EP2122182A2

EP2122182A2 - Ventilator wheel, system and transmission line

Info

Publication number: EP2122182A2
Application number: EP08707176A
Authority: EP
Inventors: Steffen Leonhard; Steffen Saar
Original assignee: SEW Eurodrive GmbH and Co KG
Current assignee: SEW Eurodrive GmbH and Co KG
Priority date: 2007-02-23
Filing date: 2008-01-22
Publication date: 2009-11-25
Anticipated expiration: 2028-01-22
Also published as: PL2122182T3; HUE045193T2; EP3214316A1; CN101617128B; WO2008101577A2; CN103410775B; DE102008010912B4; EP2122182B1; DE102008010912A1; EP3214316B1; CN101617128A; WO2008101577A3; CN103410775A

Abstract

A ventilator wheel is provided with a convex air guiding ring which forms, together with a base body of the ventilator wheel and ventilator blades, nozzle-type air channels. Said air channels extend along the periphery in irregular angular positions.

Description

Fan wheel, system and transmission series

Description:

The invention relates to a fan, a system and a transmission series.

The invention is therefore the object of developing a fan, so that the environmental impact is reduced.

According to the invention the object is achieved in the fan wheel according to the features specified in claim 1, in the system according to the features indicated in claim 26 and in the transmission series according to the features indicated in claim 31.

Important features of the invention of a fan wheel are that a first fan blade has a first angular distance to a first circumferentially adjacent fan blade and the first fan blade has a second angular distance to a second fan blade adjacent in the opposite direction, wherein the first angular distance is smaller than the second angular distance , Alternatively, the sequence in the circumferential direction of the angular distances from a respective wing to the fan blade adjacent in the circumferential direction comprises at least two different types of angular distance values. Thus, a simple embodiment is specified in which the fan blades are not necessarily arranged regularly. The advantage here is that the fan blades produce periodic excitations whose main frequency component is lower than would be the case if all angular distances were equal. In particular, the frequency component is at most half that of a regular arrangement of the fan blades.

In an advantageous embodiment, the fan blades in the circumferential direction, in particular along the circumference of the fan, are irregularly spaced. Preferably, a number n of fan blades is provided, with uniform rotation of the fan around its axis cause the fan blades when passing through a fixed reference direction a series of suggestions whose period is greater than one n-th the revolution time of the fan. Particularly preferably, the period is greater than half or equal to half the rotational speed of the fan. Most preferably, the period is equal to the revolution time of the fan. Thus is Advantageously a large and very particularly preferably the greatest possible reduction of the main frequency contribution of the fan blades caused vibration excitations reached. The noise pollution of the environment by the fan operation is thus at least subjectively reduced because the frequency of noise is placed below the hearing threshold or in areas in which the sensitivity to noise in human hearing is reduced. In addition, resonance effects between the suggestions by the fan blades and vibrations by the operation of the transmission can be reduced.

In an advantageous embodiment, each air duct is limited by at least fan blades, an air guide ring and / or a base body, wherein the cross section of

Air channel has a minimum in the course from inside to outside. Thus, air ducts are formed with a nozzle effect. These nozzles advantageously cause a directed flow of cooling air.

In an advantageous development, the minimum of the cross section of the air duct is effected by a minimum of the distance between the base body and the air guide ring, in particular by a minimum of the distance between the sectional figures of the body with an axial plane on the one hand and the air guide ring with the axial plane on the other. The fan wheel advantageously comprises a main body, fan blades and an air guide ring, wherein the base body has a frustoconical region and form at least two fan blades, a segment of the frusto-conical region and a segment of the air guide a radially extending air channel whose cross-section has a minimum in the radial course. The advantage here is that the fan is easily manufacturable, since the geometric properties of the air duct, in particular the nozzle shape, with the boundary surfaces of air guide ring and body is easy to manufacture and controllable. In addition, the main body of the fan is occupied in addition to its holding function with a Luftleitfunktion. As a result, parts can be saved.

In an advantageous embodiment, the cross section of the air guide ring is convex on its inner side and concave on its outer side, in particular shaped such that the wall thickness is substantially constant. The consistency of the wall thickness depends on the manufacturing tolerances of the production technology and on the speeds at which the fan is used. The outer shape of the air guide ring thus follows substantially the inner shape of the air guide ring, and it is an advantageous form of the air guide ring formed at the same time low material usage. The advantage here is that for the Air guide little material are used, so that its mass moment of inertia is minimized.

In an advantageous development, the base body has a frustoconical region and the air guide ring is concentrically inscribed in a mathematical cone such that the air guide touches the mathematical cone in a first and a second axial region and in a third axial region between air guide ring and the mathematical cone a minimum distance is provided, wherein the third axial region is arranged between the first axial region and the second axial region, and at least two fan blades, a segment of the frusto-conical region and a segment of the air guide ring form an outwardly extending air channel. The advantage here is that the constructional and manufacturing technology easy to handle geometric shapes, a nozzle-like air duct is available.

In an advantageous development, at least two different types of air ducts are formed on a fan. Preferably, each air channel is characterized by a geometric size, and the sequence of the geometric size of the air ducts is an irregular sequence in one revolution of the fan. More preferably, the geometric size of each air duct is the angle between the limiting fan blades or the angle of a limiting fan blade a fan-fixed reference direction. Alternatively, the geometric size of each air duct is the angular position of the center of gravity or the center plane of the air duct or the angle of an excellent direction of the air duct to a fan-fixed reference direction. Thus, simple geometric characteristics are given, which are heranziehbar to form a fan according to the invention.

In an advantageous development, the center of gravity formed by all the fan blades is in the center of the fan. The advantage here is that with reduced noise pollution additional loads on the bearings and the material can be avoided by imbalance.

In an advantageous development, the maximum axial extent of the fan blades is greater than the maximum axial extent of the air guide ring.

In an advantageous development, the maximum axial extent of the fan blades is more than twice as large as the maximum axial extent of the air guide ring. Advantageous is that a radial or laterally oblique discharge of the cooling air is possible. Thus, the fan is used in various transmissions or in general systems with fan.

In an advantageous development, the maximum radial extent of the fan blades is greater than the minimum radial extent of the air guide ring. The advantage here is that large air outlets are formed, can be conducted through the cooling air to the housing to be cooled.

In an advantageous development, the fan blades on the suction side are axially retracted up to a radius, in particular by more than one third of the maximum axial extent of the fan blades. The advantage here is that at a small distance from the fan, a fan cover can be placed, wherein at the intake ports or air inlets generated by the fan blades noise can be reduced.

In an advantageous development, each fan blade on a plane of symmetry, in which preferably the axis of rotation of the fan is. Thus, a rotationally invariable fan wheel is formed in a simple manner, and cooling air always flows in the same direction through the air channels.

In an advantageous development, the radial extent of the base body is smaller than the outer diameter of the fan wheel, in particular at least fifteen percent smaller than the inner diameter of the air guide ring. Thus, advantageous geometric conditions are formed, in which the cooling air can flow particularly effective.

In an advantageous development, the air ducts each form an air outlet, which comprises a radially aligned and an axially aligned portion. Thus, the fan on different transmissions, especially directly in front of a housing wall or on a Kegelradtopf operable.

Important features of the invention of a system, in particular a transmission, are that a fan with a fan with fan blades and a fan cover is included, wherein the fan cover at least partially surrounds the fan and the fan cover has a range with axial air inlets, the fan blades in a first portion of the region with axial air inlets have a constant distance from the fan guard and in a second subregion of the region with axial air inlets, the distance of the fan blades from the fan cowl is greater than the constant distance in the first subregion, in particular more than twice as large. Thus, particularly advantageous flow conditions are achieved, and the noise on a fan cover by passing fan blades is reduced.

In an advantageous development, the fan blades extend radially beyond the region with axial air inlets. Thus, the cooling air is particularly advantageous sucked.

In an advantageous development, the fan wheel is arranged on a shaft of the transmission, in particular of the driving shaft. Thus, a separate motor for the drive of the fan is dispensable.

Important features of the invention of a transmission series with variants, each comprising a fan with fan and at least one gear stage, are that a fan in a first variant on the driving shaft of a bevel gear is mounted and that the fan in a second variant on the driving shaft a spur gear is mounted. In the first variant, air is preferably radially passable through air ducts and, in the second variant, air is directed through the air ducts at an angle to the radial direction and at an angle to the axial direction, in particular in an axial plane of the fan wheel obliquely to the axis of the fan wheel. The advantage here is that the variety of parts is reduced in a transmission series, and that the possible variations for the fan assembly is increased.

In an advantageous development, a housing wall of the transmission partially covers the air outlet of the air ducts in the first variant, in particular the axially oriented partial region of the air outlet. Thus, advantageously, the cooling air in the radial direction can be conducted around the transmission housing. It is thus causes a good cooling performance.

Further advantages emerge from the subclaims. The invention is not limited to the combination of features of the claims. For the skilled person, further meaningful combination options of claims and / or individual claim features and / or features of the description and / or figures, in particular from the task and / or by posing the task by comparison with the prior art task. LIST OF REFERENCE NUMBERS

10 basic body

11 fan blades 5 12 air guide ring

13 hub

20 support ring

21 bearing edge

22 radial boundary edge 10 23 outer boundary edge

30 segment

31 first fan blade

32 second fan blades

33 first guide ring

15 34 second guide ring

35 frustoconical area

36 Reference direction w1, w2, w3 Angle 40 Retrieval

20 41 radial opening 42 conical jacket 43, 44 cutting circle

50 gears

51 Fan cover 25 52 Frame

53 wave

54 intermediate part

55 air inlets

56 air outlets 30 57 fans

60 space

61 bevel gear pot The invention will now be explained in more detail with reference to figures:

It shows

FIG. 1 shows a view of a fan wheel from the front, FIG. 2 shows a view of the fan wheel from FIG. 1 from the rear,

FIG. 3 shows a plan view of the front side of the fan wheel from FIG. 1,

Figure 4 shows the section of the fan along a designated in Figure 3 with A-A

axial plane,

- Figure 5 is a view of a transmission with mounted fan - Figure 6 is a side view of the transmission of Figure 5 with cut fan cover and cut fan.

Figure 1 shows a fan for a fan of a transmission. The fan wheel comprises at least one main body 10 with a hub 13, fan blades 11 and an air guide ring 12.

The fan is intended for mounting on a shaft of a gearbox. For this purpose, the hub 13 is placed on the shaft for frictional connection with the same.

The fan wheel is driven by the shaft. The shaft thus drives the fan blades 11, thereby producing an approximately radially or obliquely outwardly directed air flow. This direction of the air flow is independent of the direction of rotation of the fan wheel, since each fan blade 11 has a plane of symmetry in which the axis of rotation of the fan wheel is located.

The main body 10, the air guide ring 12 and two adjacent fan blades 11 form air channels, is passed through the air flow.

FIG. 2 shows the rear side of the fan wheel from FIG. 1. A support ring 20 of the base body 10 and the support edges 21 of each fan wheel 11 lie in a common plane. Thus, an operation of the fan is close to the housing wall of a transmission feasible, the plane described is aligned parallel to the housing wall of the transmission and arranged at a small distance to this.

The fan with basic body, fan blades and guide ring is preferably made in one piece, in particular as a cast aluminum or plastic, wherein in the case of Use of plastic, particularly preferably the plastic to avoid electrostatic charge is designed to be electrically conductive.

In an alternative embodiment, the fan is made of steel. 5

In the mounted position - as shown in Figure 2 - the radial boundary edges 22, the outer boundary edge 23 of the air guide ring 12 and the housing wall form an opening through which the air flow is directed radially outward. The air guide ring 12 thus does not extend over the entire axial length of the fan and in particular 10 of the fan blades 11th

FIG. 3 shows a plan view of the front side of the fan wheel according to FIG. 1. The fan blades 11 are mounted on the base body 10, the fan blades 11 each having a plane of symmetry which contains the axis of rotation of the fan wheel. The fan blades 15 11 are thus substantially, so apart from inclinations of the surfaces of the fan blades 11, perpendicular to an annular, truncated cone-shaped portion 35 of the body 10th

Each fan blade 11 is arranged with respect to a fan-fixed reference direction 36 in each case at a 20 angle w1. The fan blades 11 are irregularly arranged: In particular, the difference amounts of each two angles w1 can not be represented as an integer multiple of a basic amount. Thus, resonance excitations are reduced by the fan blades 11, in particular, the frequency of the resonance excitations is reduced.

In an advantageous embodiment, the fan is mounted on a gear shaft and the number of fan blades and the number of teeth of the gear shaft of the gear shaft have no common divider. Particularly preferably, the number of fan blades and the number of teeth of each gear of the transmission has no common divider. Thus, resonance effects are advantageously reduced.

30

The irregular arrangement of the fan blades causes the excitation is generated during the passage of the fan blades 11 by a radially extending, fixed reference direction, the time course has a period that coincides with the rotation time of the fan. W1.i denotes the angle w1 of the i-th fan blade, where i

35 is less than or equal to the total number n of the fan blades 11 - in the embodiment 9 - is, so is defined by the successive sequence of angles w1.1, w1.2, w1.3, ..., w1.n, w1.1, w1.2, w1.3,..., a periodic sequence of numbers whose smallest period length straight n is.

In an alternative embodiment, the period length of the sequence of numbers is a number greater than one, preferably two, more preferably n / 2 or (n-1) / 2, whichever gives an integer in the latter alternatives. Thus, during operation of the fan, the main vibration excitation occurs in a lower frequency band than would be the case with the fan blades regularly arranged.

In an alternative embodiment, the fan wheel on a mirror plane of symmetry, in which preferably the axis of rotation of the fan wheel is included.

The outer diameter of the main body 10 in Figure 3 is much smaller than the outer diameter of the fan selected. Preferably, the outer diameter of the base body 10 is two-thirds of the outer diameter of the fan and thus of the air guide ring 12, and more preferably, the outer diameter of the base body 10 relative to the inner diameter of the air guide ring 12 is reduced by ten to twenty percent. Thus, favorable flow conditions for the fan can be achieved.

The air guide ring 12 is composed of a first guide ring 33 and a second guide ring 34, which are each designed to be annular and frusto-conical. The opening angle of the second guide ring 34 is selected larger than the opening angle of the first guide ring 33.

In each case, a first fan blade 31, a second fan blade 32, a segment 30 of the frusto-conical region 35 of the base body 10 and a segment 37 of the air guide ring 12 enclosed by the two fan blades 31, 32 form an air channel through which air flows during operation.

Each of these air ducts formed in this way has an opening angle or angular distance w2, ie the angle between the delimiting fan blades 31, 32, ie between two nearest neighbors, and an angle w3 of the center plane of the air duct with respect to a reference direction 36. The opening angle w2 results thus in each case from the difference of the angle w1 to the limiting fan blades 31, 32. The angle w3 differs in the example according to the figure 3 of the angles W1 to the limiting fan blades 31, 32nd each by a constant, that is independent of the number of fan blades, amount. The sequence of opening angles w2 and the sequence of angles w3 defines an irregular sequence of numbers. In the case of asymmetrical formations of the air ducts and / or fan blades, the relationships between the angles w1, w2, w3 with one another change accordingly. In particular, for defining the angles, instead of the center planes mentioned, excellent directions, for example, directions of edges of the fan blades, are usable.

FIG. 4 shows a sectional view along the axial plane designated A-A in FIG.

10

The fan blades 11 have approximately right-angled recesses 40, so that the fan blades 11 during operation at a first range of a aufzusetzenden in Figure 4 from above fan cover at a smaller distance than in a second area. This second area contains air inlets for the air supply to the fan,

15 and by the recess 40 periodic vibration excitations at the air inlets are avoided by a Vorbeistreichen the fan blades 10 in close proximity.

The main body 10 comprises at least one hub 13 for non-positive connection of the fan wheel on a shaft and a frusto-conical region 35. This

20 truncated cone-shaped portion 35 forms with the first guide ring 33 and the second guide ring 34 a nozzle-shaped air passage, wherein the nozzle-like constriction is formed approximately at the minimum distance m of the air guide ring 12 and the base body 12. This minimum distance m causes a minimum cross section of the through a segment of the air guide ring 12, a segment of the frusto-conical region 35 and two adjacent fan blades 11th

25 limited air duct, said cross-section is assumed at about the same position as the minimum distance. The exact position of the minimum cross section with respect to the minimum distance depends on the specific configuration of the cross section of the air guide ring 12 and the frusto-conical region.

The air guide ring 12 is formed at least from a first guide ring 33 and a second guide ring 34, wherein the opening angle of the frusto-conical first guide ring 33 is smaller than the opening angle of the frusto-conical second guide ring 34. First guide ring 33 and second guide ring 34 are connected along a concentric ring , The design of the opening angle of the guide rings 33, 34 is such that the air guide ring 12 in a conical surface

35 42 can be inscribed, wherein the conical surface 42, the air guide ring 12 at two concentric Cutting circles 43, 44 touched, the conical shell 42 but the interior of the air guide ring 12 does not intersect. The air guide ring 12 thus has an axial cross section, whose outer contour is concave.

Accordingly, in order to form a constant wall thickness, a convex surface is formed on the inner side of the air guide ring 12 facing the shaft, where convex the property that the connecting line of two points on the inside of the air guide ring 12 always runs at least partially inside the air guide ring 12.

The inner contour of the cross section of the air guide ring 12 is thus curved with opposite signs as the outer contour of the cross section of the frusto-conical portion 35, in particular its radial outlet. Both contours are thus convex, with the convexities facing each other.

From the described design of first guide ring 33 and second guide ring 34 results in a constriction and a minimum distance m, which causes a nozzle effect in the associated air duct.

In alternative exemplary embodiments, the inside of the air guide ring is convex, but not described by two connected truncated cones, but by, for example, a parabolic or a circular arc-shaped cross-sectional contour. Even in these cases, a resulting cross-sectional constriction causes a nozzle effect with which an air flow can be conducted.

The air guide ring 12 does not extend axially over the entire length of the fan wheel, in particular the fan blades 1 1. Rather, the second guide ring 34 terminates at an axial distance from the plane defined by the support ring 20. In this way, a radial opening 41 is formed for the air ducts through which - in the assembled state - air in the radial direction along the housing wall of the transmission can be conducted.

Figure 5 shows a gear 50 with mounted fan 57. A fan cover 51 surrounds the fan. For illustration, only one half of the fan cowl 51 is shown in FIG. The hub 13 of the fan wheel sits on an intermediate part 54 and is non-positively connected thereto, wherein the intermediate part 54 in turn is arranged on a shaft 53 of the transmission and is at least positively connected thereto. The shaft 53 is the driving shaft of the transmission 50.

The fan cover 51 has an annular area with air inlets 55, through which the fan draws air. The axial orientation of the fan blades 11 causes, regardless of the direction of rotation is sucked in the same axial direction. Thus, the suction side of the fan is clearly defined as the side through which the air flows. The air ducts have an opening through which air therefore exits independently of the direction of rotation. Thus, an air outlet is formed.

The diameter of the area with air inlets 55 is equal to the inner diameter of the first guide ring 33.

The fan blades 11 strip past the air inlets 55 during a rotational movement. To reduce noise, the fan blades 11 each have a recess 40, so that only a portion of the area of the air inlets 55 is swept by the fan blades 11 at a small distance, while another, radially further inboard portion is covered at a greater distance. The radial extent of the radially further inner subregion is greater than the radial extent of the radially outer subregion. Thus whistling sounds are reduced.

FIG. 6 shows the fan from FIG. 5 in a side view. The fan wheel is mounted above a bevel gear pot 61.

By fan blades 11 air is moved, which are passed through the frusto-conical portion 35 and the first guide ring 33 and the second guide ring 34 on air outlets 56.

Between the fan cover 51 and the first guide ring 33, a gap 60 is provided. As can be seen by comparison with Figure 4, the recess 40 of the fan blades 11 in the axial direction is about twice as long as the axial extent of the gap 60th The along the radial boundary edge 22 of the fan blades 1 1 provided withdrawal of the second guide ring 34 allows mounting of the fan wheel on a shaft which protrudes from a side wall of the transmission 50. This is the case, for example, with spur gears. In this case, the fan is mounted directly in front of this side wall, and the moving of the fan blades 11 air flows radially outward and thus along the

Housing wall. The housing wall covers a portion of the air outlet of the air ducts, namely that portion which is axially aligned, the surface normal is thus arranged parallel to the shaft axis. Thus, when mounted in front of a housing wall, the spacing of the fan wheel from the housing of the transmission 50 created by a bevel gear pot 61 in FIG. 6 can be dispensed with, since the air is conducted radially outward in this case. As a result, a compact dimensions of the transmission with fan can be achieved.

By using a fan in different variants of transmissions, a series is formed in whose variants, such components that form the fan, in particular the fan, are uniformly used. Thus, the variety of parts of the series is reduced.

Claims

claims:

1. fan with fan blades, characterized in that a first fan blade to a first circumferentially adjacent fan blade has a first angular distance and the first fan blade adjacent to a second in the opposite direction

Fan blade has a second angular distance, wherein the first angular distance is smaller than the second angular distance.

2. fan with fan blades, characterized in that the sequence in the circumferential direction of the angular distances of a respective wing to in

Circumference direction adjacent fan blades at least two different varieties of

Includes angular distance values.

3. Fan according to at least one of the preceding claims, characterized in that the fan blades in the circumferential direction, in particular along the circumference of the fan, are irregularly spaced.

4. Fan with fan blades, characterized in that a number n is provided by fan blades, with uniform rotation of the fan around its axis cause the fan blades when passing through a fixed reference direction a series of suggestions whose period greater than a n-tel Revolution time of the fan wheel is.

5. fan according to the preceding claim, characterized in that the period is greater than half or equal to half the revolution time of the fan.

6. Fan according to the preceding claim, characterized in that the period is equal to the revolution time of the fan.

7. Fan according to at least one of the preceding claims, characterized in that a number of air ducts is provided, each air duct is limited by at least fan blades, an air guide ring and / or a body, the cross section of the air duct in the course of the inside out a minimum having.

8. Fan according to at least one of the preceding claims, characterized in that the minimum of the cross section of the air channel is effected by a minimum of the distance between the base body and the air guide, in particular by a minimum of the distance between the sectional figures of the body with an axial plane on the one hand and of the air guide ring with the axial plane on the other.

9. fan comprising fan blades and an air guide ring, characterized in that the cross section of the air guide ring is convexly formed on its inner side and is concave on its outer side.

10. impeller according to the preceding claim, characterized in that the cross section of the air guide ring is so convexly formed on its inner side and is formed concavely on its outer side, that the wall thickness of the air guide ring is substantially constant in FIG.

11. fan comprising a main body, fan blades and an air guide ring, wherein

10, the base body has a frusto-conical region and the air guide ring is concentrically inscribed into a mathematical cone in such a way that the air guide ring touches the mathematical cone in a first and a second axial region and a minimum distance is provided in a third axial region between air guide ring and the mathematical cone .

Wherein the third axial region is disposed between the first axial region and the second axial region, and at least two fan blades, a segment of the frusto-conical region, and a segment of the air guide ring form an outwardly extending air channel.

20 12. Fan according to at least one of the preceding claims, characterized in that at least two different types of air ducts are formed on a fan.

13. Fan according to at least one of the preceding claims, 25 characterized in that each air duct is characterized by a geometric size, and the sequence of the geometric size of the air ducts during a revolution of the fan is an irregular sequence.

14. Fan according to at least one of the preceding claims, characterized in that the geometric size of each air duct is the angle between the limiting fan blades or the angle of a limiting fan blade to a fan-fixed reference direction.

15. Fan according to at least one of the preceding claims, characterized in that the geometric size of each air duct is the angular position of the center of gravity or the center plane of the air duct or the angle of an excellent direction of the air duct to a fan-fixed reference direction.

16. Fan according to at least one of the preceding claims, characterized in that the center of gravity formed by all fan blades is located in the center of the fan.

17. Fan according to at least one of the preceding claims, characterized in that the maximum axial extent of the fan blades is greater than the maximum axial extent of the air guide ring.

18. Fan according to at least one of the preceding claims, characterized in that the maximum axial extent of the fan blades is more than twice as large as the maximum axial extent of the air guide ring.

19. Fan according to at least one of the preceding claims, characterized in that the maximum radial extent of the fan blades is greater than the minimum radial extent of the air guide ring.

20. Fan according to at least one of the preceding claims, characterized in that the fan blades are axially withdrawn on the suction side up to a radius, in particular by more than one third of the maximum axial extent of the fan blades.

21. Fan according to at least one of the preceding claims, characterized in that each fan blade has a plane of symmetry.

22. Fan according to at least one of the preceding claims, characterized in that each fan blade has a plane of symmetry in which the axis of rotation of the fan wheel is located.

23. Fan according to at least one of the preceding claims, characterized in that the fan has a plane of symmetry in which the axis of rotation of the fan is.

24. Fan according to at least one of the preceding claims, characterized in that the radial extent of the base body is smaller than the outer diameter of the

Fan, in particular at least fifteen percent smaller than the inner diameter of the air guide ring.

25. Fan according to at least one of the preceding claims, characterized in that the air ducts each form an air outlet, comprising a radially oriented and an axially aligned portion.

26. System, in particular gear, comprising a fan with a fan with fan blades and a fan cowl characterized in that the fan shroud surrounds the fan at least partially and the fan shroud has a range with axial air inlets, wherein the fan blades in a first portion of the range with axial Air inlets have a constant distance from the fan guard and in a second portion of the range with axial air inlets, the distance between the fan blades of the fan guard is greater than the constant distance in the first portion, in particular more than twice as large.

27. System according to at least one of the preceding claims, characterized in that the fan blades extend radially beyond the region with axial air inlets out.

28. System according to at least one of the preceding claims, wherein the system is a transmission, characterized in that the fan wheel on a shaft of the transmission, in particular the driving shaft, is arranged.

29. System according to at least one of the preceding claims, characterized in that the number of fan blades and the number of teeth of the gear of the driving shaft have no common divider.

30. System according to at least one of the preceding claims, characterized in that the number of fan blades and the number of teeth of each gear of the transmission have no common divider.

31 transmission series, with variants, each comprising a fan with fan and at least one gear stage, characterized in that

A fan impeller is mounted in a first variant on the driving shaft of a bevel gear and that the impeller is mounted in a second variant on the driving shaft of a spur gear.

10 32. Transmission series according to at least one of the preceding claims, characterized in that in the first variant, air through air ducts is radially conductive and in the second variant air through the air ducts at an angle to the radial direction and at an angle to the axial direction, in particular an axial plane of the fan 15 obliquely to the axis of the fan, is conductive.

33. Transmission series according to at least one of the preceding claims, characterized in that in the first variant, a housing wall of the transmission partially covers the air outlet of the air ducts 20, in particular the axially oriented portion of the air outlet.