Patent Publication Number: US-6216778-B1

Title: Cooling system for an off-highway vehicle

Description:
FILED OF THE INVENTION 
     This invention relates generally to motor vehicles and, more particularly, to such vehicles having means to guide and control air for power plant cooling. 
     BACKGROUND OF THE INVENTION 
     Liquid-cooled internal combustion engines used to power motorized land vehicles, e.g., passenger autos, construction machines and the like, use an engine block of the type having a multi-passage cooling “jacket.” Coolant, usually a mix of water and ethylene glycol, is pumped through the jacket passages and absorbs heat resulting from engine operation. The heated coolant is delivered to a heat exchanger (often referred to as a “radiator”) where it is cooled as it gives up heat to the atmosphere. Such coolant is then recirculated back to the cooling jacket. 
     To function most efficiently and effectively, it is required that air flow across the heat exchanger at a relatively high volumetric rate. While passenger autos are equipped with radiator fans, it is not unusual to automatically disable the fan at highway speeds; the ram-urged air through the heat exchanger is sufficient to remove heat from the coolant. And it is also noteworthy that engine rotational speed and vehicle speed over-the-road are roughly proportional to one another; a slower-running vehicle usually requires less engine cooling. Exemplary cooling systems for over-the-road vehicles are disclosed in U.S. Pat. Nos. 4,969,421 (Haner et al.); 5,046,554 (Iwasaki et al.) and 5,495,909 (Charles). 
     On the other hand, cooling the engine of an off-highway vehicle presents a different set of technical problems. There are at least three reasons why this is true. One is that even if the heat exchanger is mounted at the front of the vehicle, there is little ram-urged air available to remove heat from the coolant flowing through the heat exchanger—most off-highway vehicles are stationary or move at low ground speed when working. Therefore, some sort of air-moving apparatus must be relied upon to provide a sufficient volumetric flow rate of cooling air. 
     Another is that when working, the engine is often set to run continuously at full throttle to make available high engine horsepower. It is not unusual to run the engine of an off-highway at 2300-2700 rpm. Implement and vehicle speeds are controlled by, e.g., hydraulic valves and torque-converter-type automatic transmissions. When running at high speed, engines and cooling fans of the types commonly used in off-highway vehicles produce a good deal of noise. While quieter fans with forwardly-turned blades are known, they have not been used on off-highway vehicles, insofar as is known. 
     Yet another reason relates to the first. Often, the engine is mounted at the rear of the vehicle behind the operator and forward vehicle motion results in no ram-urged cooling air whatsoever. 
     Exemplary cooling systems for off-highway vehicles are disclosed in U.S. Pat. Nos. 3,921,603 (Bentz et al.); 4,377,203 (Ejima) and 4,815,550 (Mather et al.). The system disclosed in the Mather et al. patent seemingly presents some problems. One is that such system uses, in one embodiment, a double-bladed fan and in any event, uses two opposed inlets. Any openings in the housing around a fan provide a path for fan noise to escape and be heard by the operator and bystanders. 
     Another is that the double-outlet exhaust is directed to either side of the vehicle. This could present a modest hazard for persons passing near the vehicle while it is in operation. 
     An improved off-highway-vehicle cooling system which addresses some of the problems and shortcomings of earlier work in this field would be an important technological advance. 
     OBJECTS OF THE INVENTION 
     It is an object of the invention to provide an off-highway-vehicle cooling system which addresses some of the problems and shortcomings of the prior art. 
     Another object of the invention is to provide such a cooling system which helps reduce system noise. 
     Another object of the invention is to provide such a cooling system which, in a specific embodiment, helps draw exhaust gas through the engine muffler, thereby reducing muffler back pressure. 
     Yet another object of the invention is to provide such a cooling system which, in a particular embodiment, helps cool the engine compartment. 
     Another object of the invention is to provide such a cooling system which, in yet other embodiments, provide thermostatic control of fan speed to help reduce system noise. How these and other objects are accomplished will become apparent from the following descriptions and from the drawings. 
     SUMMARY OF THE INVENTION 
     An off-highway-vehicle cooling system includes a heat exchanger for removing heat from, e.g., the engine coolant, hydraulic oil, automatic transmission fluid or the like. A fan mechanism flows air along a flow path through the heat exchanger. In the improvement, the fan mechanism is a centrifugal fan mechanism and includes a scroll-shaped housing and a fan in the housing. The fan has forward curved blades, thereby to reduce system noise. Such fan is preferred in the invention even though its efficiency is less than the efficiencies of fans with radial tips or backward curved blades. And such fan is preferred (for reasons relating to sound reduction) even though it requires about twice as much torque as other fan types to provide a given volumetric flow rate. 
     In other aspects of the invention, the fan rotates in a plane and has an upstream portion (i.e., upstream of the plane) toward the flow path and a downstream portion away from the flow path. The fan is in a housing having a shroud covering the downstream portion. Because most off-highway vehicles are stationary or move at very low ground speed when working, there is little if any ram-urged air contributing to cooling. In other words, the fan mechanism is substantially the sole means for flowing air along the flow path. 
     The housing includes a single inlet port which is adjacent to the upstream portion of the fan. In a specific embodiment, the inlet port is circular and concentric with the fan axis of rotation. The housing also includes a discharge portion from which heat-entraining air is discharged from the cooling system. 
     In other aspects of the invention, the fan has a diameter and an axially-measured depth, i.e., a “thickness” measured parallel to the axis of rotation. The ratio of the depth to the diameter is not in excess of about 0.4 and, most preferably, is not in excess of about 0.25. 
     In particular embodiments, the new cooling system has yet other features which reduce system noise. The engine heat exchanger has engine coolant flowing through it and the fan is powered by a hydraulic motor having a thermostatic controller coupled in speed-controlling relationship to such motor. The thermostatic controller controls the speed of the hydraulic motor as a function of the temperature of the engine coolant. 
     Assuming that the vehicle is equipped with some sort of hydraulic system, the cooling system may also include a second heat exchanger for removing heat from hydraulic oil. The thermostatic controller controls the speed of the hydraulic motor as a function of the temperature of the hydraulic oil. And such thermostatic controller may be arranged to control hydraulic motor speed as a function of either the hydraulic oil or the engine coolant, depending upon which liquid is exceeding a temperature limit. 
     And that is not all. The new cooling system has yet other beneficial features. In an off-highway vehicle, the cooling system is mounted adjacent to an engine compartment having the engine within it. The cooling-air flow path has an entry opening at the rear of such vehicle and is substantially free of ram-urged air. The fan mechanism preferably urges fan discharge air upwardly away from the vehicle. 
     In a particular embodiment, the fan housing has an upwardly pointing discharge mouth and the vehicle includes an air receiving structure, sometimes referred to as a diffuser, in air flow communication with such discharge mouth and vented to ambient air. The housing and the receiving structure are spaced apart somewhat and define a venturi aperture between them. Such aperture is in air flow communication with the engine compartment and draws cooling air through such compartment and across the engine. (In the exemplary skid-steer vehicle described below, the operator sits very close to the engine. Cooling air is drawn through the operator&#39;s compartment, through small openings in the otherwise-totally-enclosed engine compartment and across the engine.) 
     In yet another specific embodiment, the above-described venturi aperture is referred to as a first venturi aperture. The engine has a muffler and muffler pipe connected to it for flowing exhaust gas from the engine exhaust manifold. The air receiving structure has an exhaust stack connected to it and the exhaust stack and the muffler pipe are spaced from one another, thereby defining a second venturi aperture, Air from the discharge mouth of the fan housing flows through the second venturi aperture and along the exhaust stack, thereby drawing exhaust gas through the muffler pipe. This helps reduce muffler back pressure, aiding engine aspiration and exhaust. 
     In yet another embodiment of the new cooling system, the fan mechanism has a single inlet port but has first and second discharge portions in downstream flow relationship to the fan. Such first and second portions direct air along first and second discharge paths which are angled with respect to one another. That is, the discharge paths are coincident with respective fan radii which define an angle between them. The fan has first and second spaced-apart rims and the fan housing has a mid-plate positioned intermediate the rims. A first scroll component of the housing is around the first rim, is attached to the mid-plate and defines the first discharge path. Similarly, the housing has a second scroll component around the second rim. Such second component is attached to the mid-plate and defines the second discharge path. 
     As with the fan mechanism having a single discharge portion, the corresponding mechanism with two discharge portions is substantially free of ram-urged air. Preferably, the fan used in such mechanism has a ratio of fan depth to fan diameter is not in excess of about 0.4 and, most preferably, not in excess of about 0.25. And as with the single-discharge-portion fan mechanism, the fan may be powered by a hydraulic motor, the speed of which is controlled as a function of the temperature of the engine coolant, as a function of the temperature of the hydraulic oil or as a function of both. 
     Further details of the invention are set forth in the following detailed descriptions and in the drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a representative perspective view of an exemplary skid-steer front end loader equipped with the new cooling system 
     FIG. 2 is a sectional elevation view of the new cooling system shown in conjunction with a vehicle engine. 
     FIG. 3 is a perspective view of the new cooling system shown in conjunction with components of the vehicle. Parts are broken away. 
     FIG. 4 is a section view of the cooling system taken along the viewing plane  4 — 4  of FIG.  2 . Parts are broken away. 
     FIG. 5 is a perspective view of the fan mechanism used in the cooling system. 
     FIG. 6 is a perspective view of the fan mechanism of FIG. 5 shown in conjunction with an air receiving structure, i.e., a diffuser. Surfaces of parts are shown in dashed outline. 
     FIG. 7 is a perspective view of the fan used in the cooling system. 
     FIG. 8 is an elevation view of a belt drive mechanism. 
     FIG. 9 is a section view of portions of the cooling system shown in conjunction with engine components. Parts are broken away. 
     FIG. 10 is a perspective view of an alternate embodiment of a fan mechanism. 
     FIG. 11 is an exploded view of the fan mechanism of FIG.  10 . 
     FIG. 12 is a diagrammatic representation of a fan speed control arrangement. 
    
    
     DETAILED DESCRIPTIONS OF PREFERRED EMBODIMENTS 
     Referring first to FIGS. 1,  2  and  3 , an exemplary off-highway vehicle  10  is equipped with the new cooling system  11 . Such vehicle  10  is of a type known as a skid-steer front end loader. The vehicle  10  includes an engine compartment, represented by the dashed-line box  13 , adjacent to the operator&#39;s compartment  15 . A rear door  17  has slots  19  therethrough and such slots  19  are in air flow communication with the cooling system  11  described below. That is, the cooling air flow path  21 , represented by the same-numbered arrow in FIGS. 2 and 3, is in a forward direction through the door  17 . Because most off-highway vehicles (like the vehicle  10 ) are stationary or move at low ground speed when working, there is little or no ram-urged air in the flow path  21 . 
     (The term “skid-steer” refers to the fact that all of the vehicle wheels are maintained perpendicular to their respective axles. Steering is effected by driving the wheels on one side of the vehicle  10  at a rotational speed which is different than that at which the wheels on the other side of the vehicle  10  are driven. The vehicle  10  may thereby be steered but the wheels skid somewhat in the process.) 
     Referring additionally to FIGS. 4,  5 ,  6  and  7 , the cooling system  11  includes a first heat exchanger  23  for removing heat from the engine coolant flowing through it. There is also a second, hydraulic oil heat exchanger  25  which has hot hydraulic oil flowing therethrough and the air moving across such heat exchanger  25  removes heat from such oil. The fan mechanism  27  draws air in through the rear door  17  and flows such air along the flow path  21  through the heat exchangers  25  and  23 , in that order from upstream to downstream. The fan mechanism  27  is closely adjacent to the heat exchanger  23  and includes a scroll-shaped housing  29  in which is positioned a fan  31  having forward curved blades  33 . The housing  29  has an intake plate  35  with the air inlet port  37  through it and in a specific embodiment, the port  37  is circular and concentric with the rotational axis  39  of the fan  31 . The fan  31  rotates in a plane  41  and the direction of fan rotation is indicated by the arrow  43 . 
     Referring particularly to FIG. 7, the fan  31  has a diameter DI and an axially-measured depth DE (i.e., a “thickness”), measured perpendicular to and parallel to the axis of rotation  39 , respectively. The ratio of the depth DE to the diameter DI is not in excess of about 0.4 and, most preferably, is not in excess of about 0.25. In addition, the fan  31  has a dished hub  45  convex in an upstream direction. As a consequence, the hydraulic motor  47  used to drive the fan  31  is, as shown in FIG. 2, partially “nested” in the hub  45 , thereby reducing the overall length of the system  11 . 
     The fan  31  has first and second spaced-apart rims  49  and  51 , respectively with the rim  49  being at the upstream portion  53  of the fan  31 , i.e., upstream of the plane  41  and toward the flow path  21 . The rim  51  is at the fan downstream portion  55  which may be said to be away from the flow path  21 . A housing shroud  57  covers the downstream portion  55  so that the fan mechanism  27  has but a single inlet, namely, the inlet port  37  described above. As shown in FIG. 2, the hydraulic motor  47  protrudes through a hole in the shroud  57  but since the shroud  57  and motor  47  are closely fitted to one another, any small interstice between the motor  47  and shroud  57  is ineffective as an inlet port. 
     (While driving the fan  31  with a hydraulic motor  47  is preferred, it should be understood that the fan  31  may be driven by a belt drive mechanism  59  like that shown in FIG.  8 . Such mechanism  59  includes a fan pulley  61 , a pulley support mechanism  63 , a belt tensioning mechanism  65  and an engine crankshaft pulley  67 . A V-belt  69  takes power from the pulley  67  and drives the pulley  61 .) 
     Referring also to FIG. 9, the housing  29  also includes an upwardly directed discharge portion  71  terminated in a mouth  73  from which heat-entraining air is discharged from the cooling system  11  in a direction away from the vehicle  10 . An air receiving structure  75 , sometimes referred to as a diffuser, is mounted above and in air flow communication with such discharge mouth  73 . The structure  75  vents to ambient air. The mouth  73  and the receiving structure  75  are spaced apart somewhat and define a first venturi aperture  77  between them. Such aperture  77  is in air flow communication with the engine compartment  13  and as represented by the arrows  79 , the system  11  thereby draws cooling air through such compartment  13  and across the engine  81 . 
     The engine has a muffler  83  and muffler pipe  85  connected to it for flowing exhaust gas from the engine exhaust manifold. The air receiving structure  75  has an exhaust stack  87  connected to it and the exhaust stack  87  and the muffler pipe  85  are spaced from one another. Such stack-pipe spacing defines a second venturi aperture  89 . Air from the discharge mouth  73  of the fan housing  29  flows through the second venturi aperture  89  and along the exhaust stack  87 , thereby slightly reducing the pressure in the region  91 . As a result, exhaust gas is better able to flow from the muffler pipe  85 . To state it in other words, the foregoing configuration helps reduce muffler back pressure, aiding engine aspiration and exhaust. 
     Referring now to FIGS. 10 and 11, another embodiment of the new cooling system  11  has a fan mechanism  27   a  with the single inlet port  37  but with first and second discharge portions  93 ,  95 , respectively, in downstream flow relationship to the fan  31 . Such first and second portions  93 ,  95  direct air along first and second discharge paths  97 ,  99 , respectively, which are angled with respect to one another. 
     In this “two-discharge-path” configuration, the fan housing  29   a  has a mid-plate  101  positioned between the rims  49 ,  51 . A first scroll component  103  of the housing  29   a  is around the first rim  49 , is attached to the mid-plate  101  and defines the first discharge path  97 . Similarly, the housing  29   a  has a second scroll component  105  around the second rim  51 . Such second component  105  also is attached to the mid-plate  101  and defines the second discharge path  99 . 
     As with the fan mechanism  27  having a single discharge portion  71 , the corresponding mechanism  27   a  with two discharge portions  93 ,  95  is substantially free of ram-urged air. Preferably, the fan  31  used in such mechanism  27   a  has a ratio of fan depth DE to fan diameter DI as described above and is otherwise configured as described above. 
     The new cooling system  11  (whether having one discharge portion  71  or two such portions  93 ,  95 ) may be configured with yet other features which reduce system noise. Referring also to FIG. 12, a thermostatic fan speed controller  107  has one, two or three input signals to it. Such signals include engine speed, represented by the symbol  109 , engine coolant temperature, represented by the symbol  111 , and hydraulic oil temperature represented by the symbol  113 . The controller  107  is coupled to a hydraulic valve  115  which responds to an output signal from the controller  107  along the line  117 . The valve  115  controls the speed of the fan drive motor  47 . 
     The graphs  119 ,  121 ,  123  represent, respectively, fan speed plotted as a function of engine speed, of engine coolant temperature and as a function of hydraulic oil temperature. The controller  107  may be configured to control the speed of the hydraulic motor  47  as a function of engine speed, as a function of the temperature of the engine coolant and/or as a function of the temperature of the hydraulic oil. As an example represented by the graph  119 , the controller  107  may be configured to increase fan speed generally in proportion to increasing engine speed until some predetermined engine speed is reached (represented by the line  125 ), at which fan speed is held constant with further increases in engine speed. 
     As other examples, fan speed may be held at a low level (represented by the straight lines  127 ) until a predetermined engine coolant temperature or a predetermined hydraulic oil temperature is reached, as represented by the lines  129 ,  131 , respectively. Thereupon, fan speed is increased generally proportionally to further increases in engine coolant or hydraulic oil temperature. And the temperatures of both liquids can be monitored with that temperature which would result in a higher fan speed being used as the “priority” signal for the controller  107 . 
     Remarkably, it has been found that the new cooling system  11  effects a noise reduction of on the order of  15  db as compared to some conventional systems. The new system  11  is suited for a wide variety of applications including but not limited to applications in off-highway vehicles, e.g., construction equipment, and in agricultural machines, e.g., combines, tractors and the like. 
     As used herein, the phrase “off-highway-vehicle” includes vehicles configured for primary use on terrain other than roads. Off-highway-vehicles include skid-steer loaders, trenchers, loader backhoes, wheel loaders, crawler tractors, agricultural tractors and combines, as examples. The phrase “off-highway-vehicle” excludes passenger vehicles and the like which are configured primarily for use on hard-surface and, occasionally, gravel roads. 
     As used herein, the phrase “ram-urged air” means air urged, by virtue of the velocity of the vehicle over the ground, into the flow path of air used for cooling engine coolant and/or hydraulic oil. As an example, passenger vehicles and the like rely in large part upon ram-urged air for removing heat from the engine coolant heat exchanger, commonly known as the radiator. 
     While the principles of the invention have been shown and described in connection with preferred embodiments, it is to be understood clearly that such embodiments are by way of example and are not limiting.