EP0856109A1

EP0856109A1 - Impeller and blower device comprising such an impeller

Info

Publication number: EP0856109A1
Application number: EP96932595A
Authority: EP
Inventors: Georg Kick
Original assignee: Georg Kick Werkzeugbau
Current assignee: Georg Kick Werkzeugbau
Priority date: 1996-08-22
Filing date: 1996-09-24
Publication date: 1998-08-05
Also published as: DE29614608U1; WO1998007991A1

Abstract

The invention concerns an impeller and a blower device comprising such an impeller, the impeller comprising a plurality of blade elements (1) which are disposed successively about a centre of rotation and have a front face and a rear face (3, 4). The base region of at least one of the blade elements (1) provided on the impeller has projections (2) extending over a surface defined by the rear face and/or front face (4, 3) of the blade. The impeller and the blower device are characterized by reduced noise emission.

Description

Impeller and blower device with such an impeller

The invention relates to an impeller for a blower device, having a center of rotation and a number of blade elements arranged in succession around the center of rotation for conveying a medium through a passage area formed between a rear side of the blade and a front side of the pressure side, and a blower device with such an impeller, wherein each blade element has a head region and a downstream foot region.

Radial design impellers (radial wheels) or axial design (axial wheels) as well as semi-axial design impellers are generally used to convey gaseous media, especially air. The pressure difference between the suction side and the outflow side generated by such an impeller is comparatively small. A gas flow conveyed by these impellers can be supplied to a heat-emitting part (electric motor, electrical circuits and circuits, cooling devices, etc.), for example, for heat exchange purposes or can also be used, for example, for conveying, ventilation or drying purposes. Impellers and blower devices of the aforementioned type are used in heating, ventilation and air conditioning purposes in a variety of ways in the automotive industry.

The operation of corresponding blower devices is generally associated with noise emissions, e.g. be perceived as extremely disruptive in the interior of motor vehicles. An attempt is therefore made to prevent the propagation of noise by means of appropriate housings and covers.

From DE-OS 25 46 280 it is also known to provide the impeller elements in their downstream region with recesses in the form of teeth in the case of a radial-shaped impeller for reducing noise. This However, recesses lead to a reduction in the effective blade depth and to a relatively strong change in the characteristic curve of the impeller or fan wheel.

The invention is therefore based on the object of improving an impeller of the type mentioned at the outset and a blower device with such an impeller such that noise emission from the impeller and a blower device equipped therewith is reduced.

This object is achieved according to the invention by an impeller and by a blower device with the features of claims 1 and 38.

The invention surprisingly clearly leads to a reduction in the noise emission of the impeller and the blower device, without significantly reducing the working efficiency of the impeller. The reduction in the volume of the noise generated by the fan wheel, as determined in the context of a test, was in the region of 10%, based on the hearing sensation of the person. The sound energy of the test impeller designed according to the invention was 5% below the sound energy of an identical comparison wheel, apart from the projections. In addition to a reduction in the intensity of the noise generated by the gas flow in the area of the tear-off edge of the blade elements, the oscillation frequency of the blade elements in the area of the tear-off edge is also reduced and the increased surface area improves damping of the vibration of the root area of the blade elements.

According to a preferred embodiment of the invention, the projections have a head region and a downstream foot region, at least the head region being tapered. This results in a particularly gentle division of the gas stream flowing around the projections. The foot region is also advantageously tapered trained so that the formation of eddies in the rear region of the projections is avoided. These tapers can be formed by rounding off the edges of the projections or by flattening the corresponding areas of the projections.

According to a preferred embodiment of the invention, the projections have a substantially streamlined cross section in a sectional plane parallel to the front or back of the blade. This streamlined cross section is advantageously a NACA profile (National Advisory Committee for Aeronautics). This profile cross section is, in particular when used on an impeller in a radial design, symmetrical to a connecting line which extends from the head region of the projection to the foot region thereof. In particular with regard to the projections arranged in a lateral region of the blade element, it is also possible in a particularly advantageous manner according to the invention to design the profile cross section in the manner of an airfoil profile, so that a certain deflection of the gas stream flowing around the respective projection is achieved. An embodiment of the projections which is particularly advantageous from the point of view of production engineering and structural mechanics is given in that they taper from their root area on the blade side to a roof area lifted off the blade element.

According to a preferred embodiment of the invention, the projections are lined up next to one another along the foot region of the blade element to form gaps. In this embodiment in particular, the projections are advantageously designed like pins. Such a configuration and arrangement of the projections results in a particularly effective reduction in the flow noise occurring in the area of the tear-off edge in conventional impellers. The projections provided according to the invention are advantageously dimensioned such that a width measured transversely to the flow direction of the projections essentially corresponds to a length of the projections measured in the flow direction. Such projections can be manufactured inexpensively from a manufacturing point of view. The height of the projections advantageously corresponds to a maximum of seven times its width.

An embodiment of the invention which is advantageous in particular for realizing even higher projections is provided in that the length of the projections in the inflow direction is greater than their width transverse to the inflow direction. This advantageously improves the bending stiffness of the projections in the inflow direction. The enlarged contact area between the projections and the flow flowing around the blade element advantageously produces a damping effect, by means of which the vibration of the blade element is reduced.

According to a special aspect of the present invention, the projections are formed on the respective blade element in the region of a tear-off edge. This makes it possible in a particularly advantageous manner to allow the flow paths flowing around the top of the blade and the rear of the blade to be merged without reducing the effective blade depth, which is advantageous in terms of reduced noise emission. In addition, the generally relatively thin-walled foot region of the blade element is stabilized by the individual projections.

The projections are preferably pin-like or column-like and protrude rearward beyond the rear tear-off edge of the blade element. In particular, in such an embodiment of the impeller, the individual projections are designed such that a center of area of the respective profile cross section behind the tear-off edge of the respective Blade element or essentially lies on this. Such an embodiment of the impeller makes it possible to effectively influence a flow field formed in the foot region of the blade element or behind it through the projections, and in particular to prevent the fluid flows meeting in the region of the tear-off edge from having relatively large deviations in direction.

As an alternative to or in combination with the aforementioned embodiment of the projections, it is also possible according to a further aspect of the present invention to arrange the projections on the blade element. In this embodiment in particular, it proves to be particularly advantageous to design the projections as relatively flat, elongated lamellae.

A further embodiment of the invention, which is advantageous in terms of reducing the running noise of the impeller, is provided in that a roof section, ie the end of the projection facing away from the respective blade element, is tapered. Such a taper can be produced by appropriate curves or by flattening the upper edges of the projections. Advantageously, a roof edge formed at the upper end of the respective projection extends essentially parallel to a streamline thread running at the same height level. This advantageously prevents the formation of local eddies in the area of the roof-side end (end facing away from the root area) of the projection. As an alternative to such a design of the roof edge, it is also possible to taper the respective projection towards its upper end. This embodiment proves to be particularly advantageous in the case of relatively thin-walled or relatively short projections and can be produced particularly inexpensively from the point of view of production technology. In particular in the case of relatively elongated and thick-walled embodiments of the projections, it proves to be advantageous to give the roof edge of the respective projection a curved course, in particular sloping towards the head region of the rotor blade. The roof edge can be made relatively sharp-edged in the head region of the respective projection and continuously lose sharpness in its course against the direction of the inflow and pass smoothly into the preferably rounded head region of the projection. In particular in combination with such a configuration of the edge course on the respective projections, it proves to be advantageous according to a further aspect of the invention with regard to a favorable flow around the projections, the roof edge formed in the upper region of the respective projection continuously and preferably without forming corners, to run into a rear edge (foot area edge of the projections).

The projections formed on the respective blade element are advantageously arranged along the tear-off edge at a distance which is greater than or equal to the width of the projections. Such an arrangement achieves effective noise reduction without noticeably impairing the working efficiency of the impeller. A further reduction in the distances between the individual protrusions is more complex from a manufacturing point of view and also results in a relatively strong increase in the flow resistance of the gate formed by the protrusions.

In particular, in one embodiment of the impeller as a radial wheel, it has proven to be advantageous to arrange the projections on the individual blade element at equal distances from one another. In an advantageous manner, it is possible to set these distances from blade element to blade element slightly differently, so that there are different natural and excitation frequencies for the structures formed in each case.

In the case of larger blade elements in particular, it proves to be advantageous from a vibration point of view to vary the distances between the projections on a blade element. Advantageously, the projections in the edge region of the respective blade element are arranged more densely, whereas the projections, for example in the center region of the blade element, are arranged at a relatively large distance from one another.

The height of the projections is preferably determined in such a way that the projections have substantially the same height with respect to a direction perpendicular to the blade surface. Such an embodiment of the projections proves to be particularly advantageous in connection with an impeller designed in a radial construction. Particularly in the case of impellers whose axial depth is relatively short compared to their diameter (for example less than 30%), it proves to be advantageous to avoid the formation of edge vortices in that the projections are elongated in the end regions of the respective blade element.

The optimal length of the respective projections may be determined empirically depending on the particular embodiment of the impeller. With the usual basic shapes of the impellers, it has proven sufficient to determine the height of the protrusions in such a way that it lies in the range of 2.5 to 7 times the thickness (measured transversely to the direction of flow of the protrusions).

A particularly effective noise reduction of the impeller can be achieved according to a further preferred exemplary embodiment in that the projections protrude like a needle in the region of the tear-off edge of the blade element over the rear side of the blade on the suction side. Alternatively or in In combination with such an arrangement of the projections, it is also possible to have the projections protrude beyond the front side of the blade. Particularly in the case of a needle-like embodiment of the projections, it proves to be particularly advantageous from a manufacturing point of view that the projections have a width which essentially corresponds to the wall thickness of the respective blade element in the blade root region. Advantageously, the projections can be formed in one piece with the blade element.

An embodiment which is particularly advantageous for mass production of the impeller is provided in that the impeller is made of a plastic material, in particular as an injection-molded component, the blade element and the projections formed thereon being formed in the course of a common injection molding cycle.

In certain applications, the projections on the blade elements can also be injected in several successive injection molding cycles, or impellers can be configured subsequently in this way. If necessary, with a corresponding material protrusion on the blade elements, a thermal and / or mechanical configuration of the material protrusion on protrusions can also be carried out subsequently.

The projections are preferably formed on a rear connecting surface between the front of the blade and the rear of the blade, in such a way that the projections project rearwards over this connecting surface and over a surface formed by the front or back of the blade. In such an embodiment of the impeller, a pressure equalization between a fluid flow on the blade pressure side and a fluid flow on the blade suction side can take place in a gap region formed between two adjacent projections, the particle movements occurring here conditions are damped by the projections and by the gas volume received in the space between the projections.

To avoid any interfering edges, the projections formed on the connecting surface in the area of the tear-off edge are preferably tapered in their root area. The root region of the respective projection is advantageously designed such that it gently runs out onto the connecting surface and / or onto the corresponding blade surface. This prevents unfavorable turbulence from forming in the lower region of the respective projections with regard to noise emission. Due to the special design of the root area, a channel can be advantageously formed which tapers from the end of the blade element on the pressure side of the blade to the end on the suction side of the blade. Such a configuration of the projection-root area surprisingly achieves a particularly favorable noise reduction. The protrusion root area is of particular importance.

According to a preferred embodiment of the invention, the projections are oriented essentially tangentially and parallel to their orbit. Alternatively, however, it is also possible that the projections each have an end edge that extends inclined radially inwards. Such an adjustment of the projections against the flow direction of the flow channel formed between the blade elements has proven to be particularly advantageous, in particular, in the case of relatively fast-running impellers. With such high-speed running wheels, the projections are advantageously made relatively low. With larger and slow-running impellers, the projections can be made relatively high. The height of the projections (ie the distance between an upper end of the projection and the corresponding blade side) is advantageously in the range between 10% to 90% of the circumferential distance between two adjacent ones ΛO

Tear-off edges. Low blade heights are preferred for impellers that rotate at relatively high speeds and are used for impellers with an axial design. High protrusion heights are advantageously achieved with relatively slow-running impellers and in particular with impellers in a radial design.

Although relatively large radial forces act on the individual projections in the case of axial-type impellers in the outer region of the impeller, according to a preferred development of the present invention the projections in the outer region of the axial wheel have a greater height in comparison to the inner projections. This counteracts the formation of vertebrae in a particularly advantageous manner.

As an alternative to or in combination with the needle-like projections, it is also possible, according to a further advantageous embodiment of the present invention, to design the projections in the manner of lamellae. By means of such lamella-like projections, the air flow flowing over the corresponding blade side can be directed particularly effectively in the region of the tear-off edge. The individual lamellae are preferably oriented such that a certain deflection of the gas flow overflowing the blade element is achieved. In an embodiment of the impeller as an axial wheel, an angular momentum is advantageously applied to the gas stream flowing over the blade element, the direction of rotation of which is opposite to the direction of rotation of an edge vortex occurring on the respective blade element.

Further advantageous refinements of the subject matter of the invention are specified in the remaining subclaims. The invention is explained in more detail below on the basis of exemplary embodiments and associated drawings. In these show:

1 is a greatly enlarged perspective view of a tear-off edge of a blade element of an impeller with teeth projecting vertically therefrom with a streamlined cross section,

Fig. 2 is a perspective view of a section of the

Foot region of a blade element of an impeller according to a further exemplary embodiment with teeth arranged perpendicular to the blade surface,

3a shows an essentially circular profile cross section of a projection,

3b shows an essentially streamlined profile cross section of a projection according to a further preferred embodiment of the invention,

3c shows a further streamlined profile cross section of a projection,

4 is a plan view of an impeller in radial design with projections in the foot area,

5 is a plan view and a grid view of an impeller in axial design,

6 shows a perspective detailed view of the foot region of a blade element with a projection of a lenticular cross section,

Fig. 7 is a perspective view of a further embodiment of the in the region of a rear tear-off edge arranged projections with a curved roof edge,

8 shows a simplified sectional illustration through a blade element of a radial impeller with projections arranged in the foot region with a continuous roof edge,

9 shows a further embodiment of a radial impeller according to a preferred embodiment of the invention in a plan view,

10 shows a side view of the impeller according to FIG. 9,

11 shows a detailed view to illustrate the detail framed in FIG. 10,

12 shows a detailed view to illustrate the detail framed in FIG. 9,

13 shows an axial section through the impeller according to FIG. 9.

1 shows, in a greatly enlarged illustration, a section of a rear tear-off edge region of a blade element 1 of an impeller with projections 2 formed thereon in one piece. The blade element 1 forms a blade front side 3 and a blade rear side 4 on the suction side the projections 2 substantially perpendicular to a plane 'defined by the back of the blade 4. A connecting surface 5 is formed between the front side 3 of the blade and the rear side 4 of the blade, which in the embodiment shown here merges into the front side 3 and the rear side 4 of the blade via slightly rounded edges 6 and 7. The edge 7 formed between the connecting surface 5 and the blade rear side 4 is preferably more rounded than the edge 6 formed between the blade front 3 and the connecting surface 5.

The projections 2 are arranged at intervals al, a2, a3, a _n along the rear tear-off edge. These distances al, a2, a3 ... a _n are each advantageously dimensioned slightly differently, so that different natural frequencies result for the flow system delimited between the respective projections.

Each of the projections 2 advantageously has a streamlined profile. Advantageously, the radius of curvature of the projection 2 in a head region 8 is greater than the radius of curvature of the projection in a foot region 9. The side surfaces 10 of the respective projection 2 are advantageously convexly curved and continuously merge into the head region 8 and the foot region 9 .

The projections 2 are advantageously designed in such a way that they taper from a root region 11 to a roof region 12.

The roof area 12 has a rounded roof edge 12 ′, which runs continuously into the head area 8 and the foot area 9 of the projection 2. The roof edge 12 'can advantageously be completely rounded. In the embodiment shown here in FIG. 1, however, it forms an obtuse angle in the uppermost region of the projection. The roof edge is advantageously designed such that its maximum height is closer to the head region 8 than the foot region 9 of the projection. The roof edge 12 * advantageously slopes more flatly towards the foot region 9 than towards the head region 8.

Each of the projections 2 sits with its root region 11 on the between the back of the blade 4 and the connecting surface. before 5 formed edge 7. Each of the projections 2 reaches its maximum width b preferably in the region of the edge 7. Each of the projections 2 penetrates with its root region 11 the plane 4 ′ defined by the rear side 4 of the blade. This section of the projection 2 which passes through the level 4 * tapers continuously towards the connecting surface 5. A run-off section 13 is thereby formed. This outlet section advantageously ends at a distance c before reaching the edge 6 formed between the front side 3 of the blade and the connecting surface 5. It can also project beyond the other side of the blade. A channel 14, which widens toward the front side 3 of the blade, is formed between two adjacent outlet sections 13. This channel 14 enables a particularly favorable pressure adjustment between the fluid streams that meet in the area of the tear-off edge. The flow volume of this channel 14 can be optimized by arbitrarily determining the radius of curvature of the edge 7.

In the embodiment of the projections shown in FIG. 1, a root area edge 13 ′ formed in the root area 13 continuously merges into the foot area 9 of the respective projection in a gently curved manner.

The transition between the respective projection 2 and the blade rear 4 is relatively sharp-edged. This avoids a separation of the flow in the transition area between the edge 7 and the root area.

The projections 2 are formed in one piece with the blade element 1. The width b of the projections is slightly smaller than a thickness t of the blade element 1 in the rear tear-off edge region. The conical tapering of each projection towards the roof area 12 of the respective projection enables a particularly favorable demolding of the projections when the blade element is manufactured from a plastic material. The illustration according to FIG. 2 likewise shows a section of a rear tear-off edge region of a blade element 1. In the alternative embodiment shown here, the edge 7 provided between the blade rear side 4 and the connecting surface 5 provided in the embodiment according to FIG. that the connecting surface 5 merges essentially continuously into the back of the blade 4 (possibly also the front of the blade). The projection 2 shown here has an essentially circular cross section and forms a conically tapering tip in its roof area 12, forming a (slightly) convexly curved outer surface. The transition between the projection 2 and the blade rear 4 or the connecting surface 5 is relatively sharp-edged.

The projection 2 is arranged in the rear region of the blade element 1 in such a way that the rear end surface or the foot region 9 of the projection 2 formed thereby does not protrude beyond the edge 6 formed between the blade front 3 and the connecting surface 5 with respect to the flow direction.

The diameter of the projection 2 or its width transverse to the flow direction is made slightly smaller than the thickness t of the blade element 1 in the rear end region of the blade element. In the detailed illustration shown in FIG. 2, only a single projection 2 is shown. However, a plurality (for example 120) of such or similar projections is preferably arranged along the connecting surface 5 in the rear end region of the blade element at intervals al, a2, a3 .... a _n . In this embodiment of the projections, too, it proves particularly advantageous to dimension the distances a1, a2, a3 a _n slightly differently. 3a, 3b and 3c each show different, preferred embodiments of the profile cross sections of the projections 2. These profile cross sections can advantageously vary over the entire length or height of the respective projection. It is thus possible in particular in an advantageous manner to give the respective projection 2 in its root area a cross section corresponding to the illustration in FIG. 3a, which gradually changes into a cross section in accordance with FIG. 3b and finally into a cross section in accordance with FIG. 3c. In this case, the cross sections are dimensioned such that the length d1, d2, d3 of the respective projection measured in the inflow direction is greater in the root area than in the middle area and in the middle area than in the roof area. The width bl, b2, b3 of the respective projection is also advantageously greater in the root region 11 of the projection than in the central region thereof and again larger in the central region than in the roof region. 3a, 3b, 3c are therefore only qualitative representations of the profile cross sections, which can be modified accordingly in the respective application and changed with regard to this dimensioning.

The illustration according to FIG. 4 shows a preferred embodiment of an impeller according to the invention as a radial impeller 14. In the embodiment shown here, the individual blade elements 1 are curved sloping towards the rear. A plurality of projections 2 are formed in the rear end region of the tear-off edge of each blade element. In the embodiment shown here, the projections 2 extend essentially tangentially to the orbit in the rear edge region of the respective blade element. Each of the blade elements has a streamlined blade cross-section that is optimized with regard to the delivery volume and the impeller speed. The projections here extend counter to the direction of rotation of the blade wheel to the rear from the respective blade rear sides 4. However, it is also possible to have such projections 2 or similar projections to form the front of the blade 3 or both on the front 3 of the blade and on the rear 4 of the blade. The projections provided in the radial impeller according to FIG. 4 advantageously correspond to the projections shown in FIG. 1.

5 shows an embodiment of an impeller according to the invention as an axial impeller 15. In this type of impeller, too, the blades are advantageously designed as a wing profile. In the embodiment according to FIG. 5, the individual projections 2 are each designed as flat, closely spaced lamellae. These thin-walled lamellae also advantageously have a streamlined profile cross section. The outflow direction of the respective blade element 1 can be actively influenced by the individual lamellae or projections 2, so that there are advantageously only slight deviations in direction between the flows flowing around the front side 3 of the blade and the rear side 4 of the blade 4.

In the embodiment of the projections shown in FIG. 5, a roof edge 12 'formed by each projection 2 runs essentially parallel to a flow thread adjacent to this roof edge 12'.

The distances between the respective projections 2 can be defined differently on each blade element 1 and are advantageously different, in particular from blade element 1 to blade element 1. This results in different natural frequencies for each vane element and for the flow system surrounding this vane element 1, whereby flow noises arising in the context of resonance cases can also be avoided in an advantageous manner. The respective projections can advantageously, as shown in FIG. 6, extend beyond the rear tear-off edge region of the blade element 1. 6, only one projection 2 on the blade element 1 is shown for the purpose of simplification. Advantageously, however, a multiplicity of such, in particular identical, projections is arranged along the rear tear-off edge or along the rear edge 7 of the blade element.

The projection 2 according to FIG. 6 is designed in the manner of a lamella and has a cross section which is narrow transversely to the inflow direction and elongated in the inflow direction. The center of gravity of the profile cross section described by the projection 2 in the root region lies slightly behind the edge 7 in the inflow direction. The projection 2 protrudes both from the front side 3 of the blade and from the rear side 4 of the blade. By arbitrarily positioning the projection 2 transversely to the direction of flow or by arbitrarily asymmetrical design of the profile cross section of the projection 2, the flow flowing around the front side 3 of the blade and the rear side 4 of the blade can be directed with regard to a reduced noise emission. Advantageous angles of attack and profile cross sections can be determined empirically. A foot edge formed in the foot region 9 of the respective projection 2 can advantageously be formed as a curved line when viewed from behind.

7 shows a further embodiment of a blade element 1 with projections 2 formed thereon in the rear tear-off edge region. The projection 2 shown here also extends from both the front side 3 of the blade and the rear side 4 of the blade. The projection 2 is in this case adjusted transversely to the direction of flow so that arbitrarily a certain deflection of the front side 3 of the blade and the rear side 4 of the blade -13 flowing flow is reached. In the illustration according to FIG. 7, the respective projection also protrudes beyond a rear edge 7 of the blade element, so that an edge running in the foot region 9 of the projection 2 runs transversely to the edge 7 and at a distance from it. As a result, as in the embodiment according to FIG. 1, a laterally delimited channel 14 is formed between two adjacent projections 2, in which the edge 7 is flowed over.

In the illustration according to FIG. 7, in contrast to the embodiment according to FIG. 6, the roof edge 12 'is curved.

The illustration according to FIG. 8 shows a further embodiment of a blade element 1 designed according to the invention, in the rear tear-off edge area of which a multiplicity of projections 2 spaced apart from one another are formed. The blade element 1 according to FIG. 8 is connected in its base region to a cage rim 17, which is advantageously also integrally formed with the blade element 1 or, when the impeller is fully assembled, is firmly connected to it, in particular glued.

The projections provided in the embodiment according to FIG. 8 are provided with a roof edge 12 'which continuously merges into the head region 8 of the projection and then gently curves towards the corresponding blade side (here the blade rear side 4).

The projection 2 provided here has an essentially streamlined profile cross section at a distance from the rear of the blade 4 corresponding to half the total height. In the embodiment shown here, the projection 2 is formed in one piece with the blade element 1, which is made of a plastic material. The illustration according to FIG. 9 shows a further embodiment of an impeller according to the invention in a radial design. The impeller according to FIG. 9 is provided with 37 blade elements 1 in the blade plane shown here. A further blade element level, in which 37 blade elements 1 are likewise arranged, is formed behind this upper or front blade element level, as can clearly be seen in FIG. The blade elements 1 of the two blade element levels are arranged in such a way that there is a certain offset between a blade element 1 of the second blade element level and the laterally adjacent blade element 1 of the first blade element level. The offset of the blade elements of one blade element level to the blade elements of the other blade element level makes it possible to offset the outlet regions formed between two successive blade elements and thereby to achieve an equalization of the pressure distribution in the outer peripheral region of the impeller.

Each of the blade elements 1 provided in the impeller according to FIG. 9 opens in its head region into or comprises a cylinder journal section 22 which extends over the entire width of the blade element 1. This cylinder journal section 22, which is formed in one piece with the blade element 1, stabilizes the blade element 1 and at the same time enables a particularly favorable flow against the blade element 1.

The blade elements 1 of the first blade element level and the blade elements 1 of the second blade element level are separated by a separating disk 23. This cutting disc 23 has a relatively small wall thickness with respect to the axial direction of the impeller. The cutting disc 23 is advantageously ring-shaped and connected to a hub portion 24 of the impeller. The connection of the cutting disc 23 to the hub section 24 is advantageously carried out via a number of connecting spokes 25 between To these connecting spokes there is a space through which a gas flow can flow. The connecting spokes 25 advantageously have a streamlined cross section and, in the embodiment shown here, are formed in one piece with the hub section 24 and the cutting disk 23.

In the embodiment shown here, the blade elements 1 are also advantageously formed in one piece with the cutting disk 23.

The blade channels formed between two respectively arranged blade elements 1 are covered on one side by the cutting disk 23. The side area of the blade channels facing away from the cutting disk 23 is open to the side in the embodiment shown here. In this side area, the blade channels are possibly covered by a housing element, on which the side edges of the respective blade element slide past at a small distance. In the outer edge region of the impeller, a cage ring 17 is provided on both sides of the impeller, which is formed in one piece with the blade elements 1 in the embodiment shown here. The foot region of each of the blade elements 1 extends into an intermediate region between the respective cage ring 17 and the cutting disc 23. In this foot region, a large number, for example 23, of fine projections are formed on the blade cage 17 and the cutting disc 23 on each blade element run perpendicular to a central surface of the respective blade element. These projections are formed on a connecting surface 5 (cf. FIG. 12 in this regard), which extends between a front side 3 of the blade and a rear side 4 of the blade.

An end face of the respective projection facing the hub or axis of rotation of the impeller is advantageous Formed as a substantially flat surface "baffle P".

As can be clearly seen from FIG. 10, the separating disk 23 divides the impeller into a first disk section 26 and into a second disk section 27. The blade elements of the first disk section 26 and the blade elements of the second disk section 27 are arranged such that at least a part of the respective Blade elements 1 are not aligned with the blade element 1 of the other disk section that is axially adjacent to it.

In the embodiment shown here, the first disk section 26 and the second disk section 27 each have the same axial width. According to a special aspect of the present invention, however, the first disk section 26 and the second disk section 27 can be designed to be of different widths with regard to their axial width, which also results in different natural frequencies for the vane elements 1 and the vane channels formed between them due to this unequal design of these sections .

The cage rings 17 which are opposite one another with respect to the cutting disk 23 and are arranged along the outer circumference of the impeller have a preferably L-shaped cross section and, like the projections, are seated on the respective connecting surface 5 of the blade elements 1 (see also FIG. 13 in this regard) ). The cage rings 17 are formed in one piece with the blade elements 1.

The projections 2 provided on this impeller are designed as needle-like pins and protrude from the rear connecting surface provided in the foot region of the blade element 1. Further details on the configuration of the projections 2, which is preferably implemented here, are shown in FIG. 11 to see, which in a simplified manner reproduces the section framed in FIG. 10.

As can be seen from FIG. 11, the projections 2 are each tapered in their roof area and in their root area. The distance between adjacent projections 2 corresponds approximately to twice the width b of the projection. The height h corresponds approximately to six to seven times the width b of the projection. In the case of an impeller with an outer diameter of approximately 150 mm, the width b of the projections is preferably 0.6 mm. The height h is advantageously about 4 mm. Over a width of approximately 26 mm, 23 projections 2 are advantageously arranged at a distance from one another. The projections 2 can have a substantially flat end face facing the axis of rotation of the impeller. In the embodiment shown here, as can clearly be seen from FIG. 12, the projections 2 do not protrude beyond the rear edge 7 of the blade element 1 to the head region of the respective blade element. The projections 2 are at least radially further outward in their root area than the rear edges 6 and 7 of the blade element and thus appear as fine, protruding teeth "attached" to the rear connecting surface 5. These fine teeth can be formed in correspondingly fine mold slots which are formed in a mold that can be lifted radially outward from the impeller. Since the mass of the respective projection 2 is relatively small compared to the total mass of the impeller, the lack of some protrusions 2 does not lead to any significant imbalance of the impeller. The size relationships of the projections to the blade elements, as can be seen from FIG. 11, in particular also from FIG. 12, and the size relationships of the width and height of the projections have proven to be advantageous in the case of larger or also smaller impellers.

From the illustration according to FIG. 12, the lateral shape is clear, the projections used in the impeller according to FIG. lent recognizable. The radii characterized by Rx and R ₂ in this illustration are preferably slightly smaller than the height h and are advantageously in the range from 0.6 to 0.9 x h. According to the embodiment shown here, the projections 2 are each made relatively pointed and extend essentially perpendicular to the central surface indicated here by the dash-dotted line M. This central surface M advantageously has a substantially uniform curvature R, the ratio between the curvature R and the height of the projection 2 being in the range of 6: 1 here. The ratio of the height h of the projections 2 to the wall thickness t of the blade element is advantageously in the range of 4: 1. The diameter of the cylinder pin section 22 formed integrally with each blade element 1 in an advantageous manner is in the range of two to three times that Wall thickness of the blade element (2 to 3 xt).

The geometry of the hub section 24 used in the impeller according to FIG. 9 can be clearly seen from the illustration according to FIG. 13. This hub section 24 is rotatably connected to a drive shaft of an electric motor, not shown here. The hub section 24 is connected to the separating disk 23 arranged between the first disk section 26 and the second disk section 27 via the connecting spokes 25 shown in FIG. The individual blade elements 1 are connected on one side to the cutting disk 23 on their axially inner side region. The cylinder journal section 22 provided in the head region of each of the blade elements 1 likewise opens into the cutting disk 23.

The measures proposed according to the invention advantageously make it possible to create a fan wheel which can be used without any special additional precautions, in particular changes to the fan wheel drive and the housing structure of a fan, of conventional design. The Fan wheel according to the invention can be used, for example, in connection with a CPU fan in a computer, a motor vehicle blower or, for example, also in a hair dryer, without having to make any special modifications to these devices, apart from replacing the fan wheel.

In the fan wheel according to the invention, the medium flowing around the blade element flows through a gate which rises up like a fence in the rear end region of the blade element, as a result of which the flow is influenced in such a sustainable manner that the flow noises that occur in particular when the flow paths divided by the blade element meet are reduced.

Depending on the type of impeller, 1500 to 2000 and more protrusions or teeth can be formed on the impeller, for example. Approximately 4 teeth / per tooth height are advantageously arranged on each blade element. The cross section of the teeth does not necessarily have to be aerodynamically designed. The teeth can form an essentially flat impact surface, in particular in their head region, whereby a particularly favorable formation of micro-vertebrae is achieved. The thickness of the teeth is advantageously in a range up to 3% of the blade depth. With small fan wheels, the thickness of the teeth is only a few 1/10 mm, for example 0.4 mm. The height of these teeth is, for example, 3.5 mm. In the case of large fan wheels, for example for room ventilation, the thickness of the teeth can be 8 mm and more, for example. The teeth are preferably relatively fine in relation to the overall dimensions of the fan wheel. The section shown in FIG. 1 has a length of 6 mm, for example.

The blade element designed according to the invention is advantageously formed in the context of a preferred production method by a multi-part molding tool, in the interior of which a molding space is provided in which the 2 <p

Blade element and the projections are formed as part of a plastic injection molding process. The inner wall of the molding tool provided for forming the front side 3 of the blade is advantageously formed by a tool part that can be moved relative to a tool part provided for forming the rear side 4 of the blade. The projections can advantageously be formed by flat conical bores which are formed in the tool part provided for forming the back of the blade.

A particularly favorable demolding of the blade element from the mold can also be achieved in that the mold space provided for forming the respective projections can also be opened. For this purpose, it is possible to define a demolding parting plane for the projections 2 in such a way that it runs essentially parallel to the edge formed in the rear end region of the blade element. This makes it possible to form the head region of the respective projection in a molding tool provided for forming the back of the blade and to form the foot region 9 of the respective projection in a tool part which is connected or formed in one piece with the tool part provided for forming the front side of the blade.

The connecting surface 5 between the front side 3 of the blade and the rear side 4 of the blade is advantageously inclined in such a way that this enables the blade element to be removed from the mold without undercuts. The dividing plane running through the projections 2 is advantageously conical in such a way that a particularly high closing force is established in the region of the closing gap opening into the mold space provided to form the projection 2.

In particular, in one embodiment of the fan wheel as a radial impeller, it is advantageously possible to form the foot region 9 of the respective projections by means of a mold segment that is radial to the axis of rotation of the shield. l τ felelementes 1 is removable from the finished molded projection 2.

In order to be able to ensure a particularly high surface quality of the projections 2 and to be able to implement different embodiments of the projections if necessary, the shaped elements provided for forming the projections, in particular strip-like elements, are advantageously exchangeably attached to the molding tool in accordance with a preferred production process. These strip elements are advantageously made of a material that has increased wear resistance compared to the rest of the mold.

In order to be able to ensure a particularly reliable filling of the mold space provided for forming the projections 2, a vacuum is advantageously generated in the mold space forming the blade element shortly before the plastic material is injected. According to a particular aspect of the present invention, an injection region for forming the respective blade elements is in the vicinity of the respective rear tear-off edge of the blade element.

The invention is not restricted to the preceding exemplary embodiments. For example, it is also possible to design the projections in different overall heights and to slightly change their distance from the rear end of the blade element from projection to projection.

Claims

Claims:

1. Impeller for a blower device, with a center of rotation and a number of blade elements (1) arranged in succession around the center of rotation for conveying a medium through a passage area formed between a blade rear side (4) on the suction side and a blade front side (3) on the pressure side, wherein each blade element (l) has a head region and a downstream foot region, characterized in that in the foot region at least one of the blade elements (1) has projections (2) which have a surface defined by the rear side of the blade and / or the front side of the blade (3) stand out.

2. Impeller according to claim 1, characterized in that the projections (2) have an upstream head region (8) and a downstream foot region (9), and that the head region (8) is tapered.

3. Impeller according to claim 1 or 2, characterized in that the foot region (9) is tapered.

4. Impeller according to one of claims l to 3, characterized in that the projections (2) have a streamlined cross section.

5. Impeller according to one of claims 1 to 4, characterized in that the cross section is a NACA profile.

6. Impeller according to one of claims l to 5, characterized in that the projections (2) are pin-like and in particular substantially perpendicular to the surface defined by the blade back (4) (4 ').

7. Impeller according to one of claims 1 to 6, characterized in that the projections (2) are arranged side by side along the foot region of the impeller to form gaps.

8. Impeller according to one of claims 1 to 7, characterized in that a width (b) measured transversely to the flow direction of the projections essentially corresponds to a length (d) of the projections (2) measured in the flow direction.

9. Impeller according to one of claims 1 to 8, characterized in that the length (d) of the projections (2) in the inflow direction is greater than their width (b) transverse to the inflow direction.

10. Impeller according to one of claims 1 to 9, characterized in that the projections <Z) on the tear-off edge of the respective blade element (1) seated on the blade element

(1) are trained.

11. Impeller according to one of claims 1 to 10, characterized in that a center of area of the profile cross section of the respective projection (2) is behind the physical tear-off edge (6; 7) of the respective blade element (1).

12. Impeller according to one of claims 1 to 11, characterized in that the respective projection (2) with the major part of its length projects beyond the tear-off edge of the associated blade element (1) downstream.

13. Impeller according to at least one of claims 1 to 12, characterized in that at least one of the projections on the blade element (1) is arranged.

14. Impeller according to at least one of claims 1 to 13, characterized in that a roof section (12) of the respective towards the projection (2) is tapered, in particular rounded.

15. Impeller according to at least one of claims 1 to 14, characterized in that a roof edge (12 ') of the respective projection (2) extends substantially parallel to an immediately adjacent streamline thread.

16. Impeller according to at least one of claims 1 to 15, characterized in that the roof edge (12 ') of the respective projection is curved, in particular on the corresponding side (3; 4) of the blade element (1) runs out.

17. Impeller according to at least one of claims 1 to 16, characterized in that the edges of the projections (2) are rounded.

18. Impeller according to one of claims l to 17, characterized in that the projections (2) along the tear-off edge are arranged at a distance (al; a2, -a ₃ ... a _n ) which is greater than or equal to the width of the Is tabs.

19. Impeller according to at least one of claims 1 to 18, characterized in that the projections (2) are arranged at unequal intervals (a _lr -a ₂ ; a ₃ ... a _n ).

20. Impeller according to at least one of claims 1 to 19, characterized in that the distances (a ₁ ; a ₂ ; a ₃ ... a _n ) between the projections (2) in the edge region of the respective blade element (1) are smaller than in a central area of the blade element (1).

21. Impeller according to at least one of claims 1 to 20, characterized in that the projections (2) have substantially the same height (h) with respect to a direction perpendicular to the blade surface.

22. Impeller according to at least one of claims 1 to 20, characterized in that the projections (2) have different heights (h) in the direction perpendicular to the blade surface.

23. Impeller according to at least one of claims 1 to 22, characterized in that the width (b) of the projections (2) corresponds essentially to the thickness of the respective blade element (l) in the foot region.

24. Impeller according to at least one of claims 1 to 23, characterized in that the projections (2) are integrally formed with the blade element (1).

25. Impeller according to at least one of claims 1 to 24, characterized in that the projections (2) are formed on a rear connecting surface (5) between the front side of the blade (3) and the rear side of the blade, and that

Protrusions (2) protrude rearward over this connecting surface (5) and run out onto this connecting surface (5).

26. Impeller according to at least one of claims 1 to 25, characterized in that the respective projection (2) tapers in its root region towards the connecting surface (5).

27. Impeller according to at least one of claims 1 to 26, characterized in that the impeller is a radial impeller.

28. Impeller according to at least one of claims 1 to 27, characterized in that the projections (2) extend substantially tangentially to their orbit.

29. Impeller according to at least one of claims 1 to 28, characterized in that the projections (2) have an end edge which extends inclined radially inwards.

30. Impeller according to at least one of claims 1 to 29, characterized in that the height of the projections (2) in the U - circumferential direction is in the range between 10% to 90% of the circumferential distance between two adjacent tear-off edges.

31. Impeller according to at least one of claims 1 to 30, characterized in that the impeller is an axial impeller.

32. impeller according to at least one of claims 1 to 31, characterized in that measured in the axial direction of the impeller, the length of radially outer projections (2) is greater than that of the inner projections (2).

33. Impeller according to at least one of claims 1 to 32, characterized in that the projections (2) are lamellar.

34. Impeller according to at least one of claims 1 to 33, characterized in that the profile of the projections (2) and the course of the projections (2) are set such that the flow impinging on the projections (2) is deflected and in particular a Rotational momentum about an axis of rotation parallel to the flow direction is introduced into the flow medium.

35. impeller according to at least one of claims 1 to 34, characterized in that the rotational momentum of a lateral edge flow around the respective blade element (1) is opposite.

36. impeller according to at least one of claims 1 to 35, characterized in that the projections (2) are aligned such that an angular difference between the suction-side and the pressure-side the blade elements (1) flowing around, in the region of the tear-off edge meet current threads in is substantially fully balanced.

37. impeller according to at least one of claims l to 36, characterized in that the surface of the blade elements (1) is roughened.

38. Blower device with a housing body, a driven impeller with a center of rotation and a number of blade elements (l) arranged in succession around the center of rotation for conveying a medium through a passage area formed between a rear side of the blade (4) and a front side of the blade (3), each Blade elements (1) have a head region and a downstream foot region, characterized in that in the foot region at least one of the blade elements has projections (2) which protrude over a surface defined by the rear side of the blade (4) and / or the front side of the blade (3) .