Electric motor assisted turbocharger

Abstract

A turbocharger comprises a turbine wheel and a compressor wheel mounted to a turbocharger shaft. An electric induction motor is provided for assisting rotation of the compressor wheel in predetermined circumstances. The motor comprises a fixed stator having motor field coils which generate a rotating magnetic field when energised by an AC control signal which induces eddy current flow in a rotor to generate a rotor magnetic field which in turn interacts with the stator magnetic field producing torque in the rotor.

Description

CROSS REFERENCE TO RELATED APPLICATIONS[0001]This application is a continuation of U.S. patent application Ser. No. 12 / 927,913 filed Nov. 29, 2010 and now abandoned, which is a continuation of U.S. patent application Ser. No. 11 / 894,265 filed Aug. 20, 2007 and now abandoned, which is a continuation of U.S. patent application Ser. No. 10 / 768,358 filed Jan. 30, 2004 and issued as U.S. Pat. No. 7,296,409 which claims priority to British Patent Application No. 0302235.7 filed Jan. 31, 2003, the entire contents of each application hereby being incorporated by reference in its entirety.BACKGROUND OF THE INVENTION[0002]This invention relates to an electric motor assisted turbocharger, and in particular to a turbocharger for an internal combustion engine.[0003]Turbochargers are well known devices for supplying air to the intake of an internal combustion engine at pressures above atmospheric (boost pressures). A conventional turbocharger essentially comprises an exhaust gas driven turbine wh...

AI Technical Summary

Benefits of technology

[0013]Since induced eddy currents are relied upon to produce the rotor magnetic field, the rotor may have an advantageously simple structure and may for instance comprise a unitary solid member. Since the motor is an induction motor commutation is not required. Moreover, since the motor is asynchronous there is no requirement to provide a variable AC control frequency in order to vary the rotational speed of the motor. These and other advantages of the present invention are described in more detail below.

[0015]This particular rotor and stator coil configuration enhances the efficiency of the motor in the manner described below. This improved motor may be used in applications other than the power assistance of turbochargers.

Problems solved by technology

However, there are other conditions, such as at engine start up or transient conditions such as a sudden requirement for a high load from the engine, in which the energy in the exhaust gas is not sufficient to enable the turbocharger to deliver the required air supply to the engine quickly enough.

Modern engines are designed to reduce engine fuelling in such circumstances to avoid high levels of exhaust emissions through incomplete combustion, and accordingly engine response suffers during such transient or other conditions.

A disadvantage of the synchronous motor is that relatively complicated control electronics are required as the excitation frequency of the stator coils must always be matched to the rotational speed of the turbocharger, so that both a variable frequency control signal and means for monitoring the speed of the turbocharger are required.

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