Abstract:
A cooling system for a work vehicle is disclosed that includes first and second heat exchangers disposed one above the other to create two discrete flow paths. The upper heat exchanger is an engine water cooler and the lower heat exchanger may be an intercooler, an oil cooler or a refrigerant condenser. The lower heat exchanger is disposed forward of the upper heat exchanger. Additional heat exchangers may be positioned in front of the first and second heat exchangers to provide additional cooling. The first and second heat exchanger may be cross-flow heat exchangers conducting the fluid to be cooled laterally through the core of the heat exchanger.

Description:
This divisional application claims priority under 35 U.S.C. §120 from U.S. patent application Ser. No. 10/845,967 filed on May 14, 2004 now abandoned by William H. Adamson et al. with the same title, the full disclosure of which is hereby incorporated by reference. 
    
    
     FIELD OF THE INVENTION 
     The invention relates generally to agricultural vehicles. More particularly, it relates to agricultural tractors. Even more particularly, it relates to cooling systems for such vehicles. 
     BACKGROUND OF THE INVENTION 
     Agricultural tractors are used to tow ground working or harvesting implements through agricultural fields. Tractors closely follow crop rows or other lines of demarcation in a field in order to properly space plants during planting and to avoid crushing growing plants during harvesting. 
     It is important that the operator be able to see around the vehicle, including in front of the vehicle with little or no restriction. To follow crop rows closely, the operator&#39;s good vision in front of the vehicle is essential. 
     Modern tractors are increasing in size resulting in larger more vision-obstructing hoods. As engine horsepower increases and the load capacity of the vehicle increases, tractors have increased proportionately in size, resulting in higher operator compartments, longer and higher hoods, and increasingly obstructed operator vision directly in front of him, where he most needs to see. 
     Newer hood arrangements are needed that lower the profile of the hood permitting the operator to see objects close to the front of the tractor. To provide improved vision, the newly designed vehicles must keep existing low hood lines at the front of the hood as the rest of the vehicle increases in size. 
     Lowering is possible only if the internal components are reconfigured to make room for the lowered hood. The traditional configurations of engine, heat exchangers and chassis have to be modified to relocate or reposition under-hood components in such a way that the front of the hood can be lowered. 
     The most important components to be reconfigured are those that are right at the front of the vehicle, particularly the heat exchangers. The heat exchangers are located at the very front of the vehicle underneath the leading edge of the hood adjacent the front grille. Their size is generally proportional to the output of the engine, and thus as the engine increases in power, the heat exchangers increase in size. Since they are located right at the front of the engine and are oriented vertically, they are the primary structures responsible for blocking the operator&#39;s view down the hood. 
     What is needed, therefore, is a tractor cooling system using an improved heat exchanger configuration that will permit the forward end of the tractor&#39;s hood to be lowered and the operator&#39;s vision improved. It is an object of this invention to provide such an improved heat exchanger configuration and cooling system. 
     SUMMARY OF THE INVENTION 
     In accordance with a first aspect of the invention, a cooling system for an agricultural tractor includes a front frame, an intercooler mounted on the frame, an engine water cooler mounted above the intercooler in a parallel air flow path. 
     The cooling system may include an inlet air conduit and an outlet air conduit coupled to the intercooler and extending vertically on either side of and in front of the engine water cooler. The intercooler may be a cross-flow cooler. The engine water cooler may be a cross-flow cooler. The engine water cooler may be recessed behind the intercooler. 
     In accordance with a second aspect of the invention, a cooling system for an agricultural tractor includes a first heat exchanger disposed in a first position adjacent to a frame of the tractor forward of a tractor engine and behind a cooling air inlet and defining a first cooling air path, and a second heat exchanger located behind and above the first heat exchanger and defining a cooling air path separate from the first cooling air path. 
     The first heat exchanger may be a cross-flow heat exchanger. The second heat exchanger may be a cross-flow heat exchanger. The cores of the first and second heat exchangers may be disposed both parallel to and adjacent to each other. The first and second heat exchangers may substantially fill the inlet of a fan shroud. The first and second heat exchangers may extend substantially the entire width of an under-hood space. 
     In accordance with a third aspect of the invention, a cooling system for a work vehicle having an elongated narrow hood disposed immediately in front of an operator&#39;s compartment, the hood having a front grille with cooling air vents, a left sidewall and a right sidewall, is provided, the system including, an engine water cooler disposed under the hood and extending from the first sidewall to the second sidewall; and a first heat exchanger disposed beneath and generally parallel to the engine water cooler. 
     The system may include a second heat exchanger disposed in front of the engine water cooler and the first heat exchanger to heat air entering both the engine water cooler and the first heat exchanger. The first and second heat exchangers may be selected from the set consisting of an oil cooler, a refrigerant condenser, a fuel cooler, and an intercooler. The engine water cooler and the first heat exchanger may not overlap. At least one of the engine water cooler and the first heat exchanger may be arranged for cross-flow cooling. The first heat exchanger may be selected from the group consisting of an oil cooler and an intercooler. The first heat exchanger may be a cross-flow intercooler and the engine water cooler is cross-flow. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of an agricultural tractor in accordance with the present invention. 
         FIG. 2  is a cross-sectional front view of the tractor of  FIG. 1  taken at section line  2 - 2  in  FIG. 1 . 
         FIG. 3  is a front perspective view of the tractor of the foregoing FIGURES with the hood removed and showing the arrangement of heat exchangers and heat exchanger conduits. 
         FIG. 4  is a cross-sectional side view of the tractor of the foregoing FIGURES taken at section line  4 - 4  in  FIG. 2  through the middle of the heat exchangers and showing the stacked arrangement of the heat exchangers. 
         FIG. 5  is a cross-sectional front view of the engine water cooler and the intercooler taken at section line  5 - 5  in  FIG. 4 . 
         FIG. 6  is a perspective view of the components illustrated in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     “Heat exchanger”, as that term is used herein, means a device for cooling a stream of fluid, the exchanger having a planar core made of a plurality of parallel tubes that are configured to carry the fluid being cooled. The tubes are covered with cooling fins, rods coils or other surface area enhancement structures and gaps between adjacent tubes are provided to permit atmospheric air to be conducted through the planar core in a direction generally perpendicular to the plane of the core. 
     “Cross-flow”, as that term is used herein, refers to the direction of flow through the core of a heat exchanger. In a cross-flow heat exchanger, the fluid being cooled travels laterally, from side to side, generally parallel to the ground, through the core of the heat exchanger. 
     Referring to  FIG. 1 , a tractor  100  has a chassis or frame  102  that is supported by rear drive wheels  104  and front wheels  106  (which may or may not be drive wheels). 
     The chassis supports an operator&#39;s compartment  108  and narrow elongated narrow hood  110  that covers an engine (not shown) and several heat exchangers (not shown) that are disposed in front of the engine and behind a front grille  112  having cooling air vents  114 . 
     Heat exchangers are configured to cool a fluid medium by transmitting it through a core of many small tubes that has cooling fins extending from the tubes to enhance heat transfer to the surrounding air. A fan or other device is provided to draw cooling air across the cooling fins and through the core to extract heat from the tubes, and hence from the fluid medium passing through the core to be cooled. 
     Once cooled, the fluid medium is returned to the engine or other structure, such structures including the engine block (for engine water coolers, which are also known as radiators), the intake manifold (for charge air coolers, which are also known as “intercoolers”), the transmission (for transmission fluid coolers), refrigerant reservoirs (for refrigeration condensers) or fuel tanks (for fuel coolers). 
     The fluid medium may be a gas (e.g. in an intercooler), it may be a liquid (e.g. in an engine water cooler or radiator, a fuel cooler, transmission fluid cooler or engine oil cooler), or it may be both a gas and a liquid (e.g. in a refrigerant condenser, in which the fluid enters as a gas and leaves as a liquid). 
     Whatever the form of heat exchanger discussed herein, whether called a condenser, a radiator or a cooler, all have a few characteristics in common: the cooling fluid, i.e. the fluid that extracts the heat, is atmospheric air, the structure of the core is planar, and the cooling air passes through the core generally perpendicular to the plane of the core. 
     In  FIG. 2 , four heat exchangers are illustrated: an engine water cooler or “radiator”  116 , a charge air cooler or “intercooler”  118 , a refrigerant condenser and fuel cooler  122 , and a transmission fluid or engine oil cooler  120 . 
     The front-most heat exchanger is a combined refrigerant condenser and fuel cooler  122 . Like all the pictured heat exchangers, it extends both vertically and laterally (side-to-side). It is different from the other heat exchangers in that it is made to simultaneously cool two separate and distinct fluids at the same time: refrigerant and tractor fuel. It has two discrete tubes for carrying two different fluids through a single core that is made of both tubes coiled together. One tube is for refrigerant and has a refrigerant inlet and a refrigerant outlet at its ends. The other tube is for tractor fuel and has a fuel inlet and fuel outlet at its ends. The two tubes define two fluid flow paths that are never commingled, but are always separate. Thus item  122  is simultaneously a refrigerant condenser and a tractor fuel cooler as well, and whatever air cools the condenser cools the fuel cooler as well. 
     A vector drawn perpendicular to the cores of all four heat exchangers extends generally fore-and-aft, parallel to the straight-ahead direction of travel of the vehicle. 
     The next heat exchanger is the engine and transmission oil cooler  120 . This heat exchanger is directly behind and larger than condenser  122 . The two heat exchangers  120 , 122  are arranged so that all air passing through the condenser  122  also passes through oil cooler  120 . However, not all air passing through oil cooler  120  passes through condenser  122 . 
     The next heat exchangers are the charge air cooler or intercooler  118  and the engine water cooler or radiator  116 . These heat exchangers are in an over-and-under arrangement as seen in  FIG. 1 : Engine water cooler  116  is on top, and intercooler  118  is on the bottom. These two heat exchangers are disposed in parallel with regard to the flow of cooling air. Cooling air passing though the engine water cooler  116  bypasses the intercooler  118 , and cooling air passing though the intercooler  118  bypasses the engine water cooler  116 . 
     The two heat exchangers  116 , 118  therefore define two separate, distinct and parallel flow paths for cooling air. This parallel arrangement is of particular advantage in the present application. The intercooler  118  and engine water cooler  116  both have high heating loads. “Heat load” refers to the amount of heat each must transfer from the hot fluid medium to the cooler atmospheric air per unit time. Of the four heat exchangers shown in the FIGURES, the engine water cooler  116  and the intercooler  118  have the highest heat loads, loads that are greater than both the oil cooler  120  and the condenser  122 . Heat transfer from a heat exchanger to the atmosphere is a function of the temperature of the air to which heat is dumped, and the area of the heat exchanger core. The cooler the air passing through the heat exchanger, the more heat the air can absorb and the smaller the heat exchanger core necessary to transfer that amount of heat. By arranging the engine water cooler  116  and the intercooler  118  in parallel, the air each gets is only heated by the condenser  122  and the oil cooler  120 . The cooling air entering the engine air cooler and the intercooler is still relatively cool. Each heat exchanger can therefore be made much smaller since the inlet air is cool. Since the heat exchangers can be made smaller, they can also be stacked one on top of the other in the over-and-under arrangement shown in  FIG. 2 . In an alternative design, if air entering the engine water cooler were already preheated by having previously passed through the intercooler, it would be so hot that a much larger engine water cooler would be required. 
     The intercooler  118  has an inlet conduit  124  and an outlet conduit  126  that are disposed on either side of the engine compartment adjacent to the sidewalls  128 ,  130  of the hood. These conduits conduct hot air from the engine&#39;s turbocharger (not shown) through the intercooler, and then back to the intake manifold (not shown) of the engine. 
     Conduit  124  extends vertically from the left side of the intercooler  118  vertically along the left side of engine water cooler  116 , adjacent to left hood sidewall  128 , and then over the top of engine water cooler  116  and back to the engine (not shown). Conduit  126  extends vertically from the right side of the intercooler  118  vertically along the right side of engine water cooler  116 , adjacent to the right hood sidewall  130 , and then over the top of engine water cooler  116  and back to the engine (not shown). Conduits  124  and  126  are coupled to and between the turbocharger and the intake manifold (not shown). 
     It might appear that conduits  124 ,  126  block air flow through at least a portion of the engine water cooler  116 , but this is not the case. Engine water cooler  116  is a cross-flow heat exchanger, in which the hot water entering cooler  116  from an inlet conduit  132  ( FIG. 6 ) fills a tank or plenum  134  disposed vertically on one side of cooler  116 , then travels through several laterally extending cooling tubes in the cooler  116  heat exchanger core). Water leaving the cooling tubes of the cooler  116  core is gathered into a second vertically extending tank or plenum  136  on the other side of the core and thence conducted away from cooler  116  by an engine cooler  116  outlet conduit  138  ( FIG. 6 ). As best seen in  FIGS. 5 and 6 , intercooler conduits  124 ,  126  are disposed directly in front of engine water cooler  116  tanks  134 ,  136 , and therefore do not block air flow through the core of engine water cooler  116 . 
     The vertical arrangement of intercooler conduits  124 ,  126  on either side of engine water cooler  116  is possible because intercooler  118  is also a cross-flow heat exchanger. Intercooler  118  has two vertically oriented tanks  140 ,  142  that are disposed on either side of the core of intercooler  118 . As in the case of the engine water cooler  116 , tanks  140 ,  142  couple left and right edges of the intercooler core to conduits  124 , 126 . 
     We now refer to  FIG. 4 , a side view of the engine compartment partially cutaway to see the orientation of the heat exchangers. In this view, the core of engine water cooler  116  can be seen in cross section disposed above and slightly to the rear of intercooler  118 . The top of intercooler  118  and the bottom of engine water cooler  116  are disposed in abutting relation such that air passes through either the engine water cooler  116  or the intercooler  118 , but not both. They define two parallel and adjacent cooling air flow paths. Air is pulled through all four heat exchangers  116 ,  118 ,  120 ,  122  by a fan  144  that is driven by the tractor engine (not shown). The fan is disposed in one end  146  of a fan shroud  148 . Engine water cooler  116  and intercooler  118  are disposed in the other end  150  of the fan shroud. When fan  144  turns, it draws air through vents  114  in hood  110 . The air is drawn backward, through condenser  122  and oil cooler  120 . It is then drawn through either engine water cooler  116  or intercooler  118 . Once it has passed through one of these two, it travels the length of shroud  148 , and is pulled through fan  144  at which point it exhausts into the engine compartment around the engine. 
     It can be seen in  FIG. 4  that air is either (1) pulled directly from the outside into engine water cooler  116  and intercooler  118 , or (2) it is pulled first through the oil cooler  120  and then through either the engine water cooler  116  or the intercooler  118 , or (3) it is pulled through both the condenser  122  and the oil cooler  120  and then through either of the engine water cooler  116  and the intercooler  118 . 
     It will be understood that changes in the details, materials, steps, and arrangements of parts which have been described and illustrated to explain the nature of the invention will occur to and may be made by those skilled in the art upon a reading of this disclosure within the principles and scope of the invention. The foregoing description illustrates the preferred embodiment of the invention; however, concepts, as based upon the description, may be employed in other embodiments without departing from the scope of the invention. Accordingly, the following claims are intended to protect the invention broadly as well as in the specific form shown.