Impeller rotator and method of assembling said impeller rotator

Abstract

An impeller rotator (21) includes a turbine impeller (11), a compressor impeller (12), a shaft (13) connecting the turbine impeller (11) to the compressor impeller (12), and a connecting member (16) fastening one of the turbine impeller and the compressor impeller to one axial end region of the shaft, and the connecting member (16) is plastic-deformed so as to decrease overall imbalance of the turbine impeller (11), the compressor impeller (12), and the shaft (13).

Claims

1. An impeller rotator comprising: a turbine impeller having imbalance around a rotary axis; a compressor impeller having imbalance around a rotary axis; a shaft configured to connect the turbine impeller to the compressor impeller; and a connecting member attached to one axial end of the shaft to fasten one of the turbine impeller or the compressor impeller to one axial end region of the shaft, the connecting member having at least one portion extending beyond the one axial end of the shaft in an axial direction, wherein the at least one portion of the connecting member extending beyond the one axial end of the shaft in the axial direction is plastic-deformed so as to decrease an overall imbalance of the turbine impeller, the compressor impeller, and the shaft.

2. The impeller rotator according to claim 1, wherein an other axial end of the shaft is integrated with an other of the turbine impeller and the compressor impeller.

3. The impeller rotator according to claim 1, wherein the connecting member is a nut screwed to the one axial end of the shaft.

4. The impeller rotator according to claim 3, wherein the at least one portion of the connecting member extending beyond the one axial end of the shaft is an axial end of the nut, and the axial end of the nut is caulked to correct rotational balance of the impeller rotator.

5. The impeller rotator according to claim 3, wherein the nut has a plurality of projections spaced around the rotary axis, and the projections are bent to correct rotational balance of the impeller rotator.

6. The impeller rotator according to claim 5, wherein the projections are arranged at an axial end of the nut, the at least one portion of the connecting member extending beyond the one axial end of the shaft comprises at least one of the projections.

7. The impeller rotator according to claim 1, wherein the at least one portion of the connecting member extending beyond the one axial end of the shaft is plastic-deformed by an amount based on the overall imbalance of the turbine impeller, the compressor impeller, and the shaft.

8. The impeller rotator according to claim 1, wherein the at least one portion of the connecting member extending beyond the one axial end of the shaft is plastic-deformed by caulking the at least one portion of the connecting member extending beyond the one axial end of the shaft to decrease the overall imbalance of the turbine impeller, the compressor impeller, and the shaft.

9. The impeller rotator according to claim 1, wherein the at least one portion of the connecting member extending beyond the one axial end of the shaft is plastic deformed by bending the at least one portion of the connecting member extending beyond the one axial end of the shaft to decrease the overall imbalance of the turbine impeller, the compressor impeller, and the shaft.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a vertical sectional view illustrating a turbo charger provided with an impeller rotator in accordance with an embodiment of the present invention.

(2) FIG. 2 is an exploded view illustrating the impeller rotator in accordance with the embodiment.

(3) FIG. 3 is a vertical sectional view illustrating imbalance distribution of the impeller rotator.

(4) FIG. 4 is a vertical enlarged sectional view illustrating a site where a shaft is screwed to a nut.

(5) FIG. 5 is a perspective view illustrating an uncaulked nut.

(6) FIG. 6 is a perspective view illustrating a caulked nut.

(7) FIG. 7 is a perspective view illustrating a nut in a modification example.

(8) FIG. 8 is a flow chart illustrating a method of assembling the impeller rotator in accordance with an embodiment of the present invention.

EMBODIMENTS OF THE INVENTION

(9) Embodiments of the present invention will be described below in detail with reference to figures.

(10) FIG. 1 is a vertical sectional view illustrating a turbo charger provided with an impeller rotator in accordance with an embodiment of the present invention, and does not show some constituents. FIG. 2 is an exploded side view illustrating the impeller rotator in accordance with the embodiment when viewed from the direction perpendicular to the rotary axis. The turbo charger in this embodiment includes a turbine impeller 11, a compressor impeller 12, a shaft 13, a bearing 14, and a center housing 15.

(11) The turbine impeller 11 has a rear face portion 11b that extends perpendicular to the rotary axis, an axial portion 11a that extends along the rotary axis, and a plurality of wing portions 11f that extend from the axial portion 11a in the outer radial direction, and are connected to the rear face portion 11b. The compressor impeller 12 has the substantially same configuration as the turbine impeller 11.

(12) The compressor impeller 12 is disposed on one side of the center housing 15 such that its rear face faces the center housing 15. The turbine impeller 11 is disposed on the other side of the center housing 15 such that the rear face portion 11b faces the center housing 15. The shaft 13 penetrates the center housing 15, and is rotatably supported by the bearing 14 provided in the center housing 15. In a modification example not shown, the shaft 13 extends in the center housing 15 without penetrating the center housing 15.

(13) The shaft 13 linearly extends along the common rotary axis of the turbine impeller 11 and the compressor impeller 12. One axial end of the shaft 13 is connected to the compressor impeller 12, and the other axial end of the shaft 13 is connected to the turbine impeller 11. Thereby, the turbine impeller 11, the compressor impeller 12, and the shaft 13 constitute one impeller rotator 21. The turbine impeller 11 is integrated with the shaft 13 to constitute a shaft-equipped impeller 22. The shaft 13 protrudes from the rear face portion 11b of the turbine impeller 11, and extends in one axial direction. A tip region 13e of the shaft 13, which is located on one axial side, has a smaller diameter than a bottom region 13r of the shaft 13, which is located on the other axial side. The outer peripheral face of the bottom region 13r is rotatably supported by the bearing 14. Although not represented as a reference numeral, a thrust bearing is interposed between the shaft 13 and the center housing. The thrust bearing receives an axial force of the shaft 13.

(14) The compressor impeller 12 has a through hole 12h extending along the rotary axis of the compressor impeller 12. The tip region 13e of the shaft 13 is inserted into the through hole 12h from the side of the center housing 15. A male screw 13m is provided on the outer periphery of the shaft tip protruding from the through hole 12h in the one axial direction, and is screwed into a nut 16. This fastens the compressor impeller 12 to the shaft 13. The shaft 13 and the compressor impeller 12 may be prevented from rotating with respect to each other by means of uneven engagement as found between a key and a groove.

(15) When the turbine impeller 11 is rotated by the exhaust gas discharged from an engine not shown in a turbo charger, the compressor impeller 12 rotates integrally with the turbine impeller 11, feeding air into the engine.

(16) FIG. 3 is a vertical sectional view illustrating imbalance distribution of the impeller rotator 21 taken along a plane including a rotary axis O. The turbine impeller 11 and the compressor impeller 12 each are manufactured such that the center-of-mass matches the rotary axis O. In fact, however, precise measurement of rotational balance of the turbine impeller 11 and the compressor impeller 12 demonstrates that the center-of-mass does not match the rotary axis O. In this embodiment, an imbalance direction 11u of the turbine impeller 11 is marked around the rotary axis O. The marking may be made on the outer edge of the rear face portion 11b or on one end of the axial portion 11a further from the rear face portion 11b. Similarly, an imbalance direction 12u of the compressor impeller 12 is marked around the rotary axis O. Then, the turbine impeller 11 is connected to the compressor impeller 12 such that the marking of the turbine impeller 11 and the marking of the compressor impeller 12 have an angle of 180 degrees therebetween.

(17) In this embodiment, as shown in FIG. 3, the imbalance amount of the turbine impeller 11 is substantially offset to the imbalance amount of the compressor impeller 12, resulting in that the imbalance amount of the impeller rotator 21 becomes smaller than conventional art or almost 0.

(18) FIG. 4 is a vertical enlarged sectional view illustrating a site where the shaft is screwed to the nut, that is, a site surrounded by a dot-and-dash line in FIG. 3. When the imbalance amount of the turbine impeller 11 is larger than the imbalance amount of the compressor impeller 12 as represented by length of arrows in FIG. 3, the compensation of the imbalance amount becomes incomplete, so that the imbalance direction of the turbine impeller 11 still remains as the imbalance direction of the impeller rotator 21.

(19) Thus, by plastic-deforming the nut 16 after assembling the impeller rotator 21, the remaining imbalance amount of the impeller rotator 21 is finally eliminated. Such correction of rotational balance is performed by first measuring the imbalance direction of the impeller rotator 21 before plastic deformation to find an imbalance direction u of the impeller rotator 21, and making a marking on the nut 16, and then, caulking one axial end of the nut 16 with reference to the marking on the nut 16. Caulking in the imbalance direction u makes the portion of the nut 16 in the imbalance direction u lost, eliminating imbalance. The imbalance direction u of the impeller rotator 21 and the imbalance amount of the impeller rotator 21 prior to plastic deformation can be calculated by subtracting the imbalance amount of the compressor impeller 12 from the imbalance amount of the turbine impeller 11.

(20) The nut 16 screwed to the one axial end of the shaft 13 has one axial end 16s extending further from the one axial end of the shaft 13 in the one axial direction. The nut 16 is caulked to correct rotational balance of the impeller rotator 21 at the one axial end 16s further from the turbine impeller 11 and the compressor impeller 12. FIG. 5 is a perspective view illustrating an uncaulked nut. FIG. 6 is a perspective view illustrating a caulked nut. By applying a force to the one axial end 16s by use of a caulking tool not shown, a caulked portion 17 is formed on the one axial end 16s, and the nut 16 is plastic-deformed as shown in FIG. 6.

(21) In place of the nuts 16 shown in FIG. 5 and FIG. 6, a nut in a modification example as shown in FIG. 7 may be used. The nut 16 shown in FIG. 7 has a plurality of projections 18, 18, . . . at the one axial end further from the turbine impeller 11 and the compressor impeller 12, which are spaced around the rotary axis O. Such crown-shaped nut 16 is screwed and fastened to the one axial end of the shaft 13, and the projections 18 located in the circumferential direction corresponding to the imbalance direction u of the impeller rotator 21 are bent, thereby correcting rotational balance of the impeller rotator 21.

(22) In the nut 16 in FIG. 8, the projections 18 are provided at the one axial end of the nut 16. Then, in the state where the male screw 13n of the shaft 13 is screwed into and fastened to the nut 16, the projections 18 protrude further from the one axial end of the shaft 13 in the one axial direction. As a result, the projections 18 can be bent in the radial direction without interfering with the one axial end of the shaft 13, preferably eliminating remaining imbalance amount of the impeller rotator 21.

(23) FIG. 8 is a flow chart illustrating a method of assembling the impeller rotator 21 in accordance with an embodiment of the present invention. First, in Step S11, the imbalance direction and the imbalance amount of each of the shaft-equipped impeller 22 and the compressor impeller 12 are measured.

(24) In next Step S12, the shaft-equipped impeller 22 is fastened to the compressor impeller 12 such that the imbalance directions are in opposite phases to have an angle of 180 degrees around the rotary axis O therebetween. Specifically, the shaft 13 is inserted into the center housing 15, allowing the tip region 13e of the shaft 13 to protrude toward one side of the center housing 15, and enter the through hole 12h of the compressor impeller 12. Then, the nut 16 is tightened in the opposite phase state. Thereby, the two impellers 11 and 12 are fastened to each other. The angle of 180 degrees can be achieved by marking the imbalance direction of the shaft-equipped impeller 22 on the outer peripheral face of the shaft-equipped impeller 22 and the imbalance direction of the compressor impeller 12 on the outer peripheral face of the compressor impeller 12, and disposing the markings with 180 degrees therebetween.

(25) In next Step S13, the remaining imbalance amount is calculated by subtracting the imbalance amount of the shaft-equipped impeller 22 from the imbalance amount of the compressor impeller 12. In next Step S14, the nut 16 is plastic-deformed such that the remaining imbalance amount falls within specifications. Preferably, the specification value in Step S14 is a possible lowest value close to 0. Thereby, the remaining imbalance amount of the impeller rotator 21 becomes almost 0, completing correction of rotational balance of the impeller rotator 21.

(26) In this embodiment, because the turbine impeller is connected to the compressor impeller such that the marking of the turbine impeller 11 and the marking of the compressor impeller 12 form an angle of 180 degrees therebetween, the imbalance direction of the turbine impeller 11 and the imbalance direction of the compressor impeller 12 are in opposite phases. Therefore, the remaining imbalance amount after assembling becomes small to achieve the impeller rotator having a good rotational balance.

(27) In this embodiment, because the remaining imbalance amount of the impeller rotator is small, and the remaining imbalance direction of the impeller rotator is identified, only slightly caulking the nut 16 enables correction of rotational balance. Therefore, the correction can be completed using a smaller number of processing steps, which is more advantageous than the conventional rotational balance correcting method including a large cut amount. Moreover, the complicated process of cutting the side of the compressor impeller to correct its rotational balance, and cutting the side of the turbine impeller to correct its rotational balance and then, repeating such cutting until rotational balance of the impeller rotator falls within a proper range can be eliminated, efficiently manufacturing the impeller rotator 21.

(28) Because the nut 16 is plastic-deformed rather than being cut, the nut 16 can be reused to reduce disposal costs of the nut 16.

(29) Although the one axial end 16s of the nut 16 is plastic-deformed as shown in FIG. 6 and FIG. 7, the other axial end not shown of the nut 16 near the compressor impeller 12 may be plastic-deformed. This can prevent loosening of the nut 16. Further, to prevent loosening of the nut 16, an anti-loosening member separated from the nut 16 may be attached to the one axial end of the shaft 13, and the final rotational balance correcting operation after assembling may be performed by plastic-deforming the anti-loosening member. Alternatively, the final rotational balance correcting operation after assembling may be performed by attaching still another member to the outer peripheral face of the shaft 13 and plastic-deforming the member.

(30) In the final rotational balance correcting operation after assembling, one site is processed in FIG. 6 and however, two or three sites that are spaced in the circumferential direction may be processed. The correction of rotational balance is not limited to the correction of one plane of the nut 16, and may be also applied to polyhedral rotators having multiple planes spaced in the axial direction.

(31) Although not shown, the nut 16 and the impeller may be coaxially disposed by providing a first tapered face on the nut 16 and a second tapered face on the impeller in contact with the nut 16, and fastening the nut 16, thereby bringing the first and second tapered faces into contact with each other for tapering engagement. The tapered face of the nut 16 herein is formed, for example, on the inner circumference of the nut or the outer circumference of the nut.

(32) The compressor impeller 12 may be connected to the tip region 13e of the shaft 13 by shrink-fitting or press-fitting an annular member, in place of the nut 16 screwed to the shaft 13, to the one axial end of the shaft 13.

(33) Although the turbo charger provided in the engine has been described in this embodiment, the present invention can be applied to other devices provided with the impeller rotator, for example, a gas turbine. The present invention can be also applied to other rotators such as a motor.

(34) Although the embodiments of the present invention have been described with reference to the figures, the present invention is not limited to the illustrated embodiments. Various changes and modifications can be made to the illustrated embodiments in the same scope as the present invention or in an equivalent scope.

INDUSTRIAL APPLICABILITY

(35) The impeller rotator according to the present invention is advantageously used in a charger of an internal combustion engine.

DESCRIPTION OF REFERENCE SIGNS

(36) 11: Turbine impeller 12: Compressor impeller 13: Shaft 14: Bearing 15: Center housing 16: Nut 17: Caulked portion 18: Projection 21: Impeller rotator 22: Shaft-equipped impeller.