EP2778424B1 - Pump unit - Google Patents

Description

The invention relates to a pump unit with a pump unit and an electric motor driving this, comprising a stator and a rotor rotating in a rotor space, wherein the stator is separated from the rotor space by a split tube.

Such pump units are often used in applications as wet rotor, in which the rotor rotates in a liquid located in the rotor chamber. As a rule, this liquid is the pumped medium. Such types of pump units can be found for example in heating circulation pumps and coolant pumps, borehole, service water and sewage pumps. In wet runner pumps, the rotor is thus washed by medium. The stator is hermetically separated from this medium by a split tube. The bearings of the rotor are lubricated by the medium. Such constructions are maintenance-free and have a long service life. DE 10 2011 014088 A1 discloses such a pump unit.

The split tube is exposed to the high pressures in the pump chamber. For this reason, split tubes must have a high strength. It is known to produce metal cans. However, these have the disadvantage that, as a result of the stator field eddy currents are generated in the can, resulting in losses and the efficiency of the electric motor is significantly reduced.

In today's effort to perform pump drives as energy efficient as possible, modern EC motors are used, which are designed to prevent eddy current losses with canned plastic tubes. To ensure that these cans withstand the sometimes large internal pressures, the wall thicknesses must be sufficiently large. As a result, the gap between the stator and the rotor becomes relatively large compared to an AC motor. This is compensated today by an increased use of magnetic material in the rotor and / or permanent magnets with high coercive field strength. However, this leads to higher production costs.

The object of the invention is to provide a pump unit with a split tube, which can be designed to achieve a high efficiency of the unit particularly thin-walled, but at the same time holds high internal pressures in the rotor or pump room.

This object is achieved by a pump unit with the features of claim 1. Advantageous developments are specified in the subclaims.

According to the invention, a pump unit with a pump unit and an electric motor driving this is proposed, which has a stator and a rotating rotor in a rotor space, the stator is separated from the rotor space by a split tube and between the gap tube and the stator is a circular wedge connection, with the the split tube is supported on the stator.

According to a first aspect of the invention, the strength of the can with respect to internal pressure is increased by supporting it against the stator, in particular the stator core. To achieve this safely, extremely precise tolerances and dimensions must be observed without any further measures. For plastic components, this is not possible depending on the material or very difficult and expensive. It is therefore proposed according to a second aspect of the invention to provide a circular spline connection between the can and stator or stator. This ensures a flush and thus safe concern of the can with the stator or stator with easily accessible tolerances and dimensions. Then split tube can thereby be extremely thin-walled and has nevertheless a high resistance to the internal pressures. In addition, due to the thinness of the magnetic gap between the rotor and stator can be kept low, so that a high efficiency of the pump unit is achieved. It should be noted that the split tube may have a bottom at one axial end, so that the split tube forms a split pot.

During assembly of the can in the stator, the can is inserted in the axial direction into the stator with play. Subsequently, the outer surfaces of the split tube are brought into contact over a large area by a relative rotation between the stator and the can with the inner surfaces of the stator. As a result, the can is clamped against the stator and there is a uniform light surface pressure along the peripheral surface of the compound.

This has a number of advantages. Tolerance fluctuations can be safely compensated by a corresponding rotation angle in a simple way and the contact between the can and the stator is guaranteed. The internal pressure resistance of the can is thus significantly increased compared to a non-supported variant. Furthermore, with the same requirements, the wall thickness of the split tube can be reduced, so that the gap between the stator and rotor can be reduced and the magnetic material can be reduced. By compensating the tolerances of the can and the stator stack, the requirements for these component tolerances can be reduced.

Since no forces have to be transmitted between the can and the stator, the clamping force, i. the angle of rotation should not be particularly great. Incidentally, it must not be too large, because canned pipe forms a thin-walled hollow body which breaks when the clamping force is too high.

Preferably, the split tube has an outer peripheral surface, which has a circumferential circle diverging from the circular inner circular spline. Seen in radial cross-section, the outer circumference of the can thus forms a base circle on which the wedge profile rises. The split tube can thus be produced immediately together with the circular spline, in particular by injection molding as a plastic molded part.

The stator can basically have any desired structure, in particular have loop windings or else concentrated windings. In both cases, the stator has a central opening, also called bore, in which the rotor rotatably rests. Preferably, an inner surface of the stator delimiting the opening has, in the circumferential direction, at least one outer circular spline profile which deviates from the circular shape and is complementary to the inner circular spline profile. Viewed in radial cross-section, the inner circumference of the stator consequently forms a base circle on which the complementary spline profile rises. The two circular splines thus complement each other form-fitting, so that the split tube can be applied flat to the stator.

Preferably, the stator has a plurality of pole shoes extending radially inwardly into the opening. Such a construction is used mainly in EC motors with concentrated windings which are arranged behind a pole piece on its pole leg. A pole piece has an inner circumferential surface which partially delimits the central opening. For example, have at least two pole pieces in the circumferential direction on a deviating from the circular, complementary to the inner circular spline outer circular spline. Thus, in the assembled state in the stator, the can is positively and non-positively connected only to these pole shoes which are formed with the complementary circular wedge profile.

Said two pole shoes, which have a circular wedge profile, are advantageously opposite one another, so that the split tube can be clamped between them. Alternatively, a plurality of pole pieces, in particular, every second pole piece can wear the outer circular spline. However, it is advantageous if all the pole shoes have an outer circular spline profile which deviates from the circular shape in the circumferential direction, so that the split tube fits all pole shoes, i. can support a large area.

In principle, the circular wedge connection can be formed by a circular wedge, two or more circular wedges and correspondingly a circular wedge, two or more complementary circular wedges. However, it is advantageous, the circular spline connection by three circular wedges on the outer peripheral surface of the split tube and three complementary Circular wedges on the inner peripheral surface of the stator form. This ensures that the circular wedge connection is self-centering and the split tube always rests concentrically in the stator.

The outer circular spline can be formed by a single circular wedge or by multiple circular wedges. Correspondingly, then also the complementary inner circular spline on the can has a single circular wedge or more circular wedges.

The circular wedge or the circular wedges can be arranged along the inner circumference of the stator such that each pole piece has on its inner peripheral surface a partial section of the circular wedge or one of the circular wedges. This means that two, more or in the case of a single circular wedge all pole shoes together form the circular wedge or a circular wedge proportionally. Also, a pole piece may have two or more circular wedges.

According to a preferred embodiment, the outer circular spline is formed by a number of circular wedges, each pole piece has on its inner peripheral surface such a circular wedge. Thus, the number of circular wedges corresponds to the number of stator poles.

It should be noted that these mentioned embodiments are not limited to electric motors with pronounced pole shoes. Also any differently shaped stator poles, especially in pole legs, the circular wedge profile according to the invention can be realized.

Since no forces are to be transmitted between the can and stator, the profile height of the inner circular spline can be comparatively small compared to the wall thickness of the can. Preferably, the inner circular spline has a profile height of 1/20 to 1/5, preferably 1/10 of the wall thickness of the can.

In an advantageous embodiment of the invention, the slope of the circular wedges of the circular wedge connection between 1:20 to 1:50, so that the circular wedge connection can be solved for disassembly purposes again.

Preferably, the contour of the circular wedges is designed as a logarithmic spiral. This has the advantage that the connection partners of the circular wedge connection not linear but surface contact. The can is optimally supported by the stator.

The circular wedge connection according to the invention offers the advantage that the split tube can also be fixed in the axial direction. For this purpose, the split tube may have on its outer circumference a radial projection which engages behind the stator, in particular a pole piece (7), in the inserted and stressed state of the split tube. During axial insertion of the can into the stator, this projection can be in the area between two pole shoes, for example. If the can is inserted axially, the projection is also twisted by its rotation and comes behind a pole piece to the plant. The split tube is thereby secured in the axial direction.

Preferably, the electric motor of the pump unit is provided with an electric motor having a wet-running rotor. This means that the rotor space is flooded with a liquid and the rotor, i. in particular the rotor core, surrounded by a liquid and in accordance with liquid flows around in operation. The pump unit thus forms a wet-running pump, which can be used in particular as a heating circulation pump.

• Figur 1: Vorderansicht des Stators
• Figur 2: Rückansicht eines Spaltrohrs mit Kreiskeilprofil an der äußeren
• Umfangsseite
• Figur 3: Explosionsdarstellung der Anordnung aus Spaltrohr und Stator
• Figur 4a: Querschnittsdarstellung des Stators
• Figur 4b: Vergrößerter Ausschnitt der Querschnittsdarstellung nach Figur 4a

Further advantages and features of the invention will be explained in more detail with reference to an embodiment and the accompanying figures. Show it:

• FIG. 1 : Front view of the stator
• FIG. 2 : Rear view of a split tube with circular wedge profile on the outside
• peripheral side
• FIG. 3 : Exploded view of the arrangement of canned and stator
• FIG. 4a : Cross-section of the stator
• FIG. 4b : Enlarged section of the cross section representation after FIG. 4a

FIG. 1 shows a stator 2 of an electric motor in the embodiment of a conventional EC motor in its front view. The electric motor drives Centrifugal pump unit. It comprises a laminated core consisting of a yoke ring 6 and six stator poles 7 attached thereto, which in turn each consist of a pole leg 7a and a pole piece 7b. The pole leg 7a is here attached by way of example via a dovetail connection 7c to the return ring 6. The pole legs 7 a each carry a winding 5, so that the electric motor has a total of six stator windings 5. Each winding 5 is wound on a winding support, which is supported by means of a rib-like structure on the back of the respective pole piece 7b.

The pole pieces 7b each have a concave inner surface which, due to the axial extent of the pole pieces 7b, substantially corresponds to a cylindrical portion. Together, the pole pieces 7b define with their inner surface a central opening 11, in which the rotor, not shown, of the electric motor is arranged.

A representation of the stator 2 in cross section without windings 5 is in FIG. 4a shown, here the view opposite FIG. 1 from behind. An enlargement of a section of this illustration, which comprises the upper stator pole 7 in cross-section, is shown in FIG FIG. 4b displayed. In FIG. 4b It can be seen that the profile of the inner surface of the pole pieces 7b of a circular section of a pure base circle 12, the in FIG. 4b is shown as a dotted line, differs in that it rises from one lateral end 4a in the circumferential direction to the other lateral end 4b and thus forms a circular wedge 4.

The circular wedge profile 4 of the next pole piece 7b then begins with respect to its profile height compared to the previous pole piece 7b set back slightly, so that in an imaginary extension of the considered circular spline 4 a return to the profile beginning of the next pole piece 7b exists. Accordingly, in the exemplary embodiment, each pole piece 7b, ie each stator pole 7 is provided with a circular wedge 4. As in FIG. 1 and FIG. 4b shown, the circular wedges 4 rise in the cross-sectional profile of the pole pieces 7b radially inwardly into the opening 11 into it.

FIG. 2 shows the rear view of a split pot, ie a closed end gap tube 1. The split tube 1 is thus closed at one axial end by a bottom 9. At its other axial end, a molded-on flange 8 extends substantially radially outwardly. This covers the directed to the pump unit, not shown, end face of the stator 2.

The outer peripheral surface of the can 1 has in cross section a deviating from the pure circular circular wedge profile with six circular wedges 3, which rise opposite the circular wedges 4 on the stator 2 in the opposite circumferential direction radially outward. The circular spline 4 on the stator and the circular spline 3 on the split tube 1 thus form complementary circular wedge profiles.

Since the circular spline 4 is located radially on the stator 2 opposite the circular spline 3 on the gap tube 1, it is referred to as "outer circular spline" in the context of the invention. Accordingly, the circular spline 3 forms the gap tube 1, an "inner circular spline". However, these designations only relate to one another within their position within the pump unit and do not provide any information about the shape of the circular spline profiles.

It should be noted at this point that FIG. 2 is a view from the rear of the can 1, while FIG. 1 a representation of the stator 2 from the front shows. The complementary property is clear when the back of the can 1 is inserted from the front into the opening 11 of the stator 2. This is in FIG. 3 shown.

FIG. 3 shows an isometric exploded view of canned tube 1 and stator 2. They are part of a centrifugal pump assembly, in particular a heating circulation pump, which or a pump unit and an electric motor which drives the pump unit in a known manner. The stator 2 and the can 1 are part of the electric motor, which also includes a rotor rotating in a rotor chamber 10. The stator 2 is separated from this rotor chamber 10 through the can 1.

For assembly, the can 1 with clearance between the circular wedge contours 3, 4 is inserted axially into the opening 11 of the stator 2. Subsequently, the split tube 1 -in relation to FIG. 3 - Turned relative to the stator 2 counterclockwise, and / or the stator 2 in the clockwise direction relative to the can 1, so that the game disappears and the circular wedges 3 can 1 flat surface with the corresponding circular wedges 4 of the pole pieces 7 come to rest flat. Thus there is a circular wedge connection 3, 4, by means of which the can 1 is supported on the stator 2 between the can 1 and the stator 2.

The rotation must be done here only by a few degrees, since no forces in particular no torques between the can 1 and the stator 2 are transmitted. Essentially, in this case, only the large contact surface achievable by the circular wedge contour, with which the can 1 can be supported on the stator 2, in particular on the pole shoes 7b, so that the strength and stability of the can 1 against high internal pressures in the rotor chamber 10 is ensured. The internal pressure resistance of the can 1 is thereby significantly increased compared to a non-supported variant.

Tolerance fluctuations are thereby safely compensated in a simple way, so that the requirements for the component tolerances can be reduced. Furthermore, with the same requirements, the wall thickness of the can 1 can be reduced, so that the magnetic gap between the stator 2 and rotor is reduced and the magnetic material can be reduced.

The can 1 is made of plastic as an injection molded part in the embodiment shown. It has a wall thickness between 0.8 and 1.2mm. The circular spline 3 on the can 1 has a profile height of about 0.1 mm.

It should be noted that the figures show only an exemplary variant of the invention. However, the invention is not limited thereto. For example, the circular wedges 4 may extend to the pole pieces 7 in the other circumferential direction. The same then applies correspondingly to the complementary circular wedges 3 on the can 1. Furthermore, it is also possible that fewer or more circular wedges 3, 4 are designed as pole shoes 7b, ie as stator poles 7 on the stator 2. It can For example, some stator poles 7 have no circular spline and accordingly not be involved in the support of the can 1. Alternatively, all stator poles 7 may have a circular wedge partial profile and in each case participate proportionally in the formation of a common circular wedge. It is alternatively possible that a stator pole 7 is involved in the formation of more than one circular wedge or even forms two or more circular wedges. The split tube 1 has in the said variants then on its outer circumference circular wedges, which form a correspondingly complementary circular wedge profile.

Claims (9)

1. Pump assembly comprising a pump unit and an electric motor which drives the said pump unit, the said electric motor comprising a stator (2) and a rotor which rotates in a rotor space (10), wherein the stator (2) is separated from the rotor space (10) by a can (1), characterized in that there is a circular spline connection (3, 4) between the can (1) and the stator (2), the can (1) being supported against the stator (2) by means of the said circular spline connection.
2. Pump assembly according to Claim 1, characterized in that the can (1) has an outer circumferential face which, in the circumferential direction, has at least one inner circular spline profile (3) which differs from the circular shape.
3. Pump assembly according to Claim 2, characterized in that the stator (2) has a stator core with a central opening (11) in which the rotor is situated, wherein an inner surface which delimits the opening (11) has, in the circumferential direction, at least one outer circular spline profile (4) which differs from the circular shape (12) and complements the inner circular spline profile (3).
4. Pump assembly according to Claim 2 or 3, characterized in that the stator (2) has a plurality of pole shoes (7b) which extend radially inward and each have an inner circumferential face and from amongst which at least two pole shoes (7) have, in the circumferential direction, an outer circular spline profile (4) which differs from the circular shape (12) and complements the inner circular spline profile (3).
5. Pump assembly according to Claim 4, characterized in that all of the pole shoes (7b) have, in the circumferential direction, an outer circular spline profile (4) which differs from the circular shape (12) and against which the can (1) is supported.
6. Pump assembly according to one of Claims 3 to 5, characterized in that the outer circular spline profile is formed by a circular spline (4) or a plurality of circular splines (4), wherein each pole shoe (7b) has, on its inner circumferential face, only a subsection of the circular spline (4) or one of the circular splines (4).
7. Pump assembly according to one of Claims 3 to 6, characterized in that the outer circular spline profile is formed by a number of circular splines (4), wherein each pole shoe (7b) has, on its inner circumferential face, its own circular spline (4).
8. Pump assembly according to one of the preceding claims, characterized in that the inner circular spline profile (3) has a profile height of 1/20 to 1/5, preferably 1/10, of the wall thickness of the can (1).
9. Pump assembly according to one of the preceding claims, characterized in that the can (1) has, on its outer circumference, a radial projection which, in the inserted and clamped state of the can (1), engages behind the stator (2), in particular a pole shoe (7b) of the stator (2).

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