Vanes for the impeller of a ventilator, impeller, and axial ventilator, diagonal ventilator, or radial ventilator

Abstract

The invention relates to vanes (2) for the impeller (1) of a ventilator, in particular of an axial ventilator, diagonal ventilator or radial ventilator, having a three-dimensionally curved trailing edge (7), wherein a plurality of serrated recesses (12) are provided over the course of the trailing edge (7) in the span width direction (8), wherein a substantially straight region of the trailing edge (7) is formed between at least two adjacent serrated recesses (12).

Description

[0001] BLADES FOR THE IMPELLER OF A FAN, IMPELLER AND AXIAL FAN, DIAGONAL FAN OR CENTRIFUGAL FAN

[0002] The invention relates to a blade for the impeller of a fan, in particular an axial fan, diagonal fan or radial fan.

[0003] Furthermore, the invention relates to an impeller equipped with corresponding blades as well as to an axial fan or diagonal fan or radial fan, each with an impeller which is equipped with corresponding blades.

[0004] Providing valves with low noise emissions while meeting certain required air performance (flow rate and pressure increase) is of fundamental interest to valve manufacturers. In particular, noise emissions should be low even for valves that are integrated into a system.

[0005] Document EP 1 338 793 A2 discloses a wind turbine blade structure that is designed to provide sufficient strength for loads and increased durability. The blade can be formed into a thinner airfoil, which is intended to improve blade performance, achieve higher wind turbine efficiency, and reduce noise caused by the Kärmänn vortex street. The trailing end element at the rear end of the main blade body has a toothing in the trailing edge area of ​​the blade. The toothing is designed in the form of triangular, trapezoidal, or sawtooth teeth.

[0006] EP 2 003 340 B1 describes a multi-blade fan provided with a plurality of notches in a blade edge on an outer side of each impeller blade. Further, a projection is described that protrudes along a thickness direction of the impeller blade in a rear portion of each notch and can be inserted into a thrust surface of the impeller blade, which receives the air pressure based on the rotation of the multi-blade fan.

[0007] The patent application DE 25 29 541 discloses an axial fan having a plurality of rotor blades with irregularities for noise reduction at the trailing edges of the blades, wherein the irregularities are a plurality of notches cut out of all blades along the trailing edges, which form a ridge in each blade along the trailing edge.

[0008] Further wings are from the publications JP 4918650 B2, EP 2 280 175 B1, EP 2 407 671 B1, CN 102162464 A, EP 2 280 176 B1, JP 4208020 B2, JP 6379788 B2, JP 5747888 B2, JP 5575288 B2, CN 106640752 A, WO 2015 / 193654 A1 and EP 1 795 755 A4 are known.

[0009] While the well-known serrated trailing edges of fan blades are advantageous in terms of reducing noise generation, a serrated profile is often complex to design and manufacture. Furthermore, there is a risk of injury during handling, transport, and assembly of the serrated blades and the fans equipped with them. Furthermore, individual serrations can break off even with relatively minor impacts, which can lead to imbalance, reduced performance, and a poor-quality appearance of the fans.

[0010] The present invention is based on the object of designing and developing blades for the impeller of a fan, in particular an axial fan, diagonal fan, or radial fan, in such a way that the acoustics are improved during operation of such a fan, in particular, noise emissions are reduced. Furthermore, the blade should be simple to design and manufacture, better able to withstand shock loads, and minimize the risk of injury. The blade should have a high-quality appearance.

[0011] The above object is achieved with respect to the wing according to the invention by the features of claim 1. According to this, the wing has a three-dimensionally wound or curved trailing edge, wherein a plurality of serrated recesses are provided along the spanwise direction of the trailing edge. A substantially straight region of the trailing edge is formed between at least two adjacent serrated recesses.

[0012] It has been recognized that the features of claim 1 achieve an improvement in acoustics by reducing trailing edge noise. In three-dimensionally curved or twisted trailing edges of radial and axial fans, a "negative" serration is realized starting from a base blade, i.e., a structural recess with a specific serration geometry. In other words, a negative serration profile is removed from the trailing edge. The essentially straight regions of the trailing edge do not run in the form of an ideal straight line, but locally correspond essentially to the possibly minimally curved course of the trailing edge without serrated recesses.The essentially straight region of the trailing edge is therefore to be understood in such a way that this region can also be slightly curved, in particular if the imaginary course of the trailing edge without jagged recesses is locally essentially straight, but overall can be slightly curved.

[0013] This special trailing edge profile is bionic inspired by the wing structure of birds and not only improves the acoustic properties but also has a high recognition value.

[0014] This blade is designed for the impeller of a fan, particularly an axial fan, diagonal fan, or radial fan, with improved acoustics during operation. Furthermore, the blade is easy to design and manufacture and can better withstand shock loads. The risk of injury is minimized, and the blade exhibits a high-quality appearance.

[0015] According to an advantageous development of the wing, essentially straight or minimally curved regions of the trailing edge are formed between the adjacent serrated cutouts, and not just between at least two adjacent serrated cutouts. In this way, the entire trailing edge can have the described advantageous profile. Preferably, serrated cutouts can be formed only in one section of the trailing edge, so that the section can be cleverly selected depending on the application with regard to particularly advantageous acoustic design, manufacturing, handling, injury reduction, and / or appearance.

[0016] With regard to a particularly advantageous geometry, a length of the essentially straight or minimally curved region in the spanwise direction can correspond to at least half of the average width of the adjacent serrated recesses. The length of the essentially straight region essentially corresponds to the distance (d) between two adjacent serrated recesses. Preferably, the length can be at least as large as the average width of the adjacent serrated recesses for at least 75% of all pairs of directly adjacent serrated recesses of a trailing edge.

[0017] Preferably, the tooth-shaped recesses can taper towards the wing center at an acute angle, preferably at an angle between 10° and 35° and particularly preferably over 15°.

[0018] The “negative serration profile” formed by the serrated cutouts tapers off at an acute angle towards the wing center. The angle or interior angle Y can preferably lie within the described ranges and thus have a large depth-to-width ratio t / b of t / b > 1.5, preferably t / b > 2. The spacing d of the punched-out serrations - in other words the remaining section of the original trailing edge - can be selected to be comparatively large so that more than half of the original curved / twisted, but smooth trailing edge remains. This results in a spacing d of the serrated cutouts that is greater than their width b. Here, d > b, preferably d > 1.25 b.

[0019] The distance d of the tooth-shaped recesses can preferably also be in the order of magnitude of the depth t, where

[0020] 0.7 t < d <1.5 t.

[0021] The distance d between two negative points (cutouts or punched-outs) can be determined without any minor rounding or chamfering at the trailing edge end of the points. The actual (material) part - the wing - thus has no pointed or protruding parts and no parts weakly attached to the wing that could cause handling problems or even lead to personnel injuries. The trailing edge noise generated by periodic vortex shedding can be reliably and significantly reduced by the cutouts / punched-outs. Since the cutouts / punched-outs themselves have a similar or even essentially the same geometry for a wing across the trailing edge in the spanwise direction, the profile can be easily constructed by patterning in CAD models or by repeatedly applying the virtual punching process along the trailing edge.If the serrated recesses are punched or cut out from a serrated semi-finished product during the manufacturing process, for example using laser technology, only a comparatively small number of punchings are required and the trimming path is comparatively short.

[0022] With a view to particularly advantageous manufacturing and operational strength, the tooth-shaped recesses can be rounded at their tooth base.

[0023] For particularly advantageous handling and injury protection, the serrated recesses can advantageously be rounded at their transitions to the original, predominantly straight or slightly curved areas of the trailing edge and / or to the suction or pressure side of the blade. The blade can be made of various materials, for example, sheet metal. Within the scope of such a design, it is advantageous if at least the trailing edge area is painted or powder-coated, specifically in the area of ​​the serrated recesses.

[0024] The wing can be manufactured from plastic by injection molding or from aluminum by die casting within the scope of a particularly simple construction / design.

[0025] If the blade is a sheet metal part, it is preferably completed by stamping or laser cutting, followed by embossing, joining, interlocking, etc., to form an impeller, which is then used in an axial fan, diagonal fan, or radial fan. The impellers are designed and manufactured according to requirements, with the blades of an axial fan extending from a hub outward to a free end.

[0026] When used in a radial fan, the blades extend between a hub ring and a shroud and are firmly connected to the hub ring and shroud. Regarding the trailing edge design, the same considerations apply to the previously discussed fan types, especially since the primary goal is to reduce noise emissions, particularly trailing edge noise, through measures related to the trailing edge.

[0027] There are now various possibilities for advantageously embodying and developing the teaching of the present invention. For this purpose, reference is made, on the one hand, to the claims subordinate to claim 1 and, on the other hand, to the following explanation of preferred embodiments of the invention with reference to the drawing. In conjunction with the explanation of the preferred embodiments of the invention with reference to the drawing, generally preferred embodiments and developments of the teaching are also explained. In the drawing, Fig. 1 shows a plan view of an embodiment of a wing according to the invention,

[0028] Fig. 2 a detailed view of the wing from Fig. 1 in the area of ​​the trailing edge,

[0029] Fig. 3 in perspective view, seen from the downstream side, a radial impeller with corresponding blades,

[0030] Fig. 4 a detailed view of the impeller from Fig. 3 in the area of ​​the transition from the trailing edge of the blade to the shroud,

[0031] Fig. 5 in perspective view, seen from the downstream side, another embodiment of a radial impeller with corresponding vanes,

[0032] Fig. 6 is a detailed view of Fig. 5 in the area of ​​the transition from the trailing edge of the wing to the cover ring,

[0033] Fig. 7 in perspective view, seen from the downstream side, an impeller of axial design with corresponding vanes and

[0034] Fig. 8 is a detailed view of Fig. 7 in the area of ​​a section of a wing trailing edge.

[0035] Fig. 1 shows a blade blank 2b as a flat sheet metal cutout of a blade 2 of a radial fan. The blade 2 has a trailing edge 7 with serrated recesses.

[0036] The wing blank 2b is a wing blank for a sheet metal wing. The wing blank 2b is therefore a sheet metal cut before the wing 2 is stamped. The wing blank 2b also has an inflowing or leading edge 6 opposite the outflowing or trailing edge 7. The finished wing 2 can then be produced from this flat blank or from the wing blank 2b using a stamping process or a similar manufacturing method. After the stamping process, the wing 2 is advantageously three-dimensionally arched / curved / twisted. In particular, the wing has a three-dimensionally curved or twisted trailing edge 7. The leading edge 6 can also be three-dimensionally curved or twisted. The wing 2 is preferably not corrugated.Leading edge 6 and trailing edge 7 extend in the span direction 8 from a hub-side wing end 9 to a cover ring-side wing end 13a or, if no cover ring is provided, to the free wing end 13b. Span S is the maximum extension of the wing 2 or its section 2b in the span direction 8.

[0037] The serrated design of the trailing edge 7 of the wing is clearly visible in the flat cut of the wing blank 2b. The recessed serrations or the serrated recesses 12 are clearly visible in Fig. 1. The recessed serrations or the serrated recesses 12 are designed as recesses in the trailing edge 7 of the otherwise unserrated wing. Although the serrated recesses 12 are delicate in their extension along the trailing edge 7 of the wing, a comparatively small number of serrated recesses 12 are spaced apart from one another, while still achieving the function of trailing edge noise reduction.

[0038] In addition, the blade blank 2b has a waviness at the leading edge 6. This is considered advantageous for low sound levels, especially in combination with the serrated trailing edge 7. The waviness at the leading edge 6 of the blade 2 is characterized by its wavelength Aw. The wavelength Aw is significantly larger, at least by a factor of 4, than the width b of the serrated recesses 12, clearly shown in Fig. 2.

[0039] Since the number of serrated recesses 12 is minimized with the described design while maintaining the required trailing edge noise reduction, the travel path for producing the wing blank 2b with a serrated trailing edge 7, for example by trimming a sheet metal with a laser or by other methods, can also be minimized, thereby reducing production time, energy consumption and costs.

[0040] Advantageously, the stamping die used to form the three-dimensionally curved wing 2 from the wing blank 2b in the case of sheet metal construction does not require its own serrations, since the serrated recesses 12 are already incorporated into the wing blank 2b as a wing blank. Thus, these delicate serrated structures do not need to be formed in the stamping tool.

[0041] If a casting process such as aluminum die casting or plastic injection molding is used instead, the casting mold can have the negative contour of the serrated recesses 12. Since the number of serrated recesses 12 is minimized in the described design while maintaining the required trailing edge noise reduction, a casting tool also has a minimized number of serrations, thereby minimizing the complexity and wear of the corresponding casting tool. The embodiment according to Fig. 1 corresponds to a sheet metal construction in which the three-dimensionally twisted wing 2 is formed from a flat sheet metal blank. Therefore, centering devices 19 are provided for the stamping tool for the stamping process.

[0042] The embodiment according to Fig. 1 corresponds to a sheet metal construction in which several individual blades 2 are joined to a base plate or a hub ring 3 and a cover ring 4 to form an impeller 1. Such an impeller can be seen in Fig. 3, which is described in more detail below. To facilitate the positioning of the components relative to one another, centering devices 17 towards the hub ring 3 are provided on the hub-side end 9 of the blade blank 2b, and centering devices 18 towards the cover ring 4 are provided on the cover ring-side wing end 13a of the blade blank 2b. In the exemplary embodiment, the centering devices 17, 18 are simple depressions / recesses or projections in the blade geometry, which can engage in corresponding projections or depressions or recesses in the base plate or cover plate.

[0043] Fig. 2 shows a detail in the area of ​​the trailing edge 7 of a blade 2 or of the blade blank 2b, for example, a trailing edge 7 of a blade 2 according to Fig. 1. However, it can also be a trailing edge 7 of a different fan blade, for example, a fan of radial, diagonal, or axial design. Tooth-shaped recesses 12 are formed on the trailing edge 7. The recessed teeth of the tooth-shaped recesses 12 have a possibly variable distance d from one another along the trailing edge 7 and do not touch one another. Therefore, alternating smooth or essentially straight regions 25 and toothed regions 26 are formed on the trailing edge 7, wherein the toothed regions are formed by tooth-shaped recesses 12. The toothed regions 26 simultaneously also form the edge of the tooth-shaped recesses 12.

[0044] The transition 20 between the serrated regions 26 of the trailing edge 7 and the smooth or substantially straight regions 25 of the trailing edge 7 can be rounded or chamfered, which is advantageous, for example, to avoid injuries when handling the blade 2 or an impeller 1 or to minimize wear on the blade 2 or on tools used to manufacture the blade 2 or the impeller 1.

[0045] For the consideration of the characteristic geometric dimensions of the jagged recesses 12 or the trailing edge 7, an imaginary wing trailing edge 7 can be considered without roundings or chamfers at the transitions 20. In other words, the transitions 20 are ignored and are mentally supplemented to form a sharp-edged shape, in particular for determining the geometric dimensions of the width b, depth t, and distance d.

[0046] The smooth or essentially straight regions 25 of the trailing edge 7 can be conceptually extended beyond the serrated recesses 12 to form a fictitious smooth trailing edge profile. The fictitious, smooth trailing edge profile is preferably only essentially straight, but not an ideal straight line. In a wing 2, the profile of the trailing edge 7 can, in particular, be curved three-dimensionally. With a wing 2 shaped in this way, further improved efficiency and acoustic values ​​can be achieved. The side flanks 11 of the serrated regions 26, without curves or chamfers, can be conceptually extended straight beyond the fictitious, smooth trailing edge profile. The corner points of the imaginary sharp-edged shape of the serrated trailing edge 7 result from the intersection points of the fictitious smooth trailing edge 7 and the extensions of the side flanks 11 of the serrated recesses 12.These vertices are used to determine the geometric dimensions of width b, depth t and distance d.

[0047] Each serrated recess 12 has a width b, measured at the possibly imaginary sharp-edged transitions 20, which can be measured along the course of the trailing edge 7, possibly approximately in the spanwise direction 8. Two adjacent serrated recesses 12 have a distance d from one another, measured along the course of the trailing edge 7. The width b and the distance d can vary over the course of a trailing edge 7, in particular if the trailing edge 7 is advantageously designed to be three-dimensionally curved or twisted. The distance d can be predominantly greater than the widths b of the serrated recesses 12 directly adjacent to the respective straight region, or at least greater than 0.5 b - in each case with respect to a transition 20 or the associated imaginary sharp-edged transition region.

[0048] The distance d characterizes the length of a smooth, essentially straight region 25 of the wing's trailing edge 7. By having a sufficiently large distance d with d > 0.5 b, preferably d > b, equivalent to the presence of a sufficiently dimensioned smooth region 25 of the trailing edge 7, the risk of injury when handling a wing 2 or an impeller 1 constructed therefrom can be greatly reduced, for example, and the susceptibility to wear or damage of the trailing edge 7 can be minimized. Furthermore, the ratio d > 0.5 b leads to a relatively low number of serrated recesses 12, which offers advantages in the manufacture of the trailing edge 7. For example, the travel path when trimming a trailing edge 7 is reduced, or the number of serrated recesses 12 to be punched out is minimized.From an aerodynamic point of view, by minimizing the number of serrated recesses 12, the reduction in air performance is only slight compared to an imaginary unserrated reference wing with the fictitious smooth trailing edge.

[0049] In order to reduce the trailing edge noise as effectively as possible, however, the distance d between two adjacent serrated recesses 12 should not be selected to be greater than four times the width b or the mean value of the two widths b of the serrated region 26 of the serrated recess 12 directly adjacent to the essentially straight region.

[0050] In order to further reduce the trailing edge noise, the serrated recesses 12 can have a design with a depth t, where t > 1.3 b.

[0051] The depth t is measured centrally in the serrated area 26 of the serrated recess 12 from the serration base 24 to the fictitious smooth rear edge 7 or to the straight connecting line of the two imaginary sharp-edged transitions 20 of the respective serrated recess 12.

[0052] This can result in an acute or small angle y of the serrated recess 12 or the side flanks 11 at the inner edge of the serrated base 24. Thus, y can advantageously be in a range of 10° to 35°, particularly preferably in a range of 15° to 30°. This achieves an advantageous reduction in trailing edge noise.

[0053] The serrated base 24 can be rounded, preferably with one or more rounding radii >= 1 mm. This simplifies or enables production. When trimming a sheet metal with a laser, the rounding is also advantageous to prevent excessive heat concentration in a sharp-edged inner corner. In tools such as casting tools or punching tools, it is particularly advantageous for the acute-angled serrated areas 26 that form the serrated recesses 12 if the serrated areas 26 in the area of ​​the serrated base 24 are not tapered to a point, but are rounded with a radius.

[0054] Fig. 3 shows a perspective view of an impeller 1 of a radial fan. The impeller 1, of radial design and made of sheet metal, comprises blades 2 with trailing edges 7. The trailing edges 7 are each provided with a plurality of serrated recesses 12.

[0055] Five vanes 2 are attached to a hub ring 3 of the impeller 1 at their hub-ring-side ends 9, extending in the span direction 8 from the hub ring 3 to a cover ring 4, to which they are attached at their cover-ring-side end 13a. On the hub ring 3, which also functions as a support for the entire impeller 1, a fastening device 10 for attaching the hub ring 3 or the impeller 1 to a motor (not shown) is provided inside. An inlet opening 14 is provided inside the cover ring 4. During operation of the then rotating impeller 1, the conveying medium, for example air, flows into the impeller 1 through the inlet opening 14 and is conveyed radially outwards, in particular as a result of the rotation of the blades 2, before it exits radially outwards from the impeller 1 at the impeller outlet, between the outflow end 16 of the cover ring 4 and the outflow end 15 of the hub ring 3.The flow medium impacts the blades 2 at the leading edges 6 and flows off over the trailing edge 7. The trailing edge 7 is three-dimensionally curved, which facilitates the achievement of particularly high efficiency and advantageous acoustic values.

[0056] The leading edge 6 has a waviness, with several wave crests and wave troughs over the course of the leading edge in the spanwise direction 8. This is advantageous for low noise generation, especially in combination with the described trailing edge 7 with jagged recesses 12.

[0057] In the embodiment shown in Fig. 3, the three-dimensionally curved blades 2 of the impeller 1 are made of sheet metal by stamping a blade blank 2b (see Fig. 1) and then joined to the hub ring 3 and cover ring 4. Joining can be achieved, for example, by welding.

[0058] Fig. 4 shows a detailed view of the impeller according to Fig. 3. The trailing edge 7 of a blade 2 is shown enlarged in the area of ​​the cover ring 4 with its inlet opening 14. The trailing edge 7, which is shown as a line in the plan view according to Fig. 1 and Fig. 2, extends across the sheet thickness in a sheet metal blade. However, the transition lines of the trailing edge 7 to the suction side and pressure side, i.e., to the two large-surface areas of the blade 2, are decisive, as described with reference to Fig. 2.

[0059] In order to dimension the characteristic sizes of the trailing edge 7 with the jagged course based on the sizes shown in Fig. 2, a “center line” of the flat trailing edge 7 can also be used.

[0060] The transition areas 20 between the smooth, possibly slightly curved, but essentially straight areas 25 and the serrated trailing edge areas 26 are rounded. This prevents injuries during handling and reduces wear on the trailing edges 7.

[0061] At the base of the tooth 24, the tooth-shaped recesses have 12 rounded sections.

[0062] Distinctive, smooth, essentially straight areas 25 are formed on the trailing edge 7. The total area of ​​the wing 2 in the section of the serrated recesses 12 is comparatively small, in particular significantly smaller than the area "remaining" in the trailing edge area on the wing 2, i.e., the area not cut out, namely in the area of ​​the wings 2 starting from the imaginary line described by the serration base 24 of the individual serrated recesses 12 of a wing 2. Thus, the serration removes less effective wing area from the wing 2, both in terms of the aerodynamic effectiveness and the strength of the wing 2. In isolated cases, adjacent recessed serrated recesses 12 can also have a smaller distance d from one another, especially if the trailing edge 7 is particularly strongly curved in the relevant area or is angled relative to the impeller axis.The criterion described above, according to which d > b / 2, preferably d > b, can apply to a predominant number of adjacent pairs of serrated recesses 12 of the trailing edge 7, for example to at least 75%.

[0063] Fig. 5 shows a perspective view of an impeller 1 of a radial fan with blades 2 having trailing edges 7 with serrated recesses 12. In contrast to the exemplary embodiment shown in Fig. 3, this is an impeller 1 of cast construction, i.e., the impeller 1 is manufactured integrally in one piece using a tool-based casting process. The casting process is preferably a plastic injection molding process.

[0064] In the exemplary embodiment, the impeller 1, including the hub ring 3, the cover ring 4, and the vanes 2 extending therebetween, is manufactured as a single piece using a plastic injection molding process, preferably with a fiber-reinforced thermoplastic. The transition at the cover ring-side vane end 13a of the vanes 2 to the cover plate 4 is rounded, just like the—not visible—transition at the hub-side vane end from the vanes 2 to the hub ring 3.

[0065] For example, in axial fans, similarly manufactured impellers 1 can be designed without a cover ring 4. In this case, the blade end is not connected to a cover ring, but is a free blade end 13b.

[0066] It is also conceivable to produce blades 2 as individual parts in a casting process and to connect them to at least one hub ring 3 to produce an impeller 1. As in the embodiment according to Fig. 3, the three-dimensionally curved trailing edges 7 with the serrated recesses 12 can be seen, which are shown in detail in Fig. 6.

[0067] The leading edges 6 are corrugated, with several wave troughs and wave crests distributed across the span of the wing 2, to ensure particularly low noise generation, particularly in combination with the serrated trailing edge 7. A mounting device 10 for connecting a motor, preferably an external rotor motor, is also integrally integrated into the cast impeller.

[0068] Fig. 6 shows a detailed view of the impeller according to Fig. 5. The trailing edge 7 of a blade 2 is shown enlarged in the area of ​​the cover ring 4 with its inlet opening 14. The trailing edge 7, which is shown as a line in Fig. 2, corresponds approximately to a line of the trailing edge 7 in the area of ​​the middle of the blade thickness of the cast blade 2. In contrast to the sheet metal blade, the trailing edge 7 is advantageously rounded with fillets 28 towards the large-surface sides - i.e., towards the suction and pressure sides - of the blade 2. The fillets 28 are preferably formed on the smooth, possibly slightly curved, but essentially straight areas 25 and / or the serrated areas 26. This prevents wear in the casting tool and on the blade 2, and the risk of injury when handling the impeller 1 is further reduced, particularly in conjunction with the injury-reducing effect of the essentially straight areas 25.

[0069] In particular, due to the serrated recesses 12 on the trailing edge 7, the smooth, possibly slightly curved, essentially straight regions 25 remain, whereby the trailing edge 7 is alternately divided into essentially straight regions 25 and serrated regions 26. Between each smooth region 25 and directly adjacent serrated regions 26 is the transition 20, which is preferably rounded or at least chamfered. The rounding or chamfering of the transition 20 is not taken into account when determining the width b of the serrated recesses 12 at the wing tip. The spanwise length of the smooth regions 25 along the imaginary course of the wing trailing edge without serrations, or the distance d, is in each case at least 50% of the mean value of the spanwise widths b of the adjacent serrated recesses 12.

[0070] The tooth-shaped recesses 12 are preferably rounded at the tooth base 24, in particular between the flanks 11 of the teeth 12, but in the case of cast blades 2 also towards the suction and / or pressure side of the blade 2.

[0071] In general, a center line of a trailing edge 7 running approximately in the spanwise direction 8 can be used as the line of the wing's trailing edge profile. With such a wing trailing edge profile, the extension of the wing 2, viewed in the direction from the leading edge 6 to the trailing edge 7, would be approximately at its maximum. In the embodiment shown in Fig. 5, for example, this is approximately the center line of the trailing edge 7 between the two large-surface sides of the wing 2, namely the suction and pressure sides.

[0072] Fig. 7 shows a perspective view of an impeller 1 of an axial fan with blades 2. The blades 2 have trailing edges 7 with serrated recesses 12. This is a cast-iron impeller 1, meaning the impeller 1 is manufactured integrally as a single piece using a tool-based casting process, preferably using a plastic injection molding process. The material of the impeller 1 is preferably a fiber-reinforced thermoplastic.

[0073] The transition from the blades 2 to the hub ring 3 is rounded. This axial fan impeller does not have a cover ring. Instead, winglets 30 are formed on the radially outer free blade end 13b in order to reduce the so-called blade tip noise in the axial fan, which, in combination with the design of the trailing edges 7 with the jagged recesses 12, results in a particularly low-noise overall fan. In the context of axial fan blades, a "winglet" 30 is generally understood to mean a special design of the radially outer free blade ends 13b, which geometrically differs from the rest of the blade profile in one or more design features. In the illustrated embodiment, the winglet 30 is characterized in particular by a noticeable curvature of the free blade end 13b towards its blade suction side.It is also conceivable to produce blades as individual parts in a casting process and to connect them with at least one hub ring to produce an impeller, for example in the case of axial fan impellers.

[0074] The leading edges 6 of the blades are corrugated, with several wave troughs and wave crests distributed across the span from the hub ring 3 to the free wing tip 13b, to achieve particularly low noise generation, particularly in combination with the serrated trailing edge 7. A mounting device 10 for connecting a motor, preferably an external rotor motor, is also integrally integrated into the cast impeller.

[0075] In the illustrated embodiment, the serrated recesses 12 are not distributed across the entire extent of the trailing edges 7 in the spanwise direction 8, but only in a radially outer section. Typically, in axial or diagonal fans, the radially outer section contributes particularly strongly to trailing edge noise generation due to the higher relative speeds between the rotating blade 2 and the flow medium there, which is why the recess of the serrations is particularly effective there.

[0076] Advantageously, the serrated recesses 12 are provided particularly or even exclusively in those sections of the trailing edges 7 that are particularly relevant for the generation of trailing edge noise. In the remaining sections, the provision of serrated recesses 12 may be omitted to reduce effort and complexity, such as in the radially inner regions of the trailing edges 7 of axial fan blades.

[0077] In the embodiment shown in Fig. 7, balancing areas 29 for attaching balancing weights are provided in a radially inner section of the trailing edges 7 of the blades 2. Such balancing areas 29 can also be provided in the radially inner region of the leading edges 6.

[0078] Fig. 8 shows a detailed view of the impeller 1 according to Fig. 7. The trailing edge 7 of a blade 2 is shown enlarged in the area of ​​the winglet 30 at the radially outer free blade end 13b. The trailing edge 7, which is shown as a line in Fig. 2, corresponds approximately to a boundary line of the trailing edge 7 toward the suction side of the blade 2—located at the rear in the view—in the cast blade 2 in Fig. 8.

[0079] In general, a line of a trailing edge 7 running in the span direction 8 can be used as the line of the wing trailing edge profile, as described in Fig. 2, so that the extension of the wing, seen in the direction from the leading edge 6 to the trailing edge 7, is approximately at its maximum. In the exemplary embodiment according to Fig. 7 and Fig. 8, this is approximately the boundary line of the trailing edge 7 to the suction side of the wing 2, which is located at the rear in the view, since here the trailing edge 7 is only rounded with fillets 28 towards the front pressure side, but transitions to the suction side with more sharp edges, which can be regarded as an advantageous embodiment.

[0080] The rounded portions 28 of the trailing edge 7 toward the pressure side are preferably formed in the smooth, substantially straight portions 25 and / or the serrated portions 26. This prevents wear in the casting tool and on the blade 2, and the risk of injury when handling the impeller 1 is further reduced, particularly in conjunction with the injury-reducing effect of the smooth portions 25. The rather sharp-edged transition of the trailing edge 7 toward the blade suction side serves as a dividing line between parts of the casting tool, for example, between the nozzle and ejector side of an injection molding tool.

[0081] In particular, due to the serrated cutouts 12 on the trailing edge 7, the smooth, possibly slightly curved, essentially straight regions 25 remain, whereby the trailing edge 7 is alternately divided into essentially straight regions 25 and serrated regions 26. Between each smooth region 25 and directly adjacent serrated regions 26 is the transition 20, which is preferably rounded or at least chamfered. The rounding or chamfering of the transition 20 is not taken into account when determining the width b of the serrated cutouts 12 at the wing tip. The length of the smooth, possibly slightly curved, essentially straight regions 25 or the distance d is in each case at least 50% of the mean value of the spanwise widths b of the adjacent serrated cutouts 12.

[0082] The tooth-shaped recesses 12 are preferably rounded at the tooth base 24, in particular between the side flanks 11 of the teeth 12, but in the case of cast blades 2 also towards the suction and / or pressure side of the blade 2.

[0083] With regard to further advantageous embodiments of the blade or impeller or fan according to the invention, reference is made to the general part of the description and to the appended claims in order to avoid repetition.

[0084] Finally, it should be expressly pointed out that the above-described embodiments of the blade or impeller or fan according to the invention serve only to explain the claimed teaching, but do not limit it to the embodiments.

[0085] List of reference symbols

[0086] 1 wheel

[0087] 2 wings

[0088] 2b wing blank

[0089] 3 Hub ring, base plate

[0090] 4 Cover ring

[0091] 6 leading edge

[0092] 7 trailing edge

[0093] 8 Span direction

[0094] 9 Hub-side wing end

[0095] 10 Impeller-motor fastening device

[0096] 11 Side flank

[0097] 12 serrated recesses

[0098] 13a Cover ring side wing tip

[0099] 13b Free wing tip

[0100] 14 Inlet opening

[0101] 15 Outflow end of the hub ring / base plate

[0102] 16 Outflow end of the cover ring

[0103] 17 Centering device wing - hub

[0104] 18 Centering device wing - cover ring

[0105] 19 Centering device wing for embossing tool

[0106] 20 Transition

[0107] 24 Zackengrund

[0108] 25 Essentially straight area

[0109] 26 Jagged area

[0110] 28 Rounding of the trailing edge of the wing towards the suction and / or

[0111] Pressure side of the wing

[0112] 29 Balancing area

[0113] 30 Winglet b Width of the notch d Distance between the notches S Span of the wing t Depth of the notch

[0114] Aw wavelength at the leading edge

[0115] Y angle

Claims

Claims 1. Blade (2) for the impeller (1) of a fan, in particular an axial fan, diagonal fan or radial fan, with a three-dimensionally curved trailing edge (7), wherein a plurality of tooth-shaped recesses (12) are provided over the course of the trailing edge (7) in the span direction (8), wherein a substantially straight region of the trailing edge (7) is formed between at least two adjacent tooth-shaped recesses (12).

2. Wing (2) according to claim 1, characterized in that substantially straight regions of the trailing edge are formed between the adjacent tooth-shaped recesses (12).

3. Wing (2) according to claim 1 or claim 2, characterized in that serrated recesses (12) are formed only in a section of the trailing edge (7).

4. Wing (2) according to one of claims 1 to 3, characterized in that a length of the substantially straight region in the spanwise direction (8) corresponds to at least half of a mean width (b) of the adjacent serrated recesses (12), preferably for at least 75% of all pairs of directly adjacent serrated recesses (12) of a trailing edge.

5. Wing (2) according to one of claims 1 to 4, characterized in that the tooth-shaped recesses (12) taper towards the wing center at an acute angle (y), preferably at an angle between 10° and 35°.

6. Wing (2) according to claim 5, wherein the tooth-shaped recesses (12) are rounded at their tooth base (24).

7. Blade (2) according to one of claims 1 to 6, wherein the blades (2) are intended for an axial or diagonal fan, characterized in that the free blade ends (13b) are equipped with winglets (30) which can preferably be bent from the pressure side to the suction side.

8. Impeller (1) with at least two, preferably three to nine blades (2) according to one of claims 1 to 7, characterized in that the blades (2) individually or the entire impeller (1) are manufactured in one piece from plastic by injection molding or from aluminum by die casting or from sheet metal by stamping or by laser cutting and embossing as well as joining / welding and / or inserting tabs into one another by means of centering devices, etc.

9. Axial fan or diagonal fan, with a hub and blades (2) extending outwards from the hub according to one of claims 1 to 7.

10. Radial fan with a hub ring, a cover ring and an impeller extending between the hub ring and the cover ring, with blades (2) according to one of claims 1 to 6. 11 . Axial fan, radial fan or diagonal fan, with a blade (2) according to one of claims 1 to 7.

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