EP2798224A1

EP2798224A1 - Pump unit

Info

Publication number: EP2798224A1
Application number: EP12813319.6A
Authority: EP
Inventors: Thomas Blad
Original assignee: Grundfos Holdings AS
Current assignee: Grundfos Holdings AS
Priority date: 2011-12-27
Filing date: 2012-12-19
Publication date: 2014-11-05
Anticipated expiration: 2032-12-19
Also published as: CN104024647A; US10024324B2; WO2013098142A1; US20150017031A1; EP2798224B1; CN104024647B; EP2798224B2

Abstract

Pump unit with an electric drive motor, which has a stator (20) and a rotor in the form of a permanent magnet rotor (14), at least one impeller (4) that is connected to the rotor (14) via a rotor shaft (12), and an axial bearing (26, 28) that is designed in such a way that it absorbs the axial forces acting on the impeller (4) and the rotor shaft (12) that are generated while the pump unit is in operation, and at least one radial bearing arranged on the rotor shaft (12), wherein the rotor (14) and the stator (20) are designed in such a way that a magnetic axial force acting in the direction of the axis of rotation (X) of the rotor (14) is generated between the rotor (14) and the stator (20), said axial force acting on the rotor in the direction of the prevailing current (E) into the impeller (4), and the rotor shaft (12) with the rotor (14) is supported so as to be movable in an axial direction (X) relative to the stator (20), and the radial bearing (22, 24) is designed in such a way that when the rotor shaft (12) is displaced axially into the impeller in the direction of the prevailing current (E), the bearing surfaces (34) of the radial bearing (22, 24) lying opposite one another disengage at least partially.

Description

description

The invention relates to a pump unit with the features specified in the preamble of claim 1.

In particular, as Heizungsumwälzpumpenaggregate pump units are known, which form a structural unit of a pump and an electric drive motor. The electric drive motors are often designed as permanent magnet rotors, ie they have a permanent magnet rotor, which rotates in the interior of a stator. At least one pump impeller, which rotates in a pump housing, is connected to this permanent magnet rotor via a rotor shaft. During operation of the pump unit, an axial force acts on the shaft, which axial force is absorbed by a thrust bearing on the rotor shaft or the rotor. These pump units are designed as wet-running pump units, ie the rotor runs inside a canned or canned pot in the liquid to be pumped. The bearings which store the rotor or the rotor shaft are usually lubricated by the liquid to be conveyed. In the case of these pump sets, there is the problem, during prolonged downtimes, that impurities contained in the liquid to be pumped can set the bearings, so that the motor can no longer start due to an insufficient starting torque. In view of this problem, it is an object of the invention to improve a pump unit to the effect that the Pump unit can start even after long standstill problems.

This object is achieved by a pump unit having the features specified in claim 1. Preferred embodiments will become apparent from the subclaims, the following description and the accompanying figures.

The pump unit according to the invention has, as known pump units on an electric drive motor, which is preferably designed as a wet-running electric drive motor. The electric drive motor has a stator and a rotor designed as a permanent magnet rotor. In the case of a wet-running rotor, the rotor is arranged inside a canned or canned pot, which separates the wet rotor space from the dry stator space in which the stator is arranged. Furthermore, the pump unit has at least one impeller, which is connected via a rotor shaft to the rotor. The impeller is preferably arranged in the interior of a pump housing, as defined in conventional centrifugal pump units, which defines the suction and pressure-side flow paths. Furthermore, a thrust bearing is provided which receives the axial forces acting on the impeller and the rotor shaft during operation of the pump assembly. These are hydraulic axial forces which, in operation, are generally directed opposite to the inflow direction in which the liquid to be conveyed flows into the suction mouth of the impeller. The flow typically enters the impeller axially and radially out of the impeller. The axial bearing is preferably arranged or formed on the rotor shaft or on the rotor. In addition to the axial bearing, at least one radial bearing is arranged on the rotor shaft. This radial bearing may be a separate component which is connected to the rotor shaft. Alternatively, the inner bearing surface of the Outer circumferential surface may be formed by the rotor shaft itself, which is on a fixed outer bearing surface in abutment.

According to the invention, the permanent magnet rotor and the stator are designed such that a magnetic axial force is generated between the rotor and the stator which acts in the direction of the axis of rotation of the rotor and which is directed in the opposite direction from the rotor to the stator of the inflow direction. Ie. Conversely, this additional axial force acts on the rotor in the direction of the inflow direction. Ie. this magnetic axial force counteracts the hydraulic axial force which occurs in normal operation and acts on the rotor. In particular, the arrangement of permanent magnet rotor and stator is designed so that this magnetic axial force also occurs when the pump unit is not in operation, ie that the permanent magnetic force acts permanently, both during operation and at standstill of the drive motor. As a result, a relief of the thrust bearing is achieved at a standstill, so that the risk of unwanted locking of the bearing is reduced at a standstill. In addition, the bearing is relieved even when starting the engine, so that the friction is reduced and so the required starting torque is reduced. Preferably, this permanent magnetic axial force results from the arrangement of the permanent magnet rotor and the stator relative to each other. Ideally, therefore, no additional permanent magnetic or soft magnetic components are required. However, it is also conceivable to arrange on the rotor and / or the stator an additional hard magnetic, ie permanent magnetic or soft magnetic element or more such elements which generate the magnetic axial force or contribute to the generation thereof. Further, the rotor shaft is slidably mounted with the rotor relative to the stator in the axial direction. This arrangement makes it possible, by the additional magnetic axial force, to cause a displacement of the rotor shaft in the axial direction in certain operating conditions or in the idle state of the pump unit. This makes it possible, as described below, preferably at least partially disengage the bearings when the pump unit is not in operation, whereby a setting of the bearings can be avoided. In addition, a seal of the rotor space, as described below, can be achieved in the idle state to prevent ingress of impurities in the rotor space.

Particularly preferably, the rotor shaft is movable so that it can move axially in the inflow of the impeller in the idle state of the pump unit. Ie. at rest, the rotor shaft would move axially in the direction in which the liquid flows axially into the impeller due to the permanent magnetic force, since an opposing hydraulic force is absent. This is the direction which is directed opposite to the axial force acting in normal operation of the pump unit. When the pump unit is put into operation, the hydraulic axial force is preferably greater than the magnetic force, so that due to the opposing action of the axial hydraulic force, the rotor shaft is again in the reverse direction, i. H. is moved against the inflow direction.

Preferably, an axial force acting on the impeller and the rotor shaft during operation of the pump assembly is greater than the oppositely directed magnetic axial force. Preferably, the hydraulic axial force is greater than the oppositely directed magnetic axial force in the entire operating range or at least in the normal operating range of the pump unit. This will ensures that the thrust bearing is held in a defined abutment on the rotor shaft or on the rotor by the hydraulic axial force during operation. When the pump set is taken out of service, the hydraulic axial force falls away and it only acts the described permanent magnetic axial force, which then leads to a displacement of the rotor, wherein the at least one radial bearing at least partially disengaged. Depending on the configuration of the magnetic arrangement, which causes the permanent magnetic force, the permanent magnetic axial force can then be reduced or canceled in the rest position. It is essential that the permanent magnetic axial force acts in operation of the pump unit against the hydraulic axial force, that the elimination of the hydraulic axial force, the magnetic axial force can cause a displacement of the rotor in the axial direction. Ie. According to the invention, the permanent magnetic axial force does not have to act on the rotor in all states of the pump unit, but only at least when the pump unit is switched off, in order then to displace the rotor shaft as desired in the axial direction. When restarting the pump unit can then be displaced by the occurring hydraulic axial force, the rotor shaft back into a position in which the at least radial thrust bearing is fully engaged.

The at least one radial bearing is configured in such a way that, when axial displacement of the rotor shaft in the inflow direction of the impeller caused by the magnetic axial force occurs, the opposing bearing surfaces of the radial bearing at least partially disengage. In normal operation of the pump unit, the bearing surfaces of the radial bearing are opposite to each other and to each other. The axial displacement ensures that the bearing surfaces are axially displaced relative to each other so that they overlap only in a smaller area, ie the overlap of the bearing surfaces is reduced, the bearing surfaces are partially disengaged. Thus, the friction is reduced in the radial bearing and the risk of immobilizing at a standstill is reduced.

The stator preferably surrounds the rotor circumferentially. In this arrangement, the permanent magnets in the rotor are usually magnetized in the radial direction or cause a radial magnetic field of the rotor. The permanent magnetic magnetic field of the permanent magnet in the rotor interacts with the iron parts of the stator, whereby an additional axial force can be generated with a corresponding arrangement and design.

For example, the additional magnetic axial force can be generated in that the rotor and the stator are designed and arranged such that at least during operation of the pump unit, the axial center of the rotor, d. H. the axial center of the magnetically active part of the rotor, in the direction opposite to the inflow direction, in which the liquid enters the impeller, is spaced from the axial center of the stator. Ie. the rotor is arranged offset relative to the stator to the inlet opening or to the suction mouth. Due to the permanent magnetic magnetic field of the rotor, however, this endeavors to center in the interior of the iron core of the stator in the axial direction. The axial offset thus generates a magnetic force which tends to pull the rotor into the centered position. Ie. Ideally, in an otherwise conventionally formed permanent magnet rotor and an associated stator solely by axial displacement of the rotor during operation of the pump unit an additional axial force can be generated in the desired direction.

The at least one impeller is preferably fixed in the axial direction on the rotor shaft. This ensures that the magnetic Axial force, which acts on the rotor, also acts on the impeller and beyond the impeller is fixed in the axial direction by the rotor.

Preferably, the thrust bearing is designed such that its bearing surfaces when moving the rotor shaft in the inflow direction in the impeller out of engagement. This ensures that, in particular in the idle state, when the hydraulic axial force does not act and the rotor shaft by the magnetic force in the inflow direction, d. H. is moved against the axial force acting in normal operation, the thrust bearing is disengaged. Thus, a setting of the bearing can be prevented at rest. In addition, the friction is reduced when restarting.

Particularly preferably, the at least one radial bearing is designed as a sliding bearing, of which a first bearing surface on the outer circumference of the rotor shaft and an opposite second bearing surface is formed in a fixed bearing ring. The fixed bearing ring is preferably formed as a ceramic bearing ring. Also, the rotor shaft may preferably be formed as a ceramic shaft or at least preferably have ceramic bearing surfaces. More preferably, the diameter of the rotor shaft relative to the diameter of this bearing surface is reduced at least one side facing the impeller of a formed on the rotor shaft bearing surface of the radial bearing. This ensures that when the rotor shaft is moved by the magnetic axial force in the direction away from the impeller, ie, the inflow direction of the impeller, the reduced diameter surface of the rotor shaft enters the radial bearing or the bearing ring, so in this area, the bearing surface on the inner circumference of the bearing ring no longer rests on the outer circumference of the rotor shaft. In this way, the bearing surfaces of the radial bearing at least partially disengaged, so that the friction when starting and the risk of setting the radial bearing is reduced.

Particularly preferably, two radial bearings are arranged on the rotor shaft, which are designed in the manner described above, wherein the two bearings are preferably located on opposite axial sides of the rotor. Ie. a radial bearing is preferably located on the side facing away from the rotor of the rotor. This radial bearing is preferably arranged in the vicinity of the bottom of a canned pot. The second radial bearing is arranged on the side facing the impeller of the rotor and may be part of a combined radial thrust bearing, which is arranged between the rotor and impeller on the rotor shaft.

According to a particularly preferred embodiment, the opposing bearing surfaces of the radial bearing are dimensioned in their axial extent and arranged relative to each other such that they are disengaged by more than 50%, preferably more than 75% in the axial displacement of the rotor shaft. Ie. Preferably, only a very narrow area of the bearing surfaces still remains in contact or engagement in order to keep the rotor and the impeller positioned and to ensure storage when the drive motor starts up. However, the majority of the bearing surfaces are out of engagement, so that the friction is significantly reduced and the risk of settling of the bearing is minimized by contamination between the bearing surfaces.

The impeller is preferably sealed at its suction mouth via a suction seal against the pump housing. there the suction seal forms a fixed component on the pump housing. Preferably, the suction seal is arranged to the impeller such that upon an axial displacement of the rotor shaft in the inflow direction of the impeller, the suction seal and the impeller at least partially, preferably completely disengage. By this configuration it is achieved that at standstill of the pump unit, when the rotor is pulled into the stator due to the magnetic force, preferably the seal on the impeller can disengage. This prevents, on the one hand, that this seal settles during standstill. On the other hand, the flowability of the pump assembly is improved at standstill, since so fluid can flow past the impeller through the pump housing and the impeller for this flow forms no or only a significantly reduced resistance. Particularly preferred is this embodiment, in which the suction of the impeller at standstill of the impeller out of engagement, in combination with the bearings, in which the bearing surfaces at least partially disengage at standstill used. However, it is to be understood that this arrangement of the suction seal on the impeller can also be realized independently of the corresponding design of the bearing.

More preferably, the rotor shaft is displaceable by a degree which is smaller than or equal to an existing during operation of the pump assembly axial distance between the axial center of the rotor and the axial center of the stator. Ie. the axial mobility of the rotor shaft is limited and to a degree which is less than or equal to the axial displacement occurring between rotor and stator in operation. This ensures that a sufficient magnetic axial force always acts on the rotor shaft in order to be able to shift it by the desired amount. According to a further preferred embodiment, an emergency bearing surface, which faces a fixed thrust bearing surface, is formed on the at least one impeller on an axial side facing the rotor. In certain operating conditions, in particular at high flow and low pressure, the hydraulic axial force acting on the impeller against the inflow direction can decrease so much that the thrust bearing receiving this force during operation is relieved. So it can happen that the bearing surfaces of this thrust bearing are no longer held in this operating condition in abutment. In order to ensure an axial bearing in the opposite direction in this operating state, the oppositely directed emergency bearing is provided. In addition, the emergency bearing is preferably used when the rotor shaft is displaced in the manner described above in the axial direction by the magnetic force. In this case, the emergency bearing serves as a stop which limits the movement of the rotor shaft in the axial direction. In the opposite direction, the movement is limited by the actual thrust bearing. Thus, the emergency bearing comes then also when starting the drive motor from the idle state, if the actual thrust bearing is not yet in abutment to effect.

The thrust bearing surface on which the emergency bearing surface comes to rest is preferably formed by an axial end face of a stationary bearing ring, a radial and / or thrust bearing of the rotor shaft. As described above, this bearing ring is preferably a ceramic component whose front side preferably forms the actual axial bearing surface. This front side is the side facing away from the impeller and the rotor facing side of the bearing ring. The radial bearing surface is formed by the inner peripheral surface of the bearing ring. The thrust bearing surface, on which the emergency bearing comes to rest, is then the axial back, which faces the impeller is. If the emergency bearing surface of the impeller comes to rest on this rear side of the bearing ring, the bearing gap between the rotor shaft and the inner circumference of the bearing ring is simultaneously closed towards the pump chamber, in which the impeller is arranged, so that contaminants can be prevented from entering the bearing gap can. Preferably, the impeller is arranged relative to the bearing ring such that the emergency bearing surface can be brought into contact with the fixed thrust bearing surface by the axial displacement of the rotor shaft. Thus, with axial displacement of the rotor shaft in the idle state, the emergency bearing can be brought to bear against the bearing ring, so that in the idle state, when the pump unit is stationary, the bearing gap is closed by the emergency bearing surface.

The emergency bearing surface is further preferably formed by an axially projecting annular projection on the impeller. The impeller is preferably made in one piece with this projection made of plastic.

During normal operation of the pump assembly, the emergency bearing surface is preferably axially spaced from the fixed thrust bearing surface. In this condition, preferably, the normal thrust bearing is engaged to receive the axial hydraulic forces acting on the impeller and rotor. Ie. the normal operating state is that in which such a hydraulic force acts opposite to the direction of inflow into the impeller. Preferably, the distance of the emergency bearing surface of the fixed thrust bearing surface is smaller than or equal to an existing in operation of the pump assembly axial distance between the axial center of the rotor and the axial center of the stator. This arrangement ensures that when shifting the rotor shaft to bring the emergency bearing in and out of engagement with the thrust bearing surface, the offset is not greater than the offset between the rotor and stator, so always a magnetic Axialkraft is given, which holds the emergency bearing surface in abutment with the thrust bearing surface, as long as no oppositely acting hydraulic axial force leads to a displacement of the rotor shaft in the opposite direction and brings the emergency bearing surface of the thrust bearing surface out of engagement.

According to a further preferred embodiment, at least one sealing element can be arranged between the rotor shaft or the impeller on the one side and a stationary bearing ring or a bearing holder on the other side, which can be brought into sealing engagement by the axial displacement of the rotor shaft. So can on the impeller z. B. an annular sealing element may be arranged, which is also sealingly engageable with the end face of a fixed bearing ring to the plant. Instead of an arrangement of the sealing element on the impeller so that it can be brought to bear against the end face of a stationary bearing ring, the sealing element on the impeller could also be arranged or formed so that it is on the surface of a bearing or the bearing ring surrounding bearing support can come to the plant. Alternatively, such a sealing element could also be arranged on the axial bearing surface of the bearing ring and the impeller come to rest there with a suitable sealing surface during axial movement of the rotor shaft. It would also be possible to arrange such an annular seal not on the impeller but on the rotor shaft so that it can come into contact, for example, with the stationary bearing ring. In all these arrangements, the seal can thus seal the bearing gap between the bearing ring and the rotor shaft in the idle state of the pump unit to prevent flow through the bearing and the ingress of contaminants.

It should be understood that this sealing of the bearing gap by axial displacement of the rotor shaft and regardless of the configuration, in which by the axial displacement of the shaft, the bearing at least partially disengaged, could be realized. If the axial displacement of the rotor shaft is only used to bring the sealing element in and out of engagement, a much smaller axial displacement of the rotor shaft may be sufficient to effect this. This has the advantage that the rotor only has to be displaced axially relative to the stator by a small amount so that the magnetic efficiency is substantially not impaired. The invention will now be described by way of example with reference to the accompanying drawings. In these shows:

1 is a partially sectioned overall view of a pump unit according to the invention,

Fig. 2 is a sectional view of the pump unit with removed

Pump housing in operating condition and

Fig. 3 is a view according to FIG. 3 in the idle state.

The pump unit according to the invention has a pump housing 2, in which an impeller 4 is arranged. The impeller 4 has an axially directed central suction mouth 6, through which the liquid to be conveyed enters the impeller 4. The suction mouth 6 is located in the interior of the pump housing 2 against a flow channel, which opens into a suction nozzle 8. Opposite to the suction nozzle 8, a pressure port 10 is arranged on the pump housing 2, which is connected via a flow channel with the peripheral region of the impeller 4, which forms a spiral channel, in connection. The impeller 4 is connected via a rotor shaft 12 with a permanent magnet rotor 14. The rotor shaft 12 is preferably made of ceramic. In the rotor 14 permanent magnets 16 are arranged, which a generate radially directed magnetic field of the rotor 14. The permanent magnet rotor 14 is arranged in the interior of a split tube 18 or a canned pot 18. The split tube 18 is surrounded by the stator 20.

The impeller 4 is rotatably fixed and also in the axial direction X fixedly connected to the Roforwelle 12. The rotor shaft 12 is slidably mounted in two ceramic bearing rings 22 and 24. The bearing ring 22 is a pure radial bearing. The bearing ring 24 simultaneously assumes the function of the thrust bearing. For this purpose, the axial end face of the bearing ring 24 facing away from the impeller 4 is designed as an axial bearing surface on which an axial bearing ring 26 connected to the Rofor shaft 12 comes to rest. The thrust bearing 26 isf fixed in the axial direction X on the Roforwelle 12.

In normal operation of the Pumpenaggregafes acts on the impeller 4 and the Roforwelle 12 directed in the direction of the longitudinal or rotational axis X Axialkraff which is the Einströmrichfung E directed in the suction mouth 6 of the impeller 4 opposite. This hydraulic axial force is transmitted from the axial bearing ring 26 to the axial side 28 of the bearing ring 24 which faces away from the rotor 4 and forms a fixed axial bearing surface.

For radial mounting, the ceramic shaft 12 with its outer peripheral surfaces on the inner circumference of the bearing rings 22 and 24 slidably.

The rotor shaft 12 is movable in the axial direction X and is held in the state shown in Fig. 2 in the normal state of operation of the pump assembly by the hydraulic Axialkraff in which the Roforwelle 12 is moved against the Einwärtfrömrichtung E so far that the Axiallagerring on the Axialseife 28th of the bearing ring 24 sliding is applied. In this state, the axial center MR of the rotor, ie the magnetically active part of the rotor, is displaced from the axial center MS of the stator 20 or the iron part 30 by a dimension a in the axial direction. However, due to the magnetic forces acting between the permanent magnets 16 and the iron portion 30 of the stator 20, the rotor 12 tends to center with respect to the iron portion 30 so that the axial center MR of the rotor 12 is congruent with the axial center MS of the iron portion 30 is. As a result, a magnetic axial force acting in the direction of the inflow direction E is produced, which acts on the rotor shaft 12 and is opposite to the axial hydraulic force acting on the impeller 4 during operation of the pump unit. The pump unit or the drive motor is designed so that this magnetic force in normal operation, ie preferably in most operating areas of the pump unit is smaller than the hydraulic force, so that the Axiallagerring 26 is held on the axial side 28 of the bearing ring 24 in abutment.

When the pump set is turned off, the hydraulic axial force acting on the rotor shaft 12 drops away and only the magnetic axial force acts, which then pulls the rotor in the direction of the longitudinal axis X to its centered position, in which the axial center MR of FIG Rotor 12 is congruent with the axial center MS of the iron part 30 of the stator 20, as shown in Fig. 3. In this state, the thrust bearing ring 26 is spaced from the axial side 28 of the bearing ring 24 and thus the thrust bearing is disengaged.

Adjacent to the regions of the rotor shaft 12, which form the bearing surfaces 22 and 24 cooperating radial bearing surfaces 34, recesses 32 are formed on the outer circumference of the rotor shaft, in the region of the outer diameter of the rotor shaft 12 is reduced. The indentations 32 adjoin the side of the impeller 4 facing the Storage surfaces 34 at. When the Roforwelle is shifted in the state shown in Fig. 3 in the rest state, these recesses 32 enter the reduced diameter in the bearing rings 22 and 24 and at the same time exits a portion of the bearing surfaces 34 at the opposite axial end of the bearing rings 22 and 24. Ie. the bearing surfaces 34 are partially disengaged from the inner peripheral surfaces of the bearing rings 22 and 24, which form their radial bearing surfaces. In this way, the friction in the radial bearings 22 and 24 is reduced at rest and minimizes the risk of setting in the camps.

The impeller 4 is sealed at its suction mouth 6 via a suction seal 35 relative to the pump housing 2. The suction seal 35 is fixed to the pump housing 2 and engages in the suction mouth 6 a. During operation of the pump assembly, the inner circumference of the suction mouth 6 thus overlaps the outer circumference of the suction seal 35, wherein the suction mouth 6 rotates relative to the suction seal 35. The suction seal may be formed in a conventional manner as a collar-shaped sheet metal component.

When the rotor shaft 12 is displaced in the axial position shown in Fig. 3 at a standstill of the pump assembly, the impeller 4 moves with the rotor shaft 12 in the direction of the stator 20. This axial displacement is in the example shown here so large that the suction port 6 of the impeller of the suction seal 35 completely disengages, so that a gap between the rotor 14 remote from the axial side of the impeller 4 and the end face of the suction seal 35 is formed. The complete disengagement of the suction seal 35 from the suction mouth 6 prevents the suction seal 35 from settling on the suction mouth 6 during standstill. In addition, the pump unit can be flowed through at a better standstill, since the flow through the gap between the suction seal 35 and the front side of the impeller 4 on the impeller over by the pump housing 2 can take place for Drucksfufzen 10. Thus, the Sfrömungswidersfand is reduced at a standstill. The impeller 4 has on its end remote from the suction mouth 6 an annular projection 36 which faces the bearing ring 24. The projection 36 is made in one piece with the impeller 4 made of plastic and forms an emergency bearing surface. In operating states in which the hydraulic axial force is insufficient to hold the thrust bearing in abutment, ie to hold the thrust bearing ring 26 in abutment against the axial side 28 of the bearing ring 24, it may happen that the rotor shaft 12 also engages in the inoperative position during operation Fig. 3 shown position moves. Then, the projection 36 as an emergency bearing axial bearing in the opposite direction, in which it comes to rest on the impeller 4 facing axial side of the bearing ring 24, which is the axial side 28, which forms the actual thrust bearing surface, facing away. Such an operating state can occur, in particular, when the pump unit starts up. In addition, in this embodiment is thus at standstill of the pump unit, the projection 36 on the rear axial side of the bearing ring 24, so that the bearing gap between the bearing ring 24 and the rotor shaft 12 toward the pump chamber out, in which the impeller 4 is arranged, is sealed. Thus, penetration of dirt into the bearing gap and the rotor space can be prevented.

In this embodiment, moreover, an annular seal 38 is shown, which is arranged circumferentially in this embodiment on the rotor shaft 12. Here, the seal 38 is arranged substantially in the region of the rotor 14 facing the axial end of the impeller 4 on the outer circumference of the rotor shaft 12. When the rotor shaft 12 in the axial position shown in Fig. 3 is, in which it is axially displaced in the inflow direction E, this seal 38 comes in the region of the bearing gap on the bearing ring 24 sealingly to the plant. Such a seal 38 could also be formed in the peripheral region of the rotor shaft 12 on the impeller 4, in particular be cast directly to the impeller 4 made of an elastic plastic. Such a seal 38 could also be used as an alternative to the projection 36, as well as the projection 36 could be used without the seal 38.

LIST OF REFERENCE NUMBERS

2 pump housings

4 impeller

5 6 suction mouth

8 sucking fumes

10 pressure fumes

12 Rofor wave

14 permanent manager

10 16 permanent magnets

18 Canned or canned pot

20 stator

22, 24 bearing rings

26 thrust bearing

15 28 axial side

30 iron part

32 punctures

34 storage areas

35 suction seal

20 36 annular projection

38 seal

X longitudinal or rotary axis

E inflow direction

25 MS axial center of the iron part

MR axial center of the permanent magnet rotor a distance

Claims

claims

1 . Pump unit with

an electric drive motor which has a stator (20) and a rotor designed as a permanent magnet rotor (14),

at least one impeller (4) which is connected via a rotor shaft (12) with the rotor (14), and

a thrust bearing (26, 28) which is designed such that it absorbs during operation of the pump assembly on the impeller (4) and the rotor shaft (12) acting axial forces, and

at least one radial bearing arranged on the rotor shaft (12)

characterized in that

the rotor (14) and the stator (20) are configured such that between the rotor (14) and the stator (20) a magnetic axial force acting in the direction of the axis of rotation (X) of the rotor (14) is generated which acts on the rotor Direction of the inflow direction (E) in the impeller (4) acts, the rotor shaft (12) with the rotor (14) relative to the stator (20) in the axial direction (X) is slidably mounted, and the radial bearing (22, 24) is configured such that at an axial displacement of the rotor shaft (12) in the inflow direction (E) in the impeller, the opposing bearing surfaces (34) of the radial bearing (22, 24) at least partially disengaged. 2. Pump unit according to claim 1, characterized in that during operation of the pump unit on the impeller (4) and the rotor shaft (12) acting hydraulic axial force is greater than the oppositely directed magnetic axial force. Pump unit according to claim 1 or 2, characterized in that the stator (20) surrounds the rotor (14) circumferentially.

Pump unit according to one of the preceding claims, characterized in that on the rotor (14) and / or the stator (20) at least one additional hard or soft magnetic element is arranged, which contributes to the generation of the magnetic axial force.

5. Pump unit according to one of the preceding claims, characterized in that the rotor (14) and the stator (20) are designed and arranged such that at least during operation of the pump unit, the axial center (MR) of the rotor (14) in the opposite direction the inflow direction (E) in the impeller from the axial center (MS) of the stator (20) is spaced.

6. Pump unit according to one of the preceding claims, characterized in that the at least one impeller is fixed in the axial direction on the rotor shaft (12). 7. Pump unit according to one of the preceding claims, characterized in that the rotor shaft (12) is movable such that it can move axially in the idle state of the pump unit in the direction of the inflow direction (E) in the impeller (4). Pump unit according to claim 7, characterized in that the axial bearing (26, 28) is formed such that its bearing surfaces (26, 28) upon displacement of the rotor shaft (12) in the inflow direction (E) into the impeller out of engagement.

Pump unit according to one of the preceding claims, characterized in that the radial bearing (22, 24) is designed as a sliding bearing, of which a first bearing surface (34) on the outer circumference of the rotor shaft (12) and an opposite second bearing surface in a fixed bearing ring (22, 24) is formed.

Pump unit according to one of the preceding claims, characterized in that at least on one of the impeller (4) facing side of a formed on the rotor shaft (12) bearing surface (34) of the radial bearing of the diameter of the rotor shaft (12) relative to the diameter of this bearing surface (34) is reduced.

Pump unit according to one of the preceding claims, characterized in that the opposing bearing surfaces are dimensioned in their axial extent and relative to each other are arranged such that they at the axial displacement of the rotor shaft (12) by more than 50%, preferably by more than 75% disengage.

Pump unit according to one of the preceding claims, characterized in that adjacent to the impeller (4) a suction seal is arranged such that upon an axial displacement of the rotor shaft (12) in the inflow direction (E) in the impeller (4), the suction seal (35 ) and the impeller (4) at least partially disengaged.

13. Pump unit according to one of the preceding claims, characterized in that the rotor shaft (12) is displaceable by a degree which is smaller than or equal to an existing during operation of the pump assembly axial distance (a) between the axial center (MR) of the rotor and the axial center (MS) of the stator (20).

14. Pump unit according to one of the preceding claims, characterized in that on the at least one impeller (4) on one of the rotor (12) facing axial side of an emergency bearing surface (36) is formed, which faces a fixed thrust bearing surface.

15. Pump unit according to claim 14, characterized in that the axial bearing surface is formed by an axial end face of a stationary bearing ring (24) of a radial and / or axial bearing of the rotor shaft (12).

16. Pump unit according to claim 14 or 15 and one of claims 7 to 15, characterized in that the impeller (4) relative to the bearing ring (24) is arranged such that by the axial displacement of the rotor shaft (12) the emergency bearing surface (36 ) can be brought into contact with the fixed thrust bearing surface, wherein during operation of the pump assembly, the emergency bearing surface (36) is preferably axially spaced from the fixed thrust bearing surface.

17. Pump unit according to claim 16, characterized in that the distance of the emergency bearing surface (36) from the fixed

Axiallagerfläche less than or equal to an existing during operation of the pump assembly axial distance (a) between the axial center (MR) of the rotor and the axial center (MS) of the stator (20).

Pump unit according to one of the preceding claims, characterized in that between the rotor shaft (12) or the impeller (4) on the one side and a stationary bearing ring (24) on the other side at least one sealing element (38) is arranged, which through the axial displacement of the rotor shaft (12) can be brought into sealing contact.