DE102006007434A1 - Electrical machine has projection in direction of shaft on side of endplate holding bearing which faces rotor and in such a manner that between a projection and shaft, arrangement is provided - Google Patents

Abstract

The electrical machine has a stator and a rotor (3), which are connected torque proof with a shaft (4). A projection (18) in the direction of the shaft is provided on side of the endplate (10) holding the bearing (5), which faces the rotor in such a manner that between a projection and shaft, an arrangement (30) is provided. The arrangement comprises stationary (31) and a co-rotating base part (32).

Description

The The invention relates to an electric machine with a stator and a rotor rotatably connected to a shaft, wherein the Shaft is stored at least in a warehouse.

In electrical machines arises, i.a. in the interior of the electric Machine, especially in the stator and rotor, heat loss, e.g. due to eddy current losses. The heat loss of the stator is over the sheet metal body of the stator to cooling channels extending in the stator or radially outward over the casing delivered to the environment. Despite all this, part of the heat loss through the air gap can be the electric machine can be registered in the rotor.

Of Furthermore, the rotor also generates losses, in part over the Air gap transferred to the stator be removed and with the above-mentioned cooling media. A big part the heat loss generated in the rotor but is transmitted to the shaft and transported from there in the axial propagation directions of the shaft.

Especially higher in electrical machines Protection class e.g. IP54, this heat loss can now only on the existing adjacent components are removed. Furthermore, increases with increasing power of the electric machine also the heat loss inside this machine. Part of this not negligible heat loss will over the wave and thus ultimately discharged through the bearings.

There However, the stock only a limited amount of heat loss from the interior to cool the electric machine Dividing the electric machine, such as Can dissipate bearing shields is the compactness of the electric machine, i. preferably a lot of power from one, to refer to the volume of construction small machine, extremely limited.

Of Further reduces with increasing thermal stress the Shelf life by reducing the lubricant service life. Become certain limits of the thermal load are exceeded, the bearings fall et al by losing their dimensional stability out. This is another operation of this electric machine without bearing change no longer possible.

Around the amount of heat loss through the To reduce bearing, an additional fan wheel can be attached to the rotor shaft is applied to additionally swirl the air inside the electric machine, so that an inner cooling circuit established. The disadvantage here is that this solution is additional Parts and therefore an increased Installation effort required. Furthermore, at higher speeds of the electric machine additional Frictional losses and noise generated.

A possibility To shift the thermal limit consists of the bearings increased loss of heat input in which they are dimensionally stable, i.e. heat treated Components executed are. The disadvantage here is that while only the dimensional accuracy the bearing is improved. An extension of the lubricant service life is not achieved.

Though can the bearings by oil quantity lubrication with elevated Lubricant service lives are provided, i. through the camp will be a larger amount of oil than pumped for lubrication, but there are additional Aggregates necessary that the oil circulation maintained. Furthermore, the camp environment is due to the now pending sealing problem much more complex.

Of Furthermore, the shaft can be cooled specifically by additional cooling elements, so that the amount of heat loss, the above the bearing is discharged, can be discharged directly from the shaft. The disadvantage here is the elaborate and thus cost-intensive realization of this solution.

For example, from the CH 381 026 describes the thermal protection of a bearing, in which the bearing bearing shaft is designed as a hollow shaft and has a thermal protection of the bearing. Thus, the bearing is protected against increased heat loss amounts of the hollow shaft and there are sufficient lubricant service life possible. The disadvantage here is that the shaft must be designed as a hollow shaft and to make increased demands on the material properties of the heat sink.

at electric machines is also known so-called by unavoidable and symmetric magnetic fields Shaft voltages in the electrically conductive part of the electrical Machine be induced. These induced voltages can too a current flow in one of the shaft of the rotor, the bearings of the Rotor and the housing lead formed loops, the so-called wave current. Other causes of the formation of wave currents can be capacitive Couplings, especially in today's increasingly used Inverter - controlled drives with high rates of change Reinforced control occur. The occurring wave currents represent in particular in Area of bearings of the rotor is a big problem.

Around To prevent the wave current, it is known the case-side Part of at least one camp against the earth potential on the the other parts of the housing the electric machine usually lies, isolate. As a result, the wave current flow in the beginning interrupted loop mentioned. However, this means a considerable Effort, because supporting parts of the electrical machine are isolated have to.

outgoing It is the object of the invention to provide an electrical Machine to create, in particular, a sufficient heat dissipation guaranteed from the rotor without reducing the storage life. Furthermore, should the wave currents derived by appropriate measures or be prevented.

The solution the task is achieved by an electric machine with a stator and a rotor rotatably connected to a shaft is, wherein the shaft is mounted at least in a bearing, wherein on the motor side facing the bearing receiving bearing plate an extension is provided in the direction of the shaft, such that between extension and shaft is an arrangement that a fixed and a co-rotating base part and an intermediate therebetween thermally conductive and electrically conductive Material is located.

Of the Extension of the bearing plate is in a preferred embodiment such executed that from the point of view of the electric machine before the actual Bearing is arranged. this leads to to no axial extension of the volume of the electrical machine. in principle the extension can also be arranged after the bearing.

Of the Extension includes the shaft of the rotor, being both on the Rotor as well as on the extension opposite corresponding Base parts are located, which are spaced apart by a gap are and wherein in the gap a liquid metal alloy is available.

These Liquid metal alloy is both a good electrical conductor and a good conductor of heat. The liquid metal is held by the advantageous embodiment of the gap in the gap, in which the adhesion forces of the liquid this pushes back into the gap. In order to Both the wave currents as well as excessive heat conduction from the eigentli Chen camp held. This leads to comparatively longer storage life.

The Bearing plate on which the extension in one piece or several parts mechanically is connected, so that an electrical contact and / or a thermal Connection takes place, is colder as the shaft itself. The end shield is cooled by, for example airflows due to convection or forced airflow due to a fan.

Of the Loss of heat flow from the shaft towards the bearing is thus mainly on the Arrangement with the liquid metal flow away and only a remaining smaller negligible part flows over that classic bearings, i. above Bearing inner ring, lubricant, balls or rollers, lubricant Bearing outer ring to the end shield.

The classic bearings will thus thermally to a considerable extent Relieved, the axially before or after the camp on the Extension and thus ultimately over the bearing plate is removed. The effect of the arrangement is the larger the larger the area between fixed and mitrotierendem part and thus this arrangement accomplished is.

In preferred embodiments these arrangements are as fluid bearings executed which are used instead of or in addition to the classic bearings.

advantageously, can especially at higher levels Protection classes at the e.g. an internal cooling circuit and an external cooling circuit is present, with extension and / or the bearing plate cooling fins or form sections of a liquid cooling circuit.

In an alternative embodiment is the classic warehouse complete through a liquid metal bearing.

The Invention and further advantageous embodiments of the invention according to the subclaims explained in more detail in schematically illustrated embodiments. there demonstrate:

1 a schematic representation of an electric motor,

2 a detailed view of an electric motor from the prior art,

3 Detail view with inventive solution,

4 and 5 further embodiments of the invention.

6 . 7 detailed views

1 shows a longitudinal section of an electric machine shown in principle 1 holding a terminal box 7 For connection of an electrical power supply. Radial below the Klem menkastens 7 there is a fan 8th placed in the space between a donor assembly 9 and a ventilation grille not shown causes an air flow, both the encoder assembly 9 as well as a bearing plate 10 cools.

The electric machine 1 has a stator 2 and a rotor 3 on, each having known heat sources. The stator 2 also has a winding system in its not shown, substantially axially extending grooves 6 due to the copper and iron losses a heat source in the stator 2 represents. Part of this heat is not shown in detail, but known per se cooling arrangements of the stator 2 dissipated. Here are axially or helically extending cooling channels 50 in the laminated core of the stator 2 and / or on the outer circumference of the stator 2 intended. In an electric machine 1 with housing, these cooling arrangements can be provided in or on the housing instead or additionally.

A detailed view after 2 represents the current state of the art. This is one towards the camp 5 dissipated heat loss 15 over a bearing inner ring 11 and the La geraußenring 12 on the conventional end shield 10 ' led, which acts as a heat sink. The one about the camp 5 flowing loss heat flow 14 corresponds to this arrangement, almost the loss heat flow 15 in the direction of the camp 5 from the electric machine 1 , in particular from the rotor 3 Coming, must be removed.

According to the invention will now according to 3 from the direction of the electric machine 1 , especially rotor 3 coming heat loss 15 divided into two heat losses, the one loss heat flow 16 over the liquid metal assembly 30 flows and only the remaining heat loss current 17 over the camp 5 is dissipated. The waste heat flows 16 . 17 be in the bearing plate 10 forwarded and there eg to the environment through eg a fan 8th caused turbulent flow of cooling air 13 issued.

There can be in a further embodiment by turbulent air flows to cooling fins 40 of the end shield 10 or liquid-cooled end shields dissipate these losses. In the case of liquid-cooled end shields with separate or integrated cooling in the cooling of the electrical machine, (in 4 are in principle cooling channels 41 in the bearing plate 10 shown), the cooling effect is extremely efficient. The cooling fins 40 are on the end shield 10 and or on the extension 18 arranged. They point at the extension 18 to the interior of the electric machine 1 , at the end plate 10 to the interior and / or to the outside.

Advantageously, now the storage life and the lubricant service life is significantly extended, since the loss of heat flow 17 only a fraction of the heat loss 16 accounts.

In 3 are more details of the bearing assembly such as not shown in cross-sectional tapers of the shaft 4 to see the bearing seat of the bearing inner ring 11 represent. The bearing outer ring 12 is through a clamping ring 20 and corresponding screw connections 21 on the bearing plate 10 fixed. Further shows 3 Boundary elements 33 the liquid metal assembly 30 that the liquid metal in the gap between the fixed 31 and co-rotating part 32 hold.

4 shows in a further embodiment, the extension 18 in turn, via a liquid metal assembly 30 to the wave 4 thermally and electrically coupled. The bearing outer ring 12 is still through a clamping ring 20 and corresponding extensions of the bearing plate 10 that are integral with the end shield 10 can be connected, fixed.

The cooling of the rotor according to the invention 3 and deriving the wave currents from the shaft 4 of the rotor 3 is through the liquid metal assembly 30 , which is advantageously designed as a liquid metal bearing guaranteed. The arrangement according to the invention is suitable for all speed ranges of the known electrical machines.

Although shows 1 a rotor 3 , which is designed as a squirrel-cage rotor, the arrangement according to the invention can be used in all known rotors, such as rotors with electrical excitation, permanent excitation, reluctance rotor, etc. The decisive factor is whether from the rotor 3 Heat is to be dissipated with simultaneous thermal relief and / or relief of wave currents of other drive components, such as bearings 5 ,

In a further embodiment according to 5 are liquid metal arrangements 30 on the front sides of the rotor 3 in addition to the existing warehouses 5 arranged. To the waste heat flows 15 towards the camp in front of these camps 5 are extensions 18 attached to the bearing plate, with an extension 18 and the liquid metal assembly 30 the wave 4 at least radially in one or more sections.

This also sets the course of the loss heat flows described above, so that the bearing 5 compared to conventional bearings and end shield assemblies has much less dissipate heat loss.

In another embodiment, the liquid metal bearings are outside the existing bearings 5 arranged, which also leads to a reduction of the waste heat flows through the classical camp 5 leads, since there find the loss of heat flows a lower heat transfer resistance.

In a further embodiment, the previous classic bearings 5 be replaced by liquid metal bearings, so that both the bearing function, as well as the transmission of the wave currents and the dissipation of the waste heat fluxes can be taken over by the liquid metal bearing.

6 shows a simple schematic representation of a liquid metal assembly 30 with their boundary elements 33 ,

7 shows an enlarged section of the gap 35 with the forces acting on the liquid metal. The resulting from the adhesion force F _A and the cohesive force F _k force F is perpendicular to the surface of the liquid metal. The force F thereby forms the surface of the liquid metal in the gap 35 , The angle α denotes the contact angle. The effect of the resulting force counteracts the tendency of the liquid metal out of the gap 35 withdraw.

The geometry of the gap 35 determined inter alia with the surface tension of the liquid metal and the material of the surface of the boundary elements 33 the magnitude of the force F, which is directed into the interior of the liquid metal. By optional design of the gap 35 and the selection of the surface material of the boundary elements 33 As well as the chemical composition of the liquid metal can thus the exit of the liquid metal from the gap 35 be prevented. The adhesion force F _A denotes the edge elements of the surface of the Be 33 force acting on the liquid metal. The cohesive force F _k denotes the coherent force between the individual molecules of the liquid metal. The capillary forces cause the liquid metal not from the gap 35 occurs. This is due to the configuration of the fixed and co-rotating part and / or by the boundary elements 33 causes.

The boundary elements 33 are executed in a further embodiment as seals, such as ferrofluid seals, brush seals or labyrinth seals.

The fixed ones 31 and the co-rotating parts 32 are of course also made of a material that has a comparatively good heat conductor and a comparatively good electrical conductivity.

When liquid metals or liquid metal compounds are doing u.a. Galium, indium, tin or selenium compounds suitable.

Claims (6)

Electric machine ( 1 ) with a stator ( 2 ) and a rotor ( 3 ), which is non-rotatable with a shaft ( 4 ), the shaft ( 4 ) at least in one warehouse ( 5 ), wherein on the rotor ( 3 ) facing side the bearing ( 5 ) receiving end shield ( 10 ) an extension ( 18 ) is provided in particular in the direction of the shaft, such that between extension ( 18 ) and wave ( 4 ) an arrangement ( 30 ), which has a fixed ( 31 ) and a co-rotating base part ( 32 ) and there is a heat-conductive and electrically conductive material therebetween. Electric machine ( 1 ) according to claim 1, characterized in that the arrangement ( 30 ) as a liquid metal assembly ( 30 ), in particular as a liquid metal bearing is formed. Electric machine ( 1 ) according to claim 1 or 2, characterized in that the extension ( 18 ) in one piece with the bearing plate ( 10 ) connected is. Electric machine ( 1 ) according to one of the preceding claims, characterized in that the extension ( 18 ) to the bearing outer ring 12 or the existing end shield 10 is flanged. Electric machine ( 1 ) according to one of the preceding claims, characterized in that the end shield ( 10 ) and / or the extension ( 18 ) Cooling fins ( 40 ) having. Electric machine ( 1 ) according to one of the preceding claims, characterized in that between the fixed ( 31 ) and mitrotierendem base part ( 32 ) existing metallic liquid by Adhä sionskräfte in the gap between the base parts ( 31 . 32 ) is held.