LU500893B1 - Wet rotor pump without axial bearings - Google Patents

Abstract

The invention relates to a glandless pump (1) with a permanent-magnetic rotor (2) and a pump chamber (4) which is delimited towards the rotor (2) by a partition (5) and in which an impeller (7) is arranged which is mounted on an axially displaceable The shaft (3) is non-rotatably mounted and has a support disk (8), a cover disk (10) and blades (9) arranged between them. The cover disk (10) is sealed radially by means of a suction neck seal (11) and a first annular wall (12) protrudes from the support disk (8) which, together with an axial projection (6) of the partition wall (5), forms a radial Throttle gap (13) forms a constant gap width. A relief bore (18) forms a fluid connection between the suction side (20) of the impeller (2) and an impeller side space located between the support disc (8) and the partition (5). The impeller (7) has a second, to the partition (5) extending annular wall (14) which divides the impeller side space between the first wall (12) and the shaft (3) into a radially outer annular space (16) and a radially inner annular space (17) and which, together with the partition (5), forms an axial throttle gap (15) which is dependent on the axial position of the impeller (7) and through which flow can flow radially. The suction neck seal (11) lies on a diameter between the radial throttle gap (13) and the axial throttle gap (15). The relief bore (18) opens into the radially inner annular space (17). As a result of this design, the gap width of the axial throttle gap (15) and thus the axial position of the impeller are adjusted automatically. This means that there is no need for an axial bearing in the glandless pump (1).

Description

WI 810055LU B LU500893 24.11.2021

WILO SE

Wilopark 1 44263 Dortmund

Wet-running pump without axial bearings

The invention relates to a wet-running pump with a permanent magnet

Rotor and a pump chamber delimited towards the rotor by a partition wall, in which an impeller is arranged, which is axially displaceable on a rotor relative to the stator

Shaft is rotatably mounted and has a support disk, a cover disk and blades arranged between them, the cover disk by means of a

Suction neck seal is sealed radially and an annular one from the support disc

Wall protrudes, which together with an axial projection of the partition wall forms an axially traversable radial throttle gap of constant gap width, and wherein a relief bore provides a fluid connection between the suction side of the

impeller and one lying between the support disc and the partition

Radseitenraum forms.

Wet-running pumps are centrifugal pumps in which the rotor is in the conveyed

medium rotates. Axial forces acting on the impellers of centrifugal pumps are

Pressure forces and impulse forces on the impeller surfaces result. Typically, the resulting axial force is in the opposite direction to the impeller inflow and must be absorbed by an axial bearing. In the case of wet-running pumps, these axial bearings are usually designed as medium-lubricated slide bearings consisting of a system consisting of a stationary and a rotating component. through a to

However, the bearing system used to absorb the axial force can have disadvantages. The axial bearing requires installation space, leading to higher costs, greater system complexity, friction losses and noise. Furthermore, it must be monitored with regard to the component quality and tolerances, it is subject to wear and harbors the risk of sticking. Therefore there is a

Need to do without the thrust bearing.

In order to reduce the losses in the bearing system by reducing the bearing load, LU500893 balancing systems were developed, which are particularly necessary for multi-stage pumps. There, the axial forces can become so large that they can no longer be absorbed by a conventional bearing of a reasonable size at a reasonable cost with acceptable losses. The reduced bearing load comes at the cost of increased volumetric and/or frictional losses in the relief system. It must therefore be checked in practice whether the advantages of the

Discharge system whose disadvantages outweigh. A relief system can, for example, by so-called back blades on the back of the

Be formed support disk of the impeller. Furthermore, form in the generic

Wet rotor pump the projecting annular wall of the support disc and the

Relief hole, e.g. in the impeller, a relief system for

Reduction of the axial forces acting on the impeller.

The object of the invention is to provide a glandless pump with an improved

Provide relief system that the axial forces in normal operation

Wet-running pump eliminated so that it can be designed without an axial bearing, whereby the relief is to be accommodated in the impeller side space of the support disk to save space.

This object is solved by the subject matter of claim 1. beneficial

Further developments are specified in the dependent claims and are explained below.

According to the invention, in the wet-running pump of the generic type, it is provided that instead of an axial bearing, the impeller has a second annular wall that extends to the partition wall, which divides the impeller side space between the first wall and the shaft into a radially outer annular space and a radially inner annular space and which is connected to the Partition forms a dependent on the axial position of the impeller, radial flow through axial throttle gap, wherein the suction neck seal on a diameter between the radial throttle gap and the axial

Throttle gap is and the relief bore opens into the radially inner annular space. As a result of this construction, the gap width of the axial

Throttle gap and thus the axial position of the impeller automatically. This means that an axial bearing can LU500893 be dispensed with in the glandless pump.

The compensation of the axial forces on the impeller is according to the invention by a

System of interacting components achieved, namely - a radial sealing gap (radial gap) with a constant gap width on an outer diameter of the impeller. This sealing gap forms a radial one

Restrictor and is flowed through axially. - An axial sealing gap (axial gap) of variable gap width on an inner one

impeller diameter. The flow through this sealing gap is radially inward and forms an axial throttle, the effect of which depends on the gap width of the axial gap, which in turn depends on the axial position of the impeller or rotor. The inner diameter is a diameter that is closer to the shaft than the outer diameter. - a radial sealing gap formed by the suction neck seal with a constant gap width on a mean diameter of the impeller, i.e. a diameter between the outer and the inner diameter, in other words between the radial gap and the axial gap. - And a relief bore, which opens between the inner diameter and the shaft in the wheel side space and thereby makes it possible to flow through the wheel side space, whereby the radial and the axial

Sealing gap become effective.

The radial restrictor ensures that the preferred direction of the hydraulic pressure forces acting on the impeller is always in the direction of the

Direction of flow at the impeller inlet shows. This ensures that the rotor is displaced by pressure and impulse forces on the impeller in such a way that the axial sealing gap closes, i.e. its gap width becomes smaller. This has one

The result is an increase in the pressure level in the impeller side space on the rear side of the impeller, which is reduced via the relief hole until a balance of forces is established.

In this equilibrium position, the rotor remains in its axial position without touching any component axially.

If the operating point of the pump changes, the forces acting on the rotor LU500893 also change and the rotor seeks a new equilibrium position by changing the axial position of the impeller and the rotor. The gap width at the axial sealing gap changes accordingly. The axial sealing gap therefore has a self-regulating function and can therefore be referred to as a regulating gap. The

Gap width at the axial throttle gap adjusts itself automatically so that the

Rotor is in an axially stable position of equilibrium.

The inventive arrangement of the column not only has the advantage of a

to cause axial force relief. It also ensures that there is no unstable condition over the entire operating range where the slider moves to a position where the control gap loses its control function.

In one embodiment variant, the projection of the partition wall can encompass the first annular wall on the outside. Encompassing the outer circumference, the radial sealing gap can be positioned as far radially as possible on the outer diameter of the impeller without having to increase the impeller diameter.

Suitably, the projection of the partition may be formed by having an annular outer portion opposite an annular inner portion

Distance of the partition to form a step protrudes. The level increases the

Rigidity of the partition. In the case of a metal partition, this step can be produced, for example, by means of deep-drawing or embossing.

In order to reduce the flow through the impeller side space to a minimum, the radial throttle gap can be sealed with a sealing ring. For example, such a sealing ring can be held on the dividing wall, in particular on its projection, and can rest in the radial direction on the first annular wall, in particular on its radial outside. The sealing ring can be a flat gasket, for example.

Preferably, the first and/or second annular wall is or are formed in one piece with the support disc, for example injection molded together with it. This simplifies the manufacture of the LU500893 according to the invention

relief system.

In one embodiment, the relief bore can be formed in the impeller. The relief bore is thus easy to produce. It is alternatively or additionally possible for the or a further relief bore to be formed in the shaft, the shaft in this case being a hollow shaft which is open towards the suction side of the impeller. The relief bore then extends radially through the

Wall of the hollow shaft through. It should be noted that two or more

Relief hole may be present, especially equidistant around the circumference

Impeller and/or distributed in the hollow shaft.

It is advantageous if the end face of the second wall facing the partition wall is conical, so that the gap width of the axial sealing gap changes in the radial direction, i.e. becomes narrower or wider. Such a conical geometry of the

Sealing gap reduces the risk of tarnishing if the sealing gap width is very small. In particular, the axial sealing gap can be conical in such a way that it becomes larger as the distance from the shaft increases.

The second wall may project axially from the first wall, with others

Words be axially longer. This ensures that in the case of a partition wall that is flat in the area radially between the first and second wall, the end face of the first wall facing the partition wall is considerably further away from the partition wall than the end face of the second wall facing the partition wall, and thus the

Partition directed end face of the first wall does not form an axial sealing gap.

Typically, the gap dimensions of the first and second sealing gap and the

Sow neck seal less than 1mm. The axial throttle gap can be variable

Have a gap width between 0.1mm and 1.0mm. Furthermore, the radial

Throttle gap have a constant gap width between 0.05mm and 1.0mm, preferably between 0.2mm and 0.5mm.

In order to avoid that it is caused by a change in the operating point of the

wet rotor pump comes into contact between rotating and stationary parts,

a magnetic auxiliary bearing can be provided. With low hydraulic forces, this can take over the axial positioning. In modern, energy-efficient glandless drives, permanent magnets are installed in the rotor, which means that the rotor has a magnetic resting position within the stator. The magnetic position of rest is characterized in that the rotor is located symmetrically or centrally with respect to its axial position relative to the stator. A magnetic one

Auxiliary storage can be realized in that this rest position is present when the gap width of the variable axial sealing gap is comparatively large, in particular at maximum. As a result, a defined, contact-free axial

Rotor position guaranteed until standstill. No additional magnetic components are necessary.

Further features, advantages and properties of the invention are explained in more detail below using exemplary embodiments. Show it:

1: a sectional view through the impeller and the rotor of a glandless pump according to a first embodiment

2: a sectional view through the impeller and the rotor of a glandless pump according to a first embodiment

3: a sectional view through the impeller and the rotor of a glandless pump according to a first embodiment

4: a diagram with three sectional views of a glandless pump with different axial positions of the impeller

Figure 1 shows a section of a centrifugal pump according to a first

Embodiment of the invention in the manner of a wet-running pump 1 in a

Sectional view along an axial plane through the pump-motor axis 26. The

Wet-running pump 1 has a permanent-magnetic rotor 2 which is mounted on a shaft 3 in a rotationally fixed manner. The shaft 3 is mounted in a front and a rear radial plain bearing 27, 28. In a surrounded by a pump housing 31 pump chamber 4 to the rotor 2 or to the rotor space through a

Partition 5 is limited, an impeller 7 is arranged, which is rotatably connected to one end of the shaft 3 with its hub 24. The rotor 2, shaft 3 and

The assembly formed by impeller 7 is axially displaceable due to the absence of a thrust bearing, as indicated by the double arrow depicted inside shaft 3 LU500893.

The impeller 7 is a so-called covered impeller. Accordingly, it comprises a support disk 8, a cover disk 10 and one arranged between them

Blades 9. The cover plate 10 has a central opening 29, the so-called suction mouth 29, which is limited in the radial direction outwards by a tubular portion 30 of the cover plate 10, which is generally referred to as

Suction neck 30 is designated. The spatial area inside, in front of and immediately behind the suction mouth 29 forms the suction side 20 of the impeller 7. In contrast, forms the

Periphery and the spatial area radially in front of the impeller 7 whose pressure side 21. The

The pump housing 31 has a suction opening 22 opening into the pump chamber 4 and a pressure opening 23 leading out of the pump chamber. The

Impeller 7 extends with its suction neck 30 in such a way into the suction opening 22 that a radial sealing gap between the outside of the suction neck 30 and the

Inside of the suction port 22 is. This sealing gap forms a

Suction neck seal 11 to prevent a hydraulic short circuit between the suction side and the pressure side 21 of the impeller 7. In other words it is

Suction neck 30 sealed radially by means of the suction neck seal 11 .

From the support disc 8, a first annular wall 12 projects, which together with an annular, extending in the axial direction projection 6 of the

Partition wall 5 forms a radial throttle gap 13 . The projection 6 is on a larger diameter than the first wall 12 and surrounds it at her

outer perimeter. This radial gap 13 can thus be flown through axially or is im

Operation of the glandless pump 1 flows through axially. He also has a constant, more precisely one of the axial position of the impeller 7 independent

gap width.

In addition to the first wall 12, the impeller 7 has a second annular wall 14 that projects from the support disk 8 to the partition wall 5, which divides the impeller side space between the first wall 12 and the shaft 3 into a radially outer annular space 16 and a radially inner annular space 17 separates. In other words, lies the second

Wall 14 relative to the pump-motor axis 26 at a lower level

diameter of the impeller 7 than the first wall 12. The second wall 14 projects axially in relation to the first wall 12, so that an axial throttle gap 15 is formed between the end face 25 of the second wall 14 and the partition wall 5.

This axial gap 15 can thus be flowed through radially or during operation

Wet rotor pump 1 flows through radially. It also has a gap width that is dependent on the axial position of the impeller 2 . The first and second walls 12, 14 are formed in one piece with the support disk 8.

The suction neck seal 11, more specifically the sealing gap between the suction neck 30 and

Pump housing 31 is based on the pump motor axis 26 on a

Diameter between the radial throttle gap 13 and the axial throttle gap 15. This ensures the function of the axial throttle gap as a control gap. Would the sealing gap between the suction neck 30 and the pump housing 31 radially further outwards than the radial throttle gap 13, no thrust reversal can be achieved and the

Control gap would not close. The control principle then does not work. And if the sealing gap between the suction neck 30 and the pump housing 31 were radially further inward than the axial throttle gap 13, the axial thrust cannot be fully compensated. Due to the upstream reversal of axial thrust, this

Impeller 7 then back against the partition 5, so that the first wall 12 forms a classic axial bearing with this partition 5 and there is no longer a control gap.

Furthermore, the impeller 7 has a relief bore 18, the one

Fluid connection between the suction side 20 of the impeller 7 and between the

Support disc 8 and the partition wall 5 lying Radseitenraum forms, specifically at a point in the impeller 7, which is closer to the shaft 3, as the axial sealing gap 15, so that the relief bore 18 opens into the radially inner annular space 17.

As a result of this relief bore 18, the glandless pump 1 is in operation

Negative pressure generated in the radially inner annular space 17. This negative pressure leads to a

Flow through the wheel side space, more precisely to a flow from the

Pressure side 21 of the impeller 7 through the radial throttle gap 13 into the radially outer annular space 16, from there through the axial throttle gap 15 into the radially inner annular space 17 and from there through the relief bore 18 to

impeller suction side.

The gap width at the axial throttle gap 15 is automatically adjusted in such a way that the rotor 2 and the impeller 7 are in an axially stable equilibrium position. If the operating point of pump 1 changes, the am

Rotor 2 attacking forces and the rotor 2 is looking for a new one

Equilibrium position by changing the axial position of the shaft 3 or the impeller 7 and the rotor 2. The gap width at the axial sealing gap 15 changes accordingly. The axial sealing gap 15 is thus self-adjusting. It is thus possible to dispense with an axial bearing in the glandless pump 1 . The

Wed-running pump 1 according to FIG. 1 accordingly has no axial bearing.

The embodiment variant in FIG. 2 differs from the first

Variant only in that the radial throttle gap 13 by a

Sealing ring 19 is sealed. Thus, the gap width of the radial throttle gap 13 is reduced. This narrower gap 13 has two main effects. On the one hand, the leakage is reduced, which increases the efficiency. On the other hand, the throttling effect at the gap 13 increases and the pressure conditions change. That gives the

Pump designers an additional degree of freedom when positioning the gap, which can be limited by space restrictions, for example. The sealing ring 19 is held radially movable in a cage with a U-shaped profile in axial section, as a result of which narrower gap dimensions can be achieved. The cage is attached to the partition wall 5, more precisely at the transition of the projection 6 into a circular ring

Partition wall section 5.

Such a sealing ring is here part of the suction neck seal 11. This sealing ring is also held radially movable in a cage with a U-shaped profile in axial section, which is attached to the pump housing 31, more precisely at the transition of

Suction opening 22 to the pump chamber 4. This also serves to limit the axial flow through the radial sealing gap on the suction neck 30 to a minimum in order to minimize hydraulic losses.

Although the embodiment variants in FIG. 2 and FIG. 3 each include two sealing rings, the glandless pump 1 can have a non-illustrated

Design variants have a sealing ring only in the suction neck seal 11 or only on the axial sealing gap 13.

Furthermore, in an embodiment not shown, the

Relief bore or an additional relief bore in the shaft 3 may be present, more precisely form a transverse bore in the wall of the hollow shaft 3, so that the flow path from the radially inner annular space 17 through the

Relief bore and the hollow shaft 3 extends to the suction side 20 of the impeller.

The embodiment variant in FIG. 3 differs from the second

Variant only in that the end face of the second wall 14 directed towards the partition wall 5 is conical, in particular such that the axial

Throttle gap 15 increases with increasing distance from the shaft 3.

In the embodiment variants shown, the axial throttle gap 15 has a variable gap width between 0.1 mm and 1.5 mm, with a sealing gap width of less than 1 mm always being present in the operating state and larger only when stationary

gap widths are possible. The radial throttle gap 13 and the sealing gap at the

In contrast, suction neck seals have a constant gap width of between 0.05mm (sealing ring) and 0.5mm (sealing gap).

The upper part of FIG. 4 shows a diagram of the axial force F_ax,res resulting from all individual forces as a function of the axial rotor position or the gap width s_gap,hub,2 of the axial throttle gap 15 with a constant

Pump operating point (delivery quantity, head, pump speed) illustrated, with the rotor positions 1, 2 and 3 identified in the diagram being shown in the three sectional images in the lower area of FIG.

The sectional view at the bottom left shows rotor position 1 with a large axial gap 15, the sectional view at the bottom center shows rotor position 2 with a central axial gap 15, and the sectional view at the bottom right shows rotor position 3 with a minimal axial gap 15.

Reference signs are largely omitted in FIG. 4 for reasons of clarity.

A magnetic LU500893 made possible by the permanent magnet rotor 2

Auxiliary storage is achieved when the glandless pump 1 is designed so that at

Rotor position 1 the magnetic rest position of the rotor 2 is present, i.e. the magnetic rest position exists when the gap width of the axial choke gap is comparatively large, in this case about 0.7 mm. A magnetic rest position is to be understood as an axially approximately central position of the rotor 2 relative to the stator when it is not in operation.

By definition, the positive force direction is towards the pump housing 31, see

Rotor position 3 in Figure 4 bottom right, i.e. against the inflow direction in the

pump chamber 4.

If impeller 7 is far away from partition 5 (rotor position 1, Figure 4 bottom left), the low pressure level in the impeller side space between impeller 7 and partition 5 (grey dashed line) causes a resulting force F_ax,res that

Rotor 2 moves to the partition wall 5 and the axial throttle gap 15 closes. At about 0.3mm gap width at the axial throttle gap 15, the impeller 7 reaches a

Equilibrium position (rotor position 2, figure 4 bottom center). Is that located?

Impeller 7 very close to partition wall 5 (rotor position 3, Figure 4 bottom right), the high pressure level in the impeller side chamber (black dashed line) causes a resultant force F_ax res, which moves rotor 2 towards pump housing 31 and opens axial throttle gap 15 again . In the case shown, the rotor finds its equilibrium position (position 2) at a gap width of approx. 0.3mm, in which the resulting axial forces cancel out.

Due to this automatic adjustment of the impeller or rotor position, and thus also the gap width s_gap,hub,2, an axial bearing can be dispensed with. The wet-running pump 1 shown in the figures is consequently constructed without an axial bearing.

This results in numerous advantages: - Axial bearing losses are eliminated and efficiency is increased. - There is no thrust bearing wear, no need for maintenance

replacement of a thrust bearing; - For EEl (Energy Efficiency Index) measurements of glandless pumps 1, run-in effects on the axial bearing no longer have to be taken into account.

- Furthermore, no axial thrust reversal has to be taken into account. LU500893 - Depending on the pump type, two axial bearing positions can even be omitted. - Due to the omission of the axial bearing(s), a reduction in costs and a reduction in installation space is achieved. - Since the rotor 2, as a wet rotor with permanent magnets, has a magnetic zero position axially, it can be positioned axially by the magnetic forces in such a way that there is no contact with the housing when it is stationary. It is thus avoided that the impeller 7 is either left on the

Pump housing 31 or on the right against the partition wall 5. Ideally, the rotor is always within these limits and never on one

Border. This results in an optimized start-up behavior without sticking. An axial emergency bearing is not necessary. Thus, the only desired

Finding contact between rotating and static parts in the radial plain bearings. - In comparison to impellers, which only have a relief hole, the volumetric losses in the solution according to the invention are reduced due to the additional, axial throttle gap 15 with a very small gap width. - Compared to non-relieved impellers, the

Relief bore (s) 18 achieves a removal of particles from the wheel side space and thus a rotor chamber protection. - The radial throttle gap 13 in Fig. 1 has a supporting effect, because it acts radially as an additional hydrodynamic bearing, carries and dampens the rotor and thus relieves the radial bearings. In the variant with narrow

However, this does not apply to the gap (FIGS. 2 and 3) since the sealing ring 19 can move radially there. - By integrating the relief system in the impeller contour (first and second wall 12, 14 are part, in particular in one piece with impeller 7), a compact design is achieved.

It should be understood that the foregoing description is given by way of example only, and does not exceed the scope of

Invention by no means restricted. Features of the invention classified as "may", "exemplary", "preferred", "optional", "ideal", "advantageous", "if necessary",

"Suitable" or the like are to be considered purely optional and also do not limit the scope of protection, which is defined solely by the claims. Insofar as elements in the above description

Components, process steps, values or information that have known, obvious or foreseeable equivalents are named as such

Equivalents included within the invention. Likewise, the invention excludes any

Changes, alterations or modifications of embodiments that require the substitution, addition, alteration or omission of elements,

Components, process steps, values or information as a subject matter, as long as the basic idea of the invention is retained, regardless of whether the change, alteration or modifications lead to an improvement or deterioration in an embodiment.

Although the above description of the invention mentions a large number of physical, non-physical or procedural features in relation to one or more specific exemplary embodiments, these features can also be used in isolation from the specific exemplary embodiment, at least insofar as they do not necessarily require the presence of further features. Conversely, these features mentioned in relation to one or more specific exemplary embodiment(s) can be combined with one another as desired and with other disclosed or undisclosed features of exemplary embodiments shown or not shown, at least insofar as the features are not mutually exclusive or lead to technical incompatibilities.

WI 810055LU L LU500893 24.11.2021

LIST OF REFERENCE NUMERALS 1 glandless pump 2 rotor 3 shaft 4 pump chamber

Partition 6 Projection 7 Impeller 8 Support disc 9 Blades

Cover plate 11 suction neck seal 12 first wall 13 radial throttle gap/radial gap 14 second wall axial throttle gap/axial gap 16 outer annular space 17 inner annular space 18 relief bore 19 sealing ring

Impeller suction side 21 Impeller discharge side 22 Suction port 23 Discharge port 24 Hub

Face 26 Pump motor axis 27 Front slide bearing 28 Rear slide bearing 29 Suction mouth

Suction neck LU500893 31 Pump body

Claims (11)

WI 810055LU C LU500893 24.11.2021 Claims 1. Wet-running pump (1) with a permanent-magnetic rotor (2) and a pump chamber (4) delimited towards the rotor (2) by a partition (5), in which an impeller (7) is arranged, which is mounted on an axially displaceable shaft ( 3) is non-rotatably mounted and has a support disk (8), a cover disk (10) and blades (9) arranged between them, the cover disk (10) being radially sealed by means of a suction neck seal (11) and the support disk (8) having a first annular wall (12) protrudes, which together with an axial projection (6) of the partition (5) forms a radial throttle gap (13) of constant gap width through which flow can flow axially, and wherein a relief bore (18) provides a fluid connection between the suction side (20 ) of the impeller (2) and an impeller side space located between the support disc (8) and the partition (5), characterized in that instead of an axial bearing, the impeller (7) has a second annular wall (14 ) which separates the impeller side space between the first wall (12) and the shaft (3) into a radially outer annular space (16) and a radially inner annular space (17) and which, with the partition (5), separates one of the axial positions of the The impeller (7) forms an axial throttle gap (15) through which flow can flow radially, with the suction neck seal (11) lying on a diameter between the radial throttle gap (13) and the axial throttle gap (15) and the relief bore (18) in the radially inner annular space (17) flows. 2. Wet-running pump (1) according to claim 1, characterized in that the projection (6) of the partition (5) surrounds the first annular wall (12) on the outside. 3. glandless pump (1) according to claim 1 or 2, characterized in that the radial throttle gap (13) is sealed by a sealing ring (19). 4. Wet-running pump (1) according to one of the preceding claims, characterized in that the first and/or second annular wall (12, 14) is/are formed in one piece with the support disc (8). 5. glandless pump (1) according to any one of the preceding claims, characterized in that the relief bore (18) is formed in the impeller (7). 6. Wet-running pump (1) according to one of the preceding claims, characterized in that the shaft (3) is a hollow shaft open to the suction side (20) and the relief bore (18) is formed in the shaft (3). 7. Wet-running pump (1) according to one of the preceding claims, characterized in that the end face (25) of the second wall (14) facing the partition (5) is conical, in particular such that the axial throttle gap (15) increases with increasing distance from the Shaft (3) becomes larger. 8. glandless pump (1) according to any one of the preceding claims, characterized in that the second wall (14) relative to the first wall (12) protrudes axially. 9. glandless pump (1) according to any one of the preceding claims, characterized in that the axial throttle gap (15) has a variable gap width between 0.1mm and 1.0mm. 10. glandless pump (1) according to any one of the preceding claims, characterized in that the radial throttle gap (15) has a constant gap width between 0.05mm and 1.0mm, preferably between 0.2mm and 0.5mm. 11. glandless pump (1) according to any one of the preceding claims, characterized in that it has an auxiliary magnetic bearing.