US20080292480A1

US20080292480A1 - Electric Motor

Info

Publication number: US20080292480A1
Application number: US11/781,684
Authority: US
Inventors: Holger Godeke; Rudolf Loffler; Sandra Maier; Oliver Kampfer; Ralf Heber; Thomas Bischof
Original assignee: Individual
Current assignee: Lindenmaier AG; SYCOTEC GmbH and Co KG
Priority date: 2007-05-24
Filing date: 2007-07-23
Publication date: 2008-11-27
Also published as: DE502007006457D1; US20110076166A1; EP1995428B1; ATE525559T1; ATE498061T1; WO2008141670A1; ES2420968T3; CN101715509A; WO2008141669A1; EP2158386B1; EP1995429A1; EP1995429B1; US20080289333A1; EP1995426A1; US8371121B2; ATE498060T1; US20110076167A1; EP2158386A1; EP1995427B1; CN101715509B

Abstract

An electric motor for conveying media includes (a) a stator; (b) a rotor including a rotor magnet; and (c) a media throughput opening between the stator and the rotor. A smallest inner diameter of the stator is 1.5- to 8-times as large as a largest outer diameter of the rotor magnet.

Description

FIELD OF INVENTION

The present invention relates to an electric motor.

BACKGROUND INFORMATION

Electric motors are known in various embodiments. For example, motors are known for conducting media, which comprise a rotor and a stator located around this, wherein the rotor is connected to a media impeller and by way of this may regulate the flow of media.
With motors leading media, one strives for a simple construction as well as highest possible integration into an existing housing system. Here, apart from observing the desired simplicity for reasons of repair, one should also take note of the sealedness, in particular with regard to the electrical conducting parts of the electric motor.

SUMMARY OF INVENTION

The present invention relates to an electric motor which has an extremely simple construction, has a good sealedness with regard to the media to be delivered and despite this has a high performance and is energy efficient.
Here, it is the case of an electric motor for delivering media, wherein this comprises a stator, a rotor with a rotor magnet, as well as a media passage opening between the stator and rotor. Here, the smaller inner diameter of the stator is 1.5- to 8-times, preferably 2- to 4-times that of the largest outer diameter of the rotor magnet.
Here, basically all substances capable of flowing are to be understood as “media”, e.g. gases, liquids, pastes, dusts or granular substances.
The “largest outer diameter” of the rotor magnet is to be understood as the diameter which the actual magnetically effective material actually has (this without sheathing around the rotor magnet). If the rotor magnet does not have a circularly round shape, then the largest outer diameter is to be understood as the largest possible inscribed circle in the respective cross section of the magnet material
The “smallest inner diameter of the stator” is to be understood as the smallest diameter of the electrically or magnetically actually effective stator. A shielding e.g. of a plastic material from the stator towards the rotor, which for example serves for corrosion protection, with this is not to be seen as part of the stator, but only the smallest diameter of the (as a rule metallic) electrically or magnetically effective parts count. With regard to the motor according to the invention, it is the case of a media gap motor, thus of a permanent magnet synchronous motor with the particular characteristic of an excessively large air gap between the stator and the rotor. This large air gap permits the transport of various media between the rotor and the stator in the axial direction. The rotor magnet here may be directly coupled to a delivery device or also integrated into this.
With conventional air gap motors, the smallest possible constructional size for the desired torque as well as a high magnetic flux with a lowest application of permanent magnetic material is desired, with a conventional design of the motor without the use of media/throughput function of the air gap. Thus with conventional motors, one thus observes a small air gap on account of the fact that the magnetic resistance in the air gap is larger than in the ferromagnetic part of the magnetic circuit.
The present media gap motor is basically constructed as a conventional permanent magnet synchronous motor, but with the particularity of a stator inner diameter which is overdimesionally large compared to the outer diameter of the rotor of the permanent magnet.
In order to produce the required magnetic flux despite the large gap between the rotor and the stator, and the high magnetic resistance which this entails, as well as the high scatter share at the pole transitions, it requires the application of magnets which have a very high remanence and a very high energy density. In particular, rare-earth magnet materials are suitable for this. The magnet height simultaneously needs to be adapted accordingly. A high motor efficiency with respect to the diameter of the rotor or magnet may be achieved despite the relatively low flux, since a relatively large winding area is available due to the large outer diameter of the stator.
It is particularly amazing for the man skilled in the art, that one may design a well functioning motor despite the unusually large air gap.
Here, the large gap between the rotor and stator even permits to rotor magnet to be displaced somewhat in the axial direction (direction of the rotation axis) without the characteristic values noticeably worsening by way of this.
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 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.
Apart from the variants mentioned above which focus on the outer surrounding of the stator, the stator may yet also be provided with a shielding towards the rotor. This serves for the protection of the stator, in particular for corrosion protection. The shielding may preferably be given in the form of a thin tube or flexible tubing, wherein this shielding is preferably designed of electrically and magnetically not-conductive material.
Thus as a whole, the hollow-cylindrical design of the stator is advantageous but not absolutely necessary.
The rotor may be designed in different manners. The motor preferably has a rotor shaft, wherein this rotor shaft is mounted in a simple or in a multiple manner over its length. In a particularly advantageous embodiment, the rotor shaft is essentially mounted on one side and projects out essentially freely on the other side. Thus the necessity of a further bearing location and, as the case may be, struts between the rotor and stator which could further increase the throughput resistance, may be done away with. A further embodiment envisages the rotor magnet in the inside being hollow in regions, for placing on a common shaft connected to a medium impeller or a medium conveyor worm. An even better integration of the rotor shaft or the drive shaft with the rotor magnet and even a part delivering medium (medium impeller medium conveyor worm) may be effected in this manner. It is advantageous on integrating the rotor magnet into the rotor shaft or the medium impeller/medium delivery worm, for the components adjacent to the rotor magnet to be of a material which is not magnetically conductive or very poorly magnetically conductive, preferably of reinforced or non-reinforced plastic.
A further advantages formation envisages the mounting of the rotor shaft being non-lubricated or being lubricated by the medium to be delivered itself (this is advantageous for example with hydrodynamic bearings). As a whole practically any media may be considered for the delivery with the electric motor according to the invention, specifically all gases (in particular air) as well as liquid media (in particular aqueous media).
One particular advantage of the medium gap motor according to the invention lies in the fact that the axial centre of the stator and the axial centre of the rotor may be displaced in the axial direction, and specifically by tenth up to a fifth of the largest axial extension of the rotor magnet. The electric motor according to the invention is particularly suitable for the use in an electrically supported turbocharger with a freely projecting electric motor, for the transport of explosive gases, dusts, vapours, sticking substances, pastes, liquids such as water or oil; decomposing products, such as foodstuffs; in ventilation devices, in pumps, in particular in pumps for aggressive media, such as salt water, chemical solutions (in particular in the orthodontic field); in disinfectable or sterilisable pumps, canned pumps (medium transport in the axial direction), metering pumps, micro-pumps, disposable pumps, multi-stage pump systems; for use in turbines, generators, delivery worms for example for granular media, fluids or pastes; in gas-, water- and steam turbines; in devices for measuring the media flow via a generator voltage.

BRIEF DESCRIPTION OF DRAWINGS

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

FIGS. 1 a to 1 d show views of a turbocharger, with which the electric motor according to an exemplary embodiment of the present invention is applied,

FIGS. 2 a and 2 b show cross-sectional views of an electric motor according to the present invention,

FIGS. 3 to 6 show views or sections of further exemplary embodiments of the electric motor according to the present invention.

DETAILED DESCRIPTION

One application example of the invention is firstly shown by way of the FIGS. 1 a to 1 d.
FIGS. 1 a to 1 d show a 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. 1 a 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. 1 c) 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. 1 a shows a continuation, to which a rotor 4 a of an electric motor is given. The rotor 4 a is attached centrally in the inlet air opening 4 e.
A stator 4 b 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 4 a. Here, the stator 4 b is even provided as an insert into a suitable opening, so that this may be assembled very easily. Here therefore in FIG. 1 a, the rotor gap between the rotor 4 a and the stator 4 b is the inlet air opening 4 e for the compressor wheel. With this, the inlet air opening 4 e is free of struts between the rotor and the stator also according to FIG. 1 a. The smallest inner diameter of the stator (see “d_s” in FIG. 1 d) is 1.5 times larger than the largest outer diameter d_Rof the rotor.
The rotor 4 a of the electric motor 4 comprises a rotor magnet 4 c which here is surrounded by an sheathing (see e.g. FIG. 1 d). 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 4 c in turn is hollow in regions for placing on a common shaft with the compressor wheel. Here, a bore 4 c of the rotor magnet is to be accordingly seen in FIG. 1 d. Furthermore, it may be seen that a sequence of elements is shown in the sequence of the rotor (consisting of the rotor magnet 4 c and sheathing 4 d), 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 4 a 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. 1 a here is 12 V, but other voltages (for example 48V for hybrid vehicles) are also possible.
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 wastegate/pressure dose for blowing out excess exhaust gas pressure, as is represented in FIG. 1 b, 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 contain 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.
FIG. 2 a shows a field line representation of the magnetic flux between the rotor 4 a and the stator 4 b.
FIG. 2 b once again shows the geometric particulars of the electric motor according to the invention. Here one may see a solid-cylindrical rotor magnet which has a largest diameter d_RM. A sheathing 4 d is attached around this rotor magnet 4 c. In turn, a medium impeller 10 a is attached on this sheathing. A medium passage opening 4 e is given around the media impeller 10 a and this is surrounded radially outwardly by a shielding 11. The actual stator 4 b, whose outer diameter is specified at d_sis then given around the shielding 11.
With the exemplary electric motor, the remanence is 1.28 Teslas, the energy density 315 kJ/m³and the rotor magnet consists of NdFeB.
Here then, an electric motor 4 for the delivery of media is shown, wherein this comprises a stator 4 b, a rotor 4 a with a rotor magnet 4 c, as well as a media passage opening 4 e between the stator and rotor. The smallest inner diameter d_sof the stator, here is 1.5-times to 8-times, preferably 2-times to 4-times as much as the largest outer diameter of the rotor magnet itself (d_RM), in the present case d_s=2×d_RM.
The rotor magnet is preferably surrounded with a sheathing for the protection from media or damage. This may be designed in a beaker-like manner. The stator is preferably designed as an insert into a corresponding opening of a surrounding housing. A shielding 11 is preferably provided to the inside, thus towards the media passage opening, and this protects the stator from corrosion and improves the flux characteristics.
This is preferably designed in the shape of a tube, wherein the tube is of an electrically and magnetically non-conductive or poorly conductive plastic e.g. glass fibres, alternatively e.g. of glass or rubber. The rotor particularly preferably has a rotor shaft, wherein this rotor shaft is mounted in a simple or multiple manner over its length. The rotor shaft here is preferably mounted on one side and thus in a “projecting” manner.
The flow resistance through the rotor is further reduced by way of this. The rotor magnet is preferably placed on a common shaft with a media impeller or a media conveyor worm or is integrated in the inside and thus centered straight away. One may again attach a media impeller or a media conveyor worm around the motor magnet (these have recesses for receiving the rotor magnet), so that an as large as possible integration of the components is possible.
FIG. 3 shows a use of an electric motor which comprises a media impeller 10 a of a plastic material. A rotor magnet 4 c is attached on the end-side of this media impeller 10 a. Bearing locations 12 mount a rotor shaft 8 which is screwed in the medium impeller. A stator 4 b is accommodated in an inner wall of a housing 6. The flow of a medium 13 is introduced from the left, and is conveyed towards the right by the media impeller 10 a. Preferably, in the present case, again there is a large gap width not only radially about the axis 14, but also axially in the direction of the axis 14. This is also due to the fact that the axial centre of the stator AZS and the axial centre of the rotor AZR are displaced in the axial direction, and specifically by a tenth to a fifth of the largest axial extension GAAR of the rotor magnet.
FIG. 4 shows a representation corresponding essentially to FIG. 3, wherein here a shielding 11 is additionally provided, which protects the stator from the medium 13.
FIG. 5 shows a further embodiment of a pump according to the invention or of a throughput meter according to the invention, with which three propellers 10 a are mounted on a rotor shaft 8. With this, the bearings are attached on the left, as well as on the right side of the three media impellers 10 a. The stator 4 b is attached in the axial direction with respect to the axis 14 centered about the rotor magnet 4 c. The media impellers have an inner cavity which accommodates the rotor shaft 8 or the rotor magnets 4 c located therein. A particularly simple and securely mounted device is given in this manner, and by way of suitable webs, on the one hand the retention of the rotor shaft 8 is ensured, and also an adequate throughput of media 13 is achieved on account of the relatively small web cross sections.
FIG. 6 shows an embodiment example which is quite similar to FIG. 5. However, here a media conveyor worm 10 b is provided instead of the three individual impellers 10, and this seals media towards the shielding 11 in a particularly good manner.

Claims

1. An electric motor for conveying media, comprising:

a stator;

a rotor including a rotor magnet; and

a media throughput opening between the stator and the rotor,

wherein a smallest inner diameter of the stator is 1.5- to 8-times as large as a largest outer diameter of the rotor magnet.

2. An electric motor according to claim 1, wherein the motor is a permanent magnet synchronous motor.

3. An electric motor according to claim 1, wherein the rotor magnet has at least one of a remanence >0.8 Teslas and a high energy density >100 kJ/m³.

4. An electric motor according to claim 1, wherein the rotor magnet consists of rare earth materials.

5. An electric motor according to claim 1, wherein the rotor magnet consists of one of NdFeB abd SmCo.

6. An electric motor according to claim 1, wherein the rotor magnet is surrounded by an sheathing.

7. An electric motor according to claim 6, wherein the sheathing of the rotor magnet has a cylinder-shaped manner.

8. An electric motor according to claim 1, wherein the stator is a part of an inner wall of a surrounding housing.

9. An electric motor according to claim 1, wherein the stator is applied as an insert into a corresponding opening of a surrounding housing.

10. An electric motor according to claim 1, wherein the media passage opening is free of struts between the rotor and the stator.

11. An electric motor according to claim 1, wherein the stator has a substantially hollow-cylindrical shape.

12. An electric motor according to claim 1, wherein the rotor magnet is prepared for integration into a shaft for integration onto a common shaft with one of a media impeller and a media conveyor worm.

13. An electric motor according to claim 1, wherein the rotor magnet is partially integrated into one of a media impeller and a media conveyor worm.

14. An electric motor according to claim 1, wherein the rotor magnet is completely integrated into one of a media impeller and a media conveyor worm.

15. An electric motor according to claim 13, wherein one of the media impeller and the media conveyor worm is composed of a material which is one of magnetically non-conductive and poorly conductive.

16. An electric motor according to claim 13, wherein one of the media impeller and the media conveyor worm is composed of one of a reinforced plastic and a non-reinforced plastic.

17. An electric motor according to claim 1, wherein the stator is provided with a shielding towards an inside.

18. An electric motor according to claim 17, wherein the shielding has a form of one of a tube and a flexible tubing.

19. An electric motor according to claim 17, wherein the shielding is composed of electrically and magnetically non-conductive material.

20. An electric motor according to claim 1, wherein the rotor comprises a rotor shaft, the rotor shaft being mounted in one of a simple manner and a multiple manner over its length.

21. An electric motor according to claim 20, wherein the rotor shaft is substantially mounted on one side and essentially freely projects on the other side.

22. An electric motor according to claim 20, wherein at least one of the rotor and the rotor magnet are integrated into a shaft to be driven by the electric motor.

23. An electric motor according to claim 20, wherein the rotor shaft is mounted in one of a non-lubricated manner and a lubricated manner by delivery medium.

24. An electric motor according to claim 1, wherein an axial centre of the stator and an axial centre of the rotor are displaced in an axial.

25. An electric motor according to claim 1, wherein an axial centre of the stator and an axial centre of the rotor are displaced in an axial direction by one tenth up to one fifth of a largest axial extension of the rotor magnet

26. An electric motor for use in an electrically aided turbocharger with a freely projecting electric motor, for a transport of explosive gases, dusts, vapours, sticking substances, pastes, liquids; decomposing products, in ventilation devices, in general pumps, in pumps for aggressive media; in disinfectable or sterilisable pumps, canned pumps, metering pumps, micro-pumps disposable pumps, multi-stage pump systems; for use in turbines, generators, conveyor worms, in devices for measuring a media flow via a generator voltage, the motor comprising:

a stator;

a rotor including a rotor magnet; and

a media throughput opening between the stator and the rotor, wherein a smallest inner diameter of the stator is 1.5- to 8-times as large as a largest outer diameter of the rotor magnet.