Title of Invention

"COMPRESSOR OF A TURBOCHARGER AND METHOD OF MANUFACTURING THEREOF"

Abstract Compressor wheel (16) and techniques for manufacturing such a wheel are provided. The wheel may include a hub (21) with a counterbore (36) internally treated to impart residual compressive stresses for enhanced endurance to stress-induced fatigue. The surface treatment allows extending the coutnerbore relatively closer to a plane (30) of typical maximum stress of the wheel. This design flexibility advantageously allows avoiding or reducing overhang of the compressor wheel, thereby improving rotor dynamics and reducing the axial length of the hub, and the overall foot print of the compressor wheel. FIG. 2
Full Text The present invention relates to a turbocharger compressor wheel having a counterbore treated for enhanced endurance to stress induced fatigue. More particularly the present invention relates to method of manufacturing of said compressor wheel.
TECHNICAL FIELD
The field of the relates to compressor wheels or impellers as maybe used in a turbocharger, supercharger and the like.
BACKROUND ART
Locomotives equipped with internal combustion engines, e.g. diesel engines, designed to meet stringed emission regulations may require relatively high air flow rates and high manifold pressures, as may be provided by a turbocharger, to meet air quality targets while maximizing fuel economy and reliability. The high boost ratios, typically 3.8 or higher, may require high tip speeds on a turbocharger compressor wheel, which may lead to high levels of tensile stress in a bore area and shortened wheel life due to low cycle fatigue. It is known that compressor wheels have used a through bore that extends through the center of the wheel along a rotation axis, and where the wheel may be securely mounted onto a shaft with a locking nut.
It is further known that so called boreless compressor wheels are able to rotate at higher speeds than compressor wheels having a through bore since a through bore removes load carrying material and thereby increases the stress level in the remaining material. That is, m ore wheel material exists at a point of maximum centrifugal load that results in higher load carrying capability.
In one known compressor wheel, a hub section of the compressor wheel that axially corresponds with the radially outermost portion of the wheel experiences the maximum centrigufal load. That is, a plane indicative of typical maximum stress exists in substantial axial alignment with the maximum radial extends of the hub. In this known compressor wheel, a threaded counterbore is provided in a hub extension for receiving the shaft. However, the counterbore must terminate well short of the plane indicative of typical maximum stress to avoid the high level of stress at that

location. Since the length of the shaft/threaded interface is generally constant for any given application, the foregoing arrangement (that causes the designer to position such an interface away from the high stress plane) may result in excessive overhang of the compressor wheel. This detrimentally affects rotor dynamics and increases the axial length of the hub extension, thus increasing the overall footprint of the compressor wheel and turbocharger.
BRIEF DESCRIPTION OF THE INVENTION
Aspects of the present invention propose to improve compressor life by using a hub with a counterbore including a base surface treated to impart residual compressive stresses for enhanced endurance to stress-induced fatigue. The surface treatment allows extending the counterbore relatively closer to a plane indicative of typical maximum stress. This design flexibility advantageously allows avoiding or reducing overhang of the compressor wheel, thereby improving rotor dynamics and reducing the axial length of the hub, and the overall foot print of. the compressor wheel and turbocharger.
Generally, the present invention fulfills the foregoing needs by providing in one aspect thereof, a method of manufacturing a compressor wheel. The method allows providing a hub extension of the compressor wheel that defines a counterbore. The method further allows imparting residual compressive stresses to a base surface of the counterbore.
In another aspect thereof, the present invention further fulfills the foregoing needs by providing a compressor wheel comprising a hub including a hub extension that defines a counterbore. The counterbore includes a base surface and the base surface of the counterbore is treated to impart residual compressive stresses thereto.
BRIEF DESCRIPTION OF THE DRAWINGS
The features and advantages of the present invention will become apparent from the following detailed description of the invention when read with the accompanying drawings in which:
, FIG. 1 illustrates a cutaway view of an exemplary turbocharger that may benefit from Ihe teachings of the present invention.
FIG. 2 shows a cross-sectional view of an exemplary compressor wheel embodying aspects of the present invention.
FIG. 3 shows configurational details regarding the compressor wheel of FIG. 2 that allow positioning a mounting counterbore relatively closer to a plane indicative of typical maximum stress of the wheel.
FIG. 4 shows a rotatable shaft assembled into a counterbore embodying aspects of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 shows a cutaway view of an exemplary turbocharger (10) that may benefit from the teachings of the present invention. Turbocharger (10) generally comprises respective compressor and turbine stages (12) and (14) including a compressor wheel (16) and a turbine wheel (18) coupled through a rotatable shaft (20). The turbine wheel (18) is disposed within a turbine housing, which includes an inlet for receiving exhaust gases from an internal combustion engine (not shown). The turbine housing guides the engine exhaust gases for communication with and expansion through the turbine wheel (18) for rotatably driving the turbine wheel. Simultaneously, the turbine wheel rotatably drives the shaft (20) and compressor wheel (16), as may be disposed within a compressor housing. The compressor wheel (16) and housing allow drawing in and compressing ambient air for supply to the intake of the engine.
Referring to FIG. 2, a cross-sectional view of an exemplary embodiment of the compressor wheel (16) is shown. Compressor wheel (16) includes a hub portion (21). The hub portion (21) defines a front face surface (22) for the compressor wheel (16), and supports a plurality of circumferentially spaced apart compressor blades (23) (only iwo of which are visible in FIG. 2) extending both radially outwardly and axially thereon. The hub portion (21) also includes a radially enlarged disc-like portion (24) which serves to support the compressor blades (23) as well as to define a
floor surface (25) for the airflow channels defined between blades (23). The disc-like portion (24) also defines a radially outer circumferential surface (26) for hub (21), as well as an axially disposed back side or back face surface (27).
As will be recognized by those skilled in the pertinent art, in operation of compressor wheel (16), a plane indicative of typical maximum stress (30) typically exists substantially in axial alignment with the maximum radial extent of the hub (21). That is, the plane of maximum stress (30) is typically coincident with surface 26 and reaches a maximum at the point where the rotation axis (34) transects plane (30), approximately at point (31).
To avoid the undesirable stress concentration of a conventional through bore and
preserve the strength of solid metal adjacent to point (31), compressor wheel (16)
includes a hub extension (38) integrally defined by hub (21) and extending axially
away from plane (30). Hub extension (38) defines an axially extending counterbore
(36). , .
The inventors of the present invention have innovatively recognized that one may advantageously improve rotor dynamics as well as reduce the axial length of the compressor wheel when a base surface (40) of counterbore (36) is treated to impart residual compressive stresses to such a base surface. Examples of techniques, such as cold working techniques, that may be used to treat the counterbore base surface may comprise shot peening, laser peening, glass beading, roll burnishing, etc. Cold working provides plastic deformation of a metal (e.g., aluminum) below its annealing temperature to cause permanent strain hardening.
Peening, as understood in the art and as used herein, means to compress a portion of a surface by forming a depression or indentation on the surface. Peening equipment generally is utilized to create a compressively stressed protection layer at the outer surface of a workpiece. The protection layer considerably increases the resistance of the workpiece to fatigue failure. A shot used in shot peening may comprise spherical particles constructed from a hard metal or any other suitable material. With shot peening systems, a stream of shot particles traveling at a high velocity is directed at an
outer surface of a workpiece, e.g., the base of the counterbore. Each shot particle that impacts with sufficient force upon the outer surface of the workpiece causes plastic deformation of the surface and a dimple is formed therein. In this manner, a compressively stressed layer is formed at the outer surface of the workpiece to increase fatigue strength of the workpiece.
In laser peening, a laser beam from a laser beam source is used to produce a strong localized compressive force on a surface. Laser peening may be utilized in lieu of shot peening to create a compressively stressed protection layer at the outer surface of a workpiece. This type of treatment also considerably increases the resistance of the workpiece to fatigue failure. Thus, peening is typically a very effective means for producing surface compression residual stress, and therefore, prolonging the useful life of the workpiece.
As shown in FIG. 3, the surface treatment of the base of the counterbore allows extending the base surface (40) of counterbore (36) relatively closer to the plane (30) indicative of typical maximum stress. This is exemplarily illustrated in FIG. 3 by the representation of the counterbore base (40') relative to the representation of the counterbore base (40). This design flexibility advantageously allows avoiding or reducing overhang of the compressor wheel, thereby improving rotor dynamics and reducing the axial length of the hub extension, and the overall foot print of the compressor wheel and turbocharger. For example, assuming the base (40) of counterbore (36) is configured to extend a distance L towards plane (30), this would allow reducing the axial length of the hub extension (38) by distance L.
In yet another aspect of the invention, as may be appreciated in FIG. 4, the extended base (40) of the counterbore allows deeper penetration of shaft (20) relative to the plane (30) of typical maximum tensile stress, thereby reducing axial overhang of the compressor wheel. In one exemplary embodiment, counterbore (36) includes alignment pilots (42) disposed to facilitate the centering of the shaft (20) received in counterbore (36). That is, alignment pilots (42) are configured to minimize eccentrity of shaft (20) relative to the walls of the counterbore. As will be appreciated by those
skilled in the art, the compressor wheel, shaft, and thrust collar (44) may rotate relative to a bearing configured to provide radial support to .the rotating structures.
While the preferred embodiments of the present invention have been shown and described herein, it will be obvious that such embodiments are provided by way of example only. Numerous variations, changes and substitutions will occur to those of skill in the art without departing from the invention herein. Accordingly, it is intended that the invention be limited only by the spirit and scope of the appended claims.







We claim:
1. A compressor wheel comprising:
a hub (21) including a hub extension (38) that defines a counterbore (36), characterized in that said counterbore including a base surface (40) not extending through a plane indicative of typical maximum tensile stress of the compressor wheel, wherein the base surface of said counterbore is treated to impart residual compressive stresses thereto.
2. The compressor wheel as claimed in claim 1, wherein the hub and hub extension comprise an integral structure.
3. A method of manufacturing a compressor wheel (16), the method comprising:
providing a hub extension (38) on a hub (21) of the compressor wheel, the hub extension defining a counterbore (36);
characterized in that the counterbore does not extend through a plane (30) indicative of typical maximum tensile stress of the compressor wheel, and in that the method further comprises imparting residual compressive stresses to a base surface (40) of the counterbore.
4. The method as claimed in claim 3 comprising configuring the counterbore to extend its base surface towards the plane (30) indicative of typical maximum tensile stress of the compressor wheel.
5. The method as claimed in claim 4 comprising reducing the axial length of the hub extension based on the distance that the base surface of the counterbore is extended towards the plane indicative of typical maximum tensile stress of the compressor wheel.
6. The method as claimed in claim 3, wherein the imparting of residual compressive stresses to the base surface of the counterbore is selected from the
group consisting of shot peening, laser peening, roll burnishing, and glass beading said surface.
7. A method for reducing the axial length of a compressor wheel, the method
comprising:
providing a hub extension (38) on a hub (21) of the compressor wheel, the hub extension defining a counterbore (36); characterized in that the method comprises:
imparting residual compressive stresses to a base surface (40) of the counterbore;
extending the base surface of said counterbore towards a plane indicative of typical maximum tensile stress of the compressor wheel; and
reducing the axial length of the compressor wheel based on the distance that the base surface of the counterbore is extended towards the plane indicative of typical maximum tensile stress.
8. The method as claimed in claim 7 wherein the imparting of residual compressive stresses to the base surface of the counterbore is selected from the group consisting of shot peening, laser peening, roll burnishing, and glass beading said surface.
9. The method as claimed in claim 7 comprising mounting a rotatable shaft (20) into the counterbore, wherein the extended base surface of said counterbore allows deeper penetration of said shaft relative to the plane indicative of typical maximum tensile stress
10. A turbocharger for an internal combustion engine, said turbocharger comprising:
a compressor wheel (16);
a hub (21) in said compressor wheel, the hub including a hub extension (38) that defines a counterbore including a base surface (40); and a rotatable shaft (20) mounted in the counterbore;
characterized in that the base surface of said counterbore is treated to impart residual compressive stresses thereto, and further wherein the base surface of said counterbore is configured to extend towards a plane (30) indicative of typical maximum tensile stress of the compressor wheel; and
wherein the extended base surface of said counterbore allows deeper penetration of said shaft relative to the plane indicative of typical maximum tensile stress.


Documents:

884-DELNP-2006-Abstract-(03-09-2009).pdf

884-delnp-2006-abstract.pdf

884-delnp-2006-assaignment.pdf

884-DELNP-2006-Claims-(03-09-2009).pdf

884-delnp-2006-claims.pdf

884-delnp-2006-correspondence -others.pdf

884-DELNP-2006-Correspondence Others-(23-03-2011).pdf

884-DELNP-2006-Correspondence-1.pdf

884-DELNP-2006-Correspondence-Others (17-02-2010).pdf

884-DELNP-2006-Correspondence-Others-(03-09-2009).pdf

884-delnp-2006-Correspondence-Others-(26-02-2010).pdf

884-DELNP-2006-Description (Complete)-(03-09-2009).pdf

884-delnp-2006-description (complete).pdf

884-delnp-2006-drawings.pdf

884-DELNP-2006-Form-1-(03-09-2009).pdf

884-delnp-2006-form-1.pdf

884-DELNP-2006-Form-18.pdf

884-DELNP-2006-Form-2-(03-09-2009).pdf

884-delnp-2006-form-2.pdf

884-DELNP-2006-Form-27-(23-03-2011).pdf

884-DELNP-2006-Form-3.pdf

884-DELNP-2006-Form-5-(03-09-2009).pdf

884-delnp-2006-form-5.pdf

884-DELNP-2006-GPA-(03-09-2009).pdf

884-delnp-2006-pct-101.pdf

884-DELNP-2006-PCT-210.pdf

884-delnp-2006-pct-237.pdf

884-delnp-2006-pct-304.pdf

884-delnp-2006-pct-311.pdf

Claims-(26-02-2010).tif


Patent Number 242899
Indian Patent Application Number 884/DELNP/2006
PG Journal Number 39/2010
Publication Date 24-Sep-2010
Grant Date 17-Sep-2010
Date of Filing 20-Feb-2006
Name of Patentee GENERAL ELECTRIC COMPANY
Applicant Address ONE RIVER ROAD, SCHENECTADY, NY 12345 USA.
Inventors:
# Inventor's Name Inventor's Address
1 FURMAN ANTHONY HOLMES 1007 ARAPAHO PATH, SCOTIA, NY 12302 USA.
2 SWENSON KENDALL ROGER 5334 FRAZIER STREET, ERIE, PA 16510 USA.
3 LORINGER DANIEL EDWARD 2253 GATESMILL DRIVE, ERIE, PA 16510 USA.
PCT International Classification Number F04D 29/26
PCT International Application Number PCT/US2004/024768
PCT International Filing date 2004-08-02
PCT Conventions:
# PCT Application Number Date of Convention Priority Country
1 10/650,839 2003-08-28 U.S.A.