Abstract:
A diesel engine including at least one combustion chamber having an exhaust flow therefrom. An injection pump having a plurality of fuel outlets has a corresponding fuel outlet for each of the plurality of fuel outlets that are in controlled fluid communication with the at least one combustion chamber. At least one aftertreatment device is configured for the exhaust flow to travel therethrough. A fuel injector is positioned to inject fuel into the exhaust flow prior to the exhaust flow reaching the aftertreatment device. A valve receives fuel from at least one of the plurality of fuel outlets and the valve is configured to divert a portion of the fuel received by the valve to the fuel injector.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method and apparatus to control the regeneration of a diesel aftertreatment device, and, more particularly, to a method and apparatus used to regenerate a diesel aftertreatment device using an injection pump to provide the pressurized fuel thereto. 
     2. Description of the Related Art 
     In modern low emission diesel engines, the fuel and air mixture is controlled and an exhaust gas recirculation system is utilized to reduce the NOx during steady state engine operation. Typically, the exhaust system directs the exhaust flow through a diesel oxidization catalyst, also known as a three-way catalyst, and through a diesel particulate filter. These devices are generally understood to be aftertreatment devices used to clean the exhaust before releasing the exhaust to the ambient atmosphere. Some aftertreatment devices require a burn off of the elements collected therein and, in order to accomplish this, diesel fuel is injected in some manner to facilitate the burn off. 
     The technology utilized to accomplish the burn off is typically expensive and complicated for the performance of the required task of regenerating, or self-cleaning the aftertreatment device, particularly for small diesel engines. The regeneration systems on large diesel engines typically use a high-pressure common rail injection system to provide the extra fuel on the exhaust stroke of the engine to thereby pump the fuel into the aftertreatment system. However, such a system is inordinately expensive for a small diesel engine. 
     What is needed in the art is a method and apparatus to regenerate an aftertreatment device for a small diesel engine without the need for a common rail injector system and the problems associated with that type of process. 
     SUMMARY OF THE INVENTION 
     The present invention relates to a method and apparatus for regenerating aftertreatment devices on small diesel engines. 
     The invention in one form is directed to a diesel engine having at least one combustion chamber having an exhaust flow therefrom. An injection pump having a plurality of fuel outlets has a corresponding fuel outlet for each of the plurality of fuel outlets that are in controlled fluid communication with the at least one combustion chamber. At least one aftertreatment device is configured for the exhaust flow to travel therethrough. A fuel injector is positioned to inject fuel into the exhaust flow prior to the exhaust flow reaching the aftertreatment device. A valve receives fuel from at least one of the plurality of fuel outlets and the valve is configured to divert a portion of the fuel received by the valve to the fuel injector. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       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: 
         FIG. 1  is a vehicle having a diesel engine utilizing an embodiment of the aftertreatment regeneration system and method of the present invention; 
         FIG. 2  is a block diagram illustrating elements of the engine of  FIG. 1 ; and 
         FIG. 3  illustrates steps of an embodiment of a method utilized in the apparatus of  FIG. 2 . 
     
    
    
     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 
     Referring now to the drawings, and more particularly to  FIG. 1 , there is illustrated a vehicle  10  in the form of an agricultural vehicle  10 , also known as a tractor  10 , having a diesel engine  12  that provides motive force for use in a propulsion system having wheels  14 . Power from diesel engine  12  also is utilized to move bucket  16 , also known as a tool  16 . Although vehicle  10  is illustrated as a tractor  10 , it is to be understood that the present invention relates to any vehicle  10 , and, more generally, to any power generating system  12  such as a small diesel engine  12 . As discussed above, the present invention is directed to small diesel engines and, for the sake of clarity, a three-cylinder diesel engine will be used in the discussion to follow although other small diesel engines of another cylinder count could likewise be utilized. 
     Now, additionally referring to  FIG. 2 , there are illustrated elements of engine  12  including the three cylinder engine block  18  having combustion chambers  1 ,  2 , and  3  as illustrated therein. The engine  12  can be of any configuration having N combustion chamber(s) producing exhaust flow, N being a non-zero positive integer equal to at least one, such that N=3 in the engine  12  of the illustrated example. Engine  12  additionally includes an injection pump  20 , injection lines  22 , an electrohydraulic valve  24 , return line  26 , fuel tank  28 , a fuel injector  30 , a controller  32 , a temperature sensor  34 , a pressure sensor  36 , a diesel oxidization catalyst  38 , and a diesel particulate filter  40 . Injection pump  20  provides fuel to the combustion chambers  18  by way of injection lines  22 . Note that injection pump  20  is illustrated as a rotatory six-plunger injection pump  20 , which would typically be utilized on a six-cylinder diesel engine. Here, in order to preserve the geometry, three of the plungers are connected to injection lines  22  directed to the engine combustion chambers  18  while three of the injector lines  22  are directed to electrohydraulic valve  24 . Now, there is an advantage of the symmetry of utilizing an injection pump  20  having a whole number multiple of injection plungers as compared to the number of cylinders in engine block  18 . This economic use of existing technology in the form of the six-cylinder rotary injection pump provides the pressurized fuel utilized by the present invention. However, it should be noted that the fuel injection pump  20  can have N+X fuel outlets, X also being a non-zero positive integer equal to at least one, such that N+X=3+3 in the rotatory six-plunger injection pump  20  of the illustrated example. Thus, each of the lines  22  separately connects a corresponding one of the N fuel outlet(s) of the injection pump  20  to a corresponding one of the N combustion chamber(s) and a corresponding one of the X fuel outlet(s) of the injection pump  20  to the electrohydraulic valve  24 . Electrohydraulic valve (EHV)  24  is under the operative control of controller  32 , which may be an engine control unit (ECU)  32 . Electrohydraulic valve  24  may be simply an on/off valve utilized to direct the fuel flow from injector lines  22  to either injector  30  or return line  26 . Alternatively, electrohydraulic valve  24  may be a proportional valve that is used to proportion the flow from lines  22  through valve  24  to injector  30 . Fuel not directed to injector  30  is sent by way of return line  26  to fuel tank  28 . Diesel engines typically have return lines from injectors and/or the injector pump so that when a relief feature of the plungers in the injection pump is triggered, the excess pressure in the fuel lines is bled off through a return line back to the fuel tank. Although typically utilized on a diesel engine, many of these details are not shown. Only one return line  26  is illustrated to more conveniently convey the operating mode of the present invention. 
     Controller  32 , in addition to being in communication with electrohydraulic valve  24 , receives information from temperature sensor  34  and from pressure sensor  36 . Sensors  34  and  36  allow controller  32  the capability of determining the temperature in the exhaust flow as well as backpressure developed in diesel particulate filter  40 . This, along with perhaps other operating information, allows controller  32  to compensate for operating conditions of diesel engine  12 , and to decide upon a time to start a regeneration process of the aftertreatment devices—catalyst  38  and/or diesel particulate filter  40 . 
     Exhaust coming from combustion chambers  1 ,  2 , and  3  of three combustion cylinder block  18  is illustrated schematically as exhaust flow  42  flowing through an exhaust pipe towards diesel oxidization catalyst  38 . When controller  32  decides to start a regeneration cycle, electrohydraulic valve  24  is turned on to allow either a full or a proportional selected flow of fuel coming from injection lines  22  to be directed to injector  30  so that fuel flow  44  enters into exhaust flow  42  directed at the aftertreatment devices. This fuel injected into the exhaust flow causes a burn off of the particulate matter or other deposits so that the aftertreatment devices can have their life extended for further cleaning of the exhaust from engine  12 . 
     Now, additionally referring to  FIG. 3 , there is illustrated a method  100  including step  102  where the need for a cleaning cycle of the aftertreatment devices is detected by controller  32 . In step  104 , controller  32  diverts a return fuel flow that would normally go to fuel tank  28  by way of return line  26  to injector  30  so that a portion of the fuel is then injected as a fuel flow  44  into exhaust flow  42 . At step  106 , electrohydraulic valve  24  is shut off so that the diverted flow is no longer sent to injector  30  but then the continuous flow from injector lines  22  going to electrohydraulic valve  24  flows entirely to fuel tank  28 . 
     The present invention eliminates the need to have a common rail system and the problems associated with such a process, which is particularly geared towards large diesel engines. The present invention utilizes a conventional rotary injection pump  20  and has the advantage of using an electrohydraulic valve  24  tied to three outlets of injection pump  20 . Although not illustrated, check valves on these lines may additionally be utilized and may be considered incorporated within the electrohydraulic valve  24  device. Electrohydraulic valve  24  is used to divert fuel that would be recirculating back to fuel tank  28  to the exhaust system when needed for regeneration of the after treatment devices. Electrohydraulic valve  24  may have a default condition in which fuel is directed to fuel tank  28  unless electrohydraulic valve  24  is energized by action of controller  32 . 
     The present invention advantageously reduces the cost of fuel injection components since available injection pumps for larger number of cylinder engines is utilized. Another advantage of the present invention is that it lowers the potential of engine damage due to the elimination of oil contamination with fuel, which is found in post combustion injection systems that are utilized with common rail injection systems. Another advantage of the present invention is that the production cost of this system is decreased over the more expensive common rail injection system. 
     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.