High efficiency, low noise, axial flow fan

Abstract: Band (18) of fan (10) is disposed axially rearwardly of hub (12). Hub is attached to shaft of electric motor (30) which is disposed in mount of shroud (28). Shroud (28) has members (40) extruding from mount to fan-surrounding portion (39) which forms air seal with fan band (18). Members (40) have straight inner portions (40A), curved intermediate portions (40C), and straight outer portions (40B).

Description: Field of the Invention 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. Background and Summary of the Invention From previously published patent documents, it is known to construct a one-piece fan that has a hub, a plurality of forwardly skewed blades that extend radially outwardly from the hub to a circular band that surrounds the hub see e.g. WO-A-90/15253. It is further known to dispose a shroud in surrounding relation to said band so that said 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. Accordingly, there is a need for such fans that can be packaged within increasingly stricter dimensional constraints, and the present invention relates to the satisfaction of this need through novel and unique constructions for both the fan and the shroud. 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. Brief Description of the Drawings Fig. 1 is a front axial end view of a fan embodying principles of the invention. Fig. 2 is a rear axial end view of the fan of Fig. 1. Fig. 2A-2A is a cross sectional view on an enlarged scale in the direction of arrows 2A-2A in Fig. 2. Fig. 3 is a cross sectional view, portions being broken away, taken in the direction of arrows 3-3 in Fig. 1. Fig. 4 is a front axial view of a shroud, excluding the fan, embodying principles of the invention. Fig. 5 is a cross sectional view taken in the direction of arrows 5-5 in Fig. 4, and including portions of the fan. Fig. 6 is a cross sectional view taken in the direction of arrows 6-6 in Fig. 4, and including portions of the fan. Fig. 7 is a cross sectional view, on an enlarged scale, through a portion of a blade for the purpose of presenting certain parameters that are used to define the blade of the example. Fig. 8 is a chart presenting specific values for the defining parameters identified in Fig. 7 for the exemplary blade. Description of the Preferred Embodiment Figs. 1, 2, 2A, and 3 illustrate an exemplary one-piece high efficiency, low noise, axial flow fan 10 embodying principles of the invention. Fan 10 comprises a hub 12 that supports the fan for rotation about an axis 14, a plurality of identical blades 16 (ten in the exemplary fan) symmetrically arranged around hub 12, and a circular outer band 18. A number (twenty 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 forwardly skewed and has a root 16R joining with sidewall 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, and includes a radial flange 24 that extends outwardly at the axially forward edge of the band. As can be best seen in Fig. 3, band 18 is spaced axially of hub 12 such that the band does not circumferentially surround the hub, but rather a projection of the band onto axis 14 along a direction that is perpendicular to axis 14 does not intercept any portion of the hub. As also seen in Fig. 3, the band is disposed rearwardly of the hub by a distance 26. As further seen in Fig. 3, each blade 16 has a radially inner portion that extends axially forwardly and radially outwardly from the hub and a radially outer portion that extends axially rearwardly and radially outwardly from the radially inner portion to join with band 18. Figs. 5-6 illustrate fan 10 in an operative association with a one-piece shroud 28, an electric motor 30 and a heat exchanger 32 to form a cooling module 34. Further details of shroud 28 also appear in Fig. 4. The cooling module is disposed on an automotive vehicle heat exchanger 32 connected in a liquid cooling circuit of a system, such as the engine cooling system, or the vehicle air conditioning system. Thus, heat exchanger 32 can represent either or both of the engine radiator and the air conditioning condenser. The illustrative automotive vehicle has a structural beam 36 that provides for the mounting of cooling module 34 on the vehicle. The points of attachment are designated by the numerals 38 in Fig. 4. Shroud 28 comprises a fan-surrounding portion 39 that is shaped for cooperation with band 18 and flange 24 in a conventional manner to form an air seal between the outer perimeter of the fan and the shroud as the fan rotates about axis 14 within the surrounding shroud. The shroud also integrally comprises six members 40 that extend radially inwardly 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 48 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 shaft 48 so that the fan is rotated in unison with the rotation of shaft 48 when motor 30 is operated. From consideration of Figs. 4,5, and 6 it can be seen that beam 36 has a central void space 50 that provides clearance for the axially rearward portion of the electric motor housing, but the extent to which the motor can be disposed rearwardly in the cooling module is limited by the presence of heater exchanger 32. Because a dimensional constraint is imposed on the available axial distance between beam 36 and another portion of the surrounding structure of the vehicle around an outer circumferential marginal portion of the fan and shroud, heretofore known high efficiency, low noise, axial flow fans and associated shrouds cannot be used. The present invention provides a solution to this problem through unique constructions for the fan and shroud. Members 40 are arranged to have other than a straight radial shape. Thus, as can be seen particular in Fig. 6 each member 40 has a radially inner portion 40A that extends substantially straight away from mount 42, a radially outer portion 40B that extends substantially straight away from shroud 28 and is non-coaxial with the radially inner portion, and a radially intermediate portion 40C that extends between the radially inner and outer portions. A radially inner and outer portions of each of four of the members are arranged to be substantially radial to axis 14 as viewed in Fig. 4. These four members are at the one, five, seven, and eleven o'clock positions. The remaining two members 40 are arranged to be substantially non-radial to axis 14 as viewed along that axis. 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 six members 40 as shown provides structural support for the motor mount, including the motor and fan. The non-radial arrangement of the two members 40 at roughly the two-three and nine-ten o'clock positions allows the location of their axial offsetting portions 40C to be placed frontally of triangular-shaped voids 45 in beam 36 so that potential interference with the beam is avoided. As shown in Fig. 7 each blade has the shape of an airfoil that can be defined geometrically by several parameters. These parameters are graphically portrayed in Fig. 7 in relation to a representative airfoil cross section. For the specific example of fan that is illustrated in Figs. 1-3, Fig. 8 provides numerical values of these parameters. The airfoil-shaped cross section of a blade is taken at a number of radial distances R as measured radially from axis 14. These radial distances are designated by the letters A-I in both Figs. 1 and 8. The Y offset is the axial offset distance of the center of the circular arc camber line measured from the back of the hub. Positive values of the Y offset are forward while negative values are rearward. The numerical values of the parameters defining each blade of the example provide a noticeable noise attenuation at a particular rotational speed of the fan, namely the normal fan operating speed in the case of a single speed motor 30. The shape of the blades also provides stiffness in the Y direction which is beneficial in minimizing noise and enabling the fan to move air efficiently from the forward high pressure region to the rearward low pressure region which exists across the fan when it is being rotated by motor 30. The fan and shroud of the invention provide high efficiency, low noise performance despite the dimensional constraint that has been imposed and despite the partial obstruction that is presented by the presence of beam 36. The numerical values presented in Fig. 8 for the exemplary fan can be converted into non-dimensional form as an aid to employment of the inventive principles in designing other exemplary fans.

Claims: A one-piece high efficiency, low noise, axial flow fan (10) comprising a hub (12) that is rotatable about an axis (14), a plurality of forwardly skewed, airfoil-shaped fan blades (16) distributed circumferentially around said hub and extending both radially and axially away from said hub, each blade (16) having a root joining with said hub, a circular band (18) that is concentric with and spaced radially outwardly from said hub, each blade having a crest joining with said band, and characterized by said band (18) being spaced axially of said hub (12) such that said band does not circumferentially surround said hub, but rather a projection of said band onto said axis (14) along a direction that is perpendicular to said axis does not intercept any portion of said hub (12). A fan as set forth in claim 1 in which said band (18) is disposed axially rearwardly of said hub (12). A fan as set forth in claim 2 in which a radially inner portion of each blade (16) extends axially forwardly and radially outwardly from said hub (12) and a radially outer portion of each blade (16) extends axially rearwardly and radially outwardly from said radially inner portion. A fan as set forth in claim 2 including a shroud (28) which is disposed in circumferentially surrounding radially outwardly spaced relation to said band (18) and within which said fan (10) is relatively rotatable about said axis (14), said shroud (28) including a plurality of members (40) which are circumferentially spaced apart about said axis (14) and project radially inwardly of said shroud (28) to an electric motor mount (42) for mounting an electric motor (30) that rotates said fan (10), each of said members (40) comprising a radially inner portion (40A) that extends substantially straight away from said electric motor mount, a radially outer portion (40B) that extends substantially straight away from said shroud (28) and is non-coaxial with its member's radially inner portion (40A) such that it is axially rearwardly offset relative to its member's radially inner portion (40A), and a radially intermediate portion (40C) that extends between said radially inner and radially outer portions. A fan as set forth in claim 2 including a shroud (28) in which said radially inner and radially outer portions (40A, 40B) of each member (40) are arranged to be substantially radial to said axis (14) as viewed in the direction of said axis. A fan as set forth in claim 4 including a shroud (28) further including additional members (40) that are like the first-mentioned members except that said radially inner and radially outer portions (40A, 40B) each of said additional members are arranged to be substantially non-radial to said axis (14) as viewed in the direction of said axis. A fan as set forth in claim 1 in which each of said blades (16) is constructed substantially in accordance with the parameters defined in Fig. 8. A shroud (28) which in use is disposed in circumferentially surrounding radially outwardly spaced relation to the radially outer band (18) of the one-piece high efficiency, low noise, axial flow fan according to any of claims 1-7, within which said fan (10) is relatively rotatable about an axis (14), said shroud (28) comprising a plurality of members (40) which are circumferentially spaced apart about said axis (14) and project radially inwardly of said shroud (28) to an electric motor mount (42) for mounting an electric motor (30) for rotating the fan, each of said members (40) comprising a radially inner portion (40A) that extends substantially straight away from said electric motor mount (42), a radially outer portion (40B) that extends substantially straight away from said shroud (28) and is non-coaxial with its member's radially inner portion (40A) such that it is axially rearwardly offset relative to its member's radially inner portion (40A), and a radially intermediate portion (40C) that extends between said radially inner and radially outer portions. A shroud (28) as set forth in claim 8 in which said radially inner and radially outer portions (40A, 40B) of each member (40) are arranged to be substantially radial to said axis as viewed in the direction of said axis (14). A shroud (28) as set forth in claim 9 further including additional members (40) that are like the first-mentioned members except that said radially inner and radially outer portions (40A, 40B) each of said additional members are arranged to be substantially non-radial to said axis as viewed in the direction of said axis (14).

Inventors: GALLIVAN WILLIAM P, PERIYATHAMBY HARAN K, GALLIVAN, WILLIAM P., PERIYATHAMBY, HARAN K.
Applicants: SIEMENS ELECTRIC LTD, SIEMENS ELECTRIC LIMITED
Application year: 1992
Main classification: F04D29
IPC codes: F04D19, F04D29