the area near the trailing edge 28 of the wing section 7 is projected radially outward from the outer circumferential surface 65 of the backplate section 67, the stress generated in the wing section 7 increases due to the centrifugal force acting on the section projected radially outward from the outer circumferential surface 65 of the backplate section 67, compared to the case without the section described above. However, with the configuration (1) above, since the first fillet 110 can carry some of the stress described above, it is possible to suppress the stress on the wing section 7 near the trailing edge 28.

[0073] Therefore, with the above configuration (1), it is possible to ensure the durability of the impeller 5 while increasing its circumferential speed. Furthermore, with the above configuration (1), in the case where the impeller 5 is manufactured by machining, it is possible to mitigate the sudden change in the angle from the trailing edge 28 to the outer circumferential surface 65 of the backplate section 67 when cutting from the trailing edge 28 to the outer circumferential surface 65 of the backplate section 67, thus facilitating processing.

[0074] (2) In some embodiments, the impeller 5 in the above configuration (1) further includes a second radius 82 connecting the hub surface 61 and a suction surface 71 of the wing section 7, and a third radius 83 connecting the hub surface 61 and a pressure surface 72 of the wing section 7. The first radius 110 includes a radius section on a suction surface 102 connecting the second radius 82 and the outer circumferential surface 65 of the backplate section 67, and a radius section on a pressure surface 103 connecting the third radius 83 and the outer circumferential surface 65 of the backplate section 67.

[0075] As described above, when the area near the trailing edge 28 of the wing section 7 is projected radially outward from the outer circumferential surface 65 of the backplate section 67, the stress generated in the wing section 7 increases due to the centrifugal force acting on the section projected radially outward from the outer circumferential surface 65 of the backplate section 67, compared to the case without the section described above. However, with the configuration (2) above, since the rounded section on a suction surface 102 and the rounded section on a pressure surface 103 can also carry some of the stress described above, it is possible to further suppress the stress on the wing section 7 near the trailing edge 28.Furthermore, with the above configuration (2), since the first rounding 110 includes the rounding section on a suction surface 102 and the rounding section on a pressure surface 103, it is possible to further improve the stiffness of the wing section 7 near the trailing edge 28. Thus, it is possible to further suppress the decrease in the natural frequency of the wing section 7.

[0076] (3) In some embodiments, in the above configuration (2) the circumferential length of the rounding section on a printing surface 103 is greater than the circumferential length of the rounding section on a suction surface 102.

[0077] In the case where the impeller 5 is manufactured by machining, if the airfoil section 7 is designed to be inclined towards the side of the pressure surface 72, it is easy to insert the tool used for cutting between the hub surface 61 and the suction surface 71 of the airfoil section 7, but it is difficult to insert the tool between the hub surface 61 and the pressure surface 72 of the airfoil section 7. Thus, despite attempts to reduce the thickness of the second fillet 82 and the third fillet 83 as much as possible, the third fillet 83 is more likely to remain thicker than the second fillet 82, and the circumferential length of the third fillet 83 is likely to be greater than that of the second fillet 82.Therefore, if the fillet section on a suction surface 102 and the fillet section on a pressure surface 103 are each formed according to the shapes of the second fillet 82 and the third fillet 83, respectively, the configuration (3) above is likely to be obtained. Conversely, in contrast to the configuration (3) above, making the circumferential length of the fillet section on a pressure surface 103 smaller than the circumferential length of the fillet section on a suction surface 102 requires time and effort for processing. Therefore, with the configuration (3) above, processing becomes simple.

[0078] (4) In some embodiments, in the configuration (2) or (3) above, the wing section 7 includes a first wing section 7A and a second wing section 7B adjacent to the first wing section 7A at an interval in a circumferential direction on one side of the suction surface 71 of the first wing section 7A. The impeller 5 further includes an intermediate wing fillet 105, which connects the fillet section on a suction surface 102, formed on the side of the suction surface 71 of the first wing section 7A, and the fillet section on a pressure surface 103, formed on one side of the pressure surface 72 of the second wing section 2B, on an outer circumferential side of the backplate section 67.

[0079] In a case where the impeller 5 is formed by cutting, if the outer circumference is cut while the impeller 5 is rotated about the axis AX, the intermediate airfoil fillet 105 is also formed in the outer circumferential section of the backplate section 67 when the first fillet 110 is formed. If the intermediate airfoil fillet 105 is not provided, it is necessary to remove it by cutting or the like, in the case where the intermediate airfoil fillet 105 is formed as described above. Therefore, with the above configuration (4), the impeller 5 is machined more simply compared to the case without the intermediate airfoil fillet 105.

[0080] (5) In some embodiments, in one of the above configurations (1) to (4), at least part of the first rounding 110 has a linear shape in a meridional cross-section of the impeller 5.

[0081] With the above configuration (5), which has the linear shape described above, processing becomes simple when the impeller 5 is formed by cutting work.

[0082] (6) In some embodiments, in one of the above configurations (1) to (5), at least part of the first rounding 110 has a curved shape in which a center of curvature is located on a radially outer side of the outer circumferential surface 65 in a meridional cross-section of the impeller 5.

[0083] With the above configuration (6), which has the curved shape described above, compared to the case without the curved shape described above, the position of the radially outer surface 110s of the first fillet 110 is on the radially inner side. Thus, compared to the case without the curved shape described above, it is possible to reduce the thickness of the first fillet 110 and suppress the stress generated by the centrifugal force.

[0084] (7) A centrifugal compressor 2 according to at least one embodiment of the present disclosure comprises the impeller 5 of the centrifugal compressor 2 according to one of the above configurations (1) to (6) and a compressor housing 10 for receiving the impeller.

[0085] With the above configuration (7), which includes the impeller 5 of the centrifugal compressor 2 according to one of the above configurations (1) to (6), it is possible to increase the compression ratio of the centrifugal compressor 2 while ensuring the durability of the centrifugal compressor 2.

[0086] (8) A turbocharger 1 according to at least one embodiment of the present disclosure comprises the centrifugal compressor 2 according to the configuration (7) above.

[0087] With the above configuration (8), which includes the centrifugal compressor 2 according to the above configuration (7), it is possible to increase the compression ratio of the centrifugal compressor 2 while ensuring the durability of the centrifugal compressor 2. List of reference symbols 1 turbocharger 2 centrifugal compressors 5 Compressor impeller (impeller) 6 hub 7 Wing section (wing) 7A First wing section 7B Second wing section 10 compressor housings 26 Leading edge 28 trailing edge 61 Hub surface 63 Back surface 65 Outer circumferential surface 67 Backplate section 71 Suction surface 72 printing surface 82 Second rounding 83 Third rounding 102 Rounding section on a suction surface 103 Rounding section on a printing surface 105 Intermediate wing rounding 110 First rounding

Claims

[1] Impeller (5) of a centrifugal compressor (2), comprising: a hub (6); at least one airfoil section (7) erected on a hub surface (61) of the hub (6), wherein the at least one airfoil section has a trailing edge (28) configured such that a distance between the trailing edge (28) and an axis of the centrifugal compressor (2) increases with increasing distance from a rear surface (63) of the hub (6); and a first fillet (110) formed on a radially outer side of an outer peripheral surface (65) of a back plate portion (67) forming a rear surface portion of the hub (6), the first fillet (110) connecting the outer peripheral surface and the trailing edge (28) of the at least one wing portion, wherein at least a part of the first fillet has a curved shape in which a center of curvature is present on the radially outer side of the outer peripheral surface (65) in a meridional cross section of the impeller (5); and wherein an end edge of the curved shape is arranged on the outer peripheral surface side of the back plate portion. [2] Impeller (5) according to claim 1, further comprising: a second fillet (82) connecting the hub surface (61) and a suction surface (71) of the wing section; and a third fillet (83) connecting the hub surface (61) and a pressure surface (72) of the wing section, where the first rounding (110) includes: a fillet portion on the suction surface connecting the second fillet (82) and the outer peripheral surface of the back plate portion; and a fillet portion on the pressure surface (72) connecting the third fillet (83) and the outer peripheral surface of the back plate portion. [3] Impeller (5) according to claim 2, wherein a circumferential length of the fillet portion on the pressure surface (72) is greater than a circumferential length of the fillet portion on the suction surface (71). [4] Impeller (5) according to claim 2 or 3, wherein the airfoil portion comprises a first airfoil portion (7A) and a second airfoil portion (7B) adjacent to the first airfoil portion at an interval in a circumferential direction on one side of the suction surface (71) of the first airfoil portion, and wherein the impeller (5) further comprises an intermediate wing fillet (105) which forms the fillet section on the suction surface (71) formed on the suction surface (71) side of the first support portion and the fillet portion on the pressure surface formed on a pressure surface (72) side of the second support portion on an outer peripheral side of the back plate portion. [5] Impeller (5) according to one of claims 1 to 4, wherein at least a part of the first fillet (110) has a linear shape in a meridional cross-section of the impeller (5). [6] Centrifugal compressor (2), comprising: the impeller (5) according to one of claims 1 to 5; and a compressor housing (10) for accommodating the impeller (5). [7] Turbocharger (1), comprising: the centrifugal compressor (2) according to claim 6.

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