Turbo Charger II

Abstract

A turbocharger includes a compressor arrangement for compressing fresh air for internal combustion engines, containing a compressor wheel as well as an electric motor with a rotor and stator. A rotor magnet of the rotor is designed such that it is partially or completely integrated into the compressor wheel, and the smallest diameter of the stator is 1.5- to 8-times the size of the largest outer diameter of the rotor. The turbocharger has a very spontaneous response behaviour in the transient range, as well as the possibility of an exact real-time regulation of the mass flow. It furthermore renders possible the energy recovery and this contributes to increasing the total efficiency.

Description

The invention relates to a turbocharger.

Internal combustion engines with turbochargers are basically known in the motor vehicle sector. Typically, an exhaust gas flow out of the combustion engine is used to drive a turbine wheel. This turbine wheel for example is coupled via a shaft to a compressor wheel which ensures a compression of supplied fresh air in the combustion space. Such a precompression or “charging” leads to an increased engine power or increased torque compared to conventional internal combustion engines. However, with internal combustion engines charged in such a manner, there exists the problem of the so-called “turbolag”, which in particular occurs on running up and accelerating from low rotational speeds of the vehicle, thus when the internal combustion engine is to be rapidly accelerated into regions of increased power. This is due to the fact that the increased air quantity requirement on the air feed side may only be provided with some delay (amongst other things caused by the inertia of the system of the turbine wheel and compressor wheel).

It is therefore the object of the present invention, to provide a turbocharger which supplies precisely the correct quantity of fresh air with the smallest possible delay, and which furthermore is simple in its construction and is susceptible to trouble as little as possible.

This object is achieved by the subject-matters of the independent patent claims.

The invention relates to a turbocharger with a compressor arrangement for compressing fresh air for internal combustion engines, containing a compressor wheel as well as an electric motor with rotor and stator, wherein a rotor magnet of the rotor is designed such that it is partially or completely integrated into the compressor wheel (thus the rotor magnet or rotor on the one hand, and the compressor wheel on the other hand are connected to one another) and the smallest inner diameter of the stator is 1.5- to 8-times as large as the largest outer diameter of the rotor. The specified lengths here, in each case relate to the largest extensions or smallest extensions of the participating elements, however only in the region of the electrically or magnetically effective elements, i.e. for example only over a length of the rotor magnet.

“Turbochargers” in the context of the present invention are to be understood as all means which may lead precompressed air to an internal combustion engine, by which means a larger air mass gets into the combustion space. (A classic compressor wheel-turbine wheel coupling is therefore not absolutely necessary).

The invention further relates to a turbocharger containing at least one compressor wheel, wherein the compressor wheel may be driven via at least one electric motor, and the electric motor comprises a rotor, a stator, as well as a rotor gap between the rotor and the stator, and the rotor gap is designed such that with a rotating compressor wheel, at least 50%, preferably at least 90% of the air mass flow to be compressed is led through the rotor gap.

The mentioned percentage numbers in each case specify minimum ranges. The percentage numbers here apply basically to the whole rotational speed range of the turbocharger or an internal combustion engine connected thereto.

In a particularly advantageous further formation, the complete airflow which is led to the respective compressor wheel, is led through this rotor gap.

The limitation with regard to the numerical values, amongst other things, has the purpose of accordingly ruling out undesired or “coincidental” leakage flows, as could occur in the state of the art. A “recirculation flow” between the rotor and the stator with subject-matter according to the state of the art, with which the rotor is attached to the outer side of the compressor wheel, very close to the stator, should however not be seen as an “air mass flow to be compressed”, since such “recirculation air” strictly speaking has already passed the compressor wheel.

What is advantageous is an “integral” construction form, with which a large part of the air mass flow to be compressed or even the complete air mass flow to be compressed, is led to the at least one compressor wheel through the rotor gap.

In contrast to the attachment of rotors on the radial outer sides of the compressor wheel, it is advantageous to arrange the rotor or its magnetically effective parts as close as possible to the rotation axis of the compressor wheel. This on the one hand is very favourable from a mechanical point of view with quickly running turbochargers, since here, under certain circumstances, mechanical damage could occur due to the very high and rapidly changing centrifugal forces. What is also advantageous is the fact that the rotation moments of inertia may be kept relatively small in this manner, since magnets lying radially at the outside usually have a high specific weight and thus a very high rotation moment of inertia. The instationary behaviour of the compressor may be considerably improved by way of this. Added to this is the fact that with magnets lying at the outside on the compressor wheel, these are also thermally loaded to a greater extent, since larger temperature increases arise at these outer sides due to the compression work, which in turn may have a negative effect on the life duration of the magnets or the rotor.

Turbochargers are known from the literature, which are used for the production of electricity. These turbochargers are designed as small gas turbines and likewise have a turbine as well as a rigidly coupled compressor. A conventional generator for the production of electricity is flanged on the rotor shaft of the turbine. The generator represents a very high flow resistance since it is arranged within the intake tract, and this flow resistance reduces the efficiency, and very high loads on the bearing components simultaneously occur.

One advantageous further design of the turbocharger according to the invention envisages this being used as a microturbine for the power/heat cogeneration or the power/cooling cogeneration. Thereby, the combustion air flows between the rotor and stator of the electric motor/generator into the compressor, and is compressed there and thus preheated to approx. 200° C. The preheated, compressed air is brought to a higher temperature level by the hot exhaust gas in a heat exchanger. The compressed, warm air together with a fuel e.g. regenerative gas, is combusted in a combustion chamber which is arranged downstream. The hot gases which thus arise, are expanded in the turbine and drive the turbine wheel and thus the compressor as well as the generator. The thermal energy of the exhaust gas, in the heat exchanger, is partly directly dispensed to the compressed combustion air. Furthermore, this turbocharger according to the invention may be coupled to a second heat exchanger, in order to utilise the total residual heat for the production of warm water, or to lead it to a heating circuit e.g. for the heating and cooling a building. The generator may be used as an electric motor for starting the process. Thus for example, the inexpensive small block-type thermal power stations may be produced with the turbocharger according to the invention, whose essential components consist of components manufactured on a large scale.

One advantageous further design envisages the mass of the rotor magnets being between 5 g and 1000 g, preferably between 10 g and 100 g for motor vehicle turbochargers. The mass moment of inertia of the magnetically (actively) effective mass of the electric motor with respect to the rotation axis of the rotor here is between 0.1 kgmm² and 10 kgmm², preferably between 0.3 kgmm² and 1.0 kgmm², for motor vehicle applications.

Thus masses as well as mass moments of inertia of the electrically or magnetically effective motor components are small on account of the fact that relatively large air gaps are possible with the rotor gap according to the invention, and a very homogonous field arises despite this.

A further advantageous design envisages the compressor wheel being mounted on a shaft and containing blades, wherein the front edges of the blades (thus the section of the compressor wheel on which the air first impinges), in the air inlet flow direction, lie upstream with respect to a magnetically effective front section of the rotor and/or a magnetically effective front section of the stator.

This thus means that the active components of the electric motor (rotor or stator) are arranged axially even more towards the air inlet, and the actual compressor wheel is arranged downstream. Amongst other things, by way of this, it is possible to lead the entire inlet air to be led to the compressor wheel, through the rotor gap.

However with regard to design, it is possible to apply the rotor into the compressor wheel or even on the side of the compressor wheel which faces the turbine wheel, in order to reduce the bending moment on the compressor wheel, but despite this, to primarily lead the air mass flow to be compressed, through the rotor.

A mixed construction of several different rotor magnets at different locations of the compressor wheel (in front of, within and/or behind) permits an optimisation of the necessary construction space with a simultaneous optimization of the motor torque, and a reduction of the bending load of the impeller shaft. Thereby, the shape of the rotor/stator does not necessarily have to be circularly cylindrical, but is may also be adapted to the shape of the compressor wheel.

The invention furthermore envisages a method for operation of the turbocharger according to the invention. The turbocharger, as mentioned above, comprises at least one compressor wheel for compressing air, and the compressor wheel may be driven by an electric motor, wherein a rotor gap is arranged between the rotor and the stator of the electric motor, and at least 50%, particularly preferably at least 90% of the air mass flow led to the compressor wheel, is led through the rotor gap in at least one operating condition of the turbocharger.

This “operating method” is already mentioned in the device claims, and that which is mentioned there accordingly applies to the operating method claimed here. What is important is that the proportionate air mass flows of at least 50% or at least 90% or even 100% mentioned above may be achieved in normal operation of the turbocharger, for example in an operating condition, with which the rotational speed of the compressor wheel is between 5000 and 300000 r.p.m, preferably between 40000 and 200000 r.p.m, or also the rotational speed of a connected combustion engine is between 50 and 200000 r.p.m, preferably between 100 and 15000 r.p.m with reciprocating engines.

It should be mentioned once again that a “turbocharger” in the context of the present invention does not necessarily have to contain a turbine wheel driven by an exhaust gas flow. What is important is merely that at least one compressor wheel (driven by whatever means) is contained for leading precompressed combustion air to a combustion engine in the “turbocharger”.

In a further design, the turbocharger according to the invention contains a turbine wheel as well as a compressor wheel connected thereto, wherein an electric motor is provided on the side of the compressor wheel which is distant to the turbine wheel, and a rotor of the electric motor which is connected to the compressor wheel in a rotationally fixed manner, is designed in a freely projecting manner.

Given an increased fresh air demand (e.g. ascertained by control electronics), the electric motor serves for an additional acceleration of the compressor wheel by the electric motor. Electric motors are favourable for this, since these may be accelerated with a large torque without a noticeable run-up delay.

It is further advantageous that the electric motor in the present case is not arranged between the turbine wheel and the compressor wheel. Such an arrangement would lead to thermal problems and represents a large design modification from conventional (purely mechanical) turbochargers. Apart from the increased design effort, the repair effort with such constructions is considerable.

It is advantageous (but also not necessary within the framework of the invention) that a sequence “turbine wheel, shaft (mounting), compressor wheel, electric motor” seen in the axial direction, is given in the present case. The electric motor is then subjected only to the temperature of the surroundings, so that a thermal decomposition of the stator winding etc. may not occur.

One advantage lies in the freely projecting end on the other side of the compressor wheel. The rotor of the electric motor is attached here. It is possible, but not absolutely necessary, to attach a further bearing location here, in order to thus mount the rotor on both sides. Such a bearing location on the one hand, under certain circumstances, may upset the electrical characteristics of the electric motor and under certain conditions would represent a static redundancy. Furthermore, the friction work in the system is increased. Moreover, under certain circumstances, the supply of fresh air is also hindered by such a bearing, since suitable struts/members reduce the inlet air opening in size towards the compressor wheel. Such a bearing location, i.e. a mounting of the compressor wheel axial on both sides, is however also easily possible.

Furthermore, the design difference to purely mechanical turbochargers is conceivably small with the “projecting” rotor, so that an electric motor may be supplemented on conventional turbochargers in this way, and in a very inexpensive, modular and easily repairable manner.

The drive system according to the invention, apart from the inventive turbocharger, comprises an internal combustion engine. An “internal combustion engine” in the context of the present invention is to be understood as any motor which requires fresh air/fresh gas as well as produces exhaust gas, so that a suitable turbocharger may be applied here. Furthermore, the drive system also comprises a storage device for electrical energy. Here, preferably the electric motor of the turbocharger is connected to the storage device for electrical energy, for the removal of electrical energy in a motor operation of the turbocharger, and for feeding electrical energy in a generator operation of the turbocharger.

The exhaust gas is blown away unused by up to 30% in many operating conditions of a turbocharger (e.g. full load, thrust operation etc.). The energy of this excess exhaust gas may be energetically additionally utilised with the described embodiment of the turbocharger, by way of using the electric motor as a generator. In this manner, on the one hand excess “thermal/kinetic energy” may be recovered as electrical energy, and the energy balance of the drive system is considerably improved by way of this. Ideally, the turbocharger may even be designed such that the combustion engine located in the vehicle no longer requires any additional dynamo.

It is also particularly advantageous with this drive system, if the electric motor of the turbocharger or the electrical storage device connected to it, may be additionally connected to an electromotoric drive of a motor vehicle. This electromotoric drive may for example be a hub electric motor (or another electric motor provided in the drive train), which is fastened on a drive wheel of the motor vehicle. In this manner, an additional provision of torque or motor power is achieved on accelerating, in modern so-called “hybrid vehicles”, since apart form the internal combustion engine motor, it is also the electrical hub motors which are responsible for the acceleration. A braking effect and thus a recovery of kinetic energy into electrical energy may be achieved with braking procedures by way of the switch-over of the electrical hub motors into generator operation, and this electrical energy is intermediately stored in a suitable storage device. If the electric motor of the turbocharger is now connected to this storage device, then the complete electrical energy may be “managed” in a central manner, in order to be able to fall back on this at any time, in a useful manner.

Apart from this, it is of course also possible for the turbocharger system and the electrical hub motors (or other motors in the drive train), to have electrical storage devices which are independent of one another.

The turbocharger according to the invention is furthermore also suitable for the application in electricity production installations which may be modulated and which may be operated with fuels such as natural gas, liquid gas, heating oil as well as regenerative gases such as bio-gas, sewage gas and waste gas, or solid fuels such a chopped word, pieced wood material, straw, etc. One may realise inexpensive installations for energy production with a high efficiency by way of this type of power/heat cogeneration. The turbocharger according to the invention may thus also be used as a basic module of a microturbine for the power/heat cogeneration.

Control electronics are preferably provided in the drive system for the control of the electrical energy, the charging and discharging procedure, or for providing an optimal torque, with a low consumption. The rotational speed of the turbine wheel or compressor wheel, actual values of the pressure conditions on the turbine housing side and the compressor housing side, as well as further characteristic variables for the internal combustion engine of relevance to the torque, serve as control parameters.

One advantageous further design envisages the turbine wheel and the compressor wheel being permanently connected to one another in a rotationally fixed manner. This means that no coupling between the turbine wheel and the compressor wheel is given, by which means the mechanical construction and the susceptibility to failure of the system would be increased. Instead of this, one strives to limit the moved rotational masses by way of a light rotor, a light compressor wheel, a light shaft and a suitably low-mass turbine wheel.

The housing of the turbocharger is preferably constructed in a modular manner, i.e. apart from a turbine housing for the turbine wheel, there is also a compressor housing for the compressor wheel. The turbine housing is preferably connected to an exhaust manifold which leads exhaust gas from the individual cylinders of the internal combustion engine, to the turbine wheel. The design demands are somewhat different than with the compressor housing which surrounds the compressor wheel, on account of the thermal loading of the turbine housing. The actual mounting of the turbine wheel and the compressor wheel preferably takes place exclusively between the turbine wheel and the compressor wheel. This means that no additional mounting is given on the side of the compressor wheel which is distant to the turbine wheel, since it is indeed here that the stator of the electric motor projects freely. Preferably, a bearing housing is provided between the turbine housing and the compressor housing, which serves for receiving bearing elements for the turbine wheel and the compressor wheel.

The electric motor preferably contains a stator which has an essentially hollow-cylindrical shape and which surrounds the rotor in a concentric manner. Here, it is advantageous that the stator may be designed as part of the inner wall of the compressor housing. The stator may for example also be applied as an insert into a corresponding opening of the compressor housing. The advantage with these embodiments is the fact that only an as small as possible design change of conventional mechanical turbochargers is necessary, so that cost- and competitive advantages may be realised by way of this, in particular with large-scale production.

The rotor of the electric motor preferably has a rotor magnet which is surrounded by a sheathing. The rotor magnet is mechanically protected by way of this. One may also have an influence on the type of magnetic field in this manner. The rotor magnet may be designed such that it is partly or completely integrated into the compressor wheel. If the compressor wheel consists of fibre-reinforced or non-reinforced plastic, then on production, the rotor magnet may be directly peripherally injected with the plastic mass, by which means an inexpensive large-scale manufacture is possible.

The sheathing of the rotor is preferably designed in the manner of a “hollow cylinder”.

It is advantageous with regard to manufacturing technology, for the rotor magnet to be hollow in the inside in regions, for placing on a common shaft with the compressor wheel. An inexpensive manufacture is possible in this manner.

The compressor wheel consists preferably of a non-magnetisable material which does not negatively compromise the electromagnetic field. The compressor wheel may also be of a non-metallic material, preferably of a reinforced or non-reinforced plastic.

One further advantageous design envisages the rotor gap between the rotor and the stator representing an (and specifically the only intended) inlet air opening for the compressor wheel. This in turn means that the electric motor hardly gets in the way of the air feed flow, and that no additional air feed openings need to be provided, which would unnecessarily increase the flow resistance. It is therefore even possible for the inlet opening to be free of struts between the rotor and stator. Here, such a provision of struts is not necessary due to the omission of the “counter bearing”. Notwithstanding, such a “counter bearing” may be applied with “classical turbochargers” with turbines, as well as with turbochargers which are designed merely as one compressor stage (for example with particularly high rotational speeds, critic natural frequencies etc.).

The inlet opening may be provided with a large cross-sectional area, depending on the dimensioning of the rotor or stator. Preferably, the smallest inner diameter of the stator is 1.2- to 10-times, preferably 1.5- to 8-times, particularly preferably 2- to 4-times the size of the largest outer diameter of the rotor. The specified lengths here in each case relate to the greatest extensions or smallest extensions of the participating elements, but only in the region of the electrically or magnetically effective elements (thus only over the length of the rotor magnet for example) and a subsequent thickening (for example in the region of the compressor wheel) is not important here. It is sufficient for the values to be fulfilled in a single cross-section (of a cross-sectional area).

A further advantageous further design envisages the compressor wheel containing a conveyor structure in the form of worms, blades or wings, wherein the front edges of the conveyor structure, in the air inlet flow direction, lie upstream or downstream with regard to a magnetically effective front edge of the rotor magnet or a magnetically effective front edge of the stator. In this context, “magnetically effective front edges” are meant as the actual electrical and magnetic components, but without insulating casings, etc. With this, one has the freedom to arrange the stator or the rotor in a practically infinite manner with respect to the compressor wheel, depending on the application case. For example, the arrangement of the front edge of the rotor magnet upstream with regard to the air inlet flow direction make sense, if a compressor wheel of a metallic material is used. The electrical or magnetic characteristics of the respective motor are particularly favourable by way of the fact that the rotor magnet projects out of the compressor wheel. If however, one demands a minimisation of constructional space, then the rotor magnet may not begin not until within a conveyor structure of the compressor wheel. This for example lends itself if the conveyor structure consists of a plastic material. The front edge of the stator may likewise be arranged downstream or upstream with respect to a front edge of the conveyor structure. Here, it is also considerations with regard to construction space as well material which are at the forefront.

A further (alternatively or cumulatively to that which is mentioned here) construction envisages the compressor wheel containing a conveyor structure in the form of blades, worms or wings, wherein the rear edges of the conveyor structure in the air inflow direction lie downstream or upstream with respect to a rear edge of the rotor magnet and/or a rear edge of the stator. Thus the elements “to be driven” may also be arranged partly downstream of the conveyor structure, depending on the dielectric or magnetic characteristics of the surrounding material, dimensions of the rotor magnet or of the stator or of the compressor wheel/conveyor structure. Particularly large or powerful stator arrangements or rotor magnets here may also be designed so long, that they axially project beyond the conveyor structure or the compressor wheel on both sides (thus downstream and upstream).

A further advantageous design envisages the stator and/or rotor being inclined with respect to an axis of the compressor wheel.

This therefore means that the outer contour or the inner contour of the rotor magnet or stator do not need to be cylindrical or hollow-cylindrical, but that also other shapes may be given here, for example truncated cone shapes or hollow truncated cone shapes. With these inclined structures, the inventive diameter or area relationships also only need to be realised in a single step, in order to realise the inventive teaching of the patent.

A further advantageous design envisages the rotor magnet being arranged radially outside the hub of the compressor wheel with respect to the axis of the compressor wheel. This arrangement, although not always desirable on account of the increased mechanical and also thermal loading of the rotor magnet, however provides for an even greater flexibility, for example the possibility of a compact hub (for example the omission of the hub in the ideal case) and of an additional airflow in the centre of the compressor. For this, the compressor wheel may also be designed such that air may be led radially within as well as radially outside the rotor magnet. Here for example, one may imagine the rotor magnet being designed in an essentially circularly annular manner, but this however may also be realised by way of an arrangement of several rotor magnets.

With regard to this, the compressor wheel may be designed such that at least 50%, preferably at least 70%, particularly preferably at least 90% of the air mass flow is led radially outside the rotor magnet.

A particularly advantageous further formation envisages the ratio of the cross-sectional area of the inlet opening to the cross-sectional area of the rotor magnet (expressed with regard to a formula: V_QE=A_{inlet opening}/A_{rotor magnet}) being between 0.5 and 100, preferably between 0.8 and 50, particularly preferably between 0.8 and 50, particularly preferably between 2 and 20.

The primary work power of the media gap motor is the delivery of media through the gap between the rotor and stator, or as a generator, the drive by the delivery medium in the media gap.

“Cross-sectional area of the inlet opening” is to be understood as the actual open cross section in which air or a fluid may be led. This is therefore the actual “net cross-sectional area of the inlet opening” in this region. For example, with a circularly round inlet opening, it is firstly assumed to be the total circular area, but however the respective cross-sectional area of the blades or the hub (including sheathing, rotor magnet etc.) is subtracted for determining the net cross-sectional area. The measure found here is thus a ratio of the actual rotor magnet (with regard to area) to the actual cross section through which air may flow.

The cross section applied for evaluating V_QE preferably runs through a region in which not only is the rotor magnet present, but also a magnetically or electrically effective section of the stator.

A further advantageous design envisages the ratio of the cross-sectional area of the stator to the cross-sectional area of the rotor magnet (expressed with regard to a formula: V_QS=A_stator/A_{rotor magnet}) being between 2 and 100, preferably between 10 and 50. Here, it is in each case the “net cross-sectional areas” of the electrically effective components of the stator or rotor magnet which are to be specified. Insulating components or components which are not electrically/magnetically effective are not taken into account. Thus with a stator, a metal base body (including copper windings for example) is taken into account in the cross-section, but not a surrounding insulating plastic. Accordingly, with regard to the rotor magnet, it is also only the actually magnetically effective areas which are taken into account, even if the rotor consists of different parts (the individual areas are then to be added accordingly, so that one may evaluate a total area of the rotor magnet).

The cross sections mentioned above preferably lie perpendicular to the axis of the compressor wheel.

A further advantageous formation envisages the rotor being connected to the compressor wheel, and the compressor wheel being axially mounted on both sides. Here, the compressor wheel may or may not be connected to a turbine wheel, what is merely important is that the compressor wheel is axially mounted on both sides, thus does not protrude.

A further advantageous design envisages the turbocharger being designed merely as a compressor system with at least one compressor wheel, and the at least one compressor wheel being axially mounted on one or both sides. In this case, the compressor wheel would therefore not be connected to the turbine wheel.

A further advantageous design envisages the turbocharger comprising a turbine wheel and the compressor wheel, wherein the electric motor is arranged on the side of the compressor wheel which faces the turbine wheel or between the side of the compressor wheel which faces the turbine wheel and the side which is distant to the turbine wheel.

A further advantageous design envisages the smallest inner diameter of the stator being 1.1 to 1.49-times, preferably 1.25 to 1.49 times larger than the largest outer diameter of the rotor.

A further advantageous design envisages the smallest inner diameter of the stator being 8.01 to 15 times, preferably 8.01 to 12 times larger than the largest outer diameter of the rotor.

The specified lengths here in each case relate to the larges extensions or smallest extensions of the participating elements, however only in the region of the electrically or magnetically effective elements (thus only for example of the rotor magnet) and a subsequent thickening, for example in the region of the compressor wheel, is not important here.

For reducing the current intensity and for increasing the energetic efficiency, here the nominal voltage of the electric motor may be more than 12 V, for example 24 or 48 V.

It is particularly advantageous for the electric motor to be able to be switched over from motor operation into generator operation. If the charging pressure (in the turbine housing) reaches a certain nominal value, then additional energy is produced whilst applying a converter capable of regeneration. Furthermore, ideally by way of the energetic conversion of braking energy, one may do away with a waste gate/pressure dose for blowing off excess exhaust gas pressure.

The control of the motor/generator operation for the first time permits the almost real-time, targeted closed-loop control of the charging procedure. The rotational speed of the compressor as well as the turbine wheel and thus the air mass flow may be evaluated in an exact manner since the electric motor is preferably controlled with a closed-loop via a frequency converter. The control of the charging procedure of the internal combustion engine is preferably integrated into the central motor control. With this, it is possible to realise a charging which is controlled in the input-output map. Thus, an exact adjustment and optimisation of the combustion parameters (fuel quantity, air quantity, charging pressure, exhaust gas return rate, ignition time etc) is possible, by which means one may achieve a significant reduction in the fuel consumption. This therefore represents an active extension of the input-output map, by which means the energy balance of the combustion engine may be considerably improved. This control loop permits the closed-loop control and optimisation of the complete combustion process within the combustion space of an internal combustion engine.

Further advantageous designs are specified in the remaining dependent claims.

The present invention is now explained by way of several figures. There are shown in:

FIG. 1a a first embodiment of a turbocharger according to the invention, in a part section;

FIG. 1b a section of the turbocharger from FIG. 1a, according to A;

FIG. 1c a section of the turbocharger of FIG. 1a, according to B;

FIG. 1d a part exploded drawing of the turbocharger of FIG. 1a;

FIG. 2a a second embodiment of a turbocharger according to the invention, in a part section;

FIG. 2b a part-exploded view of the turbocharger shown in FIG. 2a;

FIG. 3a an explanation of the proportions and arrangement of the rotor magnet, stator and compressor wheel;

FIG. 3b an embodiment of a compressor wheel with an inclined rotor and inclined stator;

FIGS. 4a to 4c an explanation of geometric relations with regard to the turbochargers according to the invention.

FIGS. 5 and 6 a further embodiment of a turbocharger according to the invention, as a microturbine for power generation.

The basics of the invention are to be shown hereinafter by way of the first embodiment according to FIGS. 1a to 1d.

FIGS. 1a to 1d show an electrically modified mechanical turbocharger 1 which may be coupled to a turbine housing 5 on an internal combustion engine. After the combustion, the exhaust gas is collected by way of the exhaust gas fans shown in FIG. 1a and is used for driving a turbine wheel 2. The turbine wheel 2 is surrounded by the turbine housing 5 and is essentially deduced from a conventional mechanical turbocharger. A bearing housing 7 connects to the turbine housing 5, and then a compressor housing 6. A compressor wheel 6 is attached in this compressor housing 6, and compresses the air fed through an inlet opening (this inlet opening is in particular easily seen in FIG. 1c) and leads it to the combustion space of the internal combustion engine in a manner which is not shown here. The compressor wheel 3 on the left side in FIG. 1a shows a continuation, to which a rotor 4a of an electric motor is given. The rotor 4a is attached centrally in the inlet air opening 4e. The air inlet flow direction 4e is indicated at LES in FIG. 1a (here coaxially to the axis of the compressor wheel).

A stator 4b which has an essentially hollow-cylindrical shape and is represented as part of the inner wall of the compressor housing in the region of the inlet air opening, is provided around the rotor 4a. Here, the stator 4b is even provided as an insert into a suitable opening, so that this may be assembled very easily. Here therefore, in FIG. 1a, the rotor gap between the rotor 4a and the stator 4b is the inlet air opening 4e for the compressor wheel. With this, the inlet air opening 4e is free of struts between the rotor and the stator also according to FIG. 1a. In the shown section, the smallest inner diameter of the stator (see “d_s” in FIG. 1d) is for example 1.5 times larger than the largest outer diameter d_R of the rotor (the drawing is schematic and only for clarifying the size relations).

The rotor 4a of the electric motor 4 comprises a rotor magnet 4c which here is surrounded by a sheathing (see e.g. FIG. 1d). With this, the sheathing is designed in an essentially “beaker-shaped” manner, wherein the base of the beaker is almost completely closed towards the compressor wheel (disregarding a centric assembly bore).

The compressor wheel may (but need not) be of a non-metallic material, here with one embodiment, for example of a non-reinforced plastic, and the influence on the electromagnetic field of the electric motor is minimised. The rotor magnet 4c in turn is hollow in regions for placing on a common shaft with the compressor wheel. Here, a bore 4c of the rotor magnet is to be accordingly seen in FIG. 1d. Furthermore, it may be seen that a sequence of elements is shown in the sequence of the rotor (consisting of the rotor magnet 4c and sheathing 4d), the compressor wheel 3, shaft 8, turbine wheel 2, which minimises a thermal loading of the electric motor. The shaft 8 here, in the present embodiment, is designed such that the turbine wheel 2, compressor wheel 3 as well as rotor 4a are firmly (rotationally fixedly) connected to one another, thus may not be separated by a rotation clutch or free-wheel. However, it is basically possible to provide such a clutch within the framework of the present invention, if it is the case for example that the turbine wheel 2 is very high, but however the design effort would in turn also be increased by way of this.

The nominal voltage of the electric motor 4 in FIG. 1a here is 12V, but other voltages (for example 48V for hybrid vehicles) are also possible.

A turbocharger with a compressor arrangement for compressing fresh air for internal combustion engines is shown in FIG. 1d, containing a compressor wheel 3 as well as an electric motor 4 with a rotor 4a and stator 4b, wherein a rotor magnet 4c of the rotor is designed such that it is partially or also completely integrated into the compressor wheel or is connected to this, and the smallest inner diameter of the stator is 1.5- to 8-times larger than the largest outer diameter of the rotor. The arrangement of the rotor magnet, the stator or the compressor wheel is variable here in the axial direction, and the later FIG. 3a is particularly referred to with regard to this. The mass of the rotor magnet 3c (the total mass, even if this is to consist of several parts) here is 50 g. The mass moment of inertia of the rotor magnet with respect to the axis of the rotor is 0.6 kgmm².

The ratio of the cross-sectional area of the inlet opening to the cross-sectional area of the rotor magnet (V_QE) is 7:1. The ratio of the cross-sectional area of the stator to the cross-sectional area of the rotor magnet is for example V_Qs=16:1.

The electric motor may be operated in motor operation (for accelerating and avoiding a “turbolag”), as well as in generator operation (for recovering energy). If the charging pressure (in the turbine housing) reaches a certain nominal value, then additional energy is produced by way of using a converter capable of return feed. Ideally, one may do away with a waste gate/pressure dose for blowing out excess exhaust gas pressure, as is represented in FIG. 1b, numeral 9, by way of this energetic conversion of the braking energy in generator operation.

The turbocharger according to the invention is used in a drive system according to the invention for motor vehicles which contains an internal combustion engine connected to the turbocharger, as well as a storage device for electrical energy. The electric motor of the turbocharger 1 here is connected to the storage device for electric energy for taking electrical energy in a motor operation of the turbocharger 1, and for feeding in electrical energy in a generator operation of the turbocharger. In a particularly preferred embodiment, the electric motor of the turbocharger is connected to an electrical storage device, wherein this electrical storage device is additionally connectable to an electromotoric drive of a motor vehicle. This may be a “hub motor” of a motor vehicle or another electric motor, which is provided in the drive train of a motor vehicle (for example in the region of the gear). This connection of the electrical turbocharger to a hybrid vehicle is particularly energy efficient.

Control electronics for determining the rotational speed of the turbine wheel 2 or the compressor wheel 3, actual values of pressure conditions on the turbine housing side and compressor housing side, as well as further values relevant to the torque for the internal combustion engine are provided for the efficient control of the drive system or the turbocharger.

The most important components of the first embodiment according to FIGS. 1a to 1d are shown in FIG. 1d, at the top right as a part exploded drawing. Here, it is to be seen that it is the case of a turbocharger 1 which comprises a turbine wheel 2 as well as a compressor wheel 3 connected thereto, wherein an electric motor 4 is provided on the side of the compressor wheel which is distant to the turbine wheel consisting of rotor 4a and stator 4b, and a rotor 4a of the electric motor 4 which is connected to the compressor wheel 3 in a rotationally fixed manner, is designed in a freely projecting manner.

This “freely projecting” manner is advantageous, since the design effort is reduced by way of this and for example a static overdimensioning of the total mounting is avoided. “Freely projecting” is to be understood as those arrangements with which the rotor is not mounted in a separate and permanent manner. Possibly provided “support cages” etc., which are to prevent a bending of the freely projecting rotor which may be too large, for example on account of bending resonance, are not to be seen in the context of “bearings”.

A second embodiment is shown in the FIGS. 2a and 2b. Here, the rotor magnet 4c has been partially integrated into the compressor wheel 3 on manufacture. The stator forms the inner contour of the compressor housing.

The electric motor may be operated in motor operation (for accelerating and avoiding a “turbolag”) as well as in generator operation (for recovering energy). If the charging pressure (in the turbine housing) reaches a certain nominal value, then additional energy is produced by way of using a converter capable of return feed. One may do away with a wastegate/pressure dose for blowing out excess exhaust gas pressure, as is represented in FIG. 1b, numeral 9, by way of this energetic conversion of the braking energy in generator operation.

FIG. 3a shows a schematic representation of the compressor wheel 3, the stator 4b as well as the rotor 4c for illustrating the geometric conditions. What is shown is the compressor wheel which is mounted on a shaft 10 on one or on both sides, and is subjected to flow in an air inlet flow direction LES. The air flow which flows in, is accelerated by the compressor wheel 3 which comprises a conveyor structure F. The front edge of the conveyor structure is indicated at VF, and the rear edge of the delivery structure is indicated at HF. The front edge of the rotor magnet 4c is indicated at VR and the rear edge of the rotor magnet 4c is indicated at HR. The front edge of the stator is indicated at VS, and the rear edge of the stator is indicated at HS (the stator here is rotationally symmetrical, but here the upper stator section has been shown for reasons of a better overview). The compressor wheel 3 thus has a conveyor structure F in the form of blades, wherein the front edges VF of the conveyor structure, in the air inlet flow direction, lie downstream with respect to a magnetically effective front edge of the rotor magnet 4c and a magnetically effective front edge VS of the stator. The compressor wheel with its rear edge HF in contrast, in the air inlet flow direction, lie upstream with respect to the rear edge HR of the rotor magnet 4c as well as the rear edge of the stator 4b.

However, other arrangements are also possible here, with which the rotor magnet or stator only project beyond one edge of the compressor wheel, and it is also possible for the rotor magnet to lie completely within the compressor wheel, and thus to be laterally enclosed by the edges of the conveyor structure.

FIG. 3b shows a further embodiment, with which the stator 4b (this is rotationally symmetrical with respect to the axis 10), is inclined with respect to the axis 10. The stator thus here has essentially the shape of a hollow truncated cone. The same also applies to the rotor 4a or the respective rotor magnets, and this too with its sections is inclined with respect to the axis 10 (thus these are not parallel/co-linear, but would intersect in their extensions).

The compressor wheel shown in FIG. 3b is mounted on both sides (see indicated bearing locations L1 and L2). However, the embodiment forms of the further figures may basically also be mounted on both sides (even if this, under certain circumstances, means more constructional effort).

With regard to FIG. 3b, it is the case that the rotor magnet 4c is arranged radially outside the hub of the compressor wheel with respect to the axis 10 of the compressor wheel 3. The compressor wheel here is designed such that air may be led radially within, as well as radially outside the rotor magnet. Here, the compressor wheel is also designed such that at least 70% of the supplied air mass (or of the supplied air mass flow), is led radially outside the rotor magnet.

FIGS. 4a and 4b serve for illustrating the evaluation of the diameter dimensions with geometries which are not the same throughout.

FIG. 4a makes it clear that the largest diameter d_R of the rotor is measured at the location at which this rotor (but only in the region of the extension of the rotor magnet) has its greatest extension. A later widening of the rotor in the region of the compressor wheel 3 is not included, since the rotor magnet is not led further there.

Accordingly, the stator is also measured at the narrowest location (see d_s) over which the respective electrically or magnetically effective component of the stator extends (indicated by the black bar which shows a laminated core with copper wire).

FIG. 4b shows a closer illustration for cross sections which are not circular. The “largest outer diameter” of the rotor magnet is to be understood as the diameter which indicates the smallest circumscribing circle around the whole rotor (see above description with respect to 4a with regard to the axial positioning). The wavy outer line shown in FIG. 4b is not circular, and the circumscribed circle is essentially tangent to the projecting locations of the outer rotor.

The same applies to the stator 4b, which likewise does not have a circular shape. Here the largest inscribed circle, is assumed with a diameter d₅.

FIG. 4c once again shows a cross section through a stator 4b and rotor 4a, according to the invention. Here one may see a rotor magnet 4c which consists of individual segments (three distributed over the periphery). Alternatively to this, one may also imagine e.g. a cylindrical single magnet for example. A sheathing 4d is attached around this rotor magnet 4c. In turn, a conveyor structure F (here in section, therefore hatched) is shown on this sheathing. An air passage or media passage opening 4e is given around the conveyor structure and is surrounded radially to the outside by a shielding 11 (this is of plastic and is magnetically/electrically insulating). The electrically effective part of the stator 4b is given around the shielding 11.

In the cross section shown in FIG. 4c, the cross-sectional area of the media passage opening or the air passage or the inlet opening 4e, to the cross-sectional area of the four segments of the rotor magnet (defined as V_QE=A_{inlet opening}/A_{rotor magnet})=4:1.

Here, the inlet opening 4e is defined as the opening which may indeed be subjected to through-flow, thus the area content within the sheathing 11, but minus the areas of the hatched conveyor structure, as well as the hub of the rotor (the hub includes the sheathing 4d as well as everything located therein). What is meant here is the “net cross-sectional area” of the inlet opening. The cross section in FIG. 5c visibly runs through the electrically and magnetically effective section of the stator 4b. In this cross section, the ratio of the cross-sectional area of the stator to the cross-sectional area of the rotor magnet (defined as V_Qs=A_stator/A_{rotor magnet})=13:1.

Here, only the electrically or magnetically effective part (thus core metal+copper wire, however minus copper wire coating as well as possible “hollow areas”) is to be understood as the cross-sectional area of the stator. Accordingly, it behaves as with the rotor magnet, and here only the cross sections of the pure rotor magnet segments in this cross section are applied.

The above-mentioned ratios for the relation of the smallest inner diameter of the stator to the largest outer diameter of the rotor, supplementarily to 1.5 to 8-fold, may also lie in other intervals, specifically 1.1- to 1.49-fold, preferably 1.25- to 1.49-fold. Accordingly however, at the other end of the scale, the smallest inner diameter of the stator may also be 8.01- to 15-fold, preferably 8.01- to 12-fold the size of the largest outer diameter of the rotor.

All turbochargers shown in the figures contain at least one compressor wheel 3 for compressing air, and may be driven by the electric motor 4, wherein a rotor gap is arranged between the rotor 4a and the stator 4b of the electric motor, and at least 50%, preferably at least 90% of the air mass flow led to the compressor wheel is led through the rotor gap in at least one operating condition of the turbocharger. With the representations in the Figures, this operating condition is given at a rotational speed between 5000 and 300000 r.p.m, preferably between 40000 and 200000 r.p.m, mainly at 100000 r.p.m. The rotational speed of the crank shaft of a connected reciprocating motor here is between 100 and 15000 r.p.m, preferably between 1500 and 8000 r.p.m., mainly for example 25000r.p.m

FIGS. 5 and 6 show the turbocharger according to the invention as a base module of a microturbine for the power/heat cogeneration. FIG. 5 shows the basic construction, FIG. 6 an explaining exploded view. An electric motor/generator is characterised with the reference numeral 11, a recuperator with the reference numeral 12, a heat exchanger with the reference numeral 13 and a heat storage device with the reference numeral 14. For this reason, the important parts (rotor, stator, compressor wheel, turbine wheel) are indicated with the same reference numerals in the figures, as with the previous embodiment examples. The manner of functioning, put in different words, is as follows (what is important here is not primarily the function of the power/heat cogeneration, but the fact that the turbocharger according to the invention which here shows a compressor wheel and a turbine wheel, may also be applied outside the car).

The combustion air flows completely between the rotor and the stator of the electric motor/generator 11, into the compressor. By way of the compression effected there to approx. 4 bar, the combustion air already heats to approx. 200° C. The heated combustion air is led out of the compressor into a first heat exchanger and is lifted to a temperature level of approx. 500° c. by the hot exhaust gases flowing past. In a combustion chamber arranged downstream, the combustion air is burnt together with a fuel e.g. a regenerative gas. The hot gases which arise in this manner, are expanded in the turbine and drive the turbine wheel and thus the compressor and the generator. The thermal energy of the exhaust gas is partly dispensed in the heat exchanger directly to the compressed combustion air again. Furthermore, this turbocharger according to the invention may be coupled to a second heat exchanger, in order to utilise the total residual heat for the supply of warm water, or may lead it to a heating circuit, e.g. for heating and cooling a building. The generator may be used as an electric motor for starting the process. Thus for example with the turbocharger according to the invention, one may for example produce inexpensive block power plants whose essential components consist of components manufactured in a large scale from the motor car industry. The noise emission as well as the body sound transmission are avoided in adjacent buildings on account of the low-oscillation running. The module is also suitable as an auxiliary drive for producing electricity in aircraft due to the compact construction and low weight.

Claims

1-44. (canceled)

45. A turbocharger, comprising:

a compressor arrangement compressing fresh air for an internal combustion engine, the compressor arrangement including a compressor wheel and an electric motor, the motor including a rotor and a stator,

wherein a rotor magnet of the rotor is one of partially integrated and completely integrated into the compressor wheel, and wherein a smallest inner diameter of the stator is between 1.5- and 8-times as large as a largest outer diameter of the rotor.

46. A turbocharger according to claim 45, wherein the rotating compressor wheel leads through a rotor gap at least 50% of an air mass flow to be compressed.

47. A turbocharger according to claim 45, wherein the rotating compressor wheel leds through a rotor gap at least 90% of an air mass flow to be compressed.

48. A turbocharger according to claim 45, further comprising:

a turbine wheel connected to the compressor wheel, the motor being arranged on a side of the compressor wheel which is distant to the turbine wheel.

49. A turbocharger according to claim 45, wherein the rotor is connected to the compressor wheel in a rotationally fixed manner, and is designed in a freely projecting manner.

50. A turbocharger according to claim 45, further comprising:

a turbine wheel permanently connected to the compressor wheel in a rotationally fixed manner.

51. A turbocharger according to claims 45, further comprising:

a turbine wheel;

a housing including a turbine housing situating the turbine wheel; and

a compressor housing situating the compressor wheel.

52. A turbocharger according to claim 51, wherein the mounting of at least one of the turbine wheel and the compressor wheel is given exclusively in a region between the turbine wheel and the compressor wheel.

53. A turbocharger according to claim 52, further comprising:

a bearing housing receiving bearing elements for the turbine wheel and the compressor wheel, the bearing housing being situated between the turbine housing and the compressor housing.

54. A turbocharger according to claim 45, wherein the rotor magnet is surrounded by a sheathing.

55. A turbocharger according to claim 51, wherein the stator has a substantially hollow-cylindrical shape.

56. A turbocharger according to claim 55, wherein the stator is part of an inner wall of the compressor housing.

57. A turbocharger according to claim 55, wherein the stator is applied, as an insert, into a corresponding opening of the compressor housing.

58. A turbocharger according to claim 45, wherein a rotor gap is located between the rotor and the stator, the rotor gap being an inlet air opening for the compressor wheel.

59. A turbocharger according to claim 58, wherein the inlet air opening is free of struts between the rotor and the stator.

60. A turbocharger according to claim 54, wherein the sheathing has a substantially cylindrical shape.

61. A turbocharger according to claim 54, wherein the rotor magnet, on an inside and in regions, is hollow for sticking onto a common shaft with the compressor wheel.

62. A turbocharger according to claim 45, wherein the compressor wheel is composed of a non-metallic material

63. A turbocharger according to claim 45, wherein the compressor wheel is composed of one of a reinforced plastic and a non-reinforced plastic.

64. A turbocharger according to claim 51, wherein the turbine housing is connected to an exhaust gas conduit of the internal combustion engine to drive of the turbine wheel using the exhaust gas flowing out of the internal combustion engine.

65. A turbocharger according to claim 45, wherein the motor is switched over from a motor operation into a generator operation.

66. A turbocharger according to claim 45, wherein a nominal voltage of the motor is one of 12, 24 and 48 V.

67. A turbocharger according to claim 45, wherein a mass of the rotor magnet is between 50 and 1000 g,

68. A turbocharger according to claim 45, wherein when the turbochager is a motor vehicle turbocharger, a mass of the rotor magnet is between 10 and 100 g.

69. A turbocharger according to claim 45, wherein a mass moment of inertia of the rotor magnet with respect to an axis of the rotor is between 0.1 kgmm2 and 10 kgmm2.

70. A turbocharger according to claim 45, wherein a mass moment of inertia of the rotor magnet with respect to an axis of the rotor for a motor vehicle application is a between 0.3 kgmm2 and 1.0 kgmm2.

71. A turbocharger according to claim 45, wherein the compressor wheel has a conveyor structure in a form of one of worms, blades and wings, and wherein front edges of the conveyor structure, in an air inlet flow direction, lie one of downstream and upstream with regard to one of a magnetically effective front edge of the rotor magnet and a magnetically effective front edge of the stator.

72. A turbocharger according to claim 45, wherein the compressor wheel has a conveyor structure in a form of one of blades, worms and wings, and wherein rear edges of the conveyor structure in an air inflow direction, lie one of downstream and upstream with respect to at least one of a rear edge of the rotor magnet and a rear edge of the stator.

73. A turbocharger according to claim 45, wherein at least one of the stator and the rotor is inclined with respect to an axis of the compressor wheel.

74. A turbocharger according to claim 45, wherein the rotor magnet with respect to an axis of the compressor wheel is arranged radially outside a hub of the compressor wheel.

75. A turbocharger according to claim 74, wherein the compressor wheel leads air radially within and radially outside the rotor magnet.

76. A turbocharger according to claim 75, wherein the compressor wheel leads at least 50% of the air mass flow radially outside the rotor magnet.

77. A turbocharger according to claim 75, wherein the compressor wheel leads at least 70% of the air mass flow radially outside the rotor magnet.

78. A turbocharger according to claim 75, wherein the compressor wheel leads at least 90% of the air mass flow radially outside the rotor magnet.

79. A turbocharger according to claim 45, wherein in at least one cross section, a ratio of a cross-sectional area of an inlet opening to a cross-sectional area of the rotor magnet is between 0.5 and 100.

80. A turbocharger according to claim 45, wherein in at least one cross section, a ratio of a cross-sectional area of an inlet opening to a cross-sectional area of the rotor magnet is between 0.8 and 50.

81. A turbocharger according to claim 45, wherein in at least one cross section, a ratio of a cross-sectional area of an inlet opening to a cross-sectional area of the rotor magnet is between 2 and 20.

82. A turbocharger according to claim 79, wherein the cross section runs through one of magnetically effective sections and electrically effective sections of the stator.

83. A turbocharger according to claim 45, wherein, in at least one cross section, a ratio of a cross-sectional area of the stator to a cross-sectional area of the rotor magnet is between 2 and 100.

84. A turbocharger according to claim 45, wherein, in at least one cross section, a ratio of a cross-sectional area of the stator to a cross-sectional area of the rotor magnet is between 10 and 50.

85. A turbocharger according to claim 79, wherein the cross section is perpendicular to an axis.

86. A turbocharger according to claim 45, wherein the rotor is connected to the compressor wheel, the compressor wheel being axially mounted on both sides.

87. A turbocharger according to claim 45, wherein the turbocharger is a compressor system having at least one compressor wheel, the at least one compressor wheel being axially mounted on one of one side and both sides.

88. A turbocharger according to claim 45, further comprising:

a turbine wheel,

wherein the motor is arranged on one of a first side of the compressor wheel which faces the turbine wheel and between the first side and a second side of the compressor wheel which is distant to the turbine wheel.

89. A turbocharger according to claim 45, wherein the smallest inner diameter of the stator is between 1.1- and 1.49-times larger than the largest outer diameter of the rotor.

90. A turbocharger according to claim 45, wherein the smallest inner diameter of the stator is between 1.25- and 1.49-times larger than the largest outer diameter of the rotor.

91. A turbocharger according to claim 45, wherein the smallest inner diameter of the stator is 8.01- to 15-times larger than the largest outer diameter of the rotor.

92. A turbocharger according to claim 45, wherein the smallest inner diameter of the stator is between 8.01- and 12-times larger than the largest outer diameter of the rotor.

93. A drive system for a motor vehicle, comprising:

an internal combustion engine;

a storage device storing an electrical energy; and

a turbocharger including a compressor arrangement compressing fresh air for an internal combustion engine, the compressor arrangement including a compressor wheel and an electric motor, the motor including a rotor and a stator, the rotor magnet of the rotor being one of partially integrated and completely integrated into the compressor wheel, and wherein a smallest inner diameter of the stator is between 1.5- and 8-times as large as a largest outer diameter of the rotor,

wherein the motor is connected to the storage device to receive the electrical energy during in a motor operation of the turbocharger and to feeding-in the electrical energy in a generator operation of the turbocharger.

94. A drive system according to claim 91, wherein the storage device is connected to an electromotoric drive of the motor vehicle.

95. A drive system according to claim 93, wherein the turbocharger includes a turbine wheel, a turbine housing and a compressor housing, the drive system further comprising:

control electronics determining a rotational speed of one of the turbine wheel and the compressor wheel, actual values of pressure conditions on a side of the turbine housing and a side of the compressor housing, and further values of the internal combustion engine of relevance to a torque.

96. A drive system according to claim 95, wherein the control electronics include a sensor.

97. A method for an operation of a turbocharger, the turbocharger including a compressor arrangement and at least one compressor wheel, the compressor arrangement compressing fresh air for an internal combustion engine, the compressor arrangement including a compressor wheel and an electric motor, the motor including a rotor and a stator,

wherein a rotor magnet of the rotor is one of partially integrated and completely integrated into the compressor wheel,

wherein a smallest inner diameter of the stator is between 1.5- and 8-times as large as a largest outer diameter of the rotor, and

wherein the least one compressor wheel is driven by the motor to compress air, a rotor gap being arranged between the rotor and the stator, at least 50% of an air mass flow led to the compressor wheel being led through the rotor gap in at least one operating condition of the turbocharger.

98. A method according to claim 97, wherein at least 90% of the air mass flow is led through the rotor gap in at least one operating condition of the turbocharger.

99. A method according to claim 97, wherein the operating condition is given at a rotational speed between 5000 and 300000 r.p.m of the compressor wheel.

100. A method according to claim 97, wherein the operating condition is given at a rotational speed between 40000 and 200000 r.p.m of the compressor wheel.

101. A method according to claim 97, wherein the operating condition is given at a rotational speed between 40000 and 60000 r.p.m of the compressor wheel.

102. A method according to claim 97, wherein the operating condition is given at a rotational speed between 50 and 20000 r.p.m of the internal combustion engine supplied by the turbocharger with fresh air.

103. A method according to claim 97, wherein the operating condition is given at a rotational speed between 100 and 1500 r.p.m of the internal combustion engine supplied by the turbocharger with fresh air.

104. A method according to claim 97, wherein the operating condition is given at a rotational speed between 2000 and 4000 r.p.m of the internal combustion engine supplied by the turbocharger with fresh air.

105. The use of a turbocharger as a basic module of a micro-turbine for a power/heat generation, the turbocharger including a compressor arrangement compressing fresh air for an internal combustion engine, the compressor arrangement including a compressor wheel and an electric motor, the motor including a rotor and a stator, wherein a rotor magnet of the rotor is one of partially integrated and completely integrated into the compressor wheel, and wherein a smallest inner diameter of the stator is between 1.5- and 8-times as large as a largest outer diameter of the rotor.