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Electric motor

Electric motor description/claims

The present invention relates to an electric motor.

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.

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.

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