Abstract:
A work machine having dual compression ignition engines each driving motor generators providing a power output to selective loads. The compression ignition engines each have an exhaust aftertreatment device requiring regeneration in accordance with a selected parameters. A controller controls motor/generators or hydraulic pump/motors associated with the diesel engines to either transfer load between one or the other of the motor/generators or pump/motors to impose a load on one of the engines sufficiently high to produce passive regeneration. In the event that loads driven by the motor/generators or pump/motors are too low, one of the engines may be shut off or the loads increased.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to work machines and more particularly to work machines including an internal combustion engine which may be used to drive primary and secondary loads. 
       BACKGROUND OF THE INVENTION 
       [0002]    A work machine, such as a construction, agriculture or forestry work machine typically includes a power unit in the form of an internal combustion (IC) engine. The IC engine may either be in the form of a compression ignition engine in which the heat of compression ignites timed and quantity selected fuel for combustion or a spark ignition engine in which a homogenous mixture is ignited by an ignition source or a homogenous charge compression ignition engine which is a hybrid of the former two. For most heavy work machines, the power unit is in the form of a diesel engine providing better torque, power and durability characteristics for work operations. 
         [0003]    The emissions regulations set forth in the original Environmental Protection Agency (EPA) laws have initially been applied to on highway vehicles. In recent years, the EPA regulations have been applied to off-highway vehicles such as work machines. The issues faced by on-highway diesel engine applications are now being faced by off-highway applications. 
         [0004]    In the usual applications, this requires an exhaust aftertreatment device which receives the products of combustion from the internal combustion engine and treats it appropriately to remove a combination of nitrous oxides, particulates and other hydrocarbons. These devices inherently require periodic regeneration to remove particulates or carbon matter so as to restore the aftertreatment device to a substantially new condition. This is necessary to maintain the effectiveness of treating the products of combustion so as to maintain both the letter and spirit of the EPA laws. 
         [0005]    The issue of regeneration becomes difficult when applied to work machines in the sense that the machines are constantly being utilized to perform an industrial or agricultural function. Any regeneration effort must not prevent continued operation of the machine so that it can achieve its intended purpose, namely the industrial or agricultural function. 
         [0006]    A number of efforts have been made to achieve regeneration and these include raising the temperature of the products of combustion to the exhaust aftertreatment device sufficiently so that any extra carbon is burned off. The devices to achieve this can be heaters, ultrasonic devices and adding hydrocarbons to the exhaust stream to achieve the temperatures required for regeneration. 
         [0007]    Unfortunately, all of these approaches require energy beyond that necessary for the particular duty cycle of the work machine. In particular, adding hydrocarbons in the form of fuel decreases the fuel efficiency and therefore the effectiveness of the work machine. Devices incorporating heaters or ultrasonic devices require additional power sources to drive the temperature increasing function. Nowhere is the need for efficiency greater than in an agricultural machine having a duty cycle that varies between one of maximum load and such as driving a combine through a field and simultaneously harvesting, collecting and processing the harvested agricultural material. The opposite of this maximum load is the time in-between actual harvesting when the engine is operating at a small fraction of the maximum power available to the device. 
         [0008]    What is needed in the art therefore, is a work machine that utilizes internal combustion engines and which efficiently and effectively regenerates exhaust aftertreatment devices associated with the internal combustion engines. 
       SUMMARY OF THE INVENTION 
       [0009]    In one form the invention is a work machine having a first air-breathing fuel consuming internal combustion (IC) engine providing a power output in producing products of combustion. The first IC engine has a first exhaust aftertreatment device receiving products of combustion from the first IC engine and requires periodic regeneration in response to a first aftertreatment device parameter. A second air-breathing fuel consuming internal combustion (IC) engine provides a power output and produces products of combustion. The second IC engine has a second exhaust aftertreatment device receiving products of combustion from the second IC engine and requiring periodic regeneration and response to a second aftertreatment device parameter. First and second devices are respectively mechanically connected to the first and second IC engines, the first and second devices being configured to each drive at least one load. Finally, a controller is configured for selective bi-directional transfer of power between the first and second devices in response to the first and second aftertreatment device parameters to selectively increase the load on one of the first and second IC engines in regenerating the aftertreatment device receiving products of combustion from the IC engine. 
         [0010]    In another form, the invention is a method of operating a work machine having first and second air-breathing fuel consuming internal combustion (IC) engines providing a power output and producing products of combustion. Each of the IC engines has an exhaust aftertreatment device receiving products of combustion from the respective IC engine and requiring periodic regeneration in response to an aftertreatment device parameter. The method includes steps of driving a first device with the first IC engine, the first device driving at least one load. Driving a second device with the second IC engine, the second device driving at least one load. The method includes the final step of bi-directionally transferring power between the first and second devices in response to the aftertreatment device parameters to produce regeneration in one of the exhaust aftertreatment devices. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  shows a schematic diagram of a work machine incorporating apparatus according to the present invention; 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0012]      FIG. 1  shows, in schematic fashion, a work machine  10  in accordance with the present invention. Work machine  10  has first and second loads  12  and  14  driven by first and second propulsion units  16  and  18 . Loads  12  and  14  may be a variety of demands from primary propulsion of the work vehicle  10  to auxiliary functions and in the case of agricultural work machines, harvesting and processing functions. Depending upon the configuration of the components set forth below, the loads  12  and  14  may be in the form of transmissions or electric motors or hydromechanical devices. 
         [0013]    The first propulsion unit  16  comprises an engine  20  having a plurality of cylinders in which pistons reciprocate to provide a rotary output by interconnection with a crank shaft, all of which is not shown to simplify the understanding of the present inventions. Engine  20  is an air breathing, fuel consuming, engine in which a fuel system, generally indicated by  22 , injects fuel into the combustion chambers for the appropriate combustion event. The products of combustion pass through an exhaust manifold  24  and through an exhaust line  26  to a turbine  28  of a turbo-charger  30 . The turbine  28  is mechanically connected to a compressor  32  via an interconnecting shaft  34 . The turbine  28  extracts energy from combustion gases flowing through line  26  and the gases from the turbine  28  pass through line  36  to an exhaust aftertreatment device  38  and line  40  to ambient A. 
         [0014]    The compressor  32  receives inlet air from ambient A via line  42  and compresses it for delivery through a line  44  to intake manifold  46  supplying air to engine  16 . It should be noted that an after cooler or intercooler (not shown) is typically provided in line  44  to reduce the temperature of the pressurized gases and therefore the density of the charge for additional power. The engine  20  is mechanically coupled to a device  48 , which will be described in detail below, by a shaft  50 . The device  48  is interconnected with load  12  by an appropriate connection indicated by line  52 . 
         [0015]    Propulsion unit  18  has an engine  54  that is also fuel consuming and air breathing. A fuel system  56  provides metered and timed fuel to be injected a plurality of cylinders in which pistons reciprocate to provide a rotary output. The internal elements are not shown to simplify the understanding of the present invention. The products of combustion from engine  54  pass through an exhaust manifold  58  through line  60  to the turbine  62  of a turbocharger  64 . Turbine  62  drives a compressor  66  by a mechanical interconnection  68 . The gases exiting from turbine  62  pass through line  70  to an exhaust aftertreatment device  72  and finally a line  74  to ambient A. 
         [0016]    The compressor  66  receives ambient air from line  76  and pressurizes it for delivery via line  78  and intake manifold  80  to engine  54 . Engine  54  provides an output to a device  82  via mechanical interconnection  84 . 
         [0017]    A controller  86  is connected to device  48  by interconnection  88  and to device  82  by interconnection  90 . The controller  86  is also interconnected with load  12  by line  92  and load  14  by line  94 . Controller  86  also has signal lines  96  and  98  receiving signals from exhaust aftertreatment devices  38  and  72 , respectively. 
         [0018]    In accordance with the present invention, the controller  86  is configured to transfer loads between engines  20  and  54  in response to signals from exhaust aftertreatment devices  38  and  72  via lines  96  and  98  to provide effective and efficient operation of the work machine for the exhaust aftertreatment devices. In one form, the devices  48  and  82  are motor/generators mechanically driven from their respective engines  20  and  54  but which are not mechanically interconnected. The motor/generators respectively drive loads  12  and  14  which perform various functions in the work machine  10 . 
         [0019]    The controller  86  may be an ECM that responds to signals from exhaust aftertreatment devices  38  and  72  to maintain proper operation. When exhaust aftertreatment devices  38  and  72  are diesel particulate filters, it is necessary to periodically regenerate the filters so as to burn off accumulated carbon particles. The controller  86  is configured so that appropriate inputs cause the controller to transfer load to either engine  20  or  54  as appropriate so that the temperature adjacent exhaust aftertreatment device  38  or  72  is approximately 300° Celsius. At this point the carbon particle will combust and be burned off of the filter. 
         [0020]    The criteria for initiating the transfer of power may be any one of a number of parameter indicators. Such indicators may be: 1. after a predetermined operating time; 2. after a predetermined operating time at given loads; 3. a predetermined pressure drop across the exhaust aftertreatment device; 4. a predetermined inlet pressure to the device; 5. a predetermined inlet temperature to the device. Various combinations of the signals may be employed to properly transfer a load from one of the engines to the other through the devices  48  and  82 . 
         [0021]    The work machine  10  is subjected a variety of loads during it duty cycle. In cases when the loads are not so high it is necessary to utilize both engines  20  and  54 , the load may be transferred to one of the two engines and the other shut off to provide the temperature necessary for regeneration. If the point in the duty cycle where the loads are below that of one of the two engines, the loads  12  or  14  may be artificially increased to cause the exhaust temperature to reach the regeneration limit. This may be the artificial adding of load. In the case of motor/generators this can be done by charging a battery, energizing a heater or other accessory device such as an unloading system. 
         [0022]    Alternatively, the devices  48  and  82  may be pump/motor combinations and the controller  86  configured so that power may be bi-directionally directed between the devices  48  and  82  in order to effect the appropriate temperature in the exhaust lines to achieve regeneration. In this case, if the duty cycle experiences a load sufficient to be driven by one of the engines, power is transferred totally to that engine and the other engine may be shut down to load the operating engine to achieve the regeneration temperatures. In the event that the load in the duty cycle at that point is even lower, artificial loads may be added at  12  or  14  by actuating various hydraulic pumps and motors to increase the load. 
         [0023]    The regeneration of the exhaust aftertreatment device may be controlled by the controller  86  in response by appropriate signals from lines  96  and  98  to stop regeneration after a predetermined burnout or a variable determined by particular operating parameters. 
         [0024]    While the exhaust aftertreatment devices  38  and  72  have been described as diesel particulate filters they may also be catalytic converters, selective catalytic reduction (SCR) devices or diesel oxidation catalysts (DOC). In each case, a parameter from the device is used by the controller  86  to achieve the appropriate transfer load from one engine to the other. 
         [0025]    The net effect of the system described above is that regeneration of the exhaust aftertreatment devices and efficient operation thereof may be achieved without the need to add hydrocarbons or other devices to increase exhaust aftertreatment device temperature to the point where regeneration occurs. This provides a significant benefit in fuel economy, since for compression ignition engines, regeneration of particulate filters is an operation that occurs with significant frequency. Furthermore the regeneration of the exhaust aftertreatment devices may be occurring while the work machine  10  is functioning for its intended purpose, thus avoiding unnecessary interruption of the work activity. 
         [0026]    Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.