US20150004032A1 - Wet rotor pump comprising power electronics - Google Patents

Abstract

A wet rotor pump with an axial flux motor that includes a stator, a containment shell, and a rotor. The stator and the containment shell are arranged in a dry zone while the rotor on an impeller is arranged in a wet zone. The wet rotor pump further has an inlet line for a fluid to be pumped by the impeller, said inlet line extending through the stator and the containment shell in an axial direction, and power electronics for controlling the stator, said power electronics being arranged within the space delimited by the stator and the containment shell.

Description

• The invention relates to a wet rotor pump for pumping a fluid, in particular a liquid.
• Document DE 10 2005 015 213 A1 makes known a wet rotor pump. The wet rotor pump comprises a rotor, which is connected to an impeller and is disposed in a wet zone, through which a pumped fluid flows. The wet zone is separated from a dry zone, in which the stator is disposed. The wet zone is demarcated from the dry zone by means of a printed circuit board, the electric lines of which form the stator such that the printed circuit board functions simultaneously as a containment shell.
• Document DE 103 03 778 A1 makes known an electrically driven pump, which comprises an electric drive motor embodied as a disk rotor. The magnetic ring of the drive motor is disposed in a region through which fluid flows.
• Axial flux motors are also known per se from the related art. In an axial flux motor, the magnetic flux extends in the air gap of the motor in the axial direction, cf. DE 100 53 400 A1, for example.
• The problem addressed by the invention is that of creating an improved wet rotor pump.
• The problem addressed by the invention is solved by the features of claim1. Embodiments of the invention are set forth in the dependent claims.
• According to embodiments of the invention, a wet rotor pump comprising an axial flux motor is created, said wet rotor pump having an inlet line for the fluid, which said inlet line extends through the stator and the containment shell. This makes it possible to dispose the power electronics for controlling the stator in the space between the stator and the containment shell. Since this space is located in the dry zone of the wet rotor pump, water-tight encapsulation of the power electronics is not required. Due to the geometry of the wet rotor pump, a particularly compact design is made possible, since the intermediate space formed by the stator, in particular the stator teeth, and the inlet line is used to accommodate the power electronics.
• According to embodiments of the invention, the power electronics are disposed on an annular printed circuit board, wherein the inlet line extends through the printed circuit board.
• According to embodiments of the invention, a wet rotor pump is created, in which an inlet line for the fluid extends through the stator, the containment shell, and the bearing for the impeller. Such a geometry has the advantage, in particular, that the wet rotor pump has a particularly compact design, i.e. a low overall height, combined with high power density.
• Embodiments of the invention are furthermore particularly advantageous since the bearing functions simultaneously as a seal at the transition between the suction side and the pressure side of the wet rotor pump. The losses due to leakage are minimized due to the relatively small gap widths and the low tolerances of the bearing.
• According to an embodiment of the invention, the fluid enters through a central opening in the containment shell. The containment shell can form an inlet connecting piece in particular.
• According to an embodiment of the invention, the stator is formed in the shape of a torus. In particular, the stator can comprise an annular stator tooth receptacle, on which stator teeth are disposed. The stator teeth can be attached to the stator tooth receptacle by means of bonding, for example.
• According to an embodiment of the invention, each of the stator teeth has a receiving region for a coil. Each of the stator teeth has an enlarged cross section at the end on the air-gap side. This has the advantage that the magnetic field is approximately homogeneous in a larger region within the air gap and therefore completely encloses the rotor magnets, which are narrower in the radial direction, thereby supporting the self-centering of the impeller. In this case, “air gap” refers to the separation between the ends of the stator teeth and the rotor, even if the gap contains no air or not only air, e.g. the fluid as well.
• According to an embodiment of the invention, the power electronics, which are used to control the coils of the stator, are disposed within the space circumscribed by the stator and the containment shell, as on an annular printed circuit board, for example. The overall height of the wet rotor pump can be further reduced in this manner.
• According to an embodiment of the invention, the containment shell is formed by an annular disk, which extends into the air gap between the stator and the rotor and separates the dry zone of the wet rotor pump from the wet zone. The annular disk has a central opening, at which the inlet connecting piece is disposed, which said inlet connecting piece extends through the center of the stator. The bearing for the impeller is disposed at the end region of the inlet connecting piece on the disk side, through which the fluid flows into the wet zone after having flowed through the dry zone, through the inlet line. The disk and the inlet connecting piece can be formed as one piece, in particular as a plastic injection-molded part. The containment shell can be embodied, in particular, as a plastic part (e.g. made of PPS/GFK/CFK) or as a non-magnetic, metallic part.
• According to an embodiment of the invention, the bearing is designed as a plain bearing, wherein a bearing bush of the plain bearing is disposed at the end region of the inlet connecting piece on the disk side, and a plain-bearing element of the plain bearing is attached to the impeller. A sliding surface of the plain-bearing element engages in the bearing bush such that radial support is provided. A further sliding surface can be provided on the bearing to provide additional unilateral axial support for absorbing the magnetic attraction force of the stator, which acts on the impeller via the rotor.
• Embodiments of the invention are particularly advantageous since, due to the axial flux motor on the impeller, a magnetic attraction force is exerted in the direction toward the stator such that the impeller requires support on only one side. This simplifies the design and further reduces the required overall height of the wet rotor pump.
• According to an embodiment of the invention, the plain-bearing element has passage holes in the radial direction, such as lubrication holes approximately 1 mm in size, for example, which are used to direct a very small portion of the volume flow of the fluid through the bearing in order to provide additional lubrication of said bearing.
• According to an embodiment of the invention, the bearing is coated with a combination of diamond-like carbon and silicon carbide (SiC), in order to ensure a particularly long service life of the bearing.
• According to an embodiment of the invention, the bearing is designed as a combination of a plain bearing and a rolling bearing, which is designed to provide axial and radial support of the impeller. The rolling bearing is used to absorb axial forces, while the plain bearing is used to absorb radial forces, wherein said plain bearing is formed with consideration for hydrodynamic aspects.
• Embodiments of the invention are particularly advantageous, since strong forces can occur in the axial direction, in particular, due to the attraction of stator and rotor magnets, which said forces can result in a high amount of wear in a plain bearing. A rolling bearing, however, is characterized by low friction, primarily in the form of rolling friction, and therefore the wear on the bearing is reduced as compared to a plain bearing.
• According to an embodiment of the invention, the rolling bearing is formed by bearing shells, which have running surfaces for accommodating rolling elements, and rolling elements. In this case, a first bearing shell is attached to the impeller, while a second bearing shell is attached to the containment shell. The rolling elements are located in the space circumscribed by the running surfaces of the bearing shells.
• According to an embodiment of the invention, the plain bearing is formed on the impeller side by the outer jacket surface of the first bearing shell, and by the jacket surface of the containment shell. On the containment-shell side, the plain bearing is formed by the inner jacket surface of the second bearing shell and the jacket surface of the impeller.
• Embodiments are particularly advantageous, since the bearing shells are part of the plain bearing and are part of the rolling bearing. Therefore, this is a hybrid bearing. This arrangement results in a bearing for a wet rotor pump that is very compact and, simultaneously, has a long service life and is robust.
• In order to further increase the service life of the bearing, in an embodiment of the invention, the jacket surfaces and/or the running surfaces of the bearing shells and/or the rolling elements are coated with silicon carbide (SiC) and/or diamond-like carbon (DLC) and/or silicon-doped DLC.
• According to an embodiment of the invention, the bearing is embodied as a combination of a plain bearing and a magnetic bearing, which is designed to provide radial support of the impeller. The magnetic bearing is used to absorb axial forces, while the plain bearing is used to absorb radial forces, wherein said plain bearing is formed with consideration for hydrodynamic aspects.
• Embodiments of the invention are particularly advantageous, since a magnetic bearing is characterized by friction that ideally disappears, which results in a markedly longer service life of the bearing as compared to a plain bearing. In addition, the efficiency of the wet rotor pump increases due to the very low losses due to friction.
• According to an embodiment of the invention, the magnetic bearing is formed by magnetic rings. In this case, a first magnetic ring is attached to the impeller, and a second magnetic ring is attached to the containment shell. The magnetization of the magnetic rings is configured such that, in the state in which said magnetic rings are installed in the wet rotor pump, these repel one another in the axial direction.
• According to an embodiment of the invention, the plain bearing is formed on the impeller side by the outer jacket surface of the first magnetic ring, and by the jacket surface of the containment shell. On the containment-shell side, the plain bearing is formed by the inner jacket surface of the second magnetic ring and the jacket surface of the impeller.
• Embodiments are particularly advantageous, since the magnetic rings are part of the plain bearing and are part of the magnetic bearing. Therefore, this is a hybrid bearing. This arrangement results in a bearing for a wet rotor pump that is very compact and, simultaneously, has a long service life and is robust.
• In order to further increase the service life of the bearing, in an embodiment of the invention, the jacket surfaces of the magnetic rings are coated with silicon carbide (SiC) and/or diamond-like carbon (DLC) and/or silicon-doped DLC.
• According to a further embodiment, the bearing is protected by a fine-strand filter to ensure that particles do not enter the bearing. As a result, the bearing is protected from damage by particles that could be carried along in the medium.
• According to an embodiment of the invention, the rotor is formed by a permanent-magnet material, namely samarium cobalt (SmCo). This is advantageous for a plurality of reasons:
• Samarium cobalt can be used at high temperatures without negatively affecting the retentivity of the magnetization. As a result, the fluid can have a temperature of up to 200° C., for example.
• Samarium cobalt has excellent corrosion characteristics and can be directly exposed to the fluid with simple corrosion protection or without corrosion protection.
• Since samarium cobalt does not need to be encapsulated in stainless steel, for example, for corrosion protection, the magnetic material can be disposed at the outermost edge of the periphery of the impeller or the drive disk, thereby permitting the permanent-magnet material to be positioned with a maximum radius.
• The permanent-magnet material forming the rotor can be disposed in the form of a plurality of individual, flat permanent magnets on the periphery of the impeller or in the form of a single magnetic ring having multipolar magnetization. In particular, the magnets or the magnetic ring can be attached directly on the periphery of the impeller or can be attached to the impeller via a drive disk.
• Embodiments of the invention are explained in greater detail in the following with reference to the drawings. In the drawings:
• FIG. 1 shows an exploded view of a wet rotor pump according to the invention,
• FIG. 2ashows a side view of a single stator tooth,
• FIG. 2bshows a front view of the stator tooth according toFIG. 2a,
• FIG. 2cshows a perspective view of the stator tooth according toFIG. 2a,
• FIG. 3ashows a top view of the stator,
• FIG. 3bshows a sectional view of the stator,
• FIG. 4ashows a top view of an embodiment of the containment shell,
• FIG. 4bshows a sectional view of the containment shell according toFIG. 4a,
• FIG. 4cshows a sectional view of the bearing bush of the containment shell according toFIG. 4a,
• FIG. 4dshows a sectional view of an embodiment of the plain-bearing element of the impeller,
• FIG. 5ashows a top view of an embodiment of the rotor,
• FIG. 5bshows a sectional view of the rotor according toFIG. 5a,
• FIG. 6 shows a sectional view of an embodiment of the drive disk,
• FIG. 7 shows a sectional view of an embodiment of the impeller,
• FIG. 8 shows a sectional view of the wet rotor pump according toFIG. 1, in the installed state,
• FIG. 9 shows a sectional view of a wet rotor pump comprising a hybrid bearing formed of a rolling bearing and a plain bearing,
• FIG. 10 shows a sectional view of a further wet rotor pump according to the invention.
• Elements of the following embodiments that correspond to one another or are identical are labelled with the same reference signs in each case.
• FIG. 1 shows an exploded view of an embodiment of awet rotor pump100 according to the invention. Thewet rotor pump100 has amotor cover102, which has acircular end face104. Anopening106 for the inflow of a fluid108 is located in the center of theend face104.
• Themotor cover102 is used to cover astator110. Thestator110 has astator tooth receptacle112, which has an annular shape and on whichstator teeth114 are disposed so as to form a circle. Each of the stator teeth has a receivingregion118, on which a coil is wound (seeFIGS. 2 and 3).
• The various coils of thestator teeth114 are electrically connected topower electronics120, which are used to control the coils.
• In the embodiment considered here, the rotor of the axial flux motor is formed of a permanent-magnet material, which, in this case, is disposed on aring124 in the form of individual permanent magnets122 (seeFIG. 5).
• Thepermanent magnets122 have magnetization in the axial direction such that the magnetic flux also extends in the axial direction of thewet rotor pump100, namely between theends126 of thestator teeth114 and thepermanent magnets122, across an air gap that exists between theends126 and thepermanent magnets122. As a result, a magnetic attraction force is exerted by thestator110 on thepermanent magnets122 and, therefore, on animpeller128 of thewet rotor pump100.
• Adisk130 of acontainment shell116 extends into the air gap between theends126 of thestator teeth114 and thepermanent magnets122. Thedisk130 hasrecesses132, which accommodate the ends of the stator teeth114 (seeFIGS. 4a,4b). The bracings located between the recesses increase the mechanical stability of the motor design and make it possible to minimize the material thickness and, therefore, to minimize the air gap. The wall thickness of thecontainment shell116 in therecesses132 is between 0.7 mm and 0.2 mm, for example. Such a thin wall thickness reduces the air gap, which, in turn, increases efficiency and power while using the same certain quantity of rare earth magnets. The mechanical stability of the motor design is improved as a result.
• Thedisk130 has an axial opening, on which aninlet connecting piece134 is disposed.
• In the installed state of the wet rotor pump100 (seeFIG. 8), theinlet connecting piece134 extends through thestator110 and theopening106 of themotor cover102, thereby allowing the fluid108 to flow in via theinlet connecting piece134.
• A space is circumscribed by thecontainment shell116 and thestator110, in which the power electronics can be disposed, for example on an annular printedcircuit board136, the outer radius of which is limited by therecesses132, and the inner radius of which is limited by the wall of theinlet connecting piece134. This printedcircuit board136 can carry the various electric and electronic components that form thepower electronics120. Since this is disposed in the dry zone of thewet rotor pump100, special encapsulation of thepower electronics120 is not absolutely necessary.
• Anattachment region138 is disposed on theinlet connecting piece134 with axial separation from thedisk130, to which said attachment region themotor cover102 is attached, by means of screwed connections, for example. Thestator110 is then held between themotor cover102 and thedisk130, wherein theends126 of thestator teeth114 extend into therecesses132 and are held there in a form-fit manner, for example.
• Theattachment region138 can be annular, for example, as shown inFIG. 1, and can have internal threads for forming screwed connections for attaching themotor cover102, which has correspondingholes140 for passage of the screws. Simultaneously, the tubular extension of the containment shell having a disk-shaped portion toward the top is also used to center the stator flux return ring, i.e. thestator tooth receptacle112.
• The wet rotor pump has afirst housing half142 and asecond housing half144, by means of which the housing of thewet rotor pump100 is formed. Thehousing half142 has anopening146 in the center thereof, which adjoins the end of theinlet connecting piece134 on the air-gap side, thereby allowing fluid108 to flow from theinlet connecting piece134 through theopening146. Thedisk130 is attached to the outer side of thehousing half142, by means of screwed connections, for example, on anannular attachment region148 of thehousing half142. In the embodiment considered here, the inlet line is therefore formed by theinlet connecting piece134 with the bearingbush156 disposed at the end thereof on the air-gap side.
• Theimpeller128 is located between thesehousing halves142 and144. The rotor is formed at theimpeller128 by virtue of the fact that thering124 comprising thepermanent magnets122 is connected to theimpeller128 via adrive disk150, by means ofscrews153, for example. According to an alternative embodiment, thepermanent magnets122 can also be disposed directly on theimpeller128. Furthermore, thepermanent magnets122 can be disposed between thering124 and thedrive disk150.
• The impeller has anextension152 for accommodating a plain-bearing element154, which, together with abearing bush156, forms a plain bearing for the radial support of the impeller128 (seeFIGS. 4cand4d). The bearing supports theimpeller128 such that said impeller has one axial degree of freedom by virtue of the fact that a magnetic attraction force is exerted on theimpeller128 via thepermanent magnets122 in the axial direction toward thestator110, whereby the axial position of theimpeller128 is also determined. The bearing formed by the plain-bearing element154 and thebearing bush156 can be designed such that this forms as an abutment for absorbing the magnetic attraction force on one side in the axial direction (seeFIGS. 4cand4d).
• This magnetic attraction force of thestator110 furthermore has a self-centering effect—during rotation—on theimpeller128, which reduces the load on the plain bearing.
• The twohousing halves142 and144 are connected to one another by means of screws or adhesive158.
• Anoutlet160 for the fluid108 is formed in this manner.
• Embodiments of the invention are particularly advantageous since the fluid108 flows in on the stator side and, in fact, through the stator. Furthermore, due to the axial flux motor, support for the impeller is required on only one side, without a rotor shaft, which makes it possible overall to obtain a particularly compact design having a high power density.
• FIG. 2ashows a front view of one of thestator teeth126 according to the embodiment shown inFIG. 1. The receivingregion118 of thestator tooth126 accommodates a plurality of windings of a coil, which is controlled by thepower electronics120 of the printedcircuit board136.
• The receivingregion118 of thestator tooth114 is closed on the air-gap side by theend126 of thestator tooth114, which has a larger cross section than the receivingregion118. This larger cross section has the advantage that the magnetic field is widened accordingly in the air gap and is approximately homogeneous in a larger spatial region. The self-centering of the impeller128 (seeFIG. 1) is supported as a result, since thepermanent magnets122 of the rotor have a width in the radial direction that is shorter than the stator flux width.
• FIG. 2ashows, as an example, how one of thepermanent magnets122 is disposed on the impeller relative to thestator tooth114. Thepermanent magnet122 is shorter in the radial direction than the extension of theend126 of thestator tooth114 in the radial direction, and therefore the stator tooth extends beyond thepermanent magnet122. Thepermanent magnet122 is positioned in the center underneath the receivingregion118, for example.
• Thestator tooth114 has a slot-shapedrecess162 in the upper region thereof, which is used to attach thestator tooth114 to the stator tooth receptacle112 (seeFIG. 3).
• FIG. 2bshows thestator tooth114 in a front view, andFIG. 2cshows said stator tooth in a perspective view.
• FIG. 3ashows a top view of thestator110 having the annularstator tooth receptacle112, which has an opening in the center thereof, through which theinlet connecting piece134 extends (seeFIG. 1). Thestator teeth114, including therecesses162 thereof, are attached on the periphery of thestator tooth receptacle112. This can be achieved by therecess162 and/or thestator tooth receptacle112 functioning as bonding surfaces in order to bond thestator tooth114, including therecess162 thereof, on the edge of thestator tooth receptacle112.FIG. 3bshows a corresponding sectional view.
• FIG. 4ashows a top view of thecontainment shell116, through theinlet connecting piece134 of which the fluid can flow in. As shown inFIG. 4a, the inlet line extends through the annular printedcircuit board136.
• FIG. 4bshows a sectional view of thecontainment shell116. As shown inFIG. 4b, the end of theinlet connecting piece134 on the air-gap side is designed to accommodate abearing bush156, as shown inFIG. 4c. For this purpose, an inner radius R is formed at the end region of theinlet connecting piece134, into which thebearing bush156 can be inserted and affixed, for example with the aid of a press fit.
• A plain-bearing element154 is attached to theextension152 of the impeller128 (seeFIG. 1) and functions as the counterpart to thebearing bush156. The plain-bearing element154 is annular and has anend section164, the outer diameter of which is reduced such that acircumferential edge166 is formed externally on the plain-bearing element154.
• The bearingbush156 therefore accommodates theend section164 of the plain-bearing element154, wherein the inner side of the bearingbush156 and the outer side of theend section164 of the plain-bearing element154 form the sliding surfaces of the plain bearing. Theimpeller128 is thereby radially supported. The axial degree of freedom of theimpeller128 is limited by thecircumferential edge166.
• That is, during operation of the axial motor, if theimpeller128 is drawn in the direction of thestator110 by the magnetic forces that occur, theedge166 impacts the front side of the bearingbush156, thereby forming an abutment for absorbing this magnetic attraction force. Although theimpeller128 is therefore supported in thecontainment shell116 such that said impeller has one axial degree of freedom, i.e. axial play, the axial position of theimpeller128 is defined by the magnetic attraction force during operation of the axial flux motor.
• Preferably, at least one of the sliding surfaces of the plain bearing is coated with diamond-like carbon (DLC) and silicon carbide (SiC) or a combination of DLC and SiC, in order to extend the service life of the bearing.
• Embodiments of the invention are particularly advantageous in which thefluid108 is suctioned through the bearing, which also contributes to the compact design of the wet rotor pump. The plain bearing can have a very narrow gap, which is approximately 0.01 mm to 0.03 mm, for example, and is therefore also simultaneously very well sealed.
• According to an embodiment of the invention, the plain-bearing element154 can have one or more radial openings, such as lubrication holes approximately 1 mm in size, for example. By means of these openings, a very small portion of the volume flow of the fluid108 is directed between the sliding surfaces of the bearing in order to provide additional lubrication of said bearing. This at least one opening is preferably disposed in theend section164 of the plain-bearing element154 and is directed toward the center.
• FIG. 5 shows a top view of the rotor having thepermanent magnets122, which are disposed on thering124. Thepermanent magnets122 are preferably formed of samarium cobalt, which has various advantages:
• Samarium cobalt can be used in relatively high temperatures without the retentivity being negatively affected thereby; the fluid108 can have a temperature of up to 200° C., in particular.
• Samarium cobalt has excellent corrosion characteristics and can therefore be exposed to the fluid108 without coating and without encapsulation.
• Since encapsulation of thepermanent magnets122 is not required, said permanent magnets can be positioned at a maximum distance away from the rotational axis, thereby ensuring that maximum torque and maximum motor output result for a given amount of magnetic material.
• As an alternative, other materials can also be used for thepermanent magnets122, such as neodymium iron boron.
• FIG. 6 shows thedrive disk150 in a cross section. Thedrive disk150 is used to mechanically connect the rotor, i.e. thering124 having thepermanent magnets122, to theimpeller128, wherein theextension152 of theimpeller128 extends through thedrive disk150, as shown inFIG. 1.
• FIG. 7 shows a sectional view of theimpeller128.FIG. 8 shows a sectional view of thewet rotor pump100 in the installed state.
• In order to operate thewet rotor pump100, the coils of thestator teeth114 are controlled by the power electronics such that torque acts on theimpeller128 via the rotor. The rotor then suctions the fluid108 through theinlet connecting piece134 and the bearing such that the fluid108 is conveyed through thewet rotor pump100 and exits said wet rotor pump at theoutlet160.
• FIG. 9 shows a sectional view of a wet rotor pump according to the invention, wherein theimpeller128 is supported by a combination of a plain bearing and a rolling bearing. In the embodiment shown here, the rolling bearing is designed as a ball bearing. It is also feasible, however, to use other variants of rolling bearings, such as roller bearings, cone bearings, needle roller bearings, or the like.
• The rolling bearing is formed by two bearingshells170 and168, which have running surfaces for accommodatingrolling elements172. In this case, thelower bearing shell168 is attached to theimpeller128, whereas theupper bearing shell170 is attached to the containment shell. The bearing shells can be bonded, shrunk-fit or pressed onto the corresponding components, or fixedly screwed thereon. The rolling elements are located in the intermediate space between the bearing shells, which said intermediate space is circumscribed by the running surfaces of the bearing shells. If the pump is intended to be operated at high impeller speeds, the rolling bearings can be connected to one another by means of a cage in order to increase the stability of the bearing.
• The plain bearing is formed by an upper plain-bearing surface174 between theupper bearing shell170 and the jacket surface of theimpeller128, and by a lower plain-bearing surface176 between thelower bearing shell168 and thecontainment shell116. The plain bearing has only slight bearing play at thebearing surface174 in particular, thereby enabling a portion of the fluid108 to enter the rolling bearing. The penetration of the rolling bearing by the pumped fluid can provide additional lubrication of the rolling bearing.
• The bearing play, which can be considered to be an annular opening, is preferably protected by a fine-strand filter178, in order to ensure that foreign objects that can be contained in the pumped fluid are kept away from the bearing region. The fine-strand filter178 is held in position by aclamping ring180.
• Correspondingly precise production can be utilized in order to minimize the bearing play at the plain-bearing surfaces, preferably holding said bearing play in the range below 0.1 mm. This prevents coarse particles that can be contained in the fluid108 from entering the rolling bearing and damaging the running surfaces of the bearing shells or the rolling bearings. In addition, this narrow hydrodynamic gap functions as a sealing surface between the suction side and the pressure side of the pump, thereby ensuring that leakage effects can be prevented, which said leakage effects typically occur when the impeller is attached to a shaft in a classic manner and is not supported via the suction side.
• In order to further increase the long service life of the bearing, it is possible to coat the running surfaces of the bearingshells168 and170 and/or the rollingelements172 and/or the plain-bearingsurfaces174 and176 with SiC, DLC or silicon-doped DLC. As an alternative, ceramic or plastic bearings, which can be used in aqueous media in a frictionless manner and without risk of corrosion, are also feasible.
• FIG. 10 shows a further embodiment of awet rotor pump200 according to the invention. This wet rotor pump differs substantially from the wet rotor pump shown inFIG. 9 by a different geometry and different dimensions of thehousing204 and themotor cover216. This is due to the fact that therotor magnets206 are now no longer attached to the drive disk, but rather are attached directly on theimpeller202. In order to ensure that the distance between the lower end of thestator teeth212 and the rotor magnets is still minimal, thestator teeth212 have been lengthened in the vertical extension thereof. As a result, thecontainment shell222, including thesuction connecting piece218, has a different shape. Thestator tooth receptacle214 is unchanged compared to the stator tooth receptacle of the wet rotor pump shown inFIG. 9.
• A further difference between thewet rotor pump200 and the wet rotor pump described with reference toFIG. 9 relates to the support of theimpeller202 in thecontainment shell222. Instead of a rolling bearing comprising the bearingshells168 and170 and the rollingelements172, theimpeller202 of thewet rotor pump200 is supported in the axial direction by two magnetic rings, which are magnetized such that, in the installed state, said magnetic rings repel one another in the axial direction. In this case, a lowermagnetic ring208 is attached to theimpeller202, whereas an uppermagnetic ring210 is attached to the containment shell. As is the case for the bearingshells168 and170 of the wet rotor pump shown inFIG. 9, the magnetic rings can be attached by means of bonding, screwing, shrink-fitting, press-fitting, or other attachment methods.
• Themagnetic rings208 and210 comprise permanent magnets, such as neodymium iron boron (NdFeB) or samarium cobalt (SmCo), and are metallically completely encapsulated in an air- and water-tight manner. The encapsulation can be implemented by laser- or friction-welding of the encapsulation components, for example. In a preferred embodiment of the encapsulation components, the encapsulation of all sides that do not face one another comprises non-magnetic metal, such as stainless steel, for example, whereas the welded-on cover plate, i.e. the two sides that face one another, comprise soft magnetic material. The magnetic flux is thereby strengthened in the region of the cover plates.
• The thickness of the encapsulation can be between 1 mm and 2 mm, for example. Themagnetic ring208, which is pressed on on the impeller side, is manufactured in a manner similar to that of thelower bearing shell168 of the wet rotor pump shown inFIG. 9 such that a hydrodynamic gap forms between the outer jacket surface of themagnetic ring208 and the inner jacket surface of thecontainment shell222, which said hydrodynamic gap also functions as a sealing gap.
• Themagnetic rings208 and210 are preferably magnetized and oriented such that the repellent effect between the magnetic rings is approximately proportional to the square of the distance between the magnetic rings. In this case, the thickness of themagnetic rings208 and210 is preferably designed such that, in the non-operative state of thewet rotor pump200, equilibrium sets in between the attractive force between therotor magnets206 and thestator teeth212 and the repulsive force between themagnetic rings208 and210. As a result, in the non-operative state, an air gap of approximately 1 mm preferably forms between the lower end of thestator teeth212 and therotor magnets206, while an air gap having a width of 3 mm forms between themagnetic rings208 and210. The magnetic field strength generated by themagnetic rings208 and210 is therefore stronger than the field strength between therotor magnets206 and thestator teeth212.
• As the speed and, therefore, the output of thewet rotor pump200 increases, the pressure differential between the suction side and the pressure side of thewet rotor pump200 and, therefore, the contact pressure of theimpeller202 increases upwardly, in the direction toward thesuction connecting piece218. Similarly, the contact pressure on the mutually repellentmagnetic rings208 and210 also increases such that the air gap between themagnetic rings208 and210 and the air gap between therotor magnets206 and the stator teeth12 is reduced. The reduction of the air gaps continues until a new equilibrium has set in between the contact pressure, the attractive force between therotor magnets206 and thestator teeth212, and the repulsive force between themagnetic rings208 and210.
• In order to prevent the rotor from being set down onto static components of thewet rotor pump200, the performance limit of the wet rotor pump can be dimensioned such that the air gap between therotor magnets206 and thestator teeth212 does not fall below a width of 0.2 mm. In addition,safety sliding surfaces220 can be mounted on the rotor, which extend upwardly beyond therotor magnets206 by 0.2 mm, for example. In the event that the aforementioned performance limit is exceeded, said safety sliding surfaces can support the rotor at thecontainment shell222 and prevent damage to theimpeller202 or therotor magnets206.
• Given that the air gap between therotor magnets206 and thestator teeth212 is reduced as the pressure output increases, the coupling between therotor magnets206 and thestator teeth212 increases due to the increasing magnetic flux density. This effectively results in an increase in output and, therefore, to increased efficiency of thewet rotor pump200.
LIST OF REFERENCE SIGNS
• • 100 wet rotor pump
  • 102 motor cover
  • 104 end face
  • 106 opening
  • 108 fluid
  • 110 stator
  • 112 stator tooth receptacle
  • 114 stator tooth
  • 116 containment shell
  • 118 receiving region
  • 120 power electronics
  • 122 permanent magnet
  • 124 ring
  • 126 end
  • 128 impeller
  • 130 disk
  • 132 recess
  • 134 inlet connecting piece
  • 136 printed circuit board
  • 138 attachment region
  • 140 hole
  • 142 housing half
  • 144 housing half
  • 146 opening
  • 148 attachment region
  • 150 drive disk
  • 152 extension
  • 153 screw
  • 154 plain-bearing element
  • 156 bearing bush
  • 158 screw
  • 160 outlet
  • 162 recess
  • 164 end section
  • 166 edge
  • 168 lower bearing shell
  • 170 upper bearing shell
  • 172 rolling element
  • 174 upper plain-bearing surface
  • 176 lower plain-bearing surface
  • 178 fine-strand filter
  • 180 clamping ring
  • 200 wet rotor pump
  • 202 impeller
  • 204 pump housing
  • 206 rotor magnets
  • 208 lower magnetic ring
  • 210 upper magnetic ring
  • 212 stator tooth
  • 214 stator tooth receptacle
  • 216 motor cover
  • 218 suction connecting piece
  • 220 safety sliding surface
  • 222 containment shell

Claims (30)

1. A wet rotor pump comprising an axial flux motor having a stator, a containment shell, and a rotor, wherein the stator and the containment shell are disposed in a dry zone and the rotor on an impeller is disposed in a wet zone, comprising an inlet line for a fluid to be pumped by the impeller, wherein the inlet line extends through the stator and the containment shell in the axial direction, and comprising power electronics for controlling the stator, wherein the power electronics are disposed in the interior of the space circumscribed between the stator and the containment shell.

2. The wet rotor pump according toclaim 1, wherein the power electronics are disposed on an annular printed circuit board, and wherein the inlet line extends through the printed circuit board in the axial direction.

3. The wet rotor pump according toclaim 1, wherein the containment shell comprises a disk, wherein the disk has a central opening, on which an inlet connecting piece for the inflow of the fluid is formed, wherein the disk has recesses, along the periphery thereof, for accommodating the air-gap side ends of the stator teeth, wherein an outer radius of the printed circuit board is limited by the recesses and an inner radius of the printed circuit board is limited by a wall of the inlet connecting piece, which is formed by the containment shell and extends in the axial direction.

4. The wet rotor pump according toclaim 1, comprising a bearing for the impeller, wherein the bearing is disposed at one end of the inlet line, and the bearing supports the impeller in such a way that the impeller has one axial degree of freedom, wherein the inlet line extends through the bearing in the axial direction.

5. The wet rotor pump according toclaim 4, wherein the inlet line is formed at least by an inlet connecting piece embodied on the containment shell, and by the bearing.

6. The wet rotor pump according toclaim 5, wherein the containment shell comprises a disk, which extends into the air gap of the axial flux motor, and the containment shell is designed as a single piece, in particular as a molded part.

7. The wet rotor pump according toclaim 1, wherein the stator is formed in the shape of a torus.

8. The wet rotor pump according toclaim 1, wherein the stator is formed by an annular stator tooth receptacle, along the periphery of which stator teeth are attached.

9. The wet rotor pump according toclaim 8, wherein the stator tooth receptacle is bonded with the stator teeth.

10. The wet rotor pump according toclaim 8, wherein each of the stator teeth comprises a receiving region for a coil, which said receiving region extends in the axial direction and is limited by an air-gap side end of the particular stator tooth, wherein the air-gap side end of the stator tooth has an end face, which is greater than the cross section of the receiving region.

11. The wet rotor pump according toclaim 1, wherein the containment shell comprises a disk, which extends into the air gap, wherein the disk has a central opening, on which an inlet connecting piece for the inflow of the fluid is formed, wherein an end region of the inlet connecting piece accommodates the bearing.

12. The wet rotor pump according toclaim 1, wherein the bearing is a plain bearing, which is designed to radially support the impeller and to axially support the impeller on one side as an abutment for the magnetic attraction force exerted by the stator onto the impeller.

13. The wet rotor pump according toclaim 12, wherein the bearing is formed, on the containment-shell side, by a bearing bush disposed in the end region of the inlet connecting piece and, on the impeller side, by a plain-bearing element, which has a sliding surface, which engages into the bearing bush.

14. The wet rotor pump according toclaim 13, wherein the plain-bearing element has a circumferential edge, which is disposed so as to form a stop at the bearing bush when a magnetic attraction force from the stator acts on the rotor in the axial direction.

15. The wet rotor pump according toclaim 14, wherein the plain-bearing element comprises one or more openings, which extend in the radial direction and are designed such that, during operation, a portion of the fluid flow is directed between the sliding surface of the plain-bearing element and the sliding surface of the bearing bush.

16. The wet rotor pump according toclaim 1, wherein the sliding surface of the plain-bearing element and/or the sliding surface of the bearing bush is coated with a combination of diamond-like carbon and silicon carbide.

17. The wet rotor pump according toclaim 1, wherein the bearing is a combination of a plain bearing and a rolling bearing, which are designed to provide radial and axial support of the impeller, wherein the rolling bearing functions as an abutment in the axial direction for the magnetic attraction force exerted by the stator onto the impeller, and the plain bearing supports the rotor in the radial direction.

18. The wet rotor pump according toclaim 17, wherein the rolling bearing is formed of bearing shells, which have a running surface for accommodating rolling elements, and rolling elements, wherein a first bearing shell is attached to the impeller and a second bearing shell is attached to the containment shell, and the rolling elements are located in the space circumscribed by the running surfaces of the two bearing shells.

19. The wet rotor pump according toclaim 17, wherein the plain bearing is formed, on the impeller side, by the outer jacket surface of the first bearing shell and the jacket surface of the containment shell and, on the containment-shell side, by the inner jacket surface of the second bearing shell and the jacket surface of the impeller.

20. The wet rotor pump according toclaim 17, wherein the running surfaces and/or the jacket surfaces of the bearing shells and/or the rolling elements are coated with silicon carbide and/or diamond-like carbon and/or silicon-doped DLC.

21. (canceled)

22. (canceled)

23. (canceled)

24. (canceled)

25. (canceled)

26. (canceled)

27. (canceled)

28. (canceled)

29. (canceled)

30. (canceled)

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