Supercharging air compressor for an internal combustion engine, internal combustion engine and method for that purpose

1. A method for cooling a supercharging air compressor for an internal combustion engine, in which a partial stream of supercharging air which is compressed in the supercharging air compressor is branched off downstream of a compressor wheel, a temperature of the partial stream is reduced and the partial stream is then fed back, as cooling air, to a compressor inlet duct upstream of the supercharging air compressor duct, wherein the temperature reducing unit is a diffuser for diffusing the partial stream.

2. The method as claimed in claim 1 , wherein the magnitude of the partial air stream is adjustable.

3. A method for cooling a supercharging air compressor for an internal combustion engine, comprising the steps of:

extracting a partial stream of compressed supercharging air discharged from the compressor into a passage connecting a compressor outlet with a compressor inlet;

reducing the temperature of the compressed supercharging air in a temperature reducing unit in the connecting passage between the compressor outlet and the compressor inlet, wherein the temperature reducing unit is a diffuser for diffusing the partial stream; and

discharging the reduced-temperature partial stream to the compressor inlet upstream of a compressor wheel of the compressor.

4. An internal combustion engine having a supercharging air compressor in an intake tract, and a temperature reducing unit which is arranged downstream of a compressor wheel, an inlet duct being arranged to receive a partial stream of supercharging air which has been compressed by the compressor wheel, wherein the partial stream is fed, as cooling air, to the inlet duct upstream of the supercharging air compressor after the partial stream has flowed through the temperature reducing unit, wherein the temperature reducing unit is a diffuser for diffusing the partial stream.

5. The internal combustion engine as claimed in claim 4 , wherein a supercharging air cooler is arranged downsteam of the supercharging air compressor in the intake tract, and wherein the partial stream of the compressed supercharging air branches off downstream of the supercharging air cooler and is fed to the temperature reducing unit.

6. The internal combustion engine as claimed in claim 4 , wherein the supercharging air compressor is part of an exhaust gas turbocharger with an exhaust gas turbine which is arranged in an exhaust gas tract and which drives the compressor wheel via a shaft.

7. A supercharging air compressor for an internal combustion engine, having a compressor wheel which is rotatably mounted in a compressor inlet duct and arranged to receive combustion air via the compressor inlet duct, said compressor inlet duct being arranged to receive a partial stream of supercharging air which has been compressed by the compressor wheel, the partial stream having branched off downstream of the compressor wheel and fed to a temperature reducing unit prior to being fed to the compressor inlet duct, wherein the temperature reducing unit is a diffuser for diffusing the branched-off partial stream.

8. The supercharging air compressor as claimed in claim 7 , wherein the temperature reducing unit is connected to a compressor housing.

9. The supercharging air compressor as claimed in claim 7 , wherein the flow outlet of the temperature reducing unit is connected to a supplementary duct which opens into the compressor inlet duct adjacent to the compressor wheel.

10. The supercharging air compressor as claimed in claim 9 , wherein the supplementary duct is part of a characteristic-diagram-stabilizing measure in the compressor housing.

11. A supercharging air compressor for an internal combustion engine, comprising:

a compressor housing;

a compressor wheel rotatably mounted in a compressor inlet duct of the housing which receives combustion air from the compressor inlet duct and discharges compressed supercharging air to a compressor outlet; and

a passage connecting the compressor outlet to the compressor inlet duct via a temperature reducing unit therebetween for passing a partial stream of the compressed supercharging air through the temperature reducing unit to the compressor inlet duct,

wherein the temperature reducing unit is a diffuser for diffusing the partial stream.

12. A supercharged internal combustion engine, comprising:

an internal combustion engine;

a supercharger compressor housing disposed in an intake air passage of the engine;

a compressor wheel rotatably mounted in a compressor inlet duct of the housing which receives combustion air from the inlet duct and discharges compressed supercharging air through a compressor outlet; and

a passage connecting the compressor outlet to the compressor inlet duct via a temperature reducing unit therebetween for passing a partial stream of the compressed supercharging air through the temperature reducing unit to the compressor inlet duct,

wherein the temperature reducing unit is a diffuser for diffusing the partial stream.