Abstract:
A shroud for a vehicle engine cooling fan mounted to a generally rectangular radiator that has fixed air guide vanes in strategic areas of the shroud outside of the periphery of the fan blades to direct and channel streams of peripheral air flowing through the corners of the radiator into these areas inward and in a swirling pattern into the fan blades and more particularly in a generally smooth and circuitous path counter to the direction of rotation of the fan and directly onto the pumping surfaces of the fan blades. This effectively feeds additional air into the fan and preloads the blades so that air pumping efficiency is resultantly improved and more air is moved through the radiator for improved heat exchange.

Description:
BACKGROUND OF THE INVENTION 
     Cross Reference to a Related Application 
     This patent application is a continuation-in-part of a previously filed and copending application by the same inventors, entitled &#34;Shroud for an Engine Cooling Fan&#34;; filed Aug. 12, 1998 assigned Ser. No. 09/132,884. 
    
    
     FIELD OF THE INVENTION 
     This invention generally relates to cooling of an internal combustion engine of a vehicle and more particularly to a new and improved fan shroud for an engine adapted to overlie a generally rectangular shaped radiator and featuring internal vanes arranged in strategic corner areas in the shroud that direct peripheral air passing through the corners of the radiator directly to the fan blades so that the blades are preloaded so as to enhance fan efficiency in pumping air through the radiator therefore improving the overall heat exchange for the engine. 
     SUMMARY OF THE INVENTION 
     Vehicles typically include an internal combustion engine, a radiator for cooling the engine, and an engine driven fan for causing air to flow through the radiator. Under idle and lower speed operation, the ability of the radiator to cool the engine is determined, in part, by the capacity of the cooling fan in producing an air flow through the radiator, often referred to as the fan efficiency or capacity. Accordingly, vehicle manufacturers are always looking for simple and inexpensive ways in which to increase engine cooling fan efficiency. 
     Most engine cooling fans are encircled by a shroud member which are designed to enhance the efficiency of the cooling fan as well as to prevent the insertion of foreign objects, such as debris, or tools, into the blades of a moving fan. Accordingly, it would be desirable to maximize the efficiency of the shroud by providing vanes which define air channels that increase air flow through the radiator and to the engine cooling fan. The subject invention provides a fan shroud intended for use with an engine driven fan which has blades that rotate in a predetermined direction. The fan shroud includes a generally flat deflecting portion having a surface spaced from and overlying the generally rectangular configured radiator. The deflecting portion is integrally connected to a tubular collar or ejector portion defining an aperture sized and positioned to receive the fan. Also, a reinforced edge is disposed along the outer perimeter of the deflecting portion. A plurality of vanes, each having a generally semi-circular shape, extend between the reinforced edge and the aperture of the collar portion. These vanes direct streams of air from the radiator, particularly corner portions thereof, to the fan receiving aperture portion and in a direction opposite to the predetermined rotation of the fan blades. In the preferred embodiment of the present invention, the vanes are arranged in substantial parallelism to form rows therebetween from the reinforced edge and the collar&#39;s aperture so as to define separate air channels between adjacent vanes. 
     The present invention overcomes several shortcomings of prior art engine fan shrouds. Foremost, the present invention increases both engine cooling performance and air conditioning performance. Further, the subject shroud is strong, durable, and easily serviced. 
     Prior to the present invention, various fan shroud arrangements have been provided for automobile engine cooling fans. U.S. Pat. No. 5,224,447 dated issued Jul. 6, 1993 for &#34;An Air Guide For A Fan Impeller Of An Internal Combustion Engine&#34; discloses a cowl ring disposed around an engine cooling fan having a plurality of outflow openings and associated external air guide vanes for improving the radial outflow of the fan to reduce pressure losses in the outflow in a radial direction. U.S. Pat. No. 5,410,992 issued May 2, 1995 for &#34;Cooling System For Automotive Engine&#34; discloses a variable geometry fan duct having a fixed barrel segment for an axial flow cooling fan and a movable barrel segment rotatably mounted on the fixed segment movable to a position in which the fan blades are completely encircled to provide the variable geometry. U.S. Pat. No. 4,329,946 issued May 18, 1982 for &#34;Shroud Arrangement For Engine Cooling Fan&#34; discloses fixed and rotatable shrouds for an associated engine cooling fan to improve the efficiency of the fan. 
     While the prior art disclosures provide different shroud structures for engine cooling fans to improve fan performance, they do not meet higher standards for improved air intake into the fan and particularly an improvement in air flow associated with the corner areas of the fan shroud and the associated rectangular radiator. Nor do they actively direct air to the pumping surfaces of the engine cooling fan blades for increasing fan pumping efficiency. More particularly the prior art does not disclose or suggest the strategic arrangement of vanes located internally of the fan shroud and particularly in the corner areas thereof for controlling and directing the air flowing through the corner regions of the radiator and creating a swirling air flow pattern directed to pass air toward the pumping surfaces of the fan blades so that the blades are preloaded and therefore more efficient to pump larger quantities of air in a more effective operational mode of air flowing through the radiator. Thus, the present invention increases the cooling performance of the radiator type cooling system for an internal combustion engine and even increases the air conditioning performance of an associated air conditioning condenser by increasing air flow therethrough at all engine and vehicle speeds. With this invention fan noises are decreased and the shroud is structurally stronger while accessibility and serviceability of the fan is maintained. 
     In a preferred embodiment of this invention, a multi-bladed axial or mixed flow fan is encircled by a collar or curved ejector portion of a fan shroud which extends rearwardly from an open box section or flow diverting portion thereof. The flow diverting portion is supported in overlying relationship to a generally rectangular radiator. Air flows through the radiator when the fan is operational, particularly when the engine is idling or under lower speeds of the vehicle. Under these conditions, an improvement in heat exchange of the radiator cooling system is very desirable. In regions radially outward of the generally circular fan, streams of peripheral air are feed to the fan, i.e., air outward of the fan&#39;s diameter passes through the comers of the radiator and radially inward to the fan. In the subject arrangement, the peripheral air flow is channeled by a plurality of curved vanes formed in the flow diverting portion of the shroud and directed inwardly in a swirling pattern in a rotational direction counter to the fan&#39;s normal rotational direction. The inwardly swirling flow of this air desirably preloads the fan blades by impinging on the working side of the fan blades so that the fan&#39;s air pumping and heat exchange efficiencies are improved. Moreover, the internal vanes provide improved structural strength to the shroud. The subject vane arrangement further reduces noise levels originating from fan operation and improves the efficiency of the air conditioning system particularly where the air conditioning condenser is located adjacent to the radiator and the shrouded fan pulls greater quantities of outside air over the total surface of the condenser. 
     Another feature and object of this invention is to provide a new and improved fan shroud, adapted to accommodate a rotatable multi-bladed engine cooling fan, having internal vanes in strategic areas such as the corners of the shroud that direct inwardly swirling streams of air into the rotating fan and in a rotational direction counter to the direction of fan rotation to preload the pumping surfaces of the fan blades to improve fan output and operating efficiency. 
     These and other features of the invention will become more apparent from the following detailed description and drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a vehicle with portions of its front end broken away, such as the radiator, to expose an engine fan and a fan shroud in accordance with the present invention; and 
     FIG. 2 is a pictorial view of an engine driven cooling fan, and associated fan shroud, a conventionally rectangularly shaped radiator for circulating engine coolant therethrough, and a vehicle air conditioning condenser; and 
     FIG. 3 is a elevational view partially in section of an engine fan, an associated fan shroud, a radiator, and also showing a portion of the vehicle engine which rotates the fan; and 
     FIG. 4 is a sectional view taken generally along section line 4 - 4 of FIG. 3; and 
     FIG. 5 is an enlarged view similar to FIG. 3 of a portion of the fan, the shroud, and the radiator; and 
     FIG. 6 is a diagram illustrating an operational improvement of the subject fan shroud. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Turning now in greater detail to the drawing, FIG. 1 shows a perspective view of a vehicle 10 with portions of a front end of the vehicle 10 broken away to expose an engine fan shroud 12 in accordance with the present invention. The shroud 12 is designed to shield an engine driven fan 14 commonly referred to as an engine cooling fan. The engine cooling fan 14 includes blades 16 which rotate in a predetermined direction. As illustrated in FIG. 1, the blades 16 of the engine cooling fan 14 rotate in counter-clockwise rotation, generally indicated by the dashed arrow. Rotation of the fan 14 draws air through an engine radiator which has been removed in FIG. 1 to better illustrate the shroud 12 and fan 14. The radiator is shown in latter views to be described hereinafter. 
     FIGS. 2 and 3 show fan shroud 12 as including integral attachment tabs 13 for receiving threaded fasteners 15 (see FIG. 5) which operatively secure the shroud to bracket structure 17 associated with an engine coolant circulating radiator 18. Radiator 18 has a conventional rectangular configuration through which air flows as indicated by arrowed lines A in FIG. 2. Alternatively, the bracket structure or other shroud support could be attached to some other structure in the engine compartment 20 of the associated vehicle. The fan shroud 12 is molded or otherwise formed from an engineering plastics or other suitable material. Preferably, the fan shroud 12 has a box-like main body portion 24 best seen in FIG. 2. The main body portion 24 has an opened front face which is bordered by and defined by a generally rectilinear wall portion 26. The shroud is supported via wall portion 26 as it includes the tab portions 13 previously discussed. The shroud 12 also includes a generally cylindrically configured collar portion 28 which extends axially from an interior surface of a back wall 30 of the main body portion 24. Collar portion 28 is adapted to encircle the fan 14 and its blades 16. This relationship with the fan serves to allow the collar portion to act as an air ejector or enabler for air flow from the interior of the main body portion 24 and thus from the radiator 18. 
     FIGS. 2 and 4 best show the interior regions of the body portion 24 of the fan shroud 12. Shroud 12 includes the wall portions 30 which extend radially inward from the outer wall portion or frame 26 to the collar or ejector portion 28. Specifically, the wall portions 30 extend from corner portions of the rectangularly configured main body portion 24 to the central collar 28. The wall portions 30 connect with the collar at an inner or leading edge portion 34 which forms a transition between the interior of the main body portion and the collar portion. The wall portions 30 supports a plurality of curved air directing vanes 36 which extend away from the interior surface. In a preferred embodiment, the vanes are integrally formed with the main body portion 24 but the vanes could be otherwise secured to the shroud. 
     The vanes 36 are located radially outward and generally upstream of collar portion 28 and spaced from one another to form air flow passages or channels 38 therebetween. Since the vanes are substantially located at the corners of the main body portion 24 of the shroud and radiator 18, these passages 38 permit air exiting peripheral or outer corner portions of the radiator to pass away from the radiator&#39;s downstream discharge surface and then flow radially inward as best illustrated in FIG. 5 by the arrowed line 40. As seen in FIG. 4, the vanes 36 also cooperatively impart an inwardly directed and rotational swirling pattern or stream of air labeled as path P. The rotation of the swirling air along paths P is counter to the fan&#39;s direction of rotation which is labeled R in FIG. 4. The path P is operated upon by the blades 16 of the fan 14 as air enters and passes through the fan shroud&#39;s ejector portion 28. 
     As best seen in FIG. 3, the fan assembly 14 includes a central hub portion 42 which is operatively attached to an internal combustion engine 44 rearwardly of the radiator 18. A conventional fan assembly 14 usually includes a viscous fluid clutch arrangement 46 which has an input portion attached to the engine shaft and driven by a &#34;V&#34; belt and pulley drive system 48. The viscous clutch unit 46 has a downstream or output side with a mounting shoulder 50 on which the fan&#39;s hub 42 is secured by fasteners 52. The fan assembly 14 has a plurality of radially extending blades 16 that are arcuately spaced from one another and extend radially outwardly from the central hub portion 42. The fan blades 16 are preferably identical and each section of the blades has a cord length defining the angle of attack with respect to the straight or head on flow of air which has directly passed through the radiator and into the plane of fan rotation. This air flow also engages the swirling flow of air from the vanes 36 and taking air paths P. 
     As previously explained, the vanes 36 are separated from one another to form air flow channels or passages 38. The vanes 36 are angled or turned in a desired direction to direct streams of air flow into contact with the fan blading 16. More particularly and as illustrated in FIG. 4, the flow of air from vanes 36 is turned in a direction P against the counter-clockwise rotation R of fan assembly 14. This flow of air against the fan blades 16 advantageously preloads the downstream or suction side of the fan blades so that fan operation is made more effective in pumping air. With the improved pumping action, the fan effectively improves the flow of air through the radiator therefore improving heat transfer efficiency of the engine cooling system. 
     In addition to an increase of the flow of air through radiator 18, the flow of air through an associated air conditioning condenser 54 is also improved. The condenser 54 is diagrammatically shown in FIG. 2 and is operatively mounted immediately in front of the radiator 18. Typically, condensers are rectangular in shape like a conventional radiator and therefore have comers which are outward of a circular fan 40 just like a rectangular radiator. The arrowed lines 56 illustrates flow of air through the condenser. 
     The graph shown in FIG. 6 represents engine cooling system performance with and without the improved fan shroud while the engine is idling which represents a difficult engine cooling condition. The plot A represents by the broken line the operational characteristics of the vehicle&#39;s cooling system with a conventional fan shroud without the corner vane structure of the subject fan shroud. As shown by plot A, the radiator coolant temperature rapidly begins to increase at time t-1 to a higher temperature level r-1. In many vehicles this increase in temperature initiates deactivation of the vehicle&#39;s air conditioning system by deactivating the compressor clutch. In plot A the air conditioner system of the vehicle is deactivated at about time t-2. 
     Plot B represents by the unbroken line the operation of the vehicle&#39;s cooling system with the subject improved fan shroud with the vane structure identified heretofore. With the improved shroud, the coolant temperature gradually increases from time t-1 until temperature level r-2 is reached. Note that temperature r-2 is cooler than temperature r-1. Also note that the air conditioning deactivation point is delayed from time t-2 to time t-3. The improved shroud accordingly provides greatly improved temperature management and improved air conditioner performance particularly while the vehicle is idling or moving slowly such as in stop and go traffic. The improved performance is manifested by area I between the two plots A and B. 
     While the invention has been shown and described by the preferred embodiment, it should be clear to those skilled in the art that various changes and modifications may be made thereto without departing from the scope of the following claims.