Fluid flow regulation assembly with vibration attenuation

Abstract

A fluid flow regulation assembly (1) includes: movable parts, for being actively mechanically driven, including at least one of a fluid flow regulating body for regulating a fluid flow and a rotor of a motor for driving the regulating body; and power electronics for controlling the motor. The movable parts and/or the power electronics are a source of vibration. Static parts are exposed to traveling vibrations originating from the source of vibration and include at least one of the group: a pump housing (3), a valve housing, a motor housing (5), a pump base and an electronics housing (7). The static parts include a structural element (11) with at least one vibration attenuation section (9) for attenuating vibrations: that originate from the source of vibration; travel along the structural element and have a vibration frequency above a pre-determined minimum vibration frequency (f.sub.min).

Claims

1. A fluid flow regulation assembly comprising: movable parts for being actively mechanically driven, wherein the movable parts include at least one fluid flow regulating body for regulating a fluid flow and a rotor of a motor for driving the regulating body; power electronics for controlling the motor, wherein at least one of the movable parts and the power electronics are a source of vibration; and static parts exposed to traveling vibrations originating from the source of vibration, wherein: the static parts include at least one of the group comprising: a pump housing, a valve housing, a motor housing, a pump base and an electronics housing; the static parts comprise a structural element with at least one vibration attenuation section for attenuating vibrations that originate from the source of vibration, travel along said structural element, and have a vibration frequency above a pre-determined minimum vibration frequency; the at least one vibration attenuation section has a material thickness decay profile in a traveling direction of the vibrations; the structural element comprises at least one wall section; the at least one vibration attenuation section is arranged at the at least one wall section; and the at least one vibration attenuation section extends over an area of rotationally asymmetric shape.

2. The fluid flow regulation assembly according to claim 1, wherein the fluid flow regulation assembly is a pump assembly, wherein the at least one fluid flow regulating body is an impeller or a displacement body, wherein the at least one vibration attenuation section is a part of the at least one wall section.

3. The fluid flow regulation assembly according to claim 1, wherein the fluid flow regulation assembly is a valve assembly, wherein the at least one fluid flow regulating body is a valve body, the at least one vibration attenuation section forming a part of the at least one wall section and the at least one vibration attenuation section defining a surface of the at least one wall section.

4. The fluid flow regulation assembly according to claim 1, wherein the material thickness decay profile is one-sided, the at least one vibration attenuation section extending continuously, without interruption, from one portion of the at least one wall section to another portion of the at least one wall section.

5. The fluid flow regulation assembly according to claim 1, wherein the structural element comprises a material thickness smoothly and/or stepwise reducing in a traveling direction of the vibrations from a rim of the at least one vibration attenuation section having a maximum material thickness to a point, line or area of minimum or zero material thickness of the at least one vibration attenuation section, the at least one vibration attenuation section being configured to dampen the vibrations in the at least one wall section.

6. The fluid flow regulation assembly according to claim 1, wherein the at least one vibration attenuation section has a functionality of an acoustic black hole in the structural element.

7. The fluid flow regulation assembly according to claim 1, wherein the structural element comprises at least one support structure, comprising a rib or a web, extending at least partly across the at least one vibration attenuation section.

8. The fluid flow regulation assembly according to claim 7, wherein the at least one support structure is defined by a locally non-reduced or less reduced material thickness of the structural element.

9. The fluid flow regulation assembly according to claim 1, wherein: the structural element defines a predictable main path of travel of the vibrations along said structural element; the predictable main path of travel extends from a first structure section of the structural element towards a second structure section of the structural element; and the at least one vibration attenuation section is arranged between the first structure section and the second structure section.

10. The fluid flow regulation assembly according to claim 1, wherein: the at least one vibration attenuation section separates a first structure section of the structural element and a second structure section of the structural element; and the first structure section is exposed to traveling vibrations caused by the source of vibration and the second structure section receives essentially only vibrations below the pre-determined minimum vibration frequency and/or vibrations attenuated by the at least one vibration attenuation section.

11. The fluid flow regulation assembly according to claim 1, wherein: the structural element comprises a first material having a first Young modulus; the at least one vibration attenuation section is at least partly covered by or equipped with a dampening element comprising a second material with a second Young modulus; and the second Young modulus is smaller than the first Young modulus.

12. The fluid flow regulation assembly according to claim 1, wherein: the structural element comprises a plurality of wall sections defined by at least one inner or outer edge between the wall sections; and the at least one vibration attenuation section is arranged at least one of at a largest one of the wall sections and at one of the wall sections being located closest to the source of vibration.

13. The fluid flow regulation assembly according to claim 1, wherein: the at least one vibration attenuation section extends over an area of at least 25 percent of the at least one wall section.

14. The fluid flow regulation assembly according to claim 1, wherein: a plurality of vibration attenuation sections are arranged at the at least one wall section; and the vibration attenuation sections are separated from each other by at least one support structure.

15. The fluid flow regulation assembly according to claim 1, wherein the structural element is at least part of the electronics housing accommodating motor control electronics.

16. The fluid flow regulation assembly according to claim 1, wherein the at least one vibration attenuation section extends in a traveling direction of the vibrations for at least three times of a material thickness that the structural element has outside of the at least one vibration attenuation section.

17. The fluid flow regulation assembly according to claim 1, wherein: the at least one vibration attenuation section has a material thickness equal to or larger than a minimum material thickness; the minimum material thickness is equal to or smaller than half of the material thickness that the structural element has outside of the at least one vibration attenuation section.

18. The fluid flow regulation assembly according to claim 1, wherein: the at least one vibration attenuation section has a material thickness equal to or larger than a minimum material thickness; the speed of sound at the minimum material thickness is equal to or smaller than 1/{square root over (2)} of the speed of sound at the material thickness that the structural element has outside of the at least one vibration attenuation section.

19. The fluid flow regulation assembly according to claim 1, wherein: the material thickness decay profile has one or more of a smoothly reducing steepness in the traveling direction of the vibrations and a stepwise reducing steepness in the traveling direction of the vibrations.

20. The fluid flow regulation assembly according to claim 1, wherein the at least one vibration attenuation section is at least partly covered by a dampening element that is an active dampening element, a semi-active dampening element or a passive dampening element, the at least one vibration attenuation section defining a portion of a material thickness of the at least one wall section.

21. The fluid flow regulation assembly according to claim 20, wherein the dampening element comprises at least one of the group comprising: a coating; an adhesive; a pad; a gel; a gasket material; one or more polymeric films; a sandwich structure of different layers of material; a sandwich structure of different layers of stiffness; a piezo element transforming energy of the vibrations into electric energy that is harvested or transformed into heat by an electrical resistance; a vibration sensing element for measuring the vibrations; a PVDF film; and a quartz crystal.

22. A fluid flow regulation assembly comprising: movable parts for being actively mechanically driven, wherein the movable parts include at least one fluid flow regulating body for regulating a fluid flow and a rotor of a motor for driving the regulating body; power electronics for controlling the motor, wherein at least one of the movable parts and the power electronics are a source of vibration; and static parts exposed to traveling vibrations originating from the source of vibration, wherein: the static parts include at least one of the group comprising: a pump housing, a valve housing, a motor housing, a pump base and an electronics housing; the static parts comprise a structural element with at least one vibration attenuation section for attenuating vibrations that originate from the source of vibration, travel along said structural element, and have a vibration frequency above a pre-determined minimum vibration frequency; the at least one vibration attenuation section has a material thickness decay profile in a traveling direction of the vibrations; the structural element comprises at least one wall section; the at least one vibration attenuation section is arranged at the at least one wall section; the at least one vibration attenuation section extends over an area of any shape; the area defines a distance (D) between two points of the area that have a largest distance to each other in the traveling direction of the vibrations; said distance (D) fulfils the formula $D0.5\frac{c_{\mathrm{red}}}{f_{\min }};$ and f.sub.min in is the minimum vibration frequency and c_red is the speed of sound along the f min structural element where a material thickness in the at least one vibration attenuation section is minimal.

23. A fluid flow regulation assembly comprising: movable parts for being actively mechanically driven, wherein the movable parts include at least one fluid flow regulating body for regulating a fluid flow and a rotor of a motor for driving the regulating body; power electronics for controlling the motor, wherein at least one of the movable parts and the power electronics are a source of vibration; and static parts exposed to traveling vibrations originating from the source of vibration, wherein: the static parts include at least one of the group comprising: a pump housing, a valve housing, a motor housing, a pump base and an electronics housing; the static parts comprise a structural element with at least one vibration attenuation section for attenuating vibrations that originate from the source of vibration, travel along said structural element, and have a vibration frequency above a pre-determined minimum vibration frequency; the at least one vibration attenuation section has a material thickness decay profile in a traveling direction of the vibrations; the structural element comprises at least one wall section; the at least one vibration attenuation section is arranged at the at least one wall section; the at least one vibration attenuation section extends over an area of any shape; the area defines a first distance along a first straight virtual line between two points of the area that have the largest distance to each other; the area defines a second distance along a second straight virtual line intersecting a center of the first virtual line at a right angle; the second distance is a distance between two points of the area on the second virtual line that have the largest distance to each other; and the first distance is at least 10% larger than the second distance.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) Embodiments of the present disclosure will now be described by way of example with reference to the following figures of which:

(2) FIGS. 1a and 1b are perspective views of different embodiments of a fluid flow regulation assembly according to the present disclosure;

(3) FIG. 2a is a perspective view on an inner side of a structural element of an example of a fluid flow regulation assembly according to the present disclosure,

(4) FIG. 2b is a perspective longitudinal cut view on an inner side of a structural element of the example of a fluid flow regulation assembly of FIG. 2a;

(5) FIG. 3a is a perspective view on an inner side of a structural element of another example of a fluid flow regulation assembly according to the present disclosure;

(6) FIG. 3b is a perspective longitudinal cut view on an inner side of a structural element of the example of a fluid flow regulation assembly according to FIG. 3a;

(7) FIG. 4 is a perspective longitudinal cut view of a different structural element of an example of a fluid flow regulation assembly according to the present disclosure;

(8) FIGS. 5a and 5b are perspective longitudinal cut views of another example of a structural element of a fluid flow regulation assembly according to the present disclosure;

(9) FIG. 6a is a perspective view of another example of a structural element of a fluid flow regulation assembly according to the present disclosure;

(10) FIG. 6b is a perspective sectional cut view of another example of a structural element of the fluid flow regulation assembly according to FIG. 6a;

(11) FIG. 7a is a perspective sectional cut view of different examples of a structural element of a fluid flow regulation assembly according to the present disclosure;

(12) FIG. 7b is a longitudinal cut view of different examples of a structural element of a fluid flow regulation assembly according to the present disclosure;

(13) FIG. 7c is a perspective sectional cut view of different examples of a structural element of a fluid flow regulation assembly according to the present disclosure;

(14) FIG. 8 is a longitudinal cut view of another example of a structural element of a fluid flow regulation assembly according to the present disclosure;

(15) FIGS. 9a, 9b, 9c, 9d, 9e, 9f, 9g, 9h, and 9i are detailed longitudinal cut views of a vibration attenuation section of an example of a structural element with different embodiments and positions of a dampening element of a fluid flow regulation assembly according to the present disclosure;

(16) FIG. 10a is a perspective view of another example of a structural element of a fluid flow regulation assembly according to the present disclosure;

(17) FIG. 10b is a longitudinal cut view of the example of a structural element of the fluid flow regulation assembly according to FIG. 10a;

(18) FIG. 10c is a perspective sectional cut view of another example of a structural element of the fluid flow regulation assembly according to FIG. 10a;

(19) FIG. 11a is a perspective view of another example of a structural element of a fluid flow regulation assembly according to the present disclosure;

(20) FIG. 11b is a longitudinal cut view of the example of the structural element of a fluid flow regulation assembly according to FIG. 11a;

(21) FIG. 11c is a perspective sectional cut view of the example of the structural element of a fluid flow regulation assembly according to FIG. 11a;

(22) FIG. 12a is a longitudinal cut view of another example of a structural element of a fluid flow regulation assembly according to the present disclosure;

(23) FIG. 12b is a perspective sectional cut view of the example of the structural element of a fluid flow regulation assembly according to FIG. 12a;

(24) FIG. 13a is a perspective view of another example of a structural element of a fluid flow regulation assembly according to the present disclosure;

(25) FIG. 13b is longitudinal cut view of another example of the structural element of a fluid flow regulation assembly according to FIG. 13a;

(26) FIG. 13c is a perspective sectional cut view of the example of the structural element of a fluid flow regulation assembly according to FIG. 13a;

(27) FIGS. 14a and 14b are schematic views showing rotationally asymmetric areas of vibration attenuation section of a structural element of a fluid flow regulation assembly according to the present disclosure; and

(28) FIGS. 15a and 15b are graphs showing different examples of decay profiles for the material thickness h(x) as a function of x, wherein x is a location variable along the decay profile against the traveling direction of the vibrations.

DETAILED DESCRIPTION

(29) FIG. 1a,b show two different examples of a fluid flow regulation assembly 1 in form of a pump assembly comprising a pump housing (impeller pump housing) 3, a motor housing 5, and an electronics housing 7. The pump housing 3, the motor housing 5 and the electronics housing 7 are static parts of the pump assembly 1. The pump housing 3 accommodates an impeller (not visible) driven to rotate about a rotor axis R by a rotor shaft (not visible) extending along the rotor axis R. The rotor shaft is driven by a rotor (not visible) of a permanent magnet synchronous motor (PMSM) residing within the motor housing 5. The rotor, the rotor shaft and the impeller are movable parts of the pump assembly 1 that are actively mechanically driven. The impeller is a fluid flow regulating body that regulates and/or drives a fluid flow through the pump housing 3. The electronics housing 7 comprises power electronics for controlling the motor within the motor housing 5. The power electronics comprises a frequency converter for controlling the speed of the motor.

(30) The movable parts of the pump assembly 1, e. g. the rotor, the rotor shaft, and the impeller, as well as the power electronics are sources of vibration that travel along the static parts, e. g. the pump housing 3, the motor housing 5 and the electronics housing 7. Such vibrations generate noise and/or negatively affect the life span of the pump assembly 1 or parts thereof. Therefore, there is a general interest in keeping the vibrations traveling along the pump assembly 1 as small as possible. Therefore, the pump assembly 1 is equipped with a vibration attenuation system in order to attenuate vibrations originating from the movable parts and/or the power electronics.

(31) The vibration attenuation system is implemented in form of at least one vibration attenuation section 9 of a structural element 11 of which at least one of the static parts of the pump assembly 1 is composed of. For instance, the structural element 11 may be a main body, a lid and/or a cap of the pump housing 3, of the motor housing 5 and/or the electronics housing 7. In FIG. 1a, the structural element 11 is a lid the electronics housing 7 as shown in FIGS. 2a,b and 3a,b, or a main body of the electronics housing 7 as shown in FIGS. 4 to 8. In FIG. 1b, the structural element 11 is a lid the electronics housing 7 as shown in FIGS. 10a-c to 13a-c.

(32) FIG. 2a shows a perspective view on the inner side of the structural element 11 in the form of a lid or cover of the electronics housing 7 as shown in FIG. 1a. The structural element 11 predominately forms a front face of the electronics housing 7 with an opening 13 for a display and/or a human-machine interface (HMI) 14 (see FIG. 1a). The structural element 11 defines a front wall 15 of the electronics housing 7 and a circumferential side wall 17. The front wall is the largest wall section of the structural element 11. A large fraction of the front wall 15 of the structural element 11 defines the vibration attenuation section 9 extending over an essentially circular area at the inner side of the front wall 15 of the structural element 11. As shown in FIG. 2b, the front wall 15 of the structural element 11 has a nominal material thickness d outside of the vibration attenuation section 9. The vibration attenuation section 9 is characterized by a decay profile in material thickness, wherein the material thickness h reduces from the nominal material thickness d at a rim 19 of the vibration attenuation section 9 towards the center of the vibration attenuation section 9. The material thickness h(x) is minimal at the center of the vibration attenuation section 9. The vibration attenuation section 9 may have just a central point or a central area of minimal material thickness h(x=0), wherein x[0,1] is a normalized location variable in the interval from 0 at minimal material thickness to 1 at the nominal material thickness d.

(33) The vibration attenuation section 9 is designed to attenuate vibrations traveling from the side walls 17 along the front wall 15 and entering the vibration attenuation section 9 at the rim 19. Due to the decay profile of the material thickness, the propagation of the vibrations along the front wall 15 is slowed down towards the center of the vibration attenuation section 9. Thereby, vibration frequencies above a minimum vibration frequency are effectively attenuated by the vibration attenuation section 9. The larger the vibration attenuation section 9 is, the lower the vibration frequencies are that can be effectively attenuated. Thus, the minimum vibration frequency is determined by the size of the area covered by the vibration attenuation section 9. Thus, the vibration attenuation section 9 is chosen to be as large as possible given the outer dimensions of the structural element 11 and the front wall 15.

(34) In order to provide sufficient structural integrity and stability for the structural element 11, it is comprised with a support structure 21 in the form of a grid of ribs or webs 23 extending across the vibration attenuation section 9. The support structure 21 is formed as an integral part of the structural element 11, which is preferably a plastic component molded as an integral single piece. As it can be seen in FIG. 2a, the structural strength of the ribs or webs 23 may be chosen to be higher in those areas of the vibration attenuation section 9, where the material thickness h(x) is smaller. Accordingly, the ribs or webs 23 can be less strong where the vibration attenuation section 9 is thicker.

(35) FIGS. 3a, b show two other embodiments of the structural element 11, wherein the structural element 11 comprises a plurality of vibration attenuation sections 9. The area covered by each of the vibration attenuation sections 9 is in these embodiments confined to the area between the ribs or webs 23 of the support structure 21. Thus, the ribs and webs 23 separate the vibration attenuation sections 9 from each other. Due to the smaller size of the area covered by each vibration attenuation section 9, the predetermined minimum vibration frequency is higher for these embodiments. However, the plurality of vibration attenuation sections 9 may be beneficial in terms of efficiently attenuating higher frequencies of vibrations. The embodiment of FIG. 3a is designed to receive vibrations traveling along the front wall 15 of the structural element 11 in any direction. Simulations and tests may show that the vibrations from the known sources of vibration, e. g. the movable parts and/or the power electronics, travel predominantly along certain axes, e. g. the longitudinal axis L as shown in FIG. 3b. Thus, the embodiment of FIG. 3b is optimized to attenuate vibrations traveling in a longitudinal direction L along the structural element 11.

(36) FIG. 4 shows a main body of an electronics housing 7 as a structural element 11 (see FIG. 1a) comprising a vibration attenuation section 9 at a rear wall 25 facing towards the motor housing 5. Similar to the embodiment shown in FIG. 2a, the vibration attenuation section 9 extends over a majority of the rear wall 25 in a circular area characterized by a certain decay profile of the material thickness of the rear wall 25. The structural element 11 further comprises a side wall 27 complementing the side wall 17 of the lid shown in FIGS. 2a, b and 3a,b.

(37) The vibration attenuation section 9 is in this embodiment covered by a dampening element 29 comprising a softer material than the material of the structural element 11. In other words, the structural element 11 comprises a first material having a first Young modulus and the dampening element 29 comprises a second material with a second Young modulus, wherein the second Young modulus is smaller than the first Young modulus. The softer dampening element 29 is beneficial for absorbing the vibrations that are slowed down by the vibration attenuation section 9.

(38) FIGS. 5a,b show different embodiments of the structural element 11. In contrast to the embodiments shown in FIG. 4, the vibration attenuation section 9 does not have a circular shape, but extends asymmetrically over the rear wall 25 of the structural element 11 in form of an annulus, arc, or banana-like shape. The range of vibration frequencies may be smaller for the embodiments of FIGS. 5a,b compared to the embodiment of FIG. 4, but may be very efficient in protecting certain structure sections of the structural element 11 from propagating vibrations. The vibration attenuation section 9 separates or fences here a first structure section 31 of the structural element 11 from a second structure section 33 of the structural element 11. The structure sections 31, 33 are here part of the rear wall 25 outside of the vibration attenuation section 9. If the first structure section 31 is exposed to traveling vibrations caused by the source of vibration, the vibration attenuation section 9 attenuates vibrations below the predetermined minimum vibration frequency, so that these traveling vibrations do not reach the second structure section 33, or at least only significantly attenuated. The decay profile of the vibration attenuation section 9 shown in FIGS. 5a, b is designed to also attenuate vibration traveling from the second structure section 33 towards the first structure section 31 as well as in the opposite direction from the first structure section 31 towards the second structure section 33. So, the vibration attenuation section 9 has here a two-sided decay profile, wherein two decay profiles are symmetrically arranged to each other, so that the material thickness reduces towards a common center line. This is particularly beneficial if both the first structure section 31 and the second structure section 33 are exposed to sources of vibration that should not reach the other one of the structure sections 33, 31 unattenuated. Similar to the embodiment shown in FIG. 4, the embodiment shown in FIG. 5a comprises a dampening element 29 covering the vibration attenuation section 9. In contrast to the embodiment shown in FIG. 5a, the embodiment shown in FIG. 5b comprises a support structure 21 in form of ribs or webs 23 extending across the vibration attenuation section 9 in order to improve the structural integrity. The ribs or webs 23 may simply be formed by locally non-reduced material thickness across the vibration attenuation section 9 as shown in FIG. 5b.

(39) The embodiment of the structural element 11 shown in FIGS. 6a, b is very similar to the embodiment shown in FIG. 5a. However, the decay profile is one-sided here, i.e. asymmetric in the sense that the vibration attenuation section 9 is designed to attenuate predominantly only vibrations traveling from the first structure section 31 of the structural element 11 towards the second structure section 33 of the structural element 11. This is beneficial if simulations or tests show that the first structure section 31 is much more exposed to traveling vibrations originating from the source of vibration than the second structure section 33. Due to the longer extension of the decay profile in traveling direction of the vibrations, the embodiment of FIGS. 6a,b is able to attenuate a wider frequency range of vibrations compared to the embodiment shown in FIGS. 5a,b. The structural element 11 may comprise one or more mounting points 35 at the second structure section 33 for mounting a printed circuit board comprising electronics. If the first structure section 31 is exposed to vibrations caused by movable parts of the pump assembly 1, the vibration attenuation section 9 separating the first structure section 31 from the second structure section 33 efficiently attenuates those vibrations and thereby protects the printed circuit board with the electronics from those propagating vibrations.

(40) FIGS. 7a-c show the embodiment of FIG. 4 in other perspectives and with more detail. As already pointed out before, the embodiment of a large vibration attenuation section 9 extending over a majority of the area of the rear wall 25 has the advantage that a large range of vibration frequencies can be effectively attenuated. As it can be seen in FIG. 8, the dampening element 29 does not have to be attached to the inner side of the structure element, where the decay profile is visible, but may alternatively, or in addition, be placed at the other side, i.e. the outer side of the structure element 11. However, for aesthetic reasons, it may be desirable to arrange both the vibration attenuation section 9 and the dampening element 29 at the inner side of the structure 11. From a technical point of view. the attenuation of vibrations may work similarly well if the vibration attenuation section 9 and/or the dampening element 29 is arranged at the outer side of the structure element 11. Thus, for safety reasons in view of flammability and/or product certification, it may be beneficial to arrange the dampening element 29 at the outer side of the structure 11.

(41) FIGS. 9a-i show different examples of dampening elements 29 and where they can be placed in relation to the vibration attenuation section 9. In FIG. 9a, the dampening element 29 covers the complete vibration attenuation section 9 from the inner side, so that the vibration attenuation is not visible from the outer side of the structure element 11. A smaller dampening element 29 covering only a part of the vibration attenuation section 9 may be sufficient to effectively adsorb vibrations of the vibration attenuation section 9. For example, as shown in FIG. 9b, only the thinner portions of the vibration attenuation section 9 may be covered by one or more layers of soft dampening material 29. FIG. 9c shows a dampening element 29 attached to the outer side of this structure element, where the material thickness of the vibration attenuation section 9 is thin. The dampening element 29 comprises a sandwich layer structure of a first layer 37 of soft material and a second layer 39 of stiffer material. The stiffer material of the second layer 39 may be the same material that the structure element 11 is made of or another material, such as aluminum. The first softer layer 37 and/or the stiffer second layer 39 may be comprised of a sandwich layer structure itself. The dampening element 29 may function as a support structure 21 as well as providing a dampening effect for adsorbing vibrations of the vibration attenuation section 9.

(42) The embodiment shown in FIG. 9d shows that the vibration attenuation section 9 may comprise a hole 41 in the structure element 11. As shown in FIG. 9e, the dampening element 29 may comprise a coating or filling material covering at least parts of the vibration attenuation section 9 and/or filling the hole 41. In the embodiment of FIG. 9f. the dampening element 29 comprises a piezo element transforming energy of the vibrations into electric energy to be harvested or transformed into heat by an electric resistance. As shown in FIG. 9g, the soft first layer 37 of the sandwich structure of the dampening element 29 may cover a larger area than the stiffer second layer 39. The stiffer second layer 39 may be a metal sheet, i.e. of aluminum. The soft first layer 37 may be located between the stiffer second layer 39 and the structure element 11 as shown in FIGS. 9c, d, g h. As shown in FIG. 9h, the embodiment of FIG. 9g may also be equipped with a piezo element for transforming energy of the vibrations into electric energy to be harvested or transformed into heat by an electrical resistance. A piezo element or another kind of vibration sensing element may also be used to measure the vibrations for monitoring purposes. In the embodiment of FIG. 9i, the damping element 29 is attached to the outer side of the structural element 11 and covers that fraction of the vibration attenuation section 9 that has a minimum material thickness.

(43) FIGS. 10a-c show a structural element 11 in the form of a lid of an electronics housing 7 of a pump assembly 1 according to FIG. 1b. Similar to the embodiment shown in FIG. 2a, the vibration attenuation section 9 extends over the majority of a front wall 15 defined by the structural element 11. However, it is important to note that the vibration attenuation section 9 extends here over an annular area at the inner side of the structural element 11. This means that the vibration attenuation section 9 rings an inner second structure section 33 to protect it from vibrations traveling from an outer first structure section 31. The vibration attenuation section 9 has a one-sided material thickness decay profile, wherein the material thickness h(x) of the vibration attenuation section 9 reduces from an outer rim 19 of the vibration attenuation section 9, where the structural element 11 has a nominal material thickness d, to a central area 43 of a minimum material thickness. The vibration attenuation section 9 has a central hole 41 formed by the inner second structure section 33. It should be noted that the decay profile is one-sided here, because there is no decay profile from the inner second structure section 33 radially outward. The structural element 11 is further equipped with a support structure 21 comprising ribs or webs 23 extending from the inner second structure section 33 radially in a star-like fashion partly across the vibration attenuation section 9 for improving the structural integrity of the structural element 11. The support structure 21 further comprises an annular reinforcement of the inner second structure section 33 around the hole 41. The embodiment of FIGS. 10a-c efficiently attenuates vibrations traveling from a side wall 17 radially inward along the front wall 15, so that the inner second structure section 33 only receives none or effectively attenuated vibrations above the predetermined minimum vibration frequency. As visible in FIGS. 10b,c, a dampening element 29 is in this embodiment attached to the outside of the structural element 11 and covers the complete vibration attenuation section 9.

(44) The embodiment shown in FIGS. 11a-c differs from the embodiment of FIG. 10a-c in that the one-sided decay profile is reversed, such that the material thickness decays from the center radially outward towards an annular outer area 43 of minimal material thickness. This is particularly beneficial if the inner second structure section 33 of the structural element 11 is exposed to vibrations originating from the source of vibrations, e.g. power electronics mounted thereto. Such vibrations are then attenuated on its way radially outward along the front wall 15 of the structural element 11, so that none or only attenuated vibrations above the predetermined minimum vibration frequency reach the outer first structure section 31 and the side walls 17 of the electronics housing 7.

(45) FIGS. 12a, b show an alternative embodiment of the dampening element 29 to be applicable in connection with the embodiment of the structural element 11 according to FIGS. 1I ac. The dampening element 29 of FIG. 11a has an annular shape covering, from the inner side, only partly the vibration attenuation section 9 in the area 43 of thinnest material at a radially outer area of the vibration attenuation section 9. This may be sufficient to efficiently absorb vibrations of the vibration attenuation section 9.

(46) The embodiment of FIGS. 13a-c shows a combination of the embodiments of FIGS. 10a-c and FIGS. 11a-c, wherein the decay profile is two-sided, i.e. the material thickness decays from the center of the structural element 11 radially outward and rises again towards the outer rim 19 of the vibration attenuation section 9. This embodiment has the advantage that vibrations traveling radially outward as well as radially inward are effectively attenuated. The range of vibration frequencies may, however, be more limited compared to the embodiments of FIGS. 10a-c and FIGS. 11a-c.

(47) FIGS. 14a, b schematically show that the vibration attenuation section 9 can have any arbitrary shape and may be in particular rotationally asymmetric. The area of the vibration attenuation section 9 defines a first distance A along a first straight virtual line between those two points of the area that have the largest distance to each other. Furthermore, the area defines a second distance B along a second straight virtual line intersecting the center of the first virtual line at a right angle. The second distance B is the distance between those two points of the area on the second virtual line that have the largest distance to each other. The first distance A is preferably larger than the second distance B at least by 10%. The direction of the decay profile should be aligned with the traveling direction of the vibrations. For the banana-like shape of the vibration attenuation section 9 shown in FIG. 14a, the traveling direction of the vibrations may be radially as indicated by dashed arrows, i.e. the distance B may correspond to the distance D. In order to effectively attenuate vibrations of a certain frequency range, the distance D should fulfil the formula

(48) $D0.5\frac{c_{\mathrm{red}}}{f_{\min }},$
wherein f.sub.min is the minimum vibration frequency and c.sub.red is the speed of sound along the structural element where its material thickness is minimal. In other words, the vibration attenuation section 9 should be large enough, such that the distance D is larger than or equal to half of the wavelength of the vibrations along the structural element where its material thickness is minimal. The minimal material thickness should be smaller than or equal to half of the nominal material thickness d of the structural element 11 outside of the vibration attenuation section 9. As shown in FIG. 14b, the material thickness may decay from a nominal material thickness d outside of the vibration attenuation section 9 along the decay profile to a minimal material thickness. The path along the decay profile may be parameterized by a normalized location variable x in the interval ranging from x=0, where the material thickness is thinnest, to x=1, where the material thickness reaches the nominal material thickness d of the structural element 9 outside of the vibration attenuation section 9.

(49) FIGS. 15a,b show different alternative shapes of the decay profile as a function h(x) of the material thickness for values of the normalized location variable x ranging from x=0 where the material thickness is minimal, i.e. h(x=0)=d.sub.min, to x=1 at the rim 19. where the material thickness corresponds to the nominal material thickness d of the structural element 11 outside of the vibration attenuation section 9, i.e. h(x=1)=d. The function h(x) of the material thickness may be parameterized by
h(x)=x.sup.m,
wherein is a small value parametrizing the inverse of the size of the area of the at least one vibration attenuation section 9 and m1, preferably m2, is an exponent value determining the steepness of the decay profile. FIG. 15a shows different alternatives of the decay profile with the same value of the E and different values of m. FIG. 14b shows the decay profile h(x) for an exponent value m=2 and different values of c parametrizing the size of the area covered by the vibration attenuation section 9. The x-axis in FIG. 15b is shown for the smallest value .sub.4, i.e. x=x.sub.4. For an efficient attenuation of a large range of vibration frequencies, the second derivative, i.e.

(50) $\frac{d^{2}h}{{\mathrm{dx}}^2},$
should be non-zero. Therefore, the exponent value m should be equal to or larger than 2. It should be noted that m is preferably an integer, but may be a real number.

(51) In order to reduce the risk of reflections, an upper limit preferably applies for the steepness of the decay profile, i.e. the first derivative

(52) $\frac{\mathrm{dh}}{\mathrm{dx}}$
of the material thickness as a function of location x along the travel path of the vibrations along the decay profile. The steepness of the thickness decay may be highest at a rim of the vibration attenuation section 9, i.e. for x=1, where the vibrations enter the vibration attenuation section 9. The steepness

(53) 0$\frac{\mathrm{dh}}{\mathrm{dx}}$
of the decay of the material thickness h(x) may fulfil the following border condition for all values of x:

(54) $\frac{\mathrm{dh}}{\mathrm{dx}}.Math.\sqrt{2{\mathrm{df}}_{\min }}{\left(\frac{12}{E}\right)}^{0.25}.Math.,$
wherein d is the nominal material thickness of the structural element 9 outside of the vibration attenuation section 9, f.sub.min is the minimum vibration frequency, is the density of the material of the structural element 9 and the E is the Young modulus of the material of the structural element 9.

(55) Where, in the foregoing description, integers or elements are mentioned which have known, obvious or foreseeable equivalents, then such equivalents are herein incorporated as if individually set forth. Reference should be made to the claims for determining the true scope of the present disclosure, which should be construed so as to encompass any such equivalents. It will also be appreciated by the reader that integers or features of the disclosure that are described as optional, preferable, advantageous, convenient or the like are optional and do not limit the scope of the independent claims.

(56) The above embodiments are to be understood as illustrative examples of the disclosure. It is to be understood that any feature described in relation to any one embodiment may be used alone, or in combination with other features described, and may also be used in combination with one or more features of any other of the embodiments, or any combination of any other of the embodiments. While at least one exemplary embodiment has been shown and described, it should be understood that other modifications, substitutions and alternatives are apparent to one of ordinary skill in the art and may be changed without departing from the scope of the subject matter described herein, and this application is intended to cover any adaptations or variations of the specific embodiments discussed herein.

(57) In addition, comprising does not exclude other elements or steps, and a or one does not exclude a plural number. Furthermore, characteristics or steps which have been described with reference to one of the above exemplary embodiments may also be used in combination with other characteristics or steps of other exemplary embodiments described above. Method steps may be applied in any order or in parallel or may constitute a part or a more detailed version of another method step. It should be understood that there should be embodied within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of the contribution to the art. Such modifications, substitutions and alternatives can be made without departing from the spirit and scope of the disclosure, which should be determined from the appended claims and their legal equivalents.

(58) While specific embodiments of the invention have been shown and described in detail to illustrate the application of the principles of the invention, it will be understood that the invention may be embodied otherwise without departing from such principles.

LIST OF REFERENCE SYMBOLS

(59) 1 fluid flow regulation assembly 3 pump housing 5 motor housing 7 electronics housing 9 vibration attenuation section 11 structural element 13 opening 14 display/HMI 15 front wall 17 side wall 19 rim of the vibration attenuation section 21 support structure 23 ribs/webs 25 rear wall 27 side wall of the electronics housing 29 dampening element 31 first structural section 33 second structural section 35 mounting point 37 first lea of dampening element 39 second lea of dampening element 41 hole 43 area of minimal material thickness R rotor axis L longitudinal axis of structural element d nominal material thickness of structural element outside of vibration attenuation section d.sub.min minimum material thickness x location variable h(x) function of material thickness along decay profile f.sub.min pre-determined minimum vibration frequency A largest distance of the two points of vibration attenuation section B largest distance of the two points of vibration attenuation section on line that intersects distance A at the center at a right angle m exponent value parameter