A mixed-flow turbine wheel includes: a plurality of rotor blades disposed on a circumferential surface of the hub at intervals in a circumferential direction and configured such that each of the plurality of rotor blades has a leading edge which includes, in a meridional view, an oblique edge portion where a distance between the leading edge and an axis of the rotational shaft decreases from a tip side toward a hub side, and a sensor detection surface having a flat shape and being applied with a marking which is detectable by an optical sensor device. The sensor detection surface is formed on at least one of the circumferential surface of the hub or an edge portion of a reference rotor blade being one of the plurality of rotor blades, such that, in the meridional view, a trailing-edge side angle of two angles formed between the axis of the rotational shaft and a normal of the sensor detection surface is smaller than a trailing-edge side angle of two angles formed between the axis of the rotational shaft and a normal of the oblique edge portion.

TECHNICAL FIELD

The present disclosure relates to a mixed-flow turbine wheel.

BACKGROUND ART

Requirements for improvement of fuel consumption and exhaust gas of engines have been increasing these years, and in return engines are downsized using turbochargers. A turbocharger includes a cartridge (hereinafter, turbo-cartridge) including a rotor joining a turbine wheel and a compressor wheel via a rotational shaft, and a bearing housing accommodating a bearing that supports the rotor rotatably, as its core components. The above turbine wheel includes, for instance, a radial turbine wheel into which gas flows in the radial direction, and a mixed-flow turbine wheel into which gas flows in a diagonal direction. Further, when the engine is in operation, as the turbine wheel disposed in the exhaust passage of the engine is rotary driven by exhaust gas, the compressor wheel disposed in the intake passage of the engine is also rotary driven, and thereby intake air of the engine is supercharged. As the rotor of the turbo-cartridge rotates at a high speed during operation of the engine, unbalance correction work is performed on the rotor during its production, so as to prevent vibration upon rotation, noise accompanying vibration, and breakage due to unbalance of the rotor.

The above unbalance correction work is normally performed for each constituent member of the rotor such as a compressor wheel and a turbine wheel, and each of the rotary member made up of the constituent members, in order. More specifically, in the unbalance correction work, the work target such as a constituent member and the rotor is actually rotated to detect its unbalance. Further, when unbalance is detected, the balance is adjusted by grinding the work target, for instance (seeFIGS.1to3, for instance). For instance, for the rotor, the unbalance detection device supports the turbo-cartridge while each of the two wheels is covered with a housing member (jig). In this state, air is supplied to the compressor wheel or the like to rotate the rotor. At this time, vibration upon rotation due to unbalance of the rotor is detected with a vibration sensor, and the rotation speed of the rotor (phase of rotation) is detected at the same time. Further, on the basis of the relationship between vibration and phase upon rotation of the rotor, the phase of the rotor that is causing the vibration is specified. Then, the rotor is ground for balancing, where the relationship between the mass to be ground and a change in the magnitude of vibration accompanying the grinding is obtained in advance through experiments by using a turbo-cartridge of the same model (production). Further, on the basis of the above vibration signal, phase, and effect vector (experiment result), grinding information that includes the optimum mass and the grinding position for balancing of the rotor is calculated, and the rotor is ground on the basis of the grinding information.

As described above, in unbalance correction works, it is necessary to detect the rotation speed of the work target object upon rotation. For instance, Patent Document 1 discloses detecting the sensor detection surface of the work target object by using a reflection-type optical sensor device. More specifically, the above sensor detection surface is disposed obliquely with respect to the side surface of the tip portion of the boss portion or the side surface of the back plate portion of the compressor wheel. Further, the optical sensor device detects the rotation speed (phase) by detecting reflection of light emitted by the optical sensor device and reflected by the sensor detection surface. The optical sensor device detects reflection light when the sensor detection surface of the rotating compressor wheel passes the front of the optical sensor device (faces the optical sensor device).

Further, in Patent Documents 2 and 3, in the unbalance correction work of the turbo-cartridge, an angular sensor (rotation detector) is disposed in the vicinity of the compressor wheel or the turbine wheel on the axis of the rotational shaft. In particular, the turbine of Patent Document 2 is a mixed-flow turbine, and the angle sensor is disposed on the tip side of the rotational portion of the compressor.

CITATION LIST

Patent Literature

SUMMARY

Problems to be Solved

Meanwhile, the portion to be ground to correct unbalance of a rotor or a wheel constituting the rotor is normally the boss portion or the back surface of the wheel. For instance, as in Patent Documents 2 and 3, when the angle sensor is disposed in the vicinity of the tip of the wheel on the axis of the rotational shaft, the angle sensor needs to be moved so as not to interfere with the tool when grinding the boss portion of the rotor (see Patent Document 2).

Further, in a case where a portion for detecting rotation with the angle sensor and a portion to be ground for unbalance correction are the same, the shape of the portion for detecting rotation by using the angle sensor gets changed, which may prevent accurate detection of the rotation angle by the angle sensor. In this regard, Patent Document 1 is advantageous in that the sensor detection surface is formed by machine-processing the side surface of the tip portion of the boss portion or the side surface of the back plate portion of the compressor wheel, and thus it is possible to avoid grinding the sensor detection surface for unbalance correction. However, applying the method of Patent Document 1 would lead to an increase in the production costs, for a turbine wheel is formed of a harder a than the compressor wheel and cannot be machine-processed to form the sensor detection surface as easily.

Thus, in the case of a radial turbine, in a meridional view, a marking (grinding or paint coating, for instance) may be applied to a leading edge of a rotor blade formed parallel to the axis of the rotational shaft to form the sensor detection surface, and the optical sensor device may be disposed along the radial direction of the rotational shaft so as to be capable of facing the sensor detection surface. A leading edge of a rotor blade of a radial turbine is a portion where it is possible to ensure a size that can be detected by the optical sensor device, and is formed parallel to the axis of the rotational shaft in a meridional view, which makes it relatively easy to install the optical sensor device. However, in a mixed-flow turbine wheel, a leading edge of a rotor blade is not formed parallel to the axis of the rotational shaft, but is oblique toward the center side of the rotational shaft. Furthermore, the optical sensor device needs to be placed so as to be capable of facing the sensor detection surface being oblique toward the center side of the rotational shaft, while being in the vicinity of the sensor detection surface. Thus, in a case where the sensor detection surface is formed on the leading edge of the rotor blade of a mixed-flow turbine wheel, the optical sensor device is positioned closer toward the center side of the rotational shaft from the leading edge. However, the bearing housing of the turbo-cartridge or the unbalance detection device exists in a position where the optical sensor device is to be installed, and thus it is difficult to provide the optical sensor device. Furthermore, the smaller the turbine wheel is, the more difficult it is to ensure a portion that can be utilized as the sensor detection surface as it is, such as the leading edge of the rotor blade.

In view of the above issue, an object of at least one embodiment of the present invention is to provide a mixed-flow turbine wheel including a sensor detection surface capable of facing an optical sensor device whereby it is possible to detect rotation of the rotor without interfering with other parts, in unbalance correction works.

Solution to the Problems

(1) According to at least one embodiment of the present invention, a mixed-flow turbine wheel includes: a hub fixed to a rotational shaft; a plurality of rotor blades disposed on a circumferential surface of the hub at intervals in a circumferential direction and configured such that each of the plurality of rotor blades has a leading edge which includes, in a meridional view, an oblique edge portion where a distance between the leading edge and an axis of the rotational shaft decreases from a tip side toward a hub side; and a sensor detection surface having a flat shape and being applied with a marking which is detectable by an optical sensor device. The sensor detection surface is formed on at least one of the circumferential surface of the hub or an edge portion of a reference rotor blade being one of the plurality of rotor blades, such that, in the meridional view, a trailing-edge side angle of two angles formed between the axis of the rotational shaft and a normal of the sensor detection surface is smaller than a trailing-edge side angle of two angles formed between the axis of the rotational shaft and a normal of the oblique edge portion.

With the above configuration (1), the normal of the sensor detection surface extends toward the trailing edge side (tip side of the hub) in the axial direction of the rotational shaft relatively compared to the normal of the oblique edge portion. That is, it is possible to install the optical sensor device in a position relatively remote from the center side of the rotational shaft. Thus, in the unbalance correction work of each of the mixed-flow turbine wheel and the turbo-cartridge including the mixed-flow turbine wheel using the unbalance detection device, it is possible to install the optical sensor device for detecting the rotational position of the mixed-flow turbine wheel so as to be capable of facing the sensor detection surface of the mixed-flow turbine wheel without physically interfering with the unbalance detection device or the bearing housing of the turbo-cartridge. Accordingly, it is possible to provide the mixed-flow turbine wheel including the sensor detection surface which enables appropriate acquisition of information required for the unbalance correction work, such as the rotation speed (rotation phase) of the mixed-flow turbine wheel.

(2) In some embodiments, in the above configuration (1), the leading edge of the reference rotor blade includes, in the meridional view, a first parallel edge portion connecting to the oblique edge portion and extending in a direction parallel to the axis of the rotational shaft, and the sensor detection surface is formed on the first parallel edge portion.

With the above configuration (2), the sensor detection surface is formed by forming the shape of the end portion side (hub-side end or tip-side end described below) of the leading edge of a reference rotor blade to be parallel to the axis of the rotational shaft, and by utilizing the thickness of the first parallel edge portion. The mixed-flow turbine wheel is formed of a hard material to withstand exposure to high-temperature exhaust gas, and is difficult to machine-process compared to the compressor wheel. Meanwhile, in the mixed-flow turbine wheel of the present invention, the leading edge of the reference rotor blade is formed so as to have the first parallel edge portion. Thus, machine-processing for forming the sensor detection surface, such as grinding the circumferential surface of the hub, is unnecessary, and thus the sensor detection surface can be also formed on a small mixed-flow turbine wheel. Furthermore, by forming the first parallel edge portion on the end portion side of the leading edge of the reference rotor blade, it is possible to reduce the extent of shape change to a typical mixed-flow turbine wheel not having the first parallel edge portion. Thus, it is possible to form the sensor detection surface easily while suppressing the influence of the first parallel edge portion on the performance of the turbocharger.

Further, for instance, in a case where the sensor detection surface is to be formed on the leading edge in a radial turbine wheel where the leading edge of the rotor blade is parallel to the axis of the rotational shaft, the optical sensor device can be installed similarly to the sensor detection surface formed on the first parallel edge portion of the mixed-flow turbine wheel of the present invention. That is, common equipment of the unbalance detection device for unbalance correction can be used for different kinds of turbine wheels, and it is possible to reduce the production costs.

(3) In some embodiments, in the above configuration (2), in the meridional view, the first parallel edge portion on the leading edge of the reference rotor blade is formed on a position including a hub-side end of the leading edge.

With the above configuration (3), by forming the first parallel edge portion on an end (the hub-side end) of the leading edge of the reference rotor blade, it is possible to form the sensor detection surface easily while suppressing the influence of the first parallel edge portion on the performance of the turbocharger. That is, the distance between the hub-side end of the leading edge and the rotational shaft is shorter than the distance between the rotational shaft and the tip-side end of the leading edge. Thus, the influence on the torque of the rotational shaft is smaller at the hub-side end of the leading edge than at the tip-side end of the leading edge. Furthermore, the first parallel edge portion formed on a position including the hub-side end is at the end of the main flow of exhaust gas supplied from the scroll part (not depicted) of the turbine, where a smaller amount of exhaust gas flows than at the oblique edge portion of the leading edge. That is, in a case where the first parallel edge portion is formed on a position including the hub-side end, the first parallel edge portion can be formed so as to be out of the position (flow path) where the flow of exhaust gas exists.

Thus, the influence of shape change of the leading edge due to formation of the first parallel edge portion on the performance of the turbocharger is smaller at the hub-side end of the leading edge than at the tip-side end of the leading edge. Thus, by providing the first parallel edge portion on the hub-side end of the leading edge, it is possible to suppress influence on the performance of the turbocharger compared to a case where the first parallel edge portion is disposed on the tip-side end of the leading edge. Furthermore, the hub has a back plate portion forming the back surface of the hub, and for instance, in a case where the sensor detection surface is formed by utilizing the first parallel edge portion and the side surface (thickness) of the back plate portion, it is possible to further reduce the extent of shape change on the hub-side end of the reference rotor blade, and thus it is possible to further reduce the influence of the first parallel edge portion on the performance of the turbocharger.

(4) In some embodiments, in the above configuration (3), in the meridional view, the oblique edge portion on the leading edge of the reference rotor blade is formed to have a linear shape.

With the above configuration (4), by forming the first parallel edge portion on the end on the hub side (the hub-side end) of the leading edge of the reference rotor blade having an oblique edge portion formed to have a linear shape, it is possible to form the sensor detection surface easily while suppressing the influence of the first parallel edge portion on the performance of the turbocharger. That is, the obtuse angle formed between the axis of the rotational shaft and the tangent to the closest end, to the hub-side end, of the oblique edge portion formed to have a linear shape is greater than the obtuse angle formed between the axis of the rotational shaft and the tangent to the closest end, to the hub-side end, of the oblique edge portion formed to have a linear shape. This means that, at the closest end of the oblique edge portion to the hub-side end, an oblique edge portion having a linear shape can connect more gradually to the first parallel edge portion than an oblique edge portion having an arc shape. In other words, for the reference rotor blade having the oblique edge portion formed to have a linear shape, by forming the first parallel edge portion on the hub-side end of the leading edge of the reference rotor blade, it is possible to reduce the shape change amount due to the first parallel edge portion.

(5) In some embodiments, in the above configuration (2), in the meridional view, the first parallel edge portion on the leading edge of the reference rotor blade is formed on a position including a tip-side end of the leading edge.

With the above configuration (5), with the first parallel edge portion being formed on the end of the tip side (tip-side end) of the leading edge of the reference rotor blade, the sensor detection surface formed on the first parallel edge portion is formed on a position remote from the rotational shaft compared to a case where the first parallel edge portion is formed on the end of the hub side (hub-side end). Herein, the optical sensor device is supported on a position away from the rotational shaft by the unbalance detection device, around the turbo-cartridge. At this time, with the first parallel edge portion being formed on the tip-side end of the leading edge of the reference rotor blade, the optical sensor device can be installed to a position closer to the support position of the optical sensor device without extending from the support position toward the vicinity of the rotational shaft, and thus it is possible to install the optical sensor device more stably and easily.

(6) In some embodiments, in the above configuration (5), in the meridional view, the oblique edge portion on the leading edge of the reference rotor blade is formed to have an arc shape which protrudes toward a line connecting a hub-side end and the tip-side end of the leading edge.

With the above configuration (6), by forming the first parallel edge portion on the end on the tip side (the tip-side end) of the leading edge of the reference rotor blade having an oblique edge portion formed to have an arc shape, it is possible to form the sensor detection surface easily while suppressing the influence of the first parallel edge portion on the performance of the turbocharger. That is, the tip-side end of the leading edge having the above oblique edge portion having an arc shape is a position that becomes more parallel to the axis of the rotational shaft towards the tip-side end. Thus, by forming the first parallel edge portion on the tip-side end instead of the hub-side end of the oblique edge portion having an arc shape, it is possible to minimize the shape change amount of the shape of the leading edge that has a great influence on the performance.

(7) In some embodiments, in any one of the above configurations (2) to (6), La/L is ⅓ or smaller, when defining L as a length of the leading edge of the reference rotor blade in a direction along the axis of the rotational shaft and La as a length of the first parallel edge portion in the direction along the axis of the rotational shaft.

With the above configuration (7), it is possible to increase the flexibility of installment of the optical sensor device while suppressing the influence of the first parallel edge portion on the performance of the turbocharger.

(8) In some embodiments, in the above configuration (1), the reference rotor blade has a trailing edge which includes, in the meridional view, a second parallel edge portion formed to have a linear shape, and the sensor detection surface is formed on the second parallel edge portion.

With the above configuration (8), the sensor detection surface is formed by forming the shape of at least a part of the trailing edge of the reference rotor blade to have a linear shape (second parallel edge portion), and by utilizing the thickness of the second parallel edge portion. In this way, similarly to the above (2), it is possible to form the sensor detection surface easily while suppressing the influence of the first parallel edge portion on the performance of the turbocharger. Furthermore, it is possible to reduce the production cost.

(9) In some embodiments, in the above configuration (1), the reference rotor blade has a shroud-side edge portion which includes, in the meridional view, a third parallel edge portion connecting to a trailing edge of the reference rotor blade and extending in a direction parallel to the axis of the rotational shaft, and the sensor detection surface is formed on the third parallel edge portion.

With the above configuration (9), the sensor detection surface is formed by forming the shape of the portion of the shroud-side edge portion of the reference rotor blade connected to the trailing edge to be parallel to the axis of the rotational shaft (the third parallel edge portion), and by utilizing the thickness of the third parallel edge portion. In particular, the shroud-side edge portion of the reference rotor blade is a portion that becomes more parallel to the axis of the rotational shaft toward the trailing edge from the leading edge, and thus the extent of shape change to a mixed-flow turbine wheel without the third parallel edge portion is small. Thus, similarly to the above (2), it is possible to form the sensor detection surface easily while suppressing the influence of the third parallel edge portion on the performance of the turbocharger. Furthermore, it is possible to reduce the production cost.

(10) In some embodiments, in the above configuration (1), the circumferential surface of the hub is formed to include: a boss region formed along the circumferential direction by a boss portion disposed on a distal end of the hub; a rotor-blade region formed along the circumferential direction, where the plurality of rotor blades are disposed; and an intermediate region disposed between the boss region and the rotor-blade region. The sensor detection surface includes a flat surface formed in the intermediate region.

With the above configuration (10), the sensor detection surface is formed by forming a flat surface partially in the intermediate region between the rotor-blade region and the boss region on the circumferential surface of the hub. Normally, the optical sensor device needs to be positioned close to the sensor detection surface so that the distance to the sensor detection surface is a few millimeters (1 to 2 mm). By forming the sensor detection surface in the intermediate region, it is possible to install the optical sensor device while avoiding physical interference with the rotor blade that rotates along with rotation of the rotational shaft.

(11) In some embodiments, in any one of the above configurations (1) to (10), the sensor detection surface applied with the marking has a refractive index which is different from a refractive index of the circumferential surface of the hub or the edge portion of the reference rotor blade other than the sensor detection surface.

With the above configuration (11), it is possible to detect the sensor detection surface S formed on the mixed-flow turbine wheel by using the optical sensor device.

(12) In some embodiments, in any one of the above configurations (1) to (11), the mixed-flow turbine wheel further includes an unbalance correction portion including a cut-out portion formed on at least one of a back surface of the hub or a boss portion of the hub.

With the above configuration (12), the unbalance correction portion is the back surface or the boss portion of the hub. That is, as described above, the sensor detection surface of the present invention is formed on the circumferential surface of the hub or the edge portion of the reference rotor blade, and thereby it is possible to prevent the sensor detection surface from being ground due to the unbalance correction work.

(13) According to at least one embodiment of the present invention, a turbo cartridge includes: a rotor connecting the mixed-flow turbine wheel according to any one of (1) to (12) and a compressor wheel via a rotational shaft; and a bearing housing accommodating a bearing which supports the rotor rotatably.

With the above configuration (13), it is possible to provide a turbo-cartridge including a mixed-flow turbine wheel that has the same effect as the above (1).

(14) According to at least one embodiment of the present invention, a method of correcting unbalance of a mixed-flow turbine wheel is for a mixed-flow turbine wheel which includes: a hub fixed to a rotational shaft; a plurality of rotor blades disposed on a circumferential surface of the hub at intervals in a circumferential direction and configured such that a leading edge of each of the plurality of rotor blades includes an oblique edge portion, in a meridional view, where a distance between the leading edge and an axis of the rotational shaft decreases from a tip side toward a hub side; and a sensor detection surface having a flat shape. The sensor detection surface is formed on at least one of the circumferential surface of the hub or an edge portion of a reference rotor blade being one of the plurality of rotor blades, such that, in the meridional view, a trailing-edge side angle of two angles formed between the axis of the rotational shaft and a normal of the sensor detection surface is smaller than a trailing-edge side angle of two angles formed between the axis of the rotational shaft and a normal of the oblique edge portion. The method includes: a marking step of applying a marking which is detectable by an optical sensor device to the sensor detection surface having a flat shape; and a sensor installment step of installing the optical sensor device so as to be capable of facing the sensor detection surface having a flat shape and being applied with the marking.

With the above configuration (14), it is possible to provide an unbalance detection method that has the same effect as the above (1).

(15) In some embodiments, in the above configuration (14), the sensor detection surface applied with the marking has a refractive index which is different from a refractive index of the circumferential surface of the hub or the edge portion of the reference rotor blade other than the sensor detection surface.

With the above configuration (15), it is possible to provide an unbalance detection method that has the same effect as the above (11).

Advantageous Effects

According to at least one embodiment of the present invention, it is possible to provide a mixed-flow turbine wheel including a sensor detection surface capable of facing an optical sensor device whereby it is possible to detect rotation of the rotor without interfering other parts, in unbalance correction works.

DETAILED DESCRIPTION

FIG.1is a schematic diagram of an unbalance detection device6according to an embodiment of the present invention, used in an unbalance correcting work for a turbo-cartridge5, illustrating a state where the turbo-cartridge5is supported by the unbalance detection device6.

The turbo-cartridge5is a core member of a turbocharger, and includes a rotor51integrally coupling a mixed-flow turbine wheel1and a compressor wheel54with a rotational shaft4, and a bearing housing52that accommodates a bearing52bsupporting the rotor51rotatably. Further, when the turbo-cartridge5is provided for an engine of a non-depicted automobile, for instance, the turbo-cartridge5is configured such that the mixed-flow turbine wheel1disposed in the exhaust passage of the engine rotates due to exhaust gas discharged from the engine, and thereby the compressor wheel54coaxially coupled by the rotational shaft4rotates in the intake passage of the engine, thereby compressing intake air to the engine.

Furthermore, the unbalance detection device6is a device for supporting a work target object during the unbalance correction work. In the embodiment depicted inFIG.1, the unbalance detection device6nips the turbo-cartridge5from both sides to support the turbo-cartridge5, with two housing members including a turbine-side housing member6tand a compressor-side housing member6c. More specifically, the unbalance detection device6supports the turbo-cartridge5by pressing at least one of the two housing members to the other one of the two housing member, with a support mechanism, while the mixed-flow turbine wheel1and the compressor wheel54of the cartridge5are housed inside the two housing members6h(6t,6c).

More specifically, in the embodiment depicted inFIG.1, the support mechanism of the unbalance detection device6includes a compressor-side support mechanism61connected to the compressor-side housing member6c, and a turbine-side support mechanism62connected to the turbine-side housing member6t. Each support mechanism (61,62) is fixed to the ground of a factory, for instance, so that the turbo-cartridge5does not move when pushed. Further, above the ground surface, the support mechanism (61,62) is connected to the two housing members6h(6t,6c) via a vibration insulating member8(e.g. elastic member such as rubber). Furthermore, the compressor-side support mechanism61includes a pressing device71configured to press the compressor-side housing member6ctoward the turbo-cartridge5. The pressing device71includes a pressing rod72connected to the housing member (6c), and a piston device73that pushes the pressing rod72out toward the housing member (6c). The piston device73pushes the pressing rod72toward the housing member (6c), and thereby the compressor-side housing member (6c) is pressed toward the turbo-cartridge5. At this time, the pressing device71, the compressor-side housing member6c, the turbo-cartridge5, the turbine-side housing member6t, and the turbine-side support mechanism62are arranged in this order along the pressing direction (direction of the arrow inFIG.1), and the pressing force by the pressing device71is transmitted to the turbine-side support mechanism62via the arrangement of the above. The turbo-cartridge5is supported by the pressing force from the pressing device71and the reactive force from the turbine-side support mechanism62. Furthermore, the pressing rod72, and an air supply pipe75for guiding air from a blower76to the housing member are coupled to each other via a coupling member74, and the air supply pipe75is configured to be movable so as to expand and contract from the blower76as the pressing rod72moves in the pressing direction.

Further, in the embodiment depicted inFIG.1, the unbalance detection device6includes an oil supply pipe77for supplying lubricant oil to the bearing52bhoused in the bearing housing52. The oil supply pipe77is supported on the tip side of a support arm78extending toward above the compressor-side support mechanism61from an upper part of the turbine-side support mechanism62. The support arm78is configured to be capable of moving the oil supply pipe77up and down along the vertical direction. Further, by moving the oil supply pipe77downward in the vertical direction (gravity direction) and connecting the oil supply pipe77to an oil supply port57formed on the bearing housing52, it is possible to supply lubricant oil to the bearing52bvia the oil supply port57. Further, the oil supply pipe77is connected to the oil supply port57of the bearing housing52via the vibration insulating member8.

Further, in the unbalance correction work, while the unbalance detection device6supports the work target object, the work target object is rotated similarly as being rotated due to exhaust gas during operation of the engine, and thereby unbalance of the work target object is detected. Specifically, in a case where the work target object is the rotor51, air (gas) is supplied to one of the compressor wheel54or the mixed-flow turbine wheel1, and thereby the rotor51is rotated. In the embodiment depicted inFIG.1, the air supply pipe75of the support mechanism and the compressor-side housing member6care connected via the vibration insulating member8, and air from the blower76is supplied to the compressor wheel54housed in the compressor-side housing member6c, via the air supply pipe75. As the compressor wheel54rotates, the mixed-flow turbine wheel1rotates. In some other embodiments, the air supply pipe75and the turbine-side housing member6tare connected, and thereby air may be supplied to the mixed-flow turbine wheel1to rotate the rotor51.

In a case where the work target object is the mixed-flow turbine wheel1, the mixed-flow turbine wheel1is rotated in a state of being coupled to only the rotational shaft4, for unbalance detection. In this case, the work target object may be supported by another unbalance detection device different than the unbalance detection device6depicted inFIG.1. That is, the above described other unbalance detection device6only needs to be able to support the mixed-flow turbine wheel1and the rotational shaft4rotatably. For instance, the unbalance detection device6may be such a device that does not include the above described two housing members (6t,6c), but rotates the mixed-flow turbine wheel1by blowing air toward the mixed-flow turbine wheel1while supporting the mixed-flow turbine wheel1without covering the same. Description will be continued below with reference toFIG.1, where the work target object is the rotor51.

Furthermore, the unbalance detection device6includes an optical sensor device9for detecting the rotation speed (phase) of the rotor51to obtain grinding information for correcting detected unbalance of the rotor51. The grinding information includes the optimum mass and the optimum grinding position for balancing the rotor51(work target object), and when unbalance is detected, the rotor51(work target object) is ground on the basis of the grinding information. Further, the optical sensor device9is disposed so as to be capable of facing the sensor detection surface S having a flat shape formed on the rotor51(work target object). In the embodiment depicted inFIG.1andFIGS.2to6described below, as depicted inFIG.2(not shown inFIGS.3to6), the optical sensor device9includes a light emission part91configured to emit light and a light receiving part92configured to receive reflection light of light that the light emission part91emits. Further, the optical sensor device9(the light emission part91and the light receiving part92) are disposed so as to pass by (face) the sensor detection surface S every time the rotor51(work target object) rotates once. Further, the sensor detection surface S having a flat shape is applied with a marking, which is grinding or paint coating, and the refractive index of the sensor detection surface S applied with a marking is different from the refractive index of a portion other than the sensor detection surface S not applied with marking. Thus, reflection light received by the optical sensor device9(light receiving part) is different between when the optical sensor device9is facing the sensor detection surface S and when facing a portion other than the sensor detection surface S. The optical sensor device9detects the sensor detection surface S on the basis of the difference of reflection light (e.g. the strength of reflection light), and detects the rotation speed (phase). The optical sensor device9may be a fiber sensor, for instance. Further, the optical sensor device9(the light emission part91and the light receiving part92) is disposed close to the sensor detection surface S to be within a range of predetermined detection limit of 1 to 2 mm, for instance. However, in the description, the distance between the optical sensor device9and the sensor detection surface S depicted inFIGS.2to6does not correspond to the actual range of detection limit.

Next, the mixed-flow turbine wheel1according to the present invention will be described with reference toFIGS.2and8.FIGS.2to6are each a schematic diagram showing a mixed-flow turbine wheel according to an embodiment of the present invention in a meridional view.FIGS.7and8are each a comparative example of a mixed-flow turbine wheel. InFIG.2, the sensor detection surface S is formed on the first parallel edge portion33positioned on the leading-edge hub side end of the reference rotor blade3s. InFIG.3, the sensor detection surface S is formed on the first parallel edge portion33positioned on the leading-edge tip side end of the reference rotor blade3s. InFIG.4, the sensor detection surface S is formed on the trailing edge of the reference rotor blade3s. InFIG.5, the sensor detection surface S is formed on the third parallel edge portion37positioned on the shroud-side edge portion36of the reference rotor blade3s. InFIG.6, the sensor detection surface S is formed in the intermediate region Rm of the circumferential surface22of the hub2. Furthermore, in the comparative example ofFIG.7, the oblique edge portion32of the leading edge31is formed to have a linear shape in a meridional view. Furthermore, in the comparative example ofFIG.8, the oblique edge portion32of the leading edge31is formed to have an arc shape in a meridional view. In the following description, the direction along the axis4L of the rotational shaft4is referred to as the axial direction, and the direction orthogonal to the axis4L of the rotational shaft4is referred to as the radial direction. Furthermore, the side of the mixed-flow turbine wheel1in the axial direction (the right side of the sheet) is referred to as the trailing edge side of the axial direction, and the opposite direction thereof (the left side of the sheet) is referred to as the leading-edge side of the axial direction.

As shown inFIGS.2to8, the mixed-flow turbine wheel1includes a hub2fixed to the rotational shaft4, and a plurality of rotor blades3disposed at intervals in the circumferential direction on the circumferential surface22of the hub2. More specifically, the circumferential surface22of the hub2includes a boss region Rb formed along the circumferential direction by a boss portion23disposed on the tip (tip of the trailing edge side in the axial direction) of the hub2, a rotor-blade region Rc formed along the circumferential direction of the rotational shaft4where a plurality of rotor blades3are installed, and an intermediate region Rm being a region between the boss region Rb and the rotor-blade region Rc (seeFIG.6). Further, the rotor blade3disposed in the rotor-blade region Rc includes edge portions including a leading edge31having an oblique edge portion32, a trailing edge34, and a shroud-side edge portion36connected to each of the tip-side end31cof the leading edge31and the trailing edge34. The tip-side end31cof the leading edge31is an end portion opposite to a hub-side end31h, where the hub-side end31hrefers to the end portion positioned on the side of the circumferential surface22of the hub2, of the end portions (31c,31h) of the leading edge31. Further, of the edge portions of the rotor blade3, the above leading edge31is a portion positioned on the inlet side supplied with exhaust gas after passing through the scroll portion (not shown) of the turbine when the turbo-cartridge5is installed in the engine, and the above trailing edge34is a portion positioned on the outlet side of exhaust gas. The shroud-side edge portion36is a portion facing the inner wall of the turbine housing (not shown) accommodating the mixed-flow turbine wheel1, of the edge portions of the rotor blade3.

Further, each of the plurality of rotor blades3of the mixed-flow turbine wheel1is configured such that the leading edge31of each of the plurality of rotor blades3includes an oblique edge portion32where the distance between the leading edge31and the axis4L of the rotational shaft4decreases from the tip side toward the hub side. Further, the oblique edge portion32of the rotor blade3includes two types: one formed to have a linear shape in a meridional view (seeFIGS.2and7); and one formed to have an arc shape protruding in a direction away from the rotational shaft4in the radial direction from the line connecting the tip-side end31cand the hub-side end31hof the leading edge31connected to the hub2(seeFIGS.3to6,8).

In the mixed-flow turbine wheel1having the above configuration, the mixed-flow turbine wheel1according to an embodiment of the present invention includes a sensor detection surface S having a flat shape applied with a marking that is detectable by the optical sensor device9as depicted inFIGS.2to6. The sensor detection surface S is formed on at least one of the circumferential surface22of the hub2or an edge portion (31,34,36) of the reference rotor blade3sbeing one of the plurality of rotor blades3, such that, in a meridional view, a trailing-edge side angle of two angles formed between the axis4L of the rotational shaft4and a normal Sn of the sensor detection surface S (hereinafter, sensor-detection-surface angle θr) is smaller than a trailing-edge side angle of two angles formed between the axis4L of the rotational shaft4and a normal32nof the oblique edge portion32(hereinafter, oblique-surface angle θs). Further, the sensor detection surface S applied with the marking has a refractive index which is different from a refractive index of the circumferential surface22of the hub2or the edge portion of the reference rotor blade3sother than the sensor detection surface S. Further, the above reference rotor blade3sis a rotor blade3on which the sensor detection surface S is to be formed, and may be any one of the plurality of rotor blades3, or at least one rotor blade may be selected as the reference rotor blade3s.

More specifically, the oblique edge portion32of the mixed-flow turbine wheel1is normally formed such that the normal32nof the oblique edge portion32is oblique toward the opposite side of the position of the boss portion23with respect to a line orthogonal to the axis4L of the rotational shaft4, whether the oblique edge portion32has a linear shape or an arc shape. Thus, the oblique-edge angle θr is an obtuse angle larger than 90 degrees (seeFIGS.2to8). Herein, the optical sensor device9needs to be disposed close to the sensor detection surface S so as to be within the range of detection limit and so as to be capable of facing the sensor detection surface S, along the extension direction of the normal32nof the sensor detection surface S. Further, normally, the boss portion23or the back surface24(back plate portion) of the mixed-flow turbine wheel1is ground for unbalance correction. The inventors of the present inventions thought that the sensor detection surface S should preferably be a position different from a portion that has the risk of being ground for unbalance correction. Thus, for instance, for the mixed-flow turbine wheel1having the oblique edge portion32having a linear shape depicted inFIG.7as a comparative example, a part of the oblique edge portion32may be used as the sensor detection surface S.

However, along the direction of extension of the normal32nof the oblique edge portion32, as depicted inFIG.1, the bearing housing52of the turbo-cartridge5, and the unbalance detection device6exist (e.g. the above described oil supply pipe77and the air supply pipe75inFIG.1). That is, the bearing housing52of the turbo-cartridge5and the unbalance detection device6may be interfered with, and thus it is difficult to install the optical sensor device9. Furthermore, as depicted inFIG.8as a comparative example, in a case where the oblique edge portion32has an arc shape, it is difficult to use the oblique edge portion32as the sensor detection surface S in the first place. Furthermore, there has been no example of using another portion as the sensor detection surface S for the mixed-flow turbine wheel1.

Under this situation, the inventors of the present invention conducted intensive researches and arrived at the idea to form the sensor detection surface S on the circumferential surface22of the hub2or the edge portion of the reference rotor blade3sby correcting the shape of the circumferential surface22of the hub2or the shape of the edge portion of the reference rotor blade3sso that the sensor-detection-surface angle θs becomes smaller than the oblique-edge angle θr. In this way, it is possible to install the optical sensor device9without interfering with the bearing housing52of the turbo-cartridge5and the unbalance detection device6. As in the embodiment depicted inFIGS.2to6described below, the sensor-detection-surface angle θs should preferably be 90 degrees or smaller (θs≤90 degrees). By installing the optical sensor device9in this direction, it is possible to install the optical sensor device9without interfering with the unbalance detection device6. Furthermore, while the shape of the rotor blade3is normally determined so as to be able to meet the required performance, as described with reference toFIGS.2to6described below, the sensor detection surface S is formed on a portion that suppresses influence of the shape correction of the reference rotor blade3son the performance.

With the above configuration, the normal Sn of the sensor detection surface S extends toward the trailing edge side (tip side of the hub2) in the axial direction of the rotational shaft4relatively compared to the normal of the oblique edge portion32. That is, it is possible to install the optical sensor device9in a position relatively remote from the center side of the rotational shaft4. Thus, in the unbalance correction work of each of the mixed-flow turbine wheel1and the turbo-cartridge5including the mixed-flow turbine wheel1using the unbalance detection device6, it is possible to provide the optical sensor device9for detecting the rotational position of the mixed-flow turbine wheel1so as to be capable of facing the sensor detection surface S of the mixed-flow turbine wheel1without physically interfering the unbalance detection device6. Accordingly, it is possible to provide the mixed-flow turbine wheel1including the sensor detection surface S which enables appropriate acquisition of information required for the unbalance correction work, such as the rotation speed (rotation phase) of the mixed-flow turbine wheel1.

Next, some embodiments related to the sensor detection surface S formed on the mixed-flow turbine wheel1will be described with reference toFIGS.2and6.

In some embodiments, as depicted inFIGS.2and3, the leading edge31of the reference rotor blade3sincludes the first parallel edge portion33connected to the oblique edge portion32and extending in a direction parallel to the axis of the rotational shaft4, and the sensor detection surface S is formed on the first parallel edge portion33. In other words, the leading edge31of the reference rotor blade3sis formed by the oblique edge portion32and the first parallel edge portion33. In the present embodiment, as depicted inFIGS.2to3, the first parallel edge portion33is parallel to the axis4L of the rotational shaft4in a meridional view, and thus the above described sensor-detection-surface angle θs is 90 degrees. On the other hand, as described above, the oblique-edge angle θr is an obtuse angle larger than 90 degrees. Thus, the sensor-detection-surface angle θs is smaller than the oblique-edge angle θr (θr>θs).

With the above configuration, the sensor detection surface S is formed by forming the shape of the end portion side of the leading edge31of the reference rotor blades3sto be parallel to the axis4L of the rotational shaft4(first parallel edge portion33), and by utilizing the thickness of the first parallel edge portion33. The mixed-flow turbine wheel1is formed of a hard material to withstand exposure to high-temperature exhaust gas, and is difficult to machine-process compared to the compressor wheel54. Meanwhile, in the mixed-flow turbine wheel1according to an embodiment of the present invention, the leading edge31of the reference rotor blade3sis formed so as to have the first parallel edge portion33. Thus, machine-processing for forming the sensor detection surface S, such as grinding the circumferential surface22of the hub2, is unnecessary, and the sensor detection surface S can be also formed on a small mixed-flow turbine wheel1. Furthermore, by forming the first parallel edge portion33on the end portion side of the leading edge31of the reference rotor blade, it is possible to reduce the extent of shape change to a typical mixed-flow turbine wheel1not having the first parallel edge portion33. Thus, it is possible to form the sensor detection surface S easily while suppressing the influence of the first parallel edge portion33on the performance of the turbocharger.

Further, for instance, in a case where the sensor detection surface S is formed on the leading edge31in a radial turbine wheel where the leading edge31of the rotor blade3is parallel to the axis4L of the rotational shaft4, the optical sensor device9can be provided similarly to the sensor detection surface S formed on the first parallel edge portion33of the mixed-flow turbine wheel1of the present invention. That is, common equipment of the unbalance detection device6for unbalance correction can be used for different kinds of turbine wheels, and it is possible to reduce the production costs.

The embodiment related to the first parallel edge portion33will be described in detail. In some embodiments as depicted inFIG.2, the first parallel edge portion33of the leading edge31of the reference rotor blade3son which the sensor detection surface S is formed is formed on a position including the hub-side end31hof the leading edge31in a meridional view. That is, the first parallel edge portion33forms the hub-side end31hof the leading edge31. Normally, the distance d1between the hub-side end31hof the leading edge and the rotational shaft4(e.g. axis4L) is shorter than the distance d2between the rotational shaft4and the tip-side end31cof the leading edge31. Thus, the influence on the torque of the rotational shaft4is smaller at the hub-side end31hof the leading edge31than at the tip-side end31c. Furthermore, the first parallel edge portion33formed on a position including the hub-side end31his at the end of the main flow of exhaust gas supplied from the scroll part (not depicted) of the turbine, where a smaller amount of exhaust gas flows than at the oblique edge portion32of the leading edge31. That is, in a case where the first parallel edge portion33is formed on a position including the hub-side end31h, the first parallel edge portion33can be formed so as to be out of the position (flow path) where the flow of exhaust gas exists.

With the above configuration, by forming the first parallel edge portion33on the hub-side end31hof the leading edge31of the reference rotor blade3s, it is possible to form the sensor detection surface S easily while suppressing the influence of the first parallel edge portion33on the performance of the turbocharger. Furthermore, the hub2has a back plate portion forming the back surface24of the hub2, and for instance, in a case where the sensor detection surface S is formed by utilizing the first parallel edge portion33and the side surface (thickness) of the back plate portion, it is possible to further reduce the extent of shape change on the hub-side end of the reference rotor blade3s(change from the oblique shape due to the oblique edge portion32to the shape parallel to the axis4L of the rotational shaft4), and thus it is possible to further reduce the influence of the first parallel edge portion33on the performance of the turbocharger.

Furthermore, particularly in the embodiment depicted inFIG.2, as shown in the drawing, the oblique edge portion32of the leading edge31of the reference rotor blade3sis formed to have a linear shape in a meridional view. That is, in a meridional view, the first parallel edge portion33formed on a position including the hub-side end31his connected to the oblique edge portion32having a linear shape and including the tip-side end31c. As described above, for the reference rotor blade3shaving the oblique edge portion32formed to have a linear shape, by forming the first parallel edge portion33on the hub-side end31hof the leading edge31of the reference rotor blade3s, it is possible to form the sensor detection surface S easily while suppressing the influence of the first parallel edge portion33on the performance of the turbocharger. That is, the obtuse angle formed between the axis4L of the rotational shaft4and the tangent to the closest end, to the hub-side end31h, of the oblique edge portion32formed to have a linear shape is greater than the obtuse angle formed between the axis4L of the rotational shaft4and the tangent to the closest end, to the hub-side end31h, of the oblique edge portion32formed to have an arc shape. This means that, when connecting to the first parallel edge portion33forming the hub-side end31h, the oblique edge portion32formed to have a linear shape can connect more smoothly than the oblique edge portion32formed to have an arc shape. In other words, for the reference rotor blade3shaving the oblique edge portion32formed to have a linear shape, by forming the first parallel edge portion33on the hub-side end31hof the leading edge31of the reference rotor blade3s, it is possible to reduce the shape change amount due to the first parallel edge portion33.

Further, in some other embodiments, the leading edge31maybe formed by the first parallel edge portion33forming the hub-side end31hand the oblique edge portion32formed to have an arc shape.

Furthermore, in some other embodiments related to the first parallel edge portion33, the first parallel edge portion33of the leading edge31of the reference rotor blade3son which the sensor detection surface S is formed is formed on a position including the tip-side end31cof the leading edge31in a meridional view.

With the above configuration, with the first parallel edge portion33being formed on the tip-side end31cof the leading edge31of the reference rotor blade3s, the sensor detection surface S formed on the first parallel edge portion33is formed on a position remote from the rotational shaft4compared to a case where the first parallel edge portion33is formed on the hub-side end31h. Herein, the optical sensor device9is supported on a position away from the rotational shaft4by the unbalance detection device6, around the turbo-cartridge5. At this time, with the first parallel edge portion33being formed on the tip-side end31cof the leading edge31of the reference rotor blade3s, the optical sensor device9can be provided to a position closer to the support position of the optical sensor device9without extending from the support position toward the vicinity of the rotational shaft4, and thus it is possible to install the optical sensor device9more stably and easily.

Furthermore, particularly in the embodiment depicted inFIG.3, as shown in the drawing, the oblique edge portion32of the leading edge31of the reference rotor blade3sis formed to have an arc shape protruding toward a line connecting the hub-side end31hand the tip-side end31cof the leading edge31in a meridional view. That is, in a meridional view, the first parallel edge portion33formed on a position including the tip-side end31cis connected to the oblique edge portion32having an arc shape and including the hub-side end31h. Further, in a case where the oblique edge portion32has an arc shape, the normal32nof the oblique edge portion32is greater than 90 degrees at any position of the oblique edge portion32having an arc shape. In this way, it is possible to form the sensor detection surface S easily while suppressing the influence of the first parallel edge portion33on the performance of the turbocharger. That is, the angle formed between the axis4L of the rotational shaft4and the tangent to the closest end, to the tip-side end31c, of the oblique edge portion32formed to have an arc shape is smaller than the angle formed between the axis4L of the rotational shaft4and the tangent to the closest end, to the tip-side end31c, of the oblique edge portion formed to have a linear shape. Thus, when connecting to the first parallel edge portion33forming the tip-side end31c, the oblique edge portion32formed to have an arc shape can connect more smoothly than the oblique edge portion32formed to have a linear shape.

Further, in some other embodiments, the leading edge31maybe formed by the first parallel edge portion33forming the tip-side end31cand the oblique edge portion32formed to have a linear shape.

Further, in some embodiments, as depicted inFIGS.2and3, in a meridional view, when defining that L is the length of the leading edge31of the reference rotor blade3sin the direction along the axis4L of the rotational shaft4and La is the length of the first parallel edge portion33in the direction along the axis4L of the rotational shaft4, La/L is not greater than ⅓ (3La≤L). By forming the first parallel edge portion33so as to satisfy this condition, it is possible to form the first parallel edge portion33while satisfying the required performance of the turbocharger. More preferably, La/L should preferably smaller, such as La/L being ⅕ or smaller, because the influence of formation of the first parallel edge portion33on the performance becomes smaller. Herein, La needs to be not smaller than the detection limit length that can be detected by the optical sensor device9.

With the above configuration, it is possible to increase the flexibility of installment of the optical sensor device while suppressing the influence of the first parallel edge portion33on the performance of the turbocharger.

Further, in some embodiments, as depicted inFIG.4, the trailing edge34of the reference rotor blade3sincludes the second parallel edge portion formed to have a linear shape, in a meridional view, and the sensor detection surface S is formed on the second parallel edge portion35. As depicted inFIG.4, the normal of the second parallel edge portion35formed on the trailing edge34of the rotor blade3(the normal Sn of the sensor detection surface S) extends toward the trailing edge side of the above described axial direction (the side with the boss portion23), and thus the above described sensor-detection-surface angle θs is smaller than 90 degrees. On the other hand, as described above, the oblique-edge angle θr is larger than 90 degrees. Thus, the sensor-detection-surface angle θs is smaller than the oblique-edge angle θr (θr>θs). In the embodiment depicted inFIG.4, the sensor detection surface S is formed on a position close to the connection portion to the shroud-side edge portion36, of the trailing edge34of the rotor blade3. However, the position of the second parallel edge portion35is not limited to the position ofFIG.4, and may be a position on the trailing edge34. Generally, the shape change of the trailing edge34of the rotor blade3has a small influence on the performance of the turbocharger. Thus, by providing the first parallel edge portion on the hub-side end of the leading edge, it is possible to form the sensor detection surface S with the second parallel edge portion35by utilizing the thickness of the trailing edge34of the reference rotor blade3sso that the sensor-detection-surface angle θs becomes smaller than the oblique-edge angle θr.

Further, in some other embodiments, as depicted inFIG.5, the shroud-side edge portion36of the reference rotor blade3sincludes the third parallel edge portion37connected to the trailing edge34and extending in a direction parallel to the axis of the rotational shaft4in a meridional view, and the sensor detection surface S is formed on the third parallel edge portion37. As depicted inFIG.5, the third parallel edge portion37is parallel to the axis4L of the rotational shaft4in a meridional view, and thus the above described sensor-detection-surface angle θs is 90 degrees. On the other hand, the above described oblique-edge angle θr is larger than 90 degrees. Thus, the sensor-detection-surface angle θs is smaller than the oblique-edge angle θr (θr>θs).

With the above configuration, the sensor detection surface S is formed by forming the shape of the portion of the shroud-side edge portion36of the reference rotor blade3sconnected to the trailing edge34to be parallel to the axis4L of the rotational shaft4(the third parallel edge portion37), and by utilizing the thickness of the third parallel edge portion37. Accordingly, the sensor-detection-surface angle θs is smaller than the oblique-edge angle θr, and thereby it is possible to install the optical sensor device9for detecting the rotational position of the mixed-flow turbine wheel without physically interfering the unbalance detection device6in unbalance correction work. In particular, the shroud-side edge portion36of the reference rotor blade3sis a portion that becomes more parallel to the axis4L of the rotational shaft4toward the trailing edge34from the leading edge31, and thus it is possible to reduce the extent of shape change to a typical mixed-flow turbine wheel1not having the third parallel edge portion37. Thus, it is possible to form the sensor detection surface S easily while suppressing the influence of the third parallel edge portion37on the performance of the turbocharger.

Further, in some other embodiments, the sensor detection surface S includes a flat surface formed in the intermediate region Rm of the circumferential surface22of the hub2. The circumferential surface22of the hub2is usually a curved surface along the circumferential direction of the rotational shaft4. Thus, in the present embodiment, it is necessary to form the sensor detection surface S having a flat shape by machine-processing a part of the intermediate region Rm of the circumferential surface22of the hub2into a flat shape, for instance. Further, as described above, the circumferential surface22of the hub2includes the boss region Rb, the rotor-blade region Rc, and the intermediate region Rm. Among the above, the boss region Rb is a portion that has the risk of being ground for unbalance correction. Thus, when the boss portion23is ground according to the above described grinding information, the sensor detection surface S having a flat shape may get ground too. If the sensor detection surface S is ground, the rotation speed can no longer be detected by the optical sensor device9, and the future balancing work may be impaired. Meanwhile, in the rotor-blade region Rc, the rotor blade3is disposed so as to extend in the radial direction beyond the detection limit range of the optical sensor device9described above, and thus it is difficult to install the optical sensor device9for the risk of interference (collision) with the rotor blade3during rotation. Thus, the intermediate region Rm of the circumferential surface22of the hub2is a region suitable for forming the sensor detection surface S.

With the above configuration, the sensor detection surface S is formed by forming a flat surface partially in the intermediate region Rm between the rotor-blade region Rc and the boss region Rb on the circumferential surface22of the hub2. Normally, the optical sensor device9needs to be positioned close to the sensor detection surface S so that the distance to the sensor detection surface S is a few millimeters (1 to 2 mm). By forming the sensor detection surface S in the intermediate region Rm, it is possible to install the optical sensor device while avoiding interference with the rotor blade3rotating along with rotation of the rotational shaft4.

Furthermore, in the above described embodiment, the first parallel edge portion33(seeFIGS.2and3), the second parallel edge portion35(seeFIG.4), and the third parallel edge portion37(seeFIG.5) are formed on each of the plurality of rotor blades. However, this embodiment is not limitative. In some other embodiments, the first parallel edge portion33, the second parallel edge portion35, and the third parallel edge portion37may be formed on only one rotor blade3being the reference rotor blade3s. In some other embodiments, the first parallel edge portion33, the second parallel edge portion35, and the third parallel edge portion37may be formed on all of the rotor blades3.

Further, in some embodiments, an unbalance correction portion including a ground portion is formed on at least one of the back surface24of the hub2or the boss portion23of the hub2. That is, the ground portion is formed by grinding, and one or more ground portions (ground locations) are collectively referred to as the unbalance correction portion. With the above configuration, the unbalance correction portion is the back surface24or the boss portion23of the hub2. That is, the sensor detection surface S is formed on the circumferential surface22of the hub2or the edge portion of the reference rotor blade3s, and thereby it is possible to prevent the sensor detection surface S from being ground due to the unbalance correction work.

Hereinafter, the unbalance correction method of the mixed-flow turbine wheel1according to an embodiment of the present invention will be described with reference toFIG.9.FIG.9is a diagram showing an unbalance correction method for a mixed-flow turbine wheel1according to an embodiment of the present invention. The unbalance correction method may be applied to unbalance correction of the rotor51of the turbo-cartridge5including the above described mixed-flow turbine wheel1(seeFIGS.2to6), or to the mixed-flow turbine wheel1(seeFIGS.2to6) connected to the rotational shaft4before assembly of the turbo-cartridge5.

Furthermore, as depicted inFIG.9, the unbalance correction method for the mixed-flow turbine wheel1includes a marking step (S1inFIG.9) and an optical sensor installment step (S3inFIG.9). Hereinafter, the unbalance correction method of the mixed-flow turbine wheel1will be described along each step ofFIG.9, provided that the work target object of the unbalance correction work is the rotor51of the turbo-cartridge5.

In step S1ofFIG.9, the marking step is executed. The marking step is a step of applying the marking detectable by the optical sensor device9to the sensor detection surface S having a flat shape. Specifically, the sensor detection surface S is formed on the first parallel edge portion33(seeFIGS.2and3), the second parallel edge portion35(seeFIG.4), and the third parallel edge portion37(seeFIG.5) described above, and these portions are applied with markings in the present step. As described above, the sensor detection surface S is formed on at least one of the circumferential surface22of the hub2or an edge portion (31,34,36) of the reference rotor blade3sbeing one of the plurality of rotor blades3, such that, in a meridional view, a trailing-edge side angle of two angles formed between the axis4L of the rotational shaft4and a normal Sn of the sensor detection surface S is smaller than a trailing-edge side angle of two angles formed between the axis4L of the rotational shaft4and a normal32nof the oblique edge portion32.

Furthermore, in the embodiment shown inFIG.9, a support step is performed in step S2. The support step is a step of nipping and supporting the turbo-cartridge5from both sides in the axial direction of the rotational shaft4via the unbalance detection device6.

In step S3, a sensor installation step is performed. The sensor installment step is a step of installing the optical sensor device9so as to be capable of facing the sensor detection surface S having a flat shape applied with a marking. For instance, the optical sensor device9is installed so that the optical sensor device9can detect the sensor detection surface S so that the normal Sn of the sensor detection surface S having a flat shape and the normal of the optical sensor device9(normal of the light irradiation surface91sof the light emission part91and normal of the light receiving surface92sof the light receiving part92) match within a possible range. By installing the optical sensor device9to be capable of facing the sensor detection surface S, the sensor detection surface S that rotates along with rotation of the mixed-flow turbine wheel1faces the optical sensor device9only for a period in a single rotation when passing the optical sensor device9, and the optical sensor device9detects the sensor detection surface S during this facing period (passing period). At this time, a vibration sensor required to obtain the above described grinding information may be installed on the turbine-side housing member6tor the bearing housing52of the turbo-cartridge5, for instance.

In step S4, a rotation step of rotating the work target object such as the rotor51is executed. For instance, with the unbalance detection device6depicted inFIG.1, the rotor51is rotated by supplying air with the blower76to the turbine-side housing member6tor the compressor-side housing member6c.

In step S5, a sensor detection step is performed. Specifically, by using the optical sensor device9, the rotation speed (phase) of the work target object such as the rotor51is detected, and at the same time, the vibration signal of vibration generated due to unbalance of the work target object is detected with the vibration sensor (not depicted). Accordingly, it is possible to determine the phase of the work target object that is causing vibration on the basis of a relationship between the vibration signal and the phase upon rotation of the work target object.

In step S6, a grinding-information calculation step of calculating grinding information is executed. The grinding information is information including the optimum weight amount and the optimum position for balancing the work target object, calculated on the basis of the signal detected in the above sensor detection step (S5). In the unbalance correction work, unbalance is corrected by grinding the work target object on the basis of the grinding information. The grinding information is calculated by using the vibration signal detected by the vibration sensor, the phase of the rotor51, and the effect vector. The effect vector is information indicating the relationship between the mass to be ground and the corresponding magnitude of vibration, which is obtained by performing a test in advice on the same product as the turbo-cartridge5under the unbalance correction work. As described above, for the mixed-flow turbine wheel1, the boss portion23or the back surface24(back plate portion) of the hub2is ground and thereby the ground portion (unbalance correction portion) is formed.

The mixed-flow turbine wheel1and the unbalance correction method thereof according to an embodiment of the present invention were described. Embodiments of the present invention were described in detail above, but the present invention is not limited thereto, and various amendments and modifications may be implemented.

While the oblique edge portion32of the mixed-flow turbine wheel1inFIGS.4to6is formed to have a linear shape in a meridional view, this is merely an illustrative example. In the embodiment depicted inFIGS.4to6, the oblique edge portion32may be formed to have an arc shape.

DESCRIPTION OF REFERENCE NUMERALS