Axial flow fan

Abstract: The invention relates to an axial flow fan of the type used to move cooling air through heat exchangers of a vehicle. The fan has a fan-surrounding structure (39) having a radially inward open groove defined by wall portions (39b, 39c, 50). When the fan rotates, a labyrinth air seal is created, thereby attenuating fan efficiency losses due to re-circulation. Also, fan noise is reduced.

Description: This invention relates to one-piece fans of the type that are used in cooling modules of automotive vehicles for moving cooling air through heat exchangers of the vehicle, i.e. the engine radiator and/or the air conditioning condenser. From previously published patent documents, it is known to construct a one-piece fan that has a hub and a plurality of forwardly skewed blades that extend radially outwardly from the hub to a circular band that surrounds the hub. It is further known to dispose a shroud in surrounding relation to the fan band so that the fan rotates within the shroud. It is also known to employ such a fan/shroud combination in a cooling module of an automotive vehicle, and in that case to construct the shroud with integral members that extend radially inwardly from the shroud to an integral electric motor mount for an electric motor that rotates the fan. These integral members are spaced axially from the fan blades so as to avoid mechanical interference therewith. The design of any given automotive vehicle may impose dimensional constraints on a cooling module such that it may not be possible to use known axial flow fan constructions that possess high efficiency and low noise, for example where there is limited axial space for a fan. Accordingly, there is a need for a high efficiency, low noise axial flow fan that can be packaged within a space that is axially limited, and the present invention relates to the satisfaction of this need through novel and unique constructional features. US-A-4 685 513 discloses a compact fan and shroud package for radiators with fan blades curved rearwardly to position rotating shroud at optimized distance from radiator for improved air flow through radiator. US-A-5 183 382 discloses a fan with a core and blades having an annular shroud of C-shape in axial section fixed to the blade tips in an axially offset position. An end of the shroud makes a labyrinth seal between two flexible rings on a surrounding enclosure. US-A-3 842 902 discloses a fan including means to form a seal at the fan tips and means to form a labyrinth seal in the shroud gap. The combination of seals increases the effective air flow of the fan, reduces the operational noise, and reduces the power required to drive the fan. WO-A-89/07717 discloses an axial fan, preferably for cooling an internal combustion engine in a motor vehicle, comprising an intake frame arranged in front of the impeller when viewed in the direction of flow of the medium, and a ring arranged at the free ends of the impeller blades and surrounding the blade ring. The face of the ring exposed to the flow is flared like a funnel, so that an axial gap is created between the frame and the ring. To obtain a particularly quiet axial fan, even in the absence of relatively close tolerances between impeller and intake frame, the fan is provided with an outer ring extending from the intake frame in the direction of flow of the medium at least as far as the funnel rim of the impeller ring, so as to create a radial gap between the impeller ring and the outer ring. US-A-4 836 148 discloses a shrouded engine cooling fan in which the interface between an outer stationary shroud fixed with respect to a radiator and an inner and rotating shroud fixed to the tips of the fan blades defines a generally toroidal chamber. In the chamber a vortex of air is generated in response to the rotational drive of the fan that acts as a seal to block the flow of recirculation air from the fan discharge to the fan entrance over a wide range of fan operating points to increase fan operating efficiency and reduce fan generated noises. According to the present invention there is provided a one-piece, high efficiency, low axial profile, low noise, axial flow fan in combination with a surrounding shroud structure, said fan comprising a hub that is rotatable about an axis, a plurality of blades distributed circumferentially around said hub and extending from said hub to a circular band that is concentric with and spaced radially outwardly from said hub, said shroud structure comprising a radially inwardly open circumferential groove, said band containing a radially outwardly directed circumferential flange that is disposed in said groove so that said groove and flange cooperatively form a labyrinth air seal when the fan rotates, and in which said groove has first, second, and third walls, said first and second walls each extending radially, said first and second walls being spaced apart axially, and said third wall extending axially, and wherein said first, second and third walls are contained in more than one part of said shroud structure, said first wall merging into said third wall and both walls being contained in one shroud part, said second wall being contained in another shroud part that is attached to said one shroud part by means of fasteners, an end of said third wall abutting a face of said second wall when said one shroud part is attached to said other shroud part, said one shroud part containing a mounting for a motor for driving said fan. Details of a specific example of a fan and shroud embodying principles of the invention will be hereinafter described with reference to the accompanying drawings. The drawings disclose a presently preferred embodiment according to the best mode contemplated at the present time for carrying out the invention. Fig. 1 is a front axial end view of a low axial profile fan embodying principles of the invention. Fig. 2 is a rear axial end view of the fan of Fig. 1. Fig. 3 is a cross sectional view in the direction of arrows 3-3 in Fig. 2. Fig. 4 is a rear axial end view of the fan in association with a shroud member. Fig. 5 is a right side elevational view of Fig. 4 with a portion sectioned away for illustrative purposes. Fig. 6 is a fragmentary view in the vicinity of the sectioned away portion of Fig. 5 illustrating the association of the fan and shroud member with a further shroud member. Figs. 7-11 are views useful in describing the inventive fan. Figs. 1, 2, and 3 illustrate an exemplary one-piece high efficiency, low axial profile, low noise, axial flow fan 10 embodying principles of the invention. Figs. 4 and 5 illustrate fan 10 in association with a one-piece shroud member 28. The fan and shroud member are fabricated by means of known processes using known materials. Fan 10 comprises a hub 12 that supports the fan for rotation about an axis 14, a plurality of identical blades 16 (seven in the exemplary fan) symmetrically arranged around hub 12, and a circular outer band 18. A number (fourteen in the exemplary fan) of stiffening ribs 23 are integrally formed on the interior of the hub as shown. Hub 12 comprises a circular end wall 20 and a circular side wall 22. At its center, end wall 20 is configured to provide accommodations for mounting of the fan to the shaft of an electric motor (hereinafter described). Blades 16 are arranged in a uniform symmetrical pattern around the hub. Each blade is skewed and has a root 16R joining with side wall 22 of hub 12 and a crest 16C that joins with band 18. Band 18 has a axial dimension equal to or just slightly greater than the axial dimension of each blade crest, and includes a radial flange 24 that extends outwardly at the axially forward edge of the band. Band 18, including flange 24, circumferentially surrounds the hub, such that, as viewed in Fig. 3, a projection of the band onto axis 14 along a direction that is perpendicular to axis 14 fully intercepts the hub. Figs. 4-5 illustrate fan 10 in an operative association with shroud member 28, which also provides mounting for an electric motor 30 that powers the fan. When installed in an automotive vehicle to form a cooling module, the fan and shroud function to draw air through a heat exchanger structure (not shown) that is disposed in front of them. Such heat exchanger can represent either or both of the engine radiator and the air conditioning condenser. The points of attachment of shroud member 28 to the vehicle are designated by the numerals 38 in Fig. 4, and they will be subsequently explained in greater detail. Shroud member 28 comprises a fan-surrounding portion 39 that is shaped for cooperation with band 18 and flange 24. The shroud also integrally comprises four members 40 that extend from the fan surrounding portion of the shroud to an integral mount 42 for electric motor 30. Motor 30 fastens to mount 42 at the three mounting locations designated by the reference numerals 46. The motor has a shaft (not shown) that points axially forwardly coaxial with axis 14, and the motor mounting accommodations in end wall 20 of hub 12 provide for the fan to be fitted onto and secured to the external end of the motor shaft so that the fan is rotated in unison with the rotation of the shaft when motor 30 is operated. Members 40 are arranged to have other than a straight radial shape. They extend from fan-surrounding portion 39 of the shroud, first axially away from portion 39, and then both axially rearwardly and radially inwardly to mount 42. The result of the constructions that have been described for both members 40 and blades 16 is that each blade is disposed sufficiently axially forwardly of each member along the radial extent of each blade that the passage of each blade past each member does not create unacceptably high turbulence that is detrimental to the desired objectives of high efficiency and low noise. The combination of the four members 40 as shown provides structural support for the motor mount, including the motor and fan. Fig. 6 depicts the association of fan 10 and shroud member 28 with a further shroud member 48. Shroud member 48 is a part of an automotive vehicle in which fan 10 and shroud member 28 are installed. Shroud member 48 comprises a wall portion 50 which is generally transverse to axis 14 and against which the forward edge of fan-surrounding portion 39 of shroud member 28 abuts. Fan surrounding portion 39 comprises a radially inner, axially extending wall portion 39a that merges axially forwardly with a radial wall portion 39b. Wall portion 39b extends radially outwardly from wall portion 39a to merge with a radially outer, axially extending wall portion 39c that extends axially forwardly from wall portion 39b. It is the forward edge of wall portion 39c that abuts wall portion 50 of shroud member 48. These constructions and cooperative associations create a fan-surrounding structure having a radially inwardly open groove defined by wall portions 39b, 39c, and 50. It is within this groove that flange 24 is received. When the fan rotates, a labyrinth air seal is created, and it is quite effective in both attenuating fan efficiency losses due to recirculation and contributing to fan noise reduction. The attachment of shroud member 28 to shroud member 48 is as follows. Shroud member 48 has an axial ledge extending axially rearwardly from wall portion 50. At a lower region that ledge contains a pair of slots. The lower two attachment points 38 of the shroud member 28 are in the form of tabs that drop into these slots. The upper two attachment points are apertured and align with respective apertures in an upper region of shroud member 48. Respective fasteners are passed through the respective aligned apertures to fasten the two shroud members together. As shown in Fig. 7 each blade 16 has the shape of an airfoil that can be defined geometrically by several parameters. Some of these parameters are graphically portrayed in Fig. 7 in relation to a representative airfoil cross section while remaining parameters are graphically portrayed in Figs. 8 and 9. Fig. 7 is representative of any of the cross sections A-I shown in Figure 1 as viewed radially downwardly from the circular band 18 and towards the axis 14. In Fig. 7, the leading and trailing edge tangent lines are referenced with respect to the circular arc camber line. Of course, the circular arc camber line is a circular arc to which the leading and trailing edge tangent lines are tangents.  is the camber angle between the leading edge and trailing edge tangent lines; ε is the stagger angle between a line parallel to the axis of rotation and the line C, which is the straight line distance between the beginning and the end of the circular arc camber line (chord length). In Fig. 8, which represents the conventional three-dimensional X, Y, and Z axes, the Y-offset is the distance in the Y-direction between the back of the hub 12 and the blade trailing edge (i.e. blade tail) of blade 16. Fig. 9 is a schematic drawing unrelated to the numerical values of Figures 10 or 11. In Fig. 9, which shows the skew angle , the middle line of the skewed blade profile is a line that passes through the middle of the chord length C for the cross section of the blade (Fig. 7) at each radial distance A-I (see Fig. 1). The skew angle is the angle between a fixed radial reference line through the centre line of the hub, and a radial line through the middle of the cord of the blade section in question (i.e. a point on the middle line of the skewed blade profile). For the specific example of fan that is illustrated in Figs. 1-3, Fig. 10 provides specific numerical values of these parameters. Fig. 11 presents the parameters of Fig. 10 on a non-dimensional or per unit (p.u.) basis. Thus, the radial distance R for each radial distance A to H is relative to the maximum radial distance I. The chord length C for each radial distance A-I is relative to the corresponding radial distance A-I. Finally, since all Y-offset values in both Figs. 10 and 11 are zero, this shows that the X and Z axes define the plane that is perpendicular to axis 14 and that contains the axially rearward face or back of the hub 12 and the blade trailing edges, as is also shown by Fig. 3. The airfoil-shaped cross section of a blade 16 Is taken at a number of radial distances R as measured radially from axis 14, which of course corresponds to axis Y of Fig. 8. These radial distances are designated by the letters A-I in Fig. 1. The Y offset is the axial offset distance of the trailing edge of the circular arc camber line measured from the back of hub 12. Positive values of the Y offset are forward while negative values are rearward. As shown by Fig. 3, the axially rearward face of hub 12, the axially rearward edge of band 18 and the tails of blades 16 occupy a common plane that is perpendicular to axis 14, i.e., the Y offset is 0 as is detailed in Figures 10 and 11. The numerical values of the parameters defining each blade of the example provide noise attenuation at higher frequency bands. The fan and shroud of the invention provide high efficiency, low noise performance with a low axial profile for the fan.

Claims: A one-piece high efficiency, low axial profile, low noise, axial flow fan (10) in combination with a surrounding shroud structure (28, 48), said fan (10) comprising a hub (12) that is rotatable about an axis (14), a plurality of blades (16) distributed circumferentially around said hub (12) and extending from said hub (12) to a circular band (18) that is concentric with and spaced radially outwardly from said hub (12), said shroud structure (28, 48) comprising a radially inwardly open circumferential groove, said band (18) containing a radially outwardly directed circumferential flange (24) that is disposed in said groove so that said groove and flange (24) cooperatively form a labyrinth air seal when the fan (10) rotates, and in which said groove has first (39b), second (50), and third (39c) walls, said first (39b) and second (50) walls each extending radially, said first (39b) and second (50) walls being spaced apart axially, and said third wall (39c) extending axially, and wherein said first (39b), second (50) and third (39c) walls are contained in more than one part (28, 48) of said shroud structure (28, 48), said first wall (39b) merging into said third wall (39c) and both walls (39b, 39c) being contained in one shroud part (28), said second wall (50) being contained in another shroud part (48) that is attached to said one shroud part (28) by means of fasteners, an end of said third wall (39c) abutting a face of said second wall (50) when said one shroud part (28) is attached to said other shroud part (48), said one shroud part (28) containing a mounting (42) for a motor (30) for driving said fan (10).

Inventors: GALLIVAN WILLAM P, JOSEPH ALEX S, PERIYATHAMBY HARAN K, GALLIVAN, WILLAM P., JOSEPH, ALEX S., PERIYATHAMBY, HARAN K.
Applicants: SIEMENS VDO AUTOMOTIVE INC, SIEMENS VDO AUTOMOTIVE INC.
Application year: 1993
Main classification: F04D29
IPC codes: F04D29