Method of spin test of impeller and connection tool

Abstract

To provide a method of a spin test of an impeller that can suppress generation of excessive shaft vibration at the time of impeller spin test, and to provide a connection tool.SOLUTION: A method of a spin test of an impeller of a supercharger including: a hub having a back surface and an outer peripheral surface that is formed on one side in an axial direction as compared to the back surface; and a plurality of vanes provided in the outer peripheral surface of the hub includes an impeller fixing step of directly fixing an end of the hub on the one side in the axial direction to a rotation shaft of a rotation test machine for rotating an impeller.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a method for spin testing an impeller and a coupling jig for coupling an impeller to a rotary drive shaft of a spin testing machine. [Background technology]

[0002] A spin test is a rotation test of the impeller installed in a turbocharger that is conducted during the manufacture of the turbocharger, in which the impeller is rotated for a predetermined period of time using a rotation tester at a speed exceeding the rated speed (for example, 120% of the rated speed). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 11-148885 Summary of the Invention [Problem to be solved by the invention]

[0004] If the impeller is designed such that the connection between the impeller and the rotating shaft loosens when the impeller expands circumferentially and contracts axially due to plastic deformation caused by centrifugal force acting during a spin test, excessive shaft vibration may occur due to a change in the imbalance caused by the plastic deformation of the impeller. Patent Document 1 does not provide detailed descriptions of a method for connecting the test equipment and the impeller, but the rotating shaft of the rotational strength tester is attached to the back side of the test impeller during the rotational strength test. The back side of the impeller may be machined to adjust the inclination of the turbocharger rotor and impeller during turbocharger manufacturing, which may make it difficult to ensure the accuracy of the attachment between the back side of the impeller and the rotating shaft during the spin test.

[0005] In view of the above circumstances, at least one embodiment of the present disclosure aims to provide an impeller spin test method and a connecting jig that can suppress the occurrence of excessive axial vibration during an impeller spin test. [Means for solving the problem]

[0006] A method for spin testing an impeller according to at least one embodiment of the present disclosure includes: A spin test method for a turbocharger impeller including a hub having a back surface and an outer peripheral surface formed on one side of the back surface in an axial direction, and a plurality of blades provided on the outer peripheral surface of the hub, The method further includes an impeller fixing step of directly fixing one end of the hub, which is the end on one side in the axial direction, to a rotation shaft of a rotation testing machine for rotating the impeller.

[0007] A connecting jig according to at least one embodiment of the present disclosure includes: A connecting jig for connecting an impeller of a turbocharger, the impeller including a hub having a back surface and an outer peripheral surface formed on one side of the back surface in the axial direction, and a plurality of blades provided on the outer peripheral surface of the hub, to a rotation drive shaft of a rotation testing machine for rotating the impeller, an extension shaft portion that extends the rotation drive shaft; a fastening portion formed on one axial side of the extension shaft portion for fastening a shaft end portion of the rotation drive shaft; and a flange portion formed on the other axial side of the extension shaft portion, which is overlapped with one side end portion, which is the end portion on one side of the hub in the axial direction, and which is fixed to the one side end portion by a fastening bolt. [Effects of the Invention]

[0008] According to at least one embodiment of the present disclosure, there is provided an impeller spin test method and a connecting jig that can suppress the occurrence of excessive axial vibration during a spin test of an impeller. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is an explanatory diagram for explaining a spin test method for an impeller according to an embodiment of the present disclosure. [Figure 2]FIG. 2 is a schematic cross-sectional view of one side end of the hub of the impeller and the rotation shaft of the rotation testing machine in one embodiment of the present disclosure. [Figure 3] FIG. 10 is a schematic cross-sectional view of an impeller according to a comparative example and a rotating shaft of a rotation testing machine. [Figure 4] FIG. 2 is a schematic diagram showing one end of a hub of an impeller according to an embodiment of the present disclosure, viewed from one side in the axial direction. DETAILED DESCRIPTION OF THE INVENTION

[0010] Hereinafter, several embodiments of the present disclosure will be described with reference to the accompanying drawings. However, the dimensions, materials, shapes, relative arrangements, etc. of components described as embodiments or shown in the drawings are merely illustrative examples and are not intended to limit the scope of the present disclosure. In this disclosure, "along a certain direction" includes not only a certain direction but also a direction inclined within a range of ±15° relative to the certain direction.

[0011] (impeller) FIG. 1 is an explanatory diagram illustrating a spin test method for an impeller 3 according to an embodiment of the present disclosure. FIG. 2 is a schematic cross-sectional view of one end portion 6 of a hub 4 of the impeller 3 and a rotating shaft 11 of a rotation testing machine 10 according to an embodiment of the present disclosure. The impeller 3, which is a test piece for the spin test, is an impeller of a supercharger (turbocharger). The spin test is a rotation test of the impeller 3 to be mounted on the supercharger, which is performed during the manufacture of the supercharger, and involves rotating the impeller 3 using the rotation testing machine 10 at a rotation speed exceeding the rated rotation speed (for example, a rotation speed that is 120% of the rated rotation speed) for a predetermined time (rotation step).

[0012] The direction in which the rotational axis LA of the impeller 3 extends (the up-and-down direction in Figure 1) is defined as the axial direction of the impeller 3 (hub 4), the direction perpendicular to the rotational axis LA is defined as the radial direction of the impeller 3 (hub 4), and the circumferential direction centered on the rotational axis LA is defined as the circumferential direction of the impeller 3 (hub 4).

[0013] The impeller 3 includes a hub 4 having a back surface 41 and an outer peripheral surface 42, and a plurality of blades 5 provided on the outer peripheral surface 42 of the hub 4. The outer peripheral surface 42 is formed on one side in the axial direction of the impeller 3 (the front side, the upper side in FIG. 1) than the back surface 41. The outer peripheral surface 42 is inclined so that the distance (radial distance) from the rotation center axis LA increases toward the other side in the axial direction of the impeller 3 (the back side, the lower side in FIG. 1). The plurality of blades 5 extend radially outward from the outer peripheral surface 42 of the hub 4 and are arranged at intervals from one another in the circumferential direction of the impeller 3.

[0014] The end portion of the hub 4 on the one axial side (front side) is defined as the one-side end portion 6. The one-side end portion 6 includes an end face 61 on the one side of the hub 4. The end face 61 is formed radially inward of the outer peripheral surface 42 of the hub 4. In the embodiment shown in FIG. 2, the one-side end portion 6 includes a boss portion 62 having an end face 61 that protrudes toward the one side beyond the edge 51 on the one side of the plurality of blades 5. The end portion of the hub 4 on the other axial side (rear side) is defined as the other-side end portion 7. The other-side end portion 7 includes an end face 71 on the other side of the hub 4. The end face 71 is formed radially inward of the rear surface 41 of the hub 4. In the illustrated embodiment, the hub 4 has a through hole 43 that penetrates from the end face 61 to the end face 71 along the axial direction of the hub 4, at a position including the central rotation axis LA.

[0015] (Rotational testing machine, connecting jig) The rotation testing machine 10 is configured to support one axial side of the rotating shaft 11 so that the rotating shaft 11 can rotate in the circumferential direction around the central rotation axis of the rotating shaft 11. In the illustrated embodiment, the rotating shaft 11 includes a rotating drive shaft 16 and a connecting jig 15 having an extension shaft portion 151 that extends the rotating drive shaft 16.

[0016] A fastening portion 152 is formed at one axial end (upper side in FIG. 2 ) of the extension shaft portion 151 for fastening a shaft end portion 161, which is the end portion of the rotation drive shaft 16 on the other axial end (lower side in FIG. 2 ). In the illustrated embodiment, a shaft insertion hole 153 for inserting the shaft end portion 161 is formed at the one axial end (upper side in FIG. 2 ) of the extension shaft portion 151. As shown in FIG. 2 , a plurality of (two in the illustrated example) recesses 154 recessed radially outward are formed on the inner circumferential surface of the shaft insertion hole 153. A plurality of (two in the illustrated example) recesses 162 recessed radially inward are formed on the outer circumferential surface of the shaft end portion 161, and each recess 162 forms a hole 18 into which a pin 17 can be inserted between the recess 154 and the recess 154 formed on the inner circumferential surface of the shaft insertion hole 153. The connecting jig 15 is mechanically connected to the rotary drive shaft 16 by inserting the shaft end portion 161 into the shaft insertion hole 153 and then inserting pins 17 into each of the multiple holes 18. In the illustrated embodiment, the fastening portion 152 includes a shaft insertion hole 153 having multiple recesses 154 formed on the inner circumferential surface. By mechanically connecting the connecting jig 15 to the rotary drive shaft 16, the extension shaft portion 151 is positioned on an extension line of the central rotation axis LC of the rotary drive shaft 16. Note that the connection between the connecting jig 15 and the rotary drive shaft 16 is not limited to the illustrated embodiment.

[0017] In the illustrated embodiment, the rotation testing machine 10 includes an electric motor 101 configured to support one axial side (upper side in FIG. 1) of the rotary drive shaft 16 so as to be rotatable in the circumferential direction about the central rotation axis LC of the rotary drive shaft 16. The electric motor 101 is driven by electric power supplied from a power source 102 to rotate the rotary drive shaft 16.

[0018] In the spin test method for the impeller 3, the impeller 3 is accommodated in a sealed space 104 formed inside a sealed structure 103. The sealed structure 103 includes a top plate 103A, a bottom plate 103B placed on a floor surface 105, and a side plate 103C connecting the top plate 103A and the bottom plate 103B and enclosing the sealed space 104. The electric motor 101 is placed on the top plate 103A. The sealed structure 103 (in the illustrated example, the side plate 103C) is formed with a communication hole 106 that connects the sealed space 104 with the outside of the sealed structure 103. One side of a pipe 108 is connected to a vacuum pump 107 that reduces the pressure in the sealed space 104 to less than atmospheric pressure, and the other side of the pipe 108 is connected to the communication hole 106. During the rotation step, the vacuum pump 107 maintains the sealed space 104 at a pressure lower than atmospheric pressure.

[0019] In the illustrated embodiment, the central rotation axis LA of the impeller 3, the central rotation axis LB of the connecting jig 15, and the central rotation axis LC of the rotary drive shaft 16 all extend vertically. The impeller 3 is suspended from the rotary shaft 11 in the sealed space 104. The impeller 3 suspended from the rotary shaft 11 has one end 6 positioned above in the vertical direction and the other end 7 positioned below in the vertical direction.

[0020] (Connection structure between impeller and rotating shaft according to comparative example) FIG. 3 is a schematic cross-sectional view of an impeller 03 according to a comparative example and a rotating shaft 011 of a rotation testing machine. Like the impeller 3, the impeller 03 includes a hub 04 having a back surface 041, an outer peripheral surface 042, and a through hole 043, and a plurality of blades 05 provided on the outer peripheral surface 042 of the hub 04. The rotating shaft 011 includes a flange portion 012 that sandwiches a spacer 201 between itself and an end face 071 of the other end 07 of the hub 04, and a protruding portion 013 that passes through the through hole 043 and protrudes axially beyond one end 06 of the hub 04. A nut 202 is attached to the protruding portion 013 of the rotating shaft 011 and threads onto a threaded portion 014 formed on the outer peripheral surface of the protruding portion 013. A washer 203 is sandwiched between the nut 202 and the end face 061 of the one end 06 of the hub 04. The impeller 3 is fixed to the rotating shaft 011 by tightening the nut 202 onto the rotating shaft 011 while applying a compressive force F to the hub 04 of the impeller 03 toward the rear side of the impeller 03 in the axial direction.

[0021] In the connection structure between the impeller 03 and the rotating shaft 011 according to the comparative example, when the impeller 03 expands in the circumferential direction and contracts in the axial direction due to plastic deformation caused by centrifugal force acting during a spin test, the connection between the impeller 03 and the rotating shaft 011 may loosen. If the connection between the impeller 03 and the rotating shaft 011 loosens during a spin test, the plastic deformation of the impeller 03 changes the imbalance, which may result in excessive shaft vibration. Furthermore, as a result of analyzing the connection structure between the impeller 03 and the rotating shaft 011 according to the comparative example, the secondary critical speed was found to be present at the maximum rotational speed (maximum rotational speed) during the spin test, and therefore it is necessary to separate the secondary critical speed from the maximum rotational speed (maximum rotational speed) during the spin test.

[0022] (Connecting structure between impeller and rotating shaft) A spin test method for an impeller 3 according to some embodiments includes an impeller fixing step. In the impeller fixing step, as shown in FIGS. 1 and 2 , one end 6 of the impeller 3 is directly fixed to a rotating shaft 11 of a rotation testing machine 10 for rotating the impeller 3. "Directly fixing" means that no other member is disposed between the rotating shaft 11 and the one end 6, which are the fixing targets, and the rotating shaft 11 and the one end 6 are fixed in abutting contact with each other. The impeller fixing step is performed before the rotation step. During the rotation step, the fixed state between the rotating shaft 11 and the one end 6 is maintained.

[0023] In the illustrated embodiment, the above-mentioned connecting jig 15 (rotating shaft 11) includes a flange portion 12 that protrudes radially outward from the extension shaft portion 151. The flange portion 12 is placed on the end face 61 of the one side end portion 6 and is fixed to the one side end portion 6 by a fastening bolt 13. In the above-mentioned impeller fixing step, the flange portion 12 is fixed to the one side end portion 6 by the fastening bolt 13.

[0024] (recess) In the embodiment shown in FIG. 2 , a recess 8 for inserting the flange portion 12 is formed at the one end 6. In the impeller fixing step, the flange portion 12 is inserted into the recess 8. The flange portion 12 is loosely inserted into the recess 8. A surface 121 on the other axial side (the lower side in FIG. 2 ) of the flange portion 12 abuts against a bottom surface 81 of the recess 8. The end surface 61 includes a flat surface 61A extending radially outward from the outer edge of the recess 8 along the radial direction of the hub 4, and the bottom surface 81 of the recess 8. In this case, inserting the flange portion 12 into the recess 8 positions the flange portion 12 relative to the one end 6. This facilitates the attachment of the flange portion 12 to the one end 6 and shortens the time required for a spin test. Furthermore, axial misalignment of the impeller 3 with respect to the rotating shaft 11 can be suppressed when attaching the impeller 3 to the rotating shaft 11. In some other embodiments, the surface 121 of the flange portion 12 may be in contact with the end surface 61 of the one side end portion 6 where the recess 8 is not formed.

[0025] 2, the flange portion 12 described above is formed with a plurality of bolt insertion holes 122 for loosely inserting the shaft portions 132 of the fastening bolts 13. The plurality of bolt insertion holes 122 are through-holes that are formed at intervals in the circumferential direction of the connecting jig 15 (rotating shaft 11) and that pass through the flange portion 12 along the connecting jig 15 (rotating shaft 11). A plurality of fastening holes 63 that are fastened to the fastening bolts 13 are formed in an end face 61 (bottom surface 81 in the illustrated example) of one side end 6 of the impeller 3. The plurality of fastening holes 63 are formed in the same number as the plurality of bolt insertion holes 122, and each fastening hole 63 is formed at a position corresponding to each bolt insertion hole 122. The shaft portion 132 of the fastening bolt 13 is inserted through the bolt insertion hole 122 and threaded into the fastening hole 63, so that the flange portion 12 is clamped between the head 131 of the fastening bolt 13 and the end face 61 (in the illustrated example, the bottom surface 81) of the one side end portion 6.

[0026] By directly fixing one end 6 of the hub 4 to the rotating shaft 11 of the rotation testing machine 10, even if the impeller 3 expands in the circumferential direction and contracts in the axial direction due to plastic deformation caused by centrifugal force, the connection between the rotating shaft 11 and one end 6 is maintained. This makes it possible to suppress changes in imbalance due to plastic deformation of the impeller 3 during a spin test, and therefore to suppress the occurrence of excessive axial vibrations of the impeller 3 during a spin test.

[0027] In the connection structure between the impeller 3 and the rotating shaft 11 of the present disclosure, the axial length from the rotation testing machine 10 to the fixed portion of the rotating shaft 11 with the one side end 6 can be made relatively short. By making the axial length relatively short, the secondary critical speed can be set higher than the maximum rotation speed (maximum rotation number) during the spin test, thereby suppressing the occurrence of excessive axial vibration due to resonance during the spin test of the impeller 3.

[0028] In the connection structure between the impeller 3 and the rotating shaft 11 of the present disclosure, the flange portion 12, which has a relatively large area, is brought into contact with the one end portion 6, thereby ensuring a sufficient contact area between the flange portion 12 and the one end portion 6, thereby providing a strong fixation between the flange portion 12 and the one end portion 6. The use of a fixing structure in which the flange portion 12 is fixed to the one end portion 6 with the fastening bolts 13 makes it easy to attach and remove the flange portion 12 to and from the one end portion 6, thereby shortening the time required for a spin test.

[0029] In some embodiments, as shown in FIG. 2 , the one side end 6 is formed with an insertion hole 9 for inserting the shaft end 14 of the connecting jig 15 (rotating shaft 11). In the impeller fixing step, the shaft end 14 is inserted into the insertion hole 9. The shaft end 14 is a portion of the extension shaft portion 151 on the other axial side of the flange portion 12, and is adapted to be inserted into the insertion hole 9. A fit tolerance is ensured between the shaft end 14 and the insertion hole 9, and the shaft end 14 is inserted into the insertion hole 9 with the fit tolerance. When a through hole 43 is formed in the hub 4, the through hole 43 may serve as the insertion hole 9.

[0030] By inserting the shaft end 14 of the rotating shaft 11 into the insertion hole 9, the rotating shaft 11 is positioned relative to the one side end 6, which makes it easier to attach the rotating shaft 11 to the one side end 6 and shortens the time required for the spin test. In addition, axial misalignment of the impeller 3 relative to the rotating shaft 11 when attaching the impeller 3 to the rotating shaft 11 can be suppressed.

[0031] FIG. 4 is a schematic diagram showing one end 6 of a hub 4 of an impeller 3 according to an embodiment of the present disclosure, viewed from one side in the axial direction. In some embodiments, as shown in FIG. 4 , four fastening holes 63 are formed in an end surface 61 (bottom surface 81 in the illustrated example) of the one end 6 of the impeller 3. The four fastening holes 63 are arranged at equal intervals in the circumferential direction of the hub 4. Specifically, if the circumferential angle between the centers (axial centers, centroids) 63C of two adjacent fastening holes 63 among the four fastening holes 63 is defined as θ, the circumferential angle θ satisfies the condition of 90°±5°. By arranging the four fastening holes 63 at equal intervals in the circumferential direction of the hub 4, the influence of tilt and anisotropy of the impeller 3 with respect to the rotation axis 11 can be suitably suppressed. Note that the number of fastening holes 63 arranged at equal intervals in the circumferential direction of the hub 4 may be a number other than four, such as three or five.

[0032] The connecting jig 15 according to some embodiments is a jig for connecting the impeller 3 described above to the rotary drive shaft 16 of the rotation testing machine 10 described above, and as shown in Fig. 2, includes the extension shaft portion 151 described above, the fastening portion 152 described above, and the flange portion 12 described above. The connecting jig 15 enables the connecting structure between the impeller 3 and the rotary shaft 11 described above, and therefore provides the above-mentioned operational effects that the connecting structure provides.

[0033] In this specification, expressions expressing relative or absolute arrangement such as "in a certain direction," "along a certain direction," "parallel," "orthogonal," "center," "concentric," or "coaxial" not only express such an arrangement strictly, but also express a state in which there is a relative displacement with a tolerance or an angle or distance to the extent that the same function is obtained. For example, expressions such as "identical," "equal," and "homogeneous" that indicate that something is in an equal state not only indicate a state of strict equality, but also indicate a state in which there is a tolerance or a difference to the extent that the same function is obtained. Furthermore, in this specification, expressions representing shapes such as a rectangular shape or a cylindrical shape not only represent rectangular shapes or cylindrical shapes in the strict geometric sense, but also represent shapes including uneven portions, chamfered portions, etc., to the extent that the same effect can be obtained. Furthermore, in this specification, the expressions "comprise," "include," or "have" a component are not exclusive expressions that exclude the presence of other components.

[0034] The present disclosure is not limited to the above-described embodiments, but also includes modifications to the above-described embodiments and appropriate combinations of these modifications.

[0035] The contents of the above-described embodiments can be understood, for example, as follows.

[0036] 1) A method for spin testing an impeller (3) according to at least one embodiment of the present disclosure, comprising: A spin test method for a turbocharger impeller (3) including a hub (4) having a back surface (41) and an outer peripheral surface (42) formed on one axial side of the back surface (41), and a plurality of blades (5) provided on the outer peripheral surface (42) of the hub (4), comprising: An impeller fixing step is provided for directly fixing one end (6) of the hub (4), which is the end on one side in the axial direction, to a rotation shaft (11) of a rotation testing machine (10) for rotating the impeller (3).

[0037] According to the method 1), by directly fixing one end 6 of the hub 4 to the rotating shaft 11 of the rotation testing machine 10, even if the impeller 3 expands in the circumferential direction and contracts in the axial direction due to plastic deformation caused by centrifugal force, the connection between the rotating shaft 11 and one end 6 is maintained. This makes it possible to suppress changes in imbalance due to plastic deformation of the impeller 3 during a spin test, thereby suppressing the occurrence of excessive axial vibration of the impeller 3 during a spin test.

[0038] According to the method 1), the axial length of the rotating shaft 11 from the rotation testing machine 10 to the fixed portion with the one end 6 can be made relatively short. By making the axial length relatively short, the secondary critical speed can be set higher than the maximum rotation speed (maximum number of revolutions) during the spin test, and therefore, excessive axial vibration due to resonance during the spin test of the impeller 3 can be suppressed.

[0039] 2) In some embodiments, a spin test method for the impeller (3) described in 1) above, comprising: The rotating shaft (11) includes a flange portion (12) that protrudes outward in the radial direction, the flange portion (12) being overlapped with the one side end portion (6) and fixed to the one side end portion (6) by a fastening bolt (13), The impeller (3) includes a fastening hole (63) formed in the one side end (6) to be fastened to the fastening bolt (13), In the impeller fixing step, the flange portion (12) is fixed to the one side end portion (6) by the fastening bolts (13).

[0040] According to the method 2), the flange portion 12, which has a relatively large area, is brought into contact with the one end portion 6, thereby ensuring a sufficient contact area between the flange portion 12 and the one end portion 6, thereby firmly fixing the flange portion 12 to the one end portion 6. The use of a fixing structure in which the flange portion 12 is fixed to the one end portion 6 with the fastening bolts 13 makes it easier to attach the flange portion 12 to the one end portion 6 and to remove the flange portion 12 from the one end portion 6, thereby shortening the time required for the spin test.

[0041] 3) In some embodiments, a spin test method for the impeller (3) described in 2) above, comprising: The impeller (3) includes a recess (8) formed at the one side end (6) into which the flange portion (12) is inserted, In the impeller fixing step, the flange portion (12) is inserted into the recess (8).

[0042] According to the method 3), the flange 12 is positioned relative to the one end 6 by inserting the flange 12 into the recess 8, which facilitates the work of attaching the flange 12 to the one end 6 and shortens the time required for the spin test. In addition, it is possible to prevent the impeller 3 from misaligning with the rotating shaft 11 when attaching the impeller 3 to the rotating shaft 11.

[0043] 4) In some embodiments, a spin test method for the impeller (3) according to any one of 1) to 3) above, comprising: The impeller (3) includes an insertion hole (9) formed in the one side end (6) for inserting the shaft end (14) of the rotating shaft (11), In the impeller fixing step, the shaft end portion (14) of the rotary shaft (11) is inserted into the insertion hole (9).

[0044] According to the method 4), the shaft end 14 of the rotating shaft 11 is inserted into the insertion hole 9 to position the rotating shaft 11 relative to the one end 6, which facilitates the work of attaching the rotating shaft 11 to the one end 6 and shortens the time required for the spin test. In addition, it is possible to prevent the impeller 3 from misaligning with the rotating shaft 11 when attaching the impeller 3 to the rotating shaft 11.

[0045] 5) At least one embodiment of the connection jig (15) according to the present disclosure includes: A connecting jig (15) for connecting an impeller (3) of a turbocharger, the impeller (3) including a hub (4) having a back surface (41) and an outer peripheral surface (42) formed on one axial side of the back surface (41), and a plurality of blades (5) provided on the outer peripheral surface (42) of the hub (4), to a rotation drive shaft (16) of a rotation testing machine (10) for rotating the impeller (3), an extension shaft portion (151) that extends the rotary drive shaft (16); a fastening portion (152, 153) formed on one axial side of the extension shaft portion (151) for fastening a shaft end portion (161) of the rotary drive shaft (16); and a flange portion (12) formed on the other axial side of the extension shaft portion (151), the flange portion (12) being overlapped with one side end portion (6), which is the end portion on one side in the axial direction of the hub (4), and fixed to the one side end portion (6) by a fastening bolt (13).

[0046] According to the configuration of 5), by directly fixing the one end 6 of the hub 4 to the connecting jig 15, even if the impeller 3 expands in the circumferential direction and contracts in the axial direction due to plastic deformation caused by centrifugal force, the connection between the connecting jig 15 and the one end 6 is maintained. This suppresses changes in imbalance due to plastic deformation of the impeller 3 during a spin test, thereby suppressing excessive axial vibration during the spin test of the impeller 3. Furthermore, according to the configuration of 5), the axial length of the connecting jig 15 can be made relatively short. By making the axial length relatively short, the secondary critical speed can be set higher than the maximum rotational speed (maximum number of revolutions) during the spin test, thereby suppressing excessive axial vibration due to resonance during the spin test of the impeller 3.

[0047] According to the configuration 5) above, by bringing the flange portion 12, which has a relatively large area, into contact with the one end portion 6, a sufficient contact area between the flange portion 12 and the one end portion 6 can be ensured, thereby providing a strong fixation between the flange portion 12 and the one end portion 6. The use of a fixing structure in which the flange portion 12 is fixed to the one end portion 6 with the fastening bolts 13 facilitates the work of attaching the flange portion 12 to the one end portion 6 and the work of removing the flange portion 12 from the one end portion 6, thereby shortening the time required for the spin test. [Explanation of symbols]

[0048] 3 impeller 4 Hub 5 wings 6 One side end 7 Other end 8 recess 9 Insertion hole 10 Rotational Testing Machine 11 Rotation axis 12 Flange 13 Fastening bolt 15 Connecting jig 16 Rotating drive shaft 41 Back 42 Outer surface 43 Through hole 63 Fastening hole 101 Electric motor 102 Power Source 103 Closed structure 104 Closed space 105 Floor 106 Communication hole 107 Vacuum Pump 108 Piping 151 Extension shaft 152 Fastening part 201 Spacer 202 Nut 203 Washer F Compression force

Claims

1. A spin test method for a turbocharger impeller including a hub having a back surface and an outer peripheral surface formed on one side of the back surface in an axial direction, and a plurality of blades provided on the outer peripheral surface of the hub, an impeller fixing step of directly fixing one end portion of the hub, which is the one end portion in the axial direction, to a rotation shaft of a rotation testing machine for rotating the impeller; Impeller spin test method.

2. the rotating shaft includes a flange portion that protrudes outward in a radial direction, the flange portion being overlapped with the one side end portion and fixed to the one side end portion by a fastening bolt, The impeller includes a fastening hole formed at the one end portion thereof, the fastening hole being fastened to the fastening bolt, In the impeller fixing step, the flange portion is fixed to the one side end portion by the fastening bolt. The method for spin testing an impeller according to claim 1.

3. the impeller includes a recess formed at the one side end into which the flange portion is inserted, In the impeller fixing step, the flange portion is inserted into the recess. The method for spin testing an impeller according to claim 2.

4. the impeller includes an insertion hole formed at the one end portion thereof into which a shaft end portion of the rotary shaft is inserted, In the impeller fixing step, the shaft end of the rotating shaft is inserted into the insertion hole. The impeller spin test method according to any one of claims 1 to 3.

5. A connecting jig for connecting an impeller of a turbocharger, the impeller including a hub having a back surface and an outer peripheral surface formed on one side of the back surface in the axial direction, and a plurality of blades provided on the outer peripheral surface of the hub, to a rotation drive shaft of a rotation testing machine for rotating the impeller, an extension shaft portion that extends the rotation drive shaft; a fastening portion formed on one axial side of the extension shaft portion for fastening a shaft end portion of the rotation drive shaft; a flange portion formed on the other axial side of the extension shaft portion, the flange portion being overlapped with one end portion of the hub, which is the end portion on one side in the axial direction, and fixed to the one end portion by a fastening bolt; Connecting jig.

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