ELECTRIC EXHAUST TURBOCHARGER

Abstract

An electric exhaust turbocharger (10) has a turbine wheel (12), a compressor wheel (14) that is non-rotatably connected to the turbine wheel (12), and an electric drive engine having an engine stator (30) and an engine rotor (54). The engine rotor (54) is fixed to a rotor shaft (52) and is connected non-rotatably to the turbine wheel (12) and the compressor wheel (14) via the rotor shaft (52). The engine rotor (54) is arranged axially between the turbine wheel (12) and the compressor wheel (14) on the rotor shaft (52). Roller bearings (60, 60) are arranged between the engine rotor (54) and the turbine wheel (12) on the one hand and between the engine rotor (54) and the compressor wheel (14) on the other hand. A single separate shaft bearing cassette (40) with a cassette frame (71) supports the two roller bearings (60, 60).

Claims

1. An electric turbocharger (10) comprising: a turbine wheel (12), a compressor wheel (14) that is non-rotatably connected to the turbine wheel (12), and an electric drive engine having an engine stator (30) and an engine rotor (54), the engine rotor (54) being fixed to a rotor shaft (52), and being connected non-rotatably to the turbine wheel (12) and the compressor wheel (14) via the rotor shaft (52), the engine rotor (54) being arranged axially between the turbine wheel (12) and the compressor wheel (14) on the rotor shaft (52), first respective roller bearings (60) being arranged between the engine rotor (54) and the turbine wheel (12), and second roller bearings (60) being arranged between the engine rotor (54) and the compressor wheel (14), and a single separate shaft bearing cassette (40) with a cassette frame (71) supporting the first and second roller bearings (60, 60).

2. The electric exhaust turbocharger (10) of claim 1, wherein the cassette frame (71) comprises first and second bearing segments (70, 74) respectively supporting the first and second roller bearings (60, 60), and an engine segment (72) having a grid structure extending between the first and second bearing segments (70, 74).

3. The electric exhaust turbocharger (10) of claim 2, wherein the engine segment (72) of the cassette frame (71) comprises substantially axially oriented grid bars (46) connecting the first and second bearing segments (70, 74).

4. The electric exhaust turbocharger (10) of claim 3, wherein the engine stator (30) comprises a stator body (34) bearing engine coils (32) and forming pole shoes (34), the pole shoes (34) being arranged between the grid bars (46).

5. The electric exhaust turbocharger (10) of claim 1, wherein the cassette frame (71) is non-ferromagnetic.

6. The electric exhaust turbocharger (10) of claim 1, wherein the cassette frame (71) is comprised of a one-piece main frame section (42) and a one-piece end frame segment (44), the one-piece main frame section (42) forming a first bearing segment (70) and the grid structure, and the one-piece end frame segment (44) forming a second bearing segment (74).

7. The electric exhaust turbocharger (10) of claim 1, wherein the inner shell or outer shell of at least one roller bearing (60, 60) is formed directly from the rotor shaft (52) or directly from the cassette frame (71).

8. The electric exhaust turbocharger (10) of claim 1, further comprising a separate charger housing (20) supporting the engine stator (30) and the shaft mounting cassette (40).

9. The electric exhaust turbocharger (10) of claim 1, wherein the engine rotor (54) is permanently magnetically formed.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0016] FIG. 1 is a schematic longitudinal section of an electric exhaust turbocharger having a separately formed shaft bearing cassette. FIG. 2 is an enlarged longitudinal section of the shaft bearing cassette of FIG. 1.

DETAILED DESCRIPTION

[0017] FIG. 1 shows a longitudinal section of an electric exhaust turbocharger 10 that is symmetrically structured in such a manner that the electric drive engine is axially arranged and approximately centered between a turbine wheel 12 and a compressor wheel 14. The exhaust turbocharger 10 is designed for speeds up to 250,000 rpm, so that high demands are placed on the accuracy of the rotor bearing to ensure long run times.

[0018] The exhaust turbocharger rotor 41 rotates about a rotor axial A and has of a rotor shaft 52 on which a permanently magnetic engine rotor 54 is axially arranged and approximately centered with the turbine wheel 12 on the drive side and the compressor wheel 14 on the compressor side. All of the aforementioned segments of the exhaust turbocharger rotor 41 are non-rotatably connected to each other.

[0019] The rotor shaft 52 is part of a shaft bearing cassette 40 having a two-piece cassette frame 71 that supports two roller bearings 60, 60. A first roller bearing 60 is arranged axially between turbine wheel 12 and the engine rotor 54, and a second roller bearing 60 is axially arranged between the engine rotor 54 and the compressor wheel 14. The two-piece cassette frame 71 has two end bearing segments 70, 74, and each supports one of the roller bearings 60, 60. An engine segment 72 is between the two end bearing segments 70, 74 and has a grid structure in the form of precisely axially oriented grid bars 46 rigidly connecting the two bearing segments 70, 74. The cassette frame 71 is made of a non-ferromagnetic metal, such as aluminum.

[0020] The drive engine includes an annular engine stator 30 that essentially comprises a punch-packed stator body 34 and engine coils 32 supported by the stator body 34. The stator body 34 forms pole shoes 34 that form the electromagnetic stator poles and, when viewed circumferentially, are arranged in the spaces between the grid bars 46. The number of pole shoes 34 therefore corresponds exactly to the number of grid bars 46. In this way, the pole shoes 34 protrude radially close to the engine rotor 54 such that the electromagnetic air gap between the engine rotor 54 and the engine stator can be kept small.

[0021] The cassette frame 71 has two sections, namely, a one-piece main frame segment 42 and a one-piece end frame segment 44. The one-piece main frame segment 42 comprises a first bearing segment 70 and the grid bars 46 of the grid structure. The one-piece end frame segment 44 forms the second bearing segment 74. The cassette frame 71 has ring grooves 90 facing radially outward at its longitudinal ends, and elastic 90 are seated in the ring grooves 90. The cassette frame 71 is supported indirectly over the ring grooves 90 in a separate charger housing 20.

[0022] The charger housing 20 is formed in two parts and comprises a pot-like main housing 22 and a housing cover 24. The pot-like main housing 22 encloses the first bearing segment 70 and the engine segment 72, and the housing cover 24 substantially encloses the second bearing segment 74. The main housing 22 and the housing cover 24 have a fluid-tight connection to each other via a flange connection with threaded screws 25.

[0023] The two roller bearings 60, 60 can be integrated or formed independently. In the embodiment shown in FIG. 1, for both integral bearings 50, the inner raceway 64, 64 is formed from the rotor shaft 52 and the corresponding outer raceway 66, 66 is formed from the main frame section 42 and the end frame section 44 itself. In the embodiment shown in FIG. 2, independent roller bearings that comprise a separate outer shell 67, 67 and inner shell 68, 68 are installed. The roller bearings 60, 60 of both embodiments are ball bearings with bearing balls 62. A spacer sleeve 95, 96 is arranged between the inner roller bearing shell 68, 68 and the engine rotor 54.

[0024] The two ring gaps between the shaft ends of the turbine wheel 12 and the compressor wheel 14 on the one hand and the corresponding opening edges of the shaft openings of the charger housing 20 are sealed in a fluid-tight manner by dynamic shaft seals 15 that prevent the penetration of combustion gases on the side of the compressor wheel 14 into the charger housing interior.