BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The present invention relates to work machines, and, more particularly, to energy load control systems for multiple engine driven harvesters. 
         [0003]    2. Description of the Related Art 
         [0004]    A work machine, such as an agricultural machine in the form of a harvester, typically includes a prime mover in the form of an internal combustion (IC) engine. The IC engine may either be in the form of an compression ignition engine such as a diesel engine, or a spark ignition engine, such as a gasoline engine. For most heavy work machines, the prime mover is in the form of a diesel engine having better lugging, pull down, and torque characteristics for work operations than the gasoline engine. 
         [0005]    An IC engine in a harvester provides input power to a transmission, which in turn is coupled with drive axles through a differential gear system. The transmission, rear end differential, and rear axles are sometimes referred to as the power train of the work machine. 
         [0006]    It is known to provide multiple engines on a harvester with electrical generators and various electrical motors. IC engines and electric motors are used to drive hybrid vehicles, and it is known to use regeneration techniques such that the generator/electric motor generates electrical power when the vehicle is executing a braking maneuver. Dual engines or even an engine having a dual crankshaft system is used to power vehicles having a transmission coupled thereto for transferring the driving torque of at least one of the engine or crankshafts to the motor/generator of the vehicle. The dual engine system utilizes both engines when additional load levels are required, such as during acceleration, climbing a hill, or pulling a heavy load. It is also known to utilize an electric motor to assist in providing the torque when additional increased loads are applied to the IC engine. 
         [0007]    When running an agricultural machine on one engine, it is easy for the operator to overload the engine by trying to do too much with the power available. Overloading an engine can increase wear on the engine and the loads, such as a threshing system, if it is under driven. Further, overloading an engine can result in premature failure of the engine and even stalling of an engine particularly at a critical time when the power is most needed. 
         [0008]    What is needed in the art is a control system that will manage a harvester power requirements while operating on one engine. 
       SUMMARY OF THE INVENTION 
       [0009]    The invention in one form is directed to a multiengine agricultural harvester including a plurality of power absorbing loads, a first engine, a second engine, and a controller. The first engine is configured to supply power to a portion of a plurality of power absorbing loads. The first engine is not capable of powering all of the plurality of power absorbing loads. The second engine is uncoupled from the plurality of power absorbing loads. The controller is configured to select less than all of the power absorbing loads to be driven dependent upon a sensed load on the first engine. 
         [0010]    The invention in another form is directed to a method of controlling a multiengine harvester including the steps of operating the harvester in a first mode, operating the harvester in a second mode, and selecting less than all of the power absorbing loads to be driven. In the first mode, the harvester is operated using a first engine and a second engine to drive the plurality of power absorbing loads. In the second mode, the harvester is operated with the second engine being uncoupled from all of the power absorbing loads. In the selecting step, less than all of the power absorbing loads are selected to be driven dependent upon the sensed load on the first engine while operating in the second mode. The first engine being incapable of driving all of the power absorbing loads. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]    The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, wherein: 
           [0012]      FIG. 1  is a side view of a harvester utilizing an embodiment of the energy control system of the present invention; 
           [0013]      FIG. 2  is a schematical block diagram representing the multiple engine load control system of  FIG. 1 ; and 
           [0014]      FIG. 3  is a schematical block diagram of an embodiment of a load control method used in the multiple engine energy control system of  FIGS. 1 and 2 . 
       
    
    
       [0015]    Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate one embodiment of the invention and such exemplifications are not to be construed as limiting the scope of the invention in any manner. 
       DETAILED DESCRIPTION OF THE INVENTION 
       [0016]    Referring now to the drawings, and more particularly to  FIG. 1 , there is shown an agricultural vehicle  10 , also more particularly illustrated as a harvester  10 , which includes a chassis  12 , cabin/controls  14 , wheels  16  and a power system  18  that include an engine  20  and an engine  22 . Harvester  10  has a variety of mechanical and electrical systems therein including a crop gathering header that directs crop material to a threshing section. The threshing section separates the grain from other crop material and directs the grain to a sieve area for further separation of the grain from the lightweight crop material. The grain is then conveyed to a storage area for later conveyance to a grain transport vehicle. 
         [0017]    Chassis  12  provides structural integrity and support for harvester  10  and is used to support mechanical and electrical systems therein. Controls  14  allow an operator the ability to direct the functions of harvester  10 . Wheels  16  support chassis  12  and allow a propulsion system to move harvester  10  as directed by the operator using controls  14 . 
         [0018]    Now, additionally referring to  FIG. 2 , power system  18  includes engines  20  and  22  that are connected to a gear box  24 , which in turn drives mechanical loads  28  and generator  26 . Generator  26  in turn supplies electrical power to electrical loads  30 . For ease of illustration, engine  20  and engine  22  are shown being connected to a gearbox  24 , the connection of which being severable in a fashion in which engine  20  or engine  22  may be uncoupled from gearbox  24 . Although gearbox  24  is illustrated, it is to be understood that this may include a transmission, clutch, and other mechanical linking devices. Further, although illustrated as one gearbox driven by engines  20  and  22 , separate mechanical structures may also be utilized with the gearboxes driving separate generators and mechanical loads with perhaps a mechanical linkage between gearboxes. It is also contemplated that engines  20  and  22  may each drive separate generators in lieu of gear box  24 , with the coupling, and uncoupling being carried out using electrical components. 
         [0019]    An engine load sensor/control  32 , a gearbox sensor/control  34 , a generator sensor/control  36 , an electrical load sensor/control  38 , and an engine sensor/control  40  are each interconnected to a controller  42 . Controller  42  is interconnected to the sensor/controls to provide interactive control so that elements of the various electrical loads  30  and mechanical loads  28  can be effectively driven if either engine  20  or  22  is uncoupled and/or shut off. Controller  42  has been illustrated as a stand alone controller for the sake of clarity, and for the explanation of the present invention; however, it is also to be understood that the functions of controller  42  can be undertaken by a controller utilized for other functions in harvester  10 . Although the interlinking between controller  42  and other elements are shown as a single line, these lines are intended to convey the understanding that information, control commands, and/or power may be routed therebetween by instructions issued by controller  42 . Battery  44  can also be thought of an additional electrical load when it is being charged and a source of power when it is being discharged. 
         [0020]    Engines  20  and  22  are internal combustion engines that are connected to gearbox  24 . Gearbox  24  mechanically drives generator  26  as well as mechanical loads  28 . The description of mechanical loads  28  is not to infer that there is not a mechanical linkage between generator  26  and gearbox  24 , but rather signifies that there is an additional mechanical load that is assigned to be driven by power system  18 . For example, mechanical loads  28  may include a grain separation mechanism within harvester  10  as well as propulsion and hydraulic systems for harvester  10 . The loads can be individually coupled and the power requirements measured by way of sensor/control  34 . Also, various electrical loads  30  can be selectively engaged or disengaged by control/sensor  38 . 
         [0021]    Now, additionally referring to  FIG. 3 , there is illustrated a method  100  in which, power system  18  can operate in a first mode with both engines  20  and  22  operating, wherein method  100 , by way of decision box  102 , simply returns to the starting point. In mode  2 , engine  22  is uncoupled so that it no longer drives gearbox  24  or provides any power that can be used to drive electrical loads  30  or mechanical loads  28 . In mode  2 , engine  20  is operating, providing power to gearbox  24 , although engine  20  is incapable of driving all possible mechanical loads  28  and electrical loads  30  of harvester  10 . At step  104  the load on engine  20  is determined and is based on the sensed engine load. Controller  42  operatively selects mechanical loads  28  and electrical loads  30  at step  106  so that engine  20  is not overloaded. At step  108 , method  100  evaluates operator commands issued with controls  14  wherein the operator of harvester  10  is engaging different aspects of harvester  10  to perform the desired function. 
         [0022]    The evaluation of operator commands and operations being undertaken by harvester  10  can be handled by controller  42  in different manners. In one embodiment of the present invention, the evaluation undertaken at step  108  can result in a decision of controller  42 , at step  110 , to start engine  22 . Once this decision is made then method  100  returns to step  102  and will remain there in mode  1 , until the loads reduce to a level where engine  20  can supply all of the needs of harvester  10 , then mode  2  is selected. 
         [0023]    In another embodiment of the present invention, the commands that are evaluated are compared to a priority of operations. For example, if the operator issues a command of a low priority, then the evaluation is such that the engine capability and the engine load, measured at step  104 , are used to determine if the additional lower priority load can be accommodated. If the commanded load can be accommodated, then it is engaged by controller  42 . If the command issued by the operator is such that it would cause an overload on engine  20  then controller  42  will not execute the command issued by the operator. Further, if the command issued by the operator is a higher priority than engaged load of a lower priority, then lower priority loads may be disengaged and the load commanded to be engaged by the operator is then engaged by controller  42 . 
         [0024]    If the engine power in the primary engine is insufficient, when the operator initiates a “Primary” power use, which is determined by an order of importance of key harvester functions. Secondary power users, which are power users that are not critical to harvester functions, are downgraded to receive a lower amount of power, or completely turned off, until controller  42  brings the second engine on line to supply adequate power for all uses. The present invention is configured to always have power available for critical harvester functions. For example, if the operator desires to engage the threshing mechanism, controller  42  may disregard that command since the threshing system would require more horsepower than the capability of engine  20  alone and still have sufficient power to move and function other aspects of harvester  10 . If the operator issues a command to extend the grain auger and to begin auguring the grain as harvester  10  is moving along, controller  42  may disengage the air conditioning system or other low priority function so that grain contained in the hopper may be off loaded. 
         [0025]    It is also contemplated that commands issued by the operator at step  108  may be partially complied with by controller  42  which may select time periods for different portions of loads  28  and  30  to be engaged for specific periods of time and then different loads are engaged other periods of time. For example, the load on engine  20  is such that charging a battery  44  and operating an air conditioning system for the cabin may be alternated so that battery  44  may be charged for a predetermined time, such as one minute, then the air conditioning system can be driven in the cabin for a two minute period followed by running of a blower fan in the cabin for three minutes. 
         [0026]    Combinations of the foregoing are also contemplated. For example a priority system can be utilized while engine  22  is started and is brought up to speed, then all the commanded loads are engaged. In this manner the transition to multi-engine power is undertaken with the stalling of one engine being avoided. It is also contemplated that controller  42  can select which engine is shut down and uncoupled based on engine parameters such as capability as well as measured performance. Visual displays of these operations are presented to the operator so that the operator is given operational information to among other things reduce impatience of the operator if commands are denied or delayed until the second engine comes online. 
         [0027]    Loads that are driven, in the form of loads  28  and  30 , may include such things as propulsion of harvester  10 , harvesting function loads, such as the threshing section or the separating section. Any harvester parameter indicative of a load can be monitored, at step  104 , by controller  42  interacting with the various controls and sensors. Such load indicators can include the fuel delivery rate to engine  20 , the engine torque being supplied by engine  20 , pressure of the hydrostatic system of harvester  10 , the electrical current drain of a particular electrical load  30  which may be used to drive a hydraulic system or other systems in harvester  10  or even an attitude of harvester  10  indicating an anticipated load or lack thereof as harvester  10  is moved along the ground. 
         [0028]    The present invention advantageously allows the operator to drive and operate harvester  10  while harvester  10  automatically adjusts power being supplied by engine  20  so as to keep engine  20  from stalling. This improves overall performance as the operator can, for example, travel to a destination during a road transport faster, while still saving a great deal of fuel that would have been consumed by running both engines  20  and  22 . This more optimal use of engines  20  and  22  allow the environmental aspects of the engines to work at higher efficiency since engine  20 &#39;s load is being managed so that it is not being over driven and engine  22  is shut off so that it no longer contributes to an environmental processing load. 
         [0029]    While this invention has been described with respect to at least one embodiment, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
A method of controlling a multiengine harvester including the steps of operating the harvester in a first mode, operating the harvester in a second mode, and selecting less than all of the power absorbing loads to be driven. In the first mode, the harvester is operated using a first engine and a second engine to drive the plurality of power absorbing loads. In the second mode, the harvester is operated with the second engine being uncoupled from all of the power absorbing loads. In the selecting step, less than all of the power absorbing loads are selected to be driven dependent upon the sensed load on the first engine while operating in the second mode. The first engine is incapable of driving all of the power absorbing loads.