Patent Description:
Heavy duty trucks spend long periods of time driving at steady states and relatively high vehicle speeds. An example of this is typical interstate driving on a freeway. When such a vehicle is being driven at relatively high speeds, motion of the vehicle is generally enough to cool the internal combustion (e.g., diesel) engine. As the vehicle travels forward, air is forced through one or more heat exchangers, cooling the engine. This air flow from vehicle motion is often referred to as ram air. Under conditions providing sufficient ram air, a fan does not need to be driven for engine cooling purposes. A typical truck or similar vehicle will employ a clutching mechanism that selectively disconnects the fan from the engine drivetrain in order to minimize parasitic power losses, which is typically referred to as the "off' condition. A clutch and associated fan can be placed in the "off' condition when sufficient ram air cooling is available.

However, the fan can still have an influence on engine cooling even in the "off" condition due to added restriction of flow from the fan. Fan solidity can be defined by the ratio of closed area of the fan's blades to the total annular area between circles defined by an outer diameter of the fan and a hub diameter. In other words, as used herein with respect to substantially axial flow fans, "solidity" is an areal measure of how much of the annular flow area measured perpendicular to an axis of rotation is occupied by fan blades and how much is open-this calculation of solidity differs from one based on chord divided by circumferential blade spacing. A high solidity fan has relatively little opening between the fan blades, if any, and a low solidity fan has relatively large openings. The greater the solidity of the fan, the more likely it is to restrict ram air flow when placed in the air stream in the un-driven state or "off" condition. Higher restriction reduces flow and the ability of the ram air flow to cool the engine, which can increase the need for the fan to be turned on occasionally to cool the engine when the fan might otherwise be off.

Running the fan can require a substantial amount of power, especially at higher fan speeds. Operation of the fan (i.e., an "on" condition) is required to cool the engine under worst case scenarios, which can include conditions where ambient temperature is high, engine load is high, and/or vehicle speed (and therefore ram air speed) is low. An example would be a fully loaded truck ascending a hill in a hot desert. Under conditions where ram air is unavailable or insufficient, the fan must develop enough pressure to draw the required cooling air flow through the vehicle's heat exchanger.

Fan solidity and the ability of the fan to build fluid pressure are related. In the same way a higher solidity fan creates more ram air resistance, in general, it also has the ability to provide more pressure, and thus more cooling flow. In this sense, while optimization of fan characteristics in isolation may suggest relatively high solidity fan designs, in order to build pressure more efficiently, such isolated fan design considerations fail to take into account the unique operating characteristics in which vehicle fans operate, because ram air cooling can avoid the need for fan operation under some circumstances. In this regard, fan design considerations used for cooling tower, air conditioner, and similar applications do not account for the unique range of conditions faced by vehicular engine cooling fans.

The current state of the art low solidity vehicular fan is typically a <NUM>-bladed fan. For example, the BorgWarner PS6 fan (available from BorgWarner Inc. , Auburn Hills, MI, USA) shown in <FIG> has been on the market for several years. The PS6 fan is molded at an outside diameter of <NUM> and the hub diameter is <NUM>. The area of the <NUM> circle is <NUM>,<NUM><NUM> and the area of the circle defined by the hub area is <NUM>,<NUM><NUM>. The area of the annulus between the hub and the fan OD is <NUM>,<NUM> - <NUM>,<NUM> = <NUM>,<NUM><NUM>. The projected area of the blades only is <NUM>,<NUM><NUM>. Therefore, the solidity of the blades to the annular flow area of the BorgWarner PS6 fan is <NUM>,<NUM> / <NUM>,<NUM> = <NUM> or <NUM>%. The BorgWarner PS6 fan therefore has a relatively high solidity, even if other comparable vehicular fans have even higher solidities. Other examples of known vehicular fans are disclosed in <CIT> and <CIT> and European Patent <CIT> (also published as <CIT>).

It is desired to provide a fan with an alternative configuration.

<CIT> relates to a fan that includes a hub rotatable about an axis, an annular band concentric with the hub and spaced radially outward from the hub, and fan blades distributed circumferentially around the hub and extending radially and axially from the hub to the annular band. Each blade has specific parameters defined by the non-dimensional radius r from the rotational axis, the stagger angle of the blade at the radial distance r, the camber angle of the blade at the radial distance r, the solidity C/S, with C being chord length and S being the circumferential blade spacing at the radial distance r, the non-dimensional chord length of the blade at the radial distance r, the non-dimensional thickness of the blade at radius r, the skew angle of the blade at the radial distance r calculated at <NUM>% chord where the skew at the hub radius is defined as zero skew, and the slope of the dihedral measured at r.

<CIT> relates to a high efficiency, low solidity, low weight, axial flow fan that includes a hub, fan blades and a circular band. The hub rotates about a rotational axis when torque is applied from a shaft rotatably driven by a power source. The circular band is concentric with the hub and is spaced radially outward from the hub. The blades are distributed circumferentially around the hub and extend radially from the hub to the circular band. The blades are configured to produce an airflow when rotated about the rotational axis. Each blade has a chord length distribution which varies along the length of the blade, such that the chord length has a local minimum value at a predetermined location between the ends of the blade. The chord length of the blades as a function of blade radius from the rotational axis has an inflection point at a predetermined distance from the hub less than the length of the blade.

In one aspect, an axial flow fan for use with a vehicle cooling system includes a hub defining an axis of rotation, and a plurality of blades supported on the hub, the plurality of blades including at least five blades. Each blade includes a leading edge, a trailing edge opposite the leading edge, a pressure side extending between the leading edge and the trailing edge, a suction side opposite the pressure side, a tip, and a root opposite the tip along a blade length. A solidity of the axial flow fan, measured as a percentage of an annular flow area between an outer diameter of the hub and an outer diameter of the tips of the plurality of blades projected onto a plane perpendicular to the axis of rotation that is occupied by the plurality of blades, is less than <NUM>%, less than <NUM>%, or less than <NUM>%. A maximum total turning angle along the blade length of each of the plurality of blades is greater than or equal to <NUM>°. The total turning angle varies along the blade length of each of the plurality of blades. In some further aspects, a minimum total turning angle along the blade length of each of the plurality of blades can be greater than or equal to <NUM>°, or greater than or equal to <NUM>°.

In another aspect, a vehicle includes an internal combustion engine, a heat exchanger for cooling the internal combustion engine, an axial flow fan according to claim <NUM>, and a clutch configured to selectively rotate the axial flow fan. The heat exchanger is exposed or is at least exposable to ram air when the vehicle is moving in at least one direction. The axial flow fan is positioned proximate to the heat exchanger, and rotation of the axial flow fan moves cooling air relative to the heat exchanger.

In yet another aspect, an axial flow fan includes, in addition to the features of claim <NUM>, exactly five blades integrally and monolithically formed with at least a portion of the hub. Each of the five blades is free-tipped and includes a hub ramp on the pressure side. A solidity of the axial flow fan, measured as a percentage of an annular flow area between an outer diameter of the hub and an outer diameter of the tips of the five blades projected onto a plane perpendicular to the axis of rotation that is occupied by the five blades, is less than <NUM>% (or is approximately <NUM>%). A maximum total turning angle along the blade length of each of the five blades approaches <NUM>° or is approximately <NUM>°.

The present summary is provided only by way of example, and not limitation. Other aspects of the present invention will be appreciated in view of the entirety of the present disclosure, including the entire text, claims and accompanying figures.

While the above-identified figures set forth one or more embodiments of the present invention, other embodiments are also contemplated, as noted in the discussion. In all cases, this disclosure presents the invention by way of representation and not limitation. It should be understood that numerous other modifications and embodiments can be devised by those skilled in the art, provided they fall within the scope of claim <NUM>. The figures may not be drawn to scale, and applications and embodiments of the present invention may include features, steps and/or components not specifically shown in the drawings.

In vehicular cooling applications, it has been discovered that the expected effects of ram air flows can alter design considerations for engine cooling fans. There is a substantial desire to minimize the ram air flow resistance caused by the fan in order to allow free air flow (i.e., ram air) to cool the engine for a greater amount of time, saving power and fuel that would be require to power the fan in an "on" condition. However, because ram air will be unavailable or insufficient under some vehicular operating conditions, fan operation will still be required, and it is therefore desired to provide a relatively low solidity fan that still provides sufficient static pressure. For instance, a static pressure that is the same or greater than that of a higher solidity fan at most operating conditions, especially at higher speed and airflow conditions, is beneficial in some applications and embodiments. Embodiments of the present invention further accomplish those flow resistance and static pressure benefits without adding depth to the blades of the fan. The blade depth is the width or thickness of the fan when measured parallel to an axis of rotation, that is, the blade depth is the axial chord or pitch width. Thus, the present disclosure provides a relatively low solidity fan, such as a five-blade fan, with a solidity less than <NUM>% (e.g., less than approximately <NUM>%, or less than approximately <NUM>%). Moreover, the fan of the present invention provides a unique blade shape with the ability to develop relatively high pressures in conjunction with only a small number of blades (e.g., five blades, or less than five blades) and a relatively low solidity (e.g., less than <NUM>%, less than <NUM>%, or less than <NUM>%). A fan according to the present invention can be an axial flow fan, which generates a fluid flow in generally the axial direction. The fan can include free-tipped (e.g., unshrouded) blades, though in alternate embodiments one or more blades can be connected to a shroud ring or partial shroud segment. Numerous features and benefits of the present invention will be recognized by those of ordinary skill in the art in view of the entirety of the present disclosure, including the accompanying figures.

In one embodiment, shown in <FIG>, a fan <NUM> has a hub <NUM> and five blades <NUM>. The blades <NUM> can each have the same shape, and are each supported on and extend outward from the hub <NUM>. The fan <NUM> can be configured to rotate clockwise about an axis of rotation A when viewed from the front, as designated by the arrow R. Moreover, the fan <NUM> of the illustrated embodiment is configured as an axial flow fan, that is, the fan <NUM> generates fluid flow (e.g., air flow) substantially parallel to the axis A when rotated. Each blade <NUM> has a pressure side <NUM>-<NUM>, a suction side <NUM>-<NUM>, a leading edge (LE) <NUM>-<NUM>, a trailing edge (TE) <NUM>-<NUM>, and a tip <NUM>-<NUM>. The LE <NUM>-<NUM> is located generally opposite the TE <NUM>-<NUM>, and the pressure side <NUM>-<NUM> is located generally opposite the suction side <NUM>-<NUM>. The pressure and suction sides <NUM>-<NUM> and <NUM>-<NUM> each extend between the LE <NUM>-<NUM> and the TE <NUM>-<NUM>. A blade length is measured radially along the blades <NUM>, with the tip <NUM>-<NUM> located at <NUM>% of a total blade length. A root <NUM>-<NUM> of each blade <NUM> is located opposite the tip <NUM>-<NUM> at <NUM>% of the total blade length. A thickness of the blades <NUM> is measured between the pressure and suction sides <NUM>-<NUM> and <NUM>-<NUM>. A chord of each blade <NUM> is measured between the LE <NUM>-<NUM> and the TE <NUM>-<NUM>. In the illustrated embodiment, the blades <NUM> are free-tipped. The fan <NUM> can further have a hub ramp <NUM>-<NUM> on a pressure side <NUM>-<NUM> of each blade <NUM> that extends upward (in both the radial and circumferential directions) from the hub <NUM>. The hub ramps <NUM>-<NUM> can be generally planar, though in alternate embodiments the shape of the hub ramps <NUM>-<NUM> can vary as desired for particular applications. In the illustrated embodiment, each hub ramp <NUM>-<NUM> extends to the LE <NUM>-<NUM> but is spaced from the TE <NUM>-<NUM>. The hub ramps <NUM>-<NUM> can produce some non-axial fluid flow during operation, though the fan <NUM> can still be considered to generate generally axial fluid flow. A portion of each blade <NUM> at the LE <NUM>-<NUM> can protrude axially forward of a front face <NUM>-<NUM> of the hub <NUM> and a portion of each blade <NUM> can protrude axially rearward of a rear edge <NUM>-<NUM> of the hub <NUM> at the TE <NUM>-<NUM>. Moreover, a portion of each blade <NUM> at the LE <NUM>-<NUM> can extend radially inward from an outer diameter of the hub <NUM>, forming a kind of scoop for fluid at the front face <NUM>-<NUM> of the hub <NUM>. The blades <NUM> and at least a portion of the hub <NUM> can be made of a moldable polymer material (e.g., nylon, with or without reinforcement fibers, fillers, etc.) and can be integrally and monolithically formed together. The hub <NUM> can further have a metallic insert <NUM>-<NUM>, which can have an open center, to facilitate attaching the fan <NUM> to a desired mounting location. The front face <NUM>-<NUM> of the hub <NUM> can be substantially planar.

An annular flow area of the fan <NUM> is established between a circle at an outer diameter (OD) of the fan <NUM> at the blade tips <NUM>-<NUM> and a circle an OD of the hub <NUM> projected onto a plane perpendicular to the axis of rotation A. Solidity of the fan <NUM> is measured based on the percentage of the annular flow area (as projected onto a plane perpendicular to the axis of rotation A) occupied by the blades <NUM>, which indicates how much of the annular flow area perpendicular to an axis of rotation A is occupied by all of the blades <NUM> and how much is open (that is, having lines of sight parallel to the axis of rotation A being unobstructed by the blades <NUM>). In the illustrated embodiment, the hub ramps <NUM>-<NUM> do not extend beyond the areas of the blades <NUM> as projected onto the plane perpendicular to the axis of rotation A, and therefore have no effect on the solidity measurement. But in alternate embodiments, hub ramps <NUM>-<NUM>, flow modification features, or other structures that reside in the annular flow area of the fan <NUM> and that limit how much of that annular flow area is open are counted toward the solidity measurement.

In one embodiment, the OD of the five-blade fan <NUM> at the blade tips <NUM>-<NUM> can be <NUM> and the OD of the hub <NUM> can be <NUM>, though larger or smaller values of the outer or hub diameters can be larger or smaller in further embodiments, such as by scaling the indicated dimensions to larger or smaller values. A total area of an <NUM> OD circle in this embodiment is <NUM>,<NUM><NUM> and an area of a <NUM> hub circle is <NUM>,<NUM><NUM>. An area of an annulus between the hub <NUM> and the fan OD at the tips <NUM>-<NUM> in this embodiment is <NUM>,<NUM> - <NUM>,<NUM> = <NUM>,<NUM><NUM>. The projected area of the five blades <NUM> is <NUM>,<NUM><NUM>, in the illustrated embodiment. Thus, the solidity within the annulus of the illustrated embodiment is <NUM>,<NUM>/<NUM>,<NUM> = <NUM> or <NUM>%.

In the illustrated embodiment (see, e.g., <FIG>), the blades <NUM> each have a relatively high camber, meaning a relatively high degree of curvature between the leading and trailing edges <NUM>-<NUM> and <NUM>-<NUM> measured as a total turning angle. The total turning angle is calculated as the difference between flow angles at the LE <NUM>-<NUM> and the TE <NUM>-<NUM>. The flow angles are measured by projecting tangents to the pressure and suctions sides <NUM>-<NUM> and <NUM>-<NUM> of the blade <NUM> (i.e., tangents at pressure and suction side surfaces where those surfaces adjoin or transition to a radiused leading or trailing edge) to an intersection point, and bisecting the angle formed by the intersecting projected lines, then measuring the angle of the bisecting line with respect to the axial direction. For example, in some embodiments, the blades <NUM> can have a total turning angle measured as the difference between flow angles at the LE <NUM>-<NUM> and the TE <NUM>-<NUM> with a maximum over the entire blade length that approaches <NUM>°, the maximum total turning angle being, according to the invention, greater than or equal to <NUM>°, optionally greater than or equal to <NUM>°, or greater than or equal to <NUM>°. Moreover, in some embodiments, a minimum total turning angle over the entire blade length can be greater than or equal to <NUM>% or greater than or equal to <NUM>%. The total turning angle can vary along the blade length.

<FIG> is a graph illustrating the leading and trailing edge flow angles and the total turning angle over the blade length (in dimensionless units) in one embodiment. Table <NUM> summarizes values of flow angles and total turning angles as shown in <FIG>, where L is the blade length location, L_blade is the total blade length, L/L_blade is a fraction of the blade length at the blade length location L (this value multiplied by <NUM> is the percentage of blade length L from the root), Beta1 is the leading edge flow angle, Beta2 is the trailing edge flow angle, and ΔBeta is the total flow angle (representative of blade camber). As shown in <FIG> and Table <NUM>, the total turning angle can decrease from the root (or at least from <NUM>% of the blade length) to approximately <NUM>% of the blade length, then increase to approximately <NUM>% of the blade length, and then decrease to the tip (<NUM>% blade length). The rate of change of the total turning angle can decrease staring at approximately <NUM>% of the blade length. Additionally, the flow and Beta1 and Beta <NUM> can each decrease from the root (or at least from <NUM>% of the blade length) to approximately <NUM>% of the blade length, then increase further away from the root. The flow angle Beta1 at the LE can be substantially constant from approximately <NUM>% to <NUM>% of the blade length, and the flow angle Beta2 at the TE can decrease slightly from approximately <NUM>% to <NUM>% of the blade length. The flow angle Beta1 at the LE can be significantly greater than the flow angle Beta2 at the TE from the root (or at least from <NUM>% of the blade length) to approximately <NUM>% to <NUM>% of the blade length and then Beta1 and Beta2 can have similar values from that point to <NUM>% of the blade length. It should be noted that the values given in Table <NUM> and <FIG> are provided by way of example only. Embodiments of the present invention can be scaled as desired for particular applications. Furthermore, in some embodiments, tip trimming of the blade tips <NUM>-<NUM> can be performed to shorten the blades <NUM> and omit tip portions described herein.

Furthermore, in some embodiments (see, e.g., <FIG>), the blades <NUM> can each have a locally increased thickness at a mid-chord location that extends from the root <NUM>-<NUM> (or at least from <NUM>% of the blade length) to approximately midway along the blade length (i.e., from <NUM>% to approximately <NUM>-<NUM>% of the total blade length). The thickness can gradually decrease from the root <NUM>-<NUM> (or at least from <NUM>% of the blade length) toward the tip <NUM>-<NUM>, such that the local thickness increase (or bulge) gradually reduces to a nominal blade thickness approximately midway along the blade length, following a hyperbolic curve in blade thickness (that is, following a mathematical hyperbolic function). Put another way, the thickness at the mid-chord location can be substantially greater than (e.g., at least twice) the thickness of either the LE <NUM>-<NUM> or the TE <NUM>-<NUM> at the root <NUM>-<NUM> (or at least from <NUM>% of the blade length), and at <NUM>% of the blade length the mid-chord thickness is the comparable to (e.g., the same or less than) the LE and/or TE thickness. This local thickness increase can help to control stresses.

<FIG> is a graph of blade thickness versus blade length location (L/L_blade) at LE mid-chord (MID) and TE locations in one embodiment. Table <NUM> summarizes dimensionless values of blade thickness as shown in <FIG>. As shown in the illustrated embodiment, the mid-chord thickness decreases rapidly from a maximum at the root (or at least from <NUM>% of the blade length), then decreases slowly to <NUM>% of the blade length, forming a generally L-shaped or "hockey stick" plot on the illustrated graph. It should be noted that the values given in Table <NUM> and <FIG> are provided by way of example only. Embodiments of the present invention can be scaled as desired for particular applications. Furthermore, in some embodiments, tip trimming of the blade tips <NUM>-<NUM> can be performed to shorten the blades <NUM> and omit tip portions described herein.

In some embodiments (see, e.g., <FIG> and <FIG>), the blades <NUM> can each have a pocket shape, with a radially outward straight section 24O and a radially inward curved section <NUM>, in which the curved section 24I provides dihedral curvature, that is, curvature measured in a direction perpendicular to chord, which can be concave at the pressure side <NUM>-<NUM> of each blade <NUM>. The straight section 24O can have essentially no dihedral curvature, at least at the TE <NUM>-<NUM> (and/or the LE <NUM>-<NUM>).

In some embodiments (see, e.g., <FIG> and <FIG>), the blades <NUM> can each have swept leading and trailing edges <NUM>-<NUM> and <NUM>-<NUM>. Measured geometrically in the tangential direction, the leading and trailing edges <NUM>-<NUM> and <NUM>-<NUM> can each have rearward then forward sweep from the root <NUM>-<NUM> (or at least from <NUM>% of the blade length) to the tip <NUM>-<NUM>. For example, the LE <NUM>-<NUM> can have rearward sweep from <NUM>% (or at least <NUM>%) to approximately <NUM>% of the blade length and forward sweep to the tip <NUM>-<NUM> (<NUM>% blade length), and the TE <NUM>-<NUM> can have rearward sweep from <NUM>% (or at least <NUM>%) to approximately <NUM>% of the blade length and forward sweep to the tip <NUM>-<NUM> (<NUM>% blade length).

<FIG> illustrates tangential sweep (or lean) measurements for the leading edge (Y_LE) and the trailing edge (Y_TE), in dimensionless units from a radial reference line S tangent to the LE <NUM>-<NUM> at <NUM>% blade length. Reference lines on the pressure side <NUM>-<NUM> of the blade <NUM> are shown in <FIG> for illustrative purposes only. <FIG> is a graph of plots of the leading and trailing edge tangential profiles versus blade length, following the measurement convention shown in <FIG>. Table <NUM> summarizes dimensionless values of edge locations and tangential chord length as shown in <FIG>. It should be noted that the values given in Table <NUM> and <FIG> are provided by way of example only. Embodiments of the present invention can be scaled as desired for particular applications. Furthermore, in some embodiments, tip trimming of the blade tips <NUM>-<NUM> can be performed to shorten the blades <NUM> and omit tip portions described herein.

In some embodiments (see, e.g., <FIG> and <FIG>), the blades <NUM> can each have a dimple that bulges outward (e.g., substantially convexly) from the suction side <NUM>-<NUM>. Put another way, the blades <NUM> can have a profile that forms an S-shape in a dihedral direction, at least at a mid-chord region.

<FIG> shows a reference grid on the suction side <NUM>-<NUM> used to establish intersection points where axial location measurements are taken relative to a reference line RL (see <FIG> illustrates an example axial measurement of a mean camber line (MCL), indicative of blade dihedral characteristics, taken relative to the projected reference line RL extending radially at a fixed axial location (e.g., coincident with a portion of the TE <NUM>-<NUM> that is axially linear, that is, appearing linear when viewed perpendicular to the axis A). <FIG> is a graph of distances Dc (in dimensionless units) of the mean camber line from the reference line RL (at the fixed axial location) versus blade length at chordally-spaced locations c, where c indicates a percentage chord position from the LE <NUM>-<NUM> to the TE <NUM>-<NUM> at the root (<NUM>% blade length). Four chordally-spaced positions (<NUM>%, <NUM>%, <NUM>% and <NUM>% chord) are plotted versus blade length as D<NUM> (or LE), D<NUM>, D<NUM> and D<NUM> in <FIG>, following the layout of the grid and reference line RL shown in <FIG> and <FIG>. Table <NUM> summarizes dimensionless values of edge locations and tangential chord length as shown in FIG. <NUM> plus at <NUM>% chord (D<NUM> or the TE). It should be noted that the values given in Table <NUM> and <FIG> and <FIG> are provided by way of example only. Embodiments of the present invention can be scaled as desired for particular applications. Furthermore, in some embodiments, tip trimming of the blade tips <NUM>-<NUM> can be performed to shorten the blades <NUM> and omit tip portions described herein.

Additionally, some embodiments of the fan <NUM> can have blades <NUM> with relatively high stagger angles, measured as the angle between a ling parallel to the axis of rotation and a projected line that intersects the LE <NUM>-<NUM> and the TE <NUM>-<NUM> (see, e.g., <FIG>). Moreover, in some embodiments (see, e.g., <FIG>), the blades <NUM> can have relatively little or no twist along the blade length between the root <NUM>-<NUM> and the tip <NUM>-<NUM>.

<FIG> is a schematic representation of a vehicle <NUM> having an internal combustion engine <NUM>, a heat exchanger (H/X) <NUM> for cooling the engine, a clutch <NUM> powered by the engine, and a fan <NUM> connected to an output of the clutch. The heat exchanger <NUM>, the clutch <NUM> and the fan <NUM> can be considered part of an engine cooling system. In one embodiment, the heat exchanger <NUM> is an air-to-liquid heat exchanger such as a radiator or the like. The fan <NUM> can be configured like the fan <NUM> shown and described with respect to <FIG>, and can be positioned proximate to the heat exchanger <NUM>, such as in between the heat exchanger <NUM> and the engine <NUM>. The clutch <NUM> can be engaged in an "on" condition to selectively rotate the fan <NUM> to generate a cooling air flow that passes through (or around or otherwise relative to) the heat exchanger <NUM> and toward the engine <NUM>. Such a cooling airflow can be drawn into an engine compartment of the vehicle <NUM> by the fan <NUM>, though a portion of the cooling airflow may be produced or augmented by movement of the vehicle <NUM> under certain operating conditions. When the clutch <NUM> and the fan <NUM> are in an "off' condition and the vehicle <NUM> is moving, ram air can flow through (or around or otherwise relative to) the heat exchanger <NUM>, past or through the fan <NUM>, and toward the engine <NUM>. In this respect, the cooling air flow can be entirely ram air when the clutch <NUM> and the fan <NUM> are in an "off' condition. However, as discussed above, the solidity of the fan <NUM> impacts the flow resistance to cooling air flow through the heat exchanger <NUM> and toward the engine <NUM>.

The present five-blade fan is capable of delivering more flow and pressure at most operating conditions, while having approximately half the solidity of typical six-blade vehicular engine cooling fans. For instance, the plot in the graph of <FIG> shows static pressure (in inches of water gauge) versus airflow (in cubic feet per minute (CFM)/<NUM>), illustrating increased static pressure (indicated by an arrow) for a fan of the present disclosure over the prior art <NUM>-blade fan of <FIG> at most airflow conditions, namely at airflow conditions of approximately <NUM>,<NUM> CFM (<NUM><NUM>/minute) and above. Although not specifically illustrated in the graph of <FIG>, the lower solidity of the tested embodiment of the present fan compared to the prior art <NUM>-blade fan (<NUM>% versus <NUM>%) also means that ram air cooling efficiency is greater than the prior art during "off" conditions. Thus, the presently disclosed fan provided improved performance over most operating conditions, including during "off" conditions and during relatively high rotation speed "on" conditions, resulting in improved overall performance across typical on-highway vehicle operational conditions.

Numerous other features and benefits of the present invention will be recognized by those of ordinary skill in the art in view of the entirety of the present disclosure, including the accompanying figures.

An axial flow fan for use with a vehicle cooling system is defined by claim <NUM>.

The axial flow fan of the preceding paragraph can optionally include, additionally, any one or more of the following features, configurations and/or additional components:.

A vehicle can include an internal combustion engine, a heat exchanger for cooling the internal combustion engine, an axial flow fan according to claim <NUM>, and a clutch for selectively rotating the axial flow fan. The heat exchanger can be exposed or be at least exposable to ram air when the vehicle is moving in at least one direction. The axial flow fan can be positioned proximate to the heat exchanger. Rotation of the axial flow fan can move cooling air relative to the heat exchanger.

An axial flow fan includes, in addition to the features of claim <NUM>, exactly five blades integrally and monolithically formed with at least a portion of the hub. Each of the five blades can be free-tipped and can include a hub ramp on the pressure side. A solidity of the axial flow fan, measured as a percentage of an annular flow area between an outer diameter of the hub and an outer diameter of the tips of the five blades projected onto a plane perpendicular to the axis of rotation that is occupied by the five blades, can be less than <NUM>%.

Any relative terms or terms of degree used herein, such as "substantially", "essentially", "generally", "approximately" and the like, should be interpreted in accordance with and subject to any applicable definitions or limits expressly stated herein. In all instances, any relative terms or terms of degree used herein should be interpreted to broadly encompass any relevant disclosed embodiments as well as such ranges or variations as would be understood by a person of ordinary skill in the art in view of the entirety of the present disclosure, such as to encompass ordinary manufacturing tolerance variations, incidental alignment variations, transient alignment or shape variations induced by thermal, rotational or vibrational operational conditions, and the like. Moreover, any relative terms or terms of degree used herein should be interpreted to encompass a range that expressly includes the designated quality, characteristic, parameter or value, without variation, as if no qualifying relative term or term of degree were utilized in the given disclosure or recitation.

Claim 1:
An axial flow fan (<NUM>; <NUM>) for use with a vehicle cooling system, the axial flow fan comprising:
a hub (<NUM>) defining an axis of rotation (A); and
a plurality of blades (<NUM>) supported on the hub, the plurality of blades including at least five blades, each blade comprising:
a leading edge (<NUM>-<NUM>);
a trailing edge (<NUM>-<NUM>) opposite the leading edge;
a pressure side (<NUM>-<NUM>) extending between the leading edge and the trailing edge;
a suction side (<NUM>-<NUM>) opposite the pressure side;
a tip (<NUM>-<NUM>); and
a root (<NUM>-<NUM>) opposite the tip along a blade length,
wherein a solidity of the axial flow fan, measured as a percentage of an annular flow area between an outer diameter of the hub and an outer diameter of the tips of the plurality of blades projected onto a plane perpendicular to the axis of rotation that is occupied by the plurality of blades, is less than <NUM>%, and wherein
a total turning angle varies along the blade length of each of the plurality of blades, characterized in that
a maximum total turning angle along the blade length of each of the plurality of blades is greater than or equal to <NUM>°.