Reduced-noise rotary pump

Abstract

Rotary pump, preferably a vane pump or a pendulum vane pump, comprising a stator, a rotor rotatable within the stator about an axis of rotation, wherein the rotor has several conveying elements radially movable with respect to the axis of rotation, and two adjacent conveying elements with the outer surface of the rotor and the inner surface of the stator define a conveying cell, wherein at least two, preferably two adjacent, conveying cells, which have a first maximum cell volume, form a first group of conveying cells, and at least two further, in particular two further adjacent, conveying cells, which have a second maximum cell volume, form a second group of conveying cells, such that the first maximum cell volume of the conveying cells of the first group of conveying cells is greater than the second maximum cell volume of the conveying cells of the second group of conveying cells.

Description

[0001] The invention relates to a rotary pump for conveying a pumping medium. The rotary pump comprises a stator and a rotor rotatable within the stator about a rotational axis. The rotor has a plurality of conveying elements distributed over the circumference of the rotor. The conveying elements are arranged on the rotor so as to be radially movable with respect to the rotational axis. Two adjacent conveying elements, together with the outer circumferential surface of the rotor, the inner circumferential surface of the stator, and axial walls (base and cover), each delimit a conveying cell, so that the rotary pump has a plurality of conveying cells. At least two conveying cells, which have a first maximum cell volume, form a first conveying cell group. At least two further conveying cells, which have a second maximum cell volume, form a second conveying cell group.

[0002] DE 2 415 620 A1 discloses a device for positive displacement hydraulic pumps and motors in which the pump rotor is designed with uneven spacing between the individual pump bodies, such as pistons or vanes. The varying geometric spacing between all pump bodies ensures that the pulses of the fluid pumped by the pump follow one another in as irregular a sequence as possible, thus reducing the overall noise level to a minimum without any form of insulation or shielding.

[0003] DE 706 484 A1 discloses a rotary piston engine or working machine with a sickle-shaped working chamber. The machine comprises a housing in which an eccentric rotor is mounted, which has slots for slide valves. To prevent rotor excitation, the distances between the slot openings on the rotor circumference, measured in radians, vary. Furthermore, the angle between the radius and the slide valve centerline varies for different slide valves.

[0004] FR 773 258 A1 also discloses a rotary piston engine whose blades are movably mounted on a piston drum within a crescent-shaped working chamber. The distances separating the blades vary.

[0005] The documents EP 1 316 729 B1, US 6 497 557 B2 and DE 10 2011 078038 A1 each disclose vane pumps with vanes at different distances, but not in such a way that they form groups in which the adjacent vanes each have the same angle.

[0006] WO 2017 / 186272 A1 and US 2018 / 106252 A1 disclose vane pumps with groups of vane cells, each of which has equal spacing between adjacent vanes within the group, with these spacings being unequal for the different groups. However, these vane pumps also explicitly feature individual cells with a wider spacing between the vanes that differs from the other spacings.

[0007] An object of the present invention is to provide a rotary pump which emits less noise during operation.

[0008] This object is achieved by the features of claim 1. Advantageous further developments emerge from the dependent claims, the description and the figures.

[0009] The rotary pump according to the invention, which is preferably designed as a vane pump or pendulum slide pump, comprises a stator and a rotor. The rotor is arranged within the stator so as to be rotatable about an axis of rotation. The rotor also has a plurality of conveying elements which are radially movable with respect to the axis of rotation. Two adjacent conveying elements, together with the outer circumferential surface of the rotor and the inner circumferential surface of the stator, delimit a conveying cell, so that the rotary pump has a plurality of conveying cells. At least two conveying cells, which have a first maximum cell volume, form a first conveying cell group. The conveying cells of the first conveying cell group are adjacent conveying cells. At least one second conveying cell group is formed by at least two further conveying cells, which have a second maximum cell volume.The discharge cells of the second discharge cell group are also adjacent discharge cells. The rotary pump only has grouped discharge cells. The rotary pump lacks discharge cells that are not assigned to one of the discharge cell groups. In other words, the rotary pump only includes discharge cells assigned to one discharge cell group. The rotary pump can have discharge cells grouped into exactly two discharge cell groups or exactly three discharge cell groups.

[0010] According to the invention, the first maximum cell volume of the conveying cells of the first conveying cell group differs from the second maximum cell volume of the conveying cells of the second conveying cell group in that it is larger, advantageously by at least 10%, particularly advantageously by at least 15%, and particularly advantageously by at least 20%. Such a grouping of the conveying cells into conveying cell groups advantageously results in the acoustic emissions of the rotary pump during operation being significantly reduced.

[0011] In particular, due to the inventive design of the pumping cells and their grouping into pumping cell groups, the pressure pulsation of a pumped medium conveyed by the rotary pump is influenced in such a way that the excitation vibrations resulting from the pressure pulsation are reduced. This, in turn, results in a minimization of the noise emitted by the rotary pump.

[0012] The term "adjacent" refers to the similar elements of the rotary pump located directly next to each other in the circumferential direction of the rotor. For example, the term "adjacent discharge cells" refers to the discharge cells located directly next to each other in the circumferential direction of the rotor. The term "adjacent discharge elements" refers to the discharge elements located directly next to each other in the circumferential direction of the rotor.

[0013] The stator preferably has a cylindrical cavity in which the rotatable rotor is arranged. The maximum outer diameter of the rotor is advantageously smaller than the minimum inner diameter of the cylindrical cavity of the stator. The cylindrical cavity of the stator can have a circular cross-section, an elliptical cross-section, or a different cross-section.

[0014] The radial movement of the conveying elements relates, in a technically sensible manner, to the axis of rotation of the rotor. Preferably, the radial movement of the conveying elements in the direction of the axis of rotation is limited by the structure of the rotor and / or a support means, for example a support ring. The radial movement of the conveying elements away from the axis of rotation can be limited by the inner circumferential surface of the stator and / or by a support means of the stator. For example, with a rotating rotor, the conveying elements can be moved radially outward due to the centrifugal force acting on the conveying elements, whereby this movement is limited by the inner circumferential surface of the stator.

[0015] Each delivery cell has a cell volume which can be filled with the medium to be delivered during operation of the rotary pump, in particular when the rotor rotates about the axis of rotation. Advantageously, the cell volume of each delivery cell changes when the rotor rotates about its axis of rotation. For example, in a multi-flow rotary pump, the cell volume can change several times, in particular periodically, from a maximum cell volume to a minimum cell volume and then a maximum cell volume when the rotor rotates 360°. In a single-flow rotary pump, the cell volume of the delivery cells will change, for example, only once, from a maximum cell volume to a minimum cell volume and then a maximum cell volume when the rotor rotates 360°.

[0016] As already mentioned, there is at least one rotational angle position of the rotor at which the conveyor cells have a maximum cell volume. Alternatively or additionally, the conveyor cells can also have the maximum cell volume over a rotational angle range of the rotor. Advantageously, this is the rotational angle position and / or the rotational angle range of the rotor at which the conveyor cells pass through a circumferential position at which the distance between the outer surface of the rotor and the inner surface of the stator is maximum.

[0017] To convey fluid, the conveying cells expand as the rotor rotates up to their maximum cell volume and then shrink again. For each complete rotation of the rotor, the conveying cells have a maximum cell volume for the respective conveying cell, i.e., a cell-specific maximum cell volume. Over the course of a 360° rotor rotation, the respective conveying cell reaches its maximum cell volume, but does not exceed it. There is no rotational angle position of the rotor in which the respective conveying cell has a cell volume that is greater than its maximum cell volume.

[0018] In first designs, the rotary pump can be designed such that the delivery cells each reach their cell-specific maximum cell volume only once during a complete rotation of the rotor, particularly in designs in which the rotary pump only has one working flow, i.e. is single-flow. If the pump is multi-flow, in second designs it can be designed such that the delivery cells each reach their cell-specific maximum cell volume several times during a complete rotation of the rotor, for example if the working flows of the pump are the same over the stroke. If the pump is multi-flow, in third designs it can instead be designed such that the delivery cells each reach their cell-specific maximum cell volume only once during a complete rotation of the rotor, for example if the working flows of the pump differ from one another over the stroke.

[0019] The conveyor cells of the first conveyor cell group preferably have an at least substantially identical first maximum cell volume. The shape of the conveyor cells of the first conveyor cell group can be different and / or identical. The conveyor cells of the second conveyor cell group preferably have an at least substantially identical second maximum cell volume, regardless of the design of the conveyor cells of the first conveyor cell group. The shape of the conveyor cells of the second conveyor cell group can be different and / or identical. An "at least substantially identical maximum cell volume" should be understood in particular to mean that two cell volumes can differ from one another by a maximum of 10%, advantageously by a maximum of 5%, and particularly advantageously only due to manufacturing tolerances.

[0020] In an advantageous development, the conveying elements that delimit a conveying cell of the first conveying cell group are each arranged at a first angular distance from one another on the rotor. The conveying elements that delimit a conveying cell of the second conveying cell group can each be arranged at a second angular distance from one another on the rotor. The angular distances are defined such that they describe the angle enclosed by two straight lines. The straight lines each connect a mounting point of two adjacent conveying elements on the rotor with the vertex of the angle on the rotor's axis of rotation.

[0021] Preferably, the first angular distance between two conveyor elements of the first conveyor cell group is at least substantially equal, and the second angular distance between two conveyor elements of the second conveyor cell group is at least substantially equal, with the first angular distance differing from the second angular distance. An "at least substantially equal angular distance" should be understood in particular to mean that two angular distances can differ from one another by a maximum of 1°, advantageously a maximum of 0.5°, and particularly advantageously only due to manufacturing tolerances. Advantageously, the first angular distance is greater than the second angular distance, advantageously by at least 1°, particularly advantageously by at least 3°, and particularly advantageously by at least 5°. For example, the first angular distance can be between 40° and 45°, preferably 43°.The second angular distance can be, for example, 35-40°, preferably 38.5°.

[0022] In a further embodiment of the rotary pump, the number of delivery cells in the first delivery cell group is different from the number of delivery cells in the second delivery cell group. In general, the number of delivery cells in each delivery cell group can be varied as desired, as long as each delivery cell group has at least two delivery cells. Preferably, the number of delivery cells in the first delivery cell group is greater than the number of delivery cells in the second delivery cell group. For example, the first delivery cell group can have three delivery cells, while the second delivery cell group has six delivery cells. In such an embodiment, the rotary pump comprises a total of nine delivery cells.

[0023] In a further development, the circumferential distance along the inner surface of the stator between two adjacent conveying elements that define a conveying cell of the first conveying cell group is greater than the circumferential distance along the inner surface of the stator between two adjacent conveying elements that define a conveying cell of the second conveying cell group. For example, in such a further development, all conveying elements can be arranged at a constant angular distance from one another on the rotor without projecting radially perpendicularly from the rotor. Rather, the conveying elements can be arranged radially obliquely on the rotor.

[0024] Advantageously, the circumferential distance along the outer surface of the rotor between two adjacent conveying elements that define a conveying cell of the first conveying cell group is greater than the circumferential distance along the outer surface of the rotor between two adjacent conveying elements that define a conveying cell of the second conveying cell group. For example, in rotary pumps in which the circumferential distance along the inner surface of the stator between all conveying elements is constant, the first maximum cell volume of the conveying cells of the first conveying cell group can be larger than the second maximum cell volume of the conveying cells of the second conveying cell group. In such an embodiment, the conveying elements are preferably arranged radially obliquely on the rotor.

[0025] In possible further developments, the rotary pump can have three delivery cell groups. The maximum cell volume of the delivery cells of each delivery cell group is not equal to the maximum cell volumes of the delivery cells of the other delivery cell group. This means that the delivery cells of the first delivery cell group have a first maximum cell volume, the delivery cells of the second delivery cell group have a second maximum cell volume, and the delivery cells of the third delivery cell group have a third maximum cell volume. The first maximum cell volume is advantageously greater than the second maximum cell volume, and the second maximum cell volume is advantageously greater than the third maximum cell volume.

[0026] In an example not falling within the scope of the claims, in which the rotary pump has more than three delivery cell groups, the maximum cell volumes of the delivery cells of non-adjacent delivery cell groups can be the same. Thus, an embodiment of the rotary pump with six delivery cell groups not falling within the scope of the claims can be configured such that two non-adjacent delivery cell groups comprise delivery cells that have the same maximum cell volume.

[0027] In a preferred embodiment of the rotary pump, the rotor is arranged eccentrically with respect to the stator. In other words, the stator, in particular the cylindrical cavity in which the rotor is arranged, can have a central axis. In an eccentric arrangement, the central axis of the stator is spaced from the axis of rotation of the rotor. This causes the distance between the outer circumferential surface of the rotor and the inner circumferential surface of the stator to vary and / or be non-constant over the circumference of the rotor. Such eccentricity is advantageous, for example, in single-flow rotary pumps.

[0028] In a further development, the eccentricity between the stator and the rotor is variable. For example, the stator can be variable in its relative position to the rotor such that the distance between the central axis of the stator and the axis of rotation of the rotor is variable. A variable eccentricity between the stator and the rotor advantageously means that the pumping power of the rotary pump can be controlled during operation, in particular when the rotor is rotating. For example, the rotary pump can have maximum pumping power at maximum eccentricity, in particular at a maximum distance between the central axis of the stator and the axis of rotation of the rotor, and minimum pumping power at minimum eccentricity, in particular at a minimum distance between the central axis of the stator and the axis of rotation of the rotor.

[0029] Advantageously, the area in which the distance between the outer surface of the rotor and the inner surface of the stator increases in the direction of rotation of the rotor forms a suction area of ​​the rotary pump. For example, the suction area begins at the circumferential position of the stator at which the distance between the outer surface of the rotor and the inner surface of the stator is smallest. Advantageously, when the delivery cells reach the beginning of the suction area as a result of the rotation of the rotor, they have a minimum cell volume. The suction area can end at the circumferential position of the stator at which the distance between the outer surface of the rotor and the inner surface of the stator is greatest. Advantageously, when the delivery cells reach the end of the suction area as a result of the rotation of the rotor, they have a maximum cell volume.The suction area of ​​the rotary pump is preferably connected to a suction connection via which the pumped medium can be provided.

[0030] The region in which the distance between the outer surface of the rotor and the inner surface of the stator decreases in the direction of rotation of the rotor can form a pressure region of the rotary pump. For example, the pressure region begins at the circumferential position of the stator at which the distance between the outer surface of the rotor and the inner surface of the stator is greatest. Advantageously, the delivery cells have a maximum cell volume when they reach the beginning of the pressure region as a result of rotation of the rotor. The pressure region can end at the circumferential position of the stator at which the distance between the outer surface of the rotor and the inner surface of the stator is smallest. Advantageously, the delivery cells have a minimum cell volume when they reach the end of the pressure region as a result of rotation of the rotor.

[0031] The pressure area of ​​the rotary pump is preferably connected to a pressure connection through which the pumped medium can be discharged.

[0032] In a further embodiment, the rotary pump can comprise a stator having a cylindrical cavity with an elliptical cross-section, allowing the rotary pump to convey the fluid in multiple flow directions. The term "multiflow" means that the rotary pump has multiple suction and pressure zones.

[0033] In a rotary pump designed as a vane pump, the conveying elements are designed as vanes. In a rotary pump designed as a pendulum-slide pump, the conveying elements are designed as pendulums, which are arranged on the rotor, preferably pivotable in the circumferential direction relative to the outer surface of the rotor. Advantageously, in this embodiment, the stator is designed as a rotatable outer rotor, which is connected to the pendulums in such a way that the rotary motion of the rotor can be transmitted to the outer rotor via the pendulums.

[0034] The rotary pump is particularly intended for use in a motor vehicle. Accordingly, the rotary pump can be designed as a motor vehicle pump. The rotary pump is preferably intended for conveying a liquid, in particular a lubricant, coolant, and / or actuating agent. Accordingly, the rotary pump can be designed as a liquid pump. The rotary pump is preferably intended for supplying, lubricating, and / or cooling a motor vehicle drive engine or a motor vehicle transmission. The liquid is preferably embodied as an oil, in particular as an engine lubricating oil or transmission oil. The rotary pump can be designed as an engine lubricant pump for a motor vehicle or as a transmission pump for a motor vehicle.

[0035] Various exemplary features of the invention can be combined with one another according to the invention, provided this is technically reasonable and suitable. Further features and advantages of the invention will become apparent from the following description of exemplary embodiments with reference to the figures. The figures show: Figure 1: A schematic sectional view of a first embodiment of the rotary pump according to the invention; Figure 2: A second schematic sectional view of the first embodiment of the rotary pump according to the invention; Figure 3: A third schematic sectional view of the first embodiment of the rotary pump according to the invention; Figure 4: A sectional view of a second embodiment of the rotary pump according to the invention.

[0036] Figure 1shows a schematic sectional view of a first embodiment of the rotary pump 1. In the first embodiment, the rotary pump 1 is designed as a vane pump 1, which has a stator 2 with a circular cylindrical cavity.

[0037] Within the circular cylindrical cavity of the stator 2, a rotor 3 is arranged, rotatable about a rotational axis D. The outer diameter of the rotor 3 is smaller than the inner diameter of the circular cylindrical cavity of the stator 2, so that the outer circumferential surface of the rotor 3 is spaced from the inner circumferential surface of the stator 2. Preferably, the rotational axis D also forms the central axis of the rotor 3. In the illustrated embodiment, the rotor 3 is arranged eccentrically to the stator 2.

[0038] As in Figure 1As shown, the rotor 3 has a plurality of conveying elements 4 distributed over the circumference of the rotor 3. The conveying elements 4 protrude radially from the rotor 3 with respect to the axis of rotation D and are attached or arranged on the rotor 3 such that they are movable in the radial direction. A radial movement of the conveying elements 4 directed outwards away from the axis of rotation D is limited by the inner circumferential surface of the stator 2.

[0039] Together with the inner surface of the stator 2 and the outer surface of the rotor 3, two adjacent conveying elements 4 each define a conveying cell 11-13, 21-24. Figure 1 The embodiment shown comprises a total of seven conveyor cells 11-13, 21-24. Due to the eccentricity of the rotor 3 relative to the stator 2, each conveyor cell 11-13, 21-24 has a maximum cell volume. For example, in the Figure 1In the illustrated vane pump 1, each delivery cell 11-13, 21-24 has its maximum cell volume when it is in the "12 o'clock" position due to the rotation of the rotor 3. Consequently, the delivery cell 12 has Figure 1 shown state of the vane cell pump 1 reaches its maximum cell volume.

[0040] The three adjacent conveyor cells 11-13 have the same first maximum cell volume at the "12 o'clock" position and together form a first conveyor cell group 10. The four adjacent conveyor cells 21-24 have the same second maximum cell volume at the "12 o'clock" position and together form a second conveyor cell group 20. The first maximum cell volume of the conveyor cells 11-13 is greater than the second maximum cell volume of the conveyor cells 21-24.

[0041] The area between the outer surface of the rotor 3 and the inner surface of the stator 2 on the right half side of the Figure 1The illustrated vane pump 1 forms a suction zone when the rotor 3 rotates counterclockwise. Within the suction zone, the cell volumes of the delivery cells 11-13, 21-24 increase from a minimum cell volume at the "6 o'clock" position to the maximum cell volume at the "12 o'clock" position. In advantageous embodiments of the vane pump 1, the suction zone is connected to a suction connection (not shown) for the pumped medium, so that the pumped medium is sucked in via the suction connection due to the increase in the delivery volumes of the individual delivery cells 11-13, 21-24.

[0042] The area between the outer surface of the rotor 3 and the inner surface of the stator 2 on the left half of the Figure 1The vane pump 1 shown forms a pressure zone when the rotor 3 rotates counterclockwise. Within the pressure zone, the cell volumes of the delivery cells 11-13, 21-24 decrease from the maximum cell volume at the "12 o'clock" position to the minimum cell volume at the "6 o'clock" position. In advantageous embodiments of the vane pump 1, the pressure zone is connected to a pressure connection (pressure outlet) (not shown) for the pumped medium, so that the pumped medium is pumped out via the pressure connection (pressure outlet) as the delivery volumes of the individual delivery cells 11-13, 21-24 decrease.

[0043] Due to the advantageous design of the pumping cells 11-13, 21-24 and their grouping into two pumping groups 10, 20, the pressure pulsation of the pumped medium at the pressure connection (pressure outlet) is influenced in such a way that the excitation vibrations resulting from the pressure pulsation are reduced. This, in turn, minimizes the noise emitted by the vane pump 1.

[0044] Figure 2shows a further schematic sectional view of the first exemplary embodiment of the rotary pump 1, wherein the angular distances α, β of the individual conveying elements 4 from one another are shown. The conveying elements 4, which delimit the conveying cells 11-13 of the first conveying cell group 10, are arranged at a first angular distance α from one another on the rotor 3. The conveying elements 4, which delimit the conveying cells 21-24 of the second conveying cell group 20, are arranged at a second angular distance β from one another on the rotor 3. The first angular distance α is greater than the second angular distance β. This means that the respective first maximum cell volume of the conveying cells 11-13 of the first conveying cell group 10 is greater than the respective second maximum cell volume of the conveying cells 21-24 of the second conveying cell group 20.

[0045] Furthermore, Figure 2a circumferential distance UI is shown, which extends between two adjacent conveying elements 4 along the inner surface of the stator 2. A circumferential distance UA extends between two adjacent conveying elements 4 along the outer surface of the rotor 3. In the Figure 2In the illustrated embodiment of the rotary pump 1, both the circumferential distance UI and the circumferential distance UA of the conveying cells 11-13 of the first conveying cell group 10 are greater than the circumferential distances UI, UA of the conveying cells 21-24 of the second conveying cell group 20. In particular, in an embodiment of the rotary pump 1 not shown, in which the conveying elements 4 are arranged at a constant winding distance on the rotor 3, but do not protrude vertically radially outwards from the outer surface of the rotor 3, the maximum cell volume of the conveying cells 11-13 of the first conveying cell group 10 can be different in relation to the maximum cell volume of the conveying cells 21-24 of the second conveying cell group 20 due to a different circumferential distance UI and / or a different circumferential distance UA.

[0046] Figure 3 shows that in Figure 1illustrated embodiment of the rotary pump 1, wherein the axis of rotation D of the rotor 2 and the central axis M of the stator 2 are shown. The axis of rotation D has an offset from the central axis M, so that the rotor 3 is arranged eccentrically to the stator 2. This eccentricity causes the area between the outer circumferential surface of the rotor 3 and the inner circumferential surface of the stator 2 on the right-hand half of the rotary pump 1 to form a suction area. In contrast, the area between the outer circumferential surface of the rotor 3 and the inner circumferential surface of the stator 2 on the left-hand half of the rotary pump 1 forms a pressure area.

[0047] In the case of further training in Figure 3In the illustrated embodiment of the rotary pump 1, the eccentricity of the rotor 3 relative to the stator 2 can be designed to be variable. For example, the position of the stator 2 relative to the rotor 2 could be changed such that the central axis M coincides with the axis of rotation D in a second position of the stator 2. This has the result that the distance between the outer circumferential surface of the rotor 3 and the inner circumferential surface of the stator 2 remains constant over the entire circumference. During operation, the rotary pump 1 would be in the so-called zero pass when the stator 2 is in the second position. In this case, the pumping power of the rotary pump 1 would be greatly reduced or eliminated. Ultimately, the pumping power of the rotary pump can be controlled via the eccentricity of the stator 2 relative to the rotor 3.

[0048] Figure 4shows a sectional view of a second embodiment of a rotary pump 1. In the second embodiment, the rotary pump 1 is also designed as a vane pump 1. In the second embodiment, the vane pump 1 comprises a total of nine conveying cells 11-13, 21-26. The first conveying cell group 10 is formed by the adjacent conveying cells 11-13. The adjacent conveying cells 11-13 are delimited by conveying elements 4, which are arranged on the rotor 3 at a first angular distance α of 43° from one another (not shown). The second conveying cell group 20 is formed by the adjacent conveying cells 21-26. The adjacent conveying cells 21-26 are delimited by conveying elements 4, which are arranged on the rotor 3 at a second angular distance β of 38.5° from one another (not shown). List of reference symbols

[0049] 1Vane pump 2Stator 3Rotor 4Conveying elements 10first conveyor cell group 11conveyor cell 12conveyor cell 13conveyor cell 20second conveyor cell group 21conveyor cell 22conveyor cell 23conveyor cell 24conveyor cell 25conveyor cell 26conveyor cell αfirst angular distance βsecond angular distance Drotational axis of the rotor MCenter axis of the stator UI Circumferential distance along the inner surface of the stator UA Circumferential distance along the outer surface of the rotor

Claims

1. A rotary pump (1), preferably a vane cell pump or a pendulum slider pump, comprising (a) a stator (2) and (b) a rotor (3) which can rotate about a rotational axis (D) within the stator (2), wherein (c) the rotor (3) comprises multiple delivery elements (4) which can move radially in relation to the rotational axis (D), and (d) two adjacent delivery elements (4) limit a delivery cell (11 to 13, 21 to 26) together with the outer surface area of the rotor (3) and the inner surface area of the stator (2), wherein (e) at least two adjacent delivery cells (11 to 13) which exhibit a first maximum cell volume form a first delivery cell group (10) and (f) at least two other adjacent delivery cells (21 to 26) which exhibit a second maximum cell volume form a second delivery cell group (20) (g) and optionally another at least two other adjacent delivery cells which exhibit a third maximum cell volume form a third delivery cell group, wherein (h) the first maximum cell volume of the delivery cells (11 to 13) of the first delivery cell group (10) is larger than the second maximum cell volume of the delivery cells (21 to 26) of the second delivery cell group (20), and the second maximum cell volume is larger than the third maximum cell volume, if the third delivery cell group is provided, and (i) the delivery elements (4) which limit a delivery cell (11 to 13) of the first delivery cell group (10) are each arranged at a first angular distance (α) from each other on the rotor (3), and the delivery elements (4) which limit a delivery cell (21 to 26) of the second delivery cell group (20) are each arranged at a second angular distance (β) from each other on the rotor (3), wherein the first angular distance (α) is larger than the second angular distance (β), characterised in that (j) the rotary pump contains only delivery cells which are assigned to the first delivery cell group (10) or to the second delivery cell group (20) or to the third delivery cell group, if provided.

2. The rotary pump (1) according to the preceding claim, characterised in that the number of delivery cells (11 to 13) in the first delivery cell group (10) is not equal to the number of delivery cells (21 to 26) in the second delivery cell group (20).

3. The rotary pump (1) according to any one of the preceding claims, characterised in that the number of delivery cells (11 to 13) in the first delivery cell group (10) is smaller than the number of delivery cells (21 to 26) in the second delivery cell group (20).

4. The rotary pump (1) according to any one of the preceding claims, characterised in that the first delivery cell group (10) comprises at least two and at most six and in particular three delivery cells (11 to 13), wherein the adjacent delivery elements (4) of the first delivery cell group (10) are arranged at a first angular distance (α) of 40° to 45°, in particular at a first angular distance (α) of 43°, from each other on the rotor (3).

5. The rotary pump (1) according to any one of the preceding claims, characterised in that the second delivery cell group (20) comprises at least four and at most ten and in particular six delivery cells (21 to 26), wherein the adjacent delivery elements (4) of the second delivery cell group (20) are arranged at a second angular distance (β) of 35° to 40°, in particular at a second angular distance (β) of 38.5°, from each other on the rotor (3).

6. The rotary pump (1) according to any one of the preceding claims, characterised in that the rotary pump (1) comprises a total of at least six and at most sixteen and in particular exactly nine delivery cells (11 to 13, 21 to 26).

7. The rotary pump (1) according to any one of the preceding claims, characterised in that the circumferential distance (UI) along the inner surface area of the stator (2) between two adjacent delivery elements (4) which limit a delivery cell (11 to 13) of the first delivery cell group (10) is larger than the circumferential distance (UI) along the inner surface area of the stator (2) between two adjacent delivery elements (4) which limit a delivery cell (21 to 26) of the second delivery cell group (20).

8. The rotary pump (1) according to any one of the preceding claims, characterised in that the circumferential distance (UA) along the outer surface area of the rotor (3) between two adjacent delivery elements (4) which limit a delivery cell (11 to 13) of the first delivery cell group (10) is larger than the circumferential distance (UA) along the outer surface area of the rotor (3) between two adjacent delivery elements (4) which limit a delivery cell (21 to 26) of the second delivery cell group (20).

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