Cast titanium compressor wheel

• US 20020185244A1
• Filed: 05/07/2002
• Published: 12/12/2002
• Est. Priority Date: 06/06/2001
• Status: Active Grant

• Current Assignee: BorgWarner Incorporated
• Original Assignee: Examiner Thai Ba Trieu
• Inventors: Decker, David M., Roby, Steven
• Granted Patent: US 6,629,556 B2
• Time in Patent Office: Days
• US Class Current: 164/35
• CPC Class Codes: B22C 7/02 Lost patterns
• CPC Class Codes: B22C 9/04 Use of lost patterns
• CPC Class Codes: F04D 29/023 especially adapted for elastic fluid pumps
• CPC Class Codes: F04D 29/284 for compressors
• CPC Class Codes: F05D 2230/211 by precision casting, e.g. microfusing or investment casting
• CPC Class Codes: F05D 2300/133 Titanium

Abstract

A compressor wheel is re-designed to permit die inserts (20), which occupy the air passage and define the blades (4, 5) during a process of forming a wax pattern (21) of a compressor wheel, to be pulled without being impeded by the blades. This modified blade design enables the automated production of wax patterns (21) using simplified tooling. These wax patterns (21) can be used in a large-scale investment casting process, and produce an economical cast titanium compressor wheel which performs aerodynamically at high boost pressure/RPM. The compressor wheel improves low cycle fatigue, withstands high temperatures and temperature changes, and permits operation at high boost pressure ratio while, on the other hand, having low weight, low inertial drag, and high responsiveness. The invention further concerns an economical method for operating an internal combustion engine, comprising providing said engine with an easily manufactured, long-life titanium compressor wheel and driving the titanium compressor wheel at high RPM for increasing combustion air throughput and density.

Claims

1. A titanium compressor wheel formed by an investment casting process, and including:

a hub (1) defining an axis of rotation, and

aerodynamic blades (4, 5) carried on the surface of said hub,

wherein said titanium compressor wheel is formed by investment casting in a mold,

wherein said mold is formed by a lost wax process around a compressor wheel pattern (21), and

wherein said compressor wheel pattern is formed by casting a sacrificial material into a die comprised of a plurality of die inserts (20), followed by extracting said die inserts (20) radially or along a curve to expose said compressor wheel pattern.

2. A titanium compressor wheel as in claim 1, wherein air passages are defined between said blades, and wherein said die comprises one die insert (20) per air passage.

3. A titanium compressor wheel as in claim 2, wherein said die inserts are extracted simultaneously.

4. A titanium compressor wheel as in claim 1, wherein air passages are defined between said blades, and wherein said die comprises at least a first and a second die insert (20, 20′

) per air passage.

5. A titanium compressor wheel as in claim 4, wherein said first die inserts (20) are extracted simultaneously and said second die inserts (20′

) are subsequently extracted simultaneously.

6. A titanium compressor wheel as in claim 1, wherein said aerodynamic blades comprise alternating full blades (4) and splitter blades (5).

7. A cast titanium compressor wheel comprising:

an annular hub (1), and

a plurality of blades (4, 5), each blade including a leading edge (18), an outer edge adapted for close passage to a compressor housing, and a trailing edge (16),

wherein said leading edge (18) is substantially a straight edge,

wherein said blades (4, 5) are designed such that a single die insert (20) defining the space between adjacent blades can be inserted between adjacent blades and retracted along a radial or curved path.

8. A cast titanium compressor wheel as in claim 7, wherein said compressor wheel is comprised of a material selected from titanium and titanium-aluminum alloy.

9. A cast titanium compressor wheel comprising:

an annular hub (1), and

a plurality of blades (4, 5), each blade including a leading edge (18), an outer edge adapted for close passage to a compressor housing, and a trailing edge (16),

wherein said leading edge (18) is substantially a straight edge,

wherein said blades are designed such that a compound die insert comprising first and second die inserts (20, 20′

) defining one air passage between adjacent blades (4, 5) can be inserted between adjacent blades, and wherein said first and second die inserts (20, 20′

) can be retracted along a radial or curved path.

10. A method for operating an internal combustion engine, comprising providing said engine with an titanium compressor wheel and driving the titanium compressor wheel with a trailing edge tip speed of up to 725 m/s for increasing combustion air throughput and density.

11. A method as in claim 10, wherein said titanium compressor wheel is driven with a trailing edge tip speed of up to 750 m/s.