Abstract:
An exhaust temperature control system for a displacement on demand (DOD) diesel engine includes a first and a second cylinder and an air intake that selectively enables air flow into the first cylinder. A fuel injector selectively enables fuel flow into the first cylinder. A controller increases an exhaust temperature of the diesel engine by closing the air intake and disabling fuel flow through the fuel injector to deactivate the first cylinder.

Description:
FIELD OF THE INVENTION  
         [0001]    The present invention relates to diesel engines, and more particularly to improved exhaust temperature control for displacement on demand diesel engines.  
         BACKGROUND OF THE INVENTION  
         [0002]    During the combustion process, fuel is oxidized, and hydrogen (H) and carbon (C) combine with air. Various chemical compounds are formed including carbon dioxide (CO 2 ), water (H 2 O), carbon monoxide (CO), nitrogen oxides (NO x ), unburned hydrocarbons (HC), sulfur oxides (SO x ), and other compounds. Automobile exhaust systems include an exhaust treatment device, such as a three-way catalytic converter, that reduces CO, HC and NO x  in the exhaust gas. The exhaust treatment device must be heated to a sufficient temperature for optimum performance.  
           [0003]    Diesel engines have improved thermal efficiency as compared to gasoline engines. As a result, the exhaust temperature of a diesel engine is lower than that of a gasoline engine. The exhaust provides heat that is used to warm the exhaust treatment device. Because the exhaust temperatures of diesel engines are lower than that of gasoline engines, the diesel exhaust does not consistently heat the exhaust treatment device to desired operating temperatures.  
         SUMMARY OF THE INVENTION  
         [0004]    The present invention provides an exhaust temperature control system for a displacement on demand (DOD) diesel engine. The control system includes first and second cylinders and an air intake that selectively enables air flow into the first cylinder. A fuel injector selectively enables fuel flow into the first cylinder. A controller increases exhaust temperature of the diesel engine by closing the air intake and disabling fuel flow through the fuel injector to deactivate the first cylinder.  
           [0005]    In one feature, the controller increases fuel flow to the second cylinder to maintain torque output of the diesel engine.  
           [0006]    In another feature, an intake valve is disposed within the air intake to selectively enable air flow through the air intake.  
           [0007]    In still another feature, the air intake is only partially closed to enable a reduced air flow into the first cylinder.  
           [0008]    In yet another feature, the fuel injector is electronically controlled to cease fuel injection into the first cylinder.  
           [0009]    Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]    The present invention will become more fully understood from the detailed description and the accompanying drawings, wherein:  
         [0011]    [0011]FIG. 1 is a functional block diagram of a displacement on demand (DOD) diesel engine; and  
         [0012]    [0012]FIG. 2 is a flowchart illustrating an exhaust temperature control for the (DOD) diesel engine according to the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0013]    The following description of the preferred embodiment is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. For purposes of clarity, the same reference numbers will be used in the drawings to identify similar elements. As used herein, activated refers to operation using all of the engine cylinders. Deactivated refers to operation using less than all of the cylinders of the engine (one or more cylinders not active).  
         [0014]    Referring now to FIG. 1, a vehicle  10  includes a diesel engine  12  that outputs exhaust gases to an exhaust system  14 . The engine  12  includes N cylinders  18 . One or more of the cylinders  18  are selectively deactivated during engine operation. Although FIG. 1 depicts six cylinders (N=6), it can be appreciated that the engine  12  may include additional or fewer cylinders  18 . For example, engines having 4, 5, 6, 8, 10, 12 and 16 cylinders are contemplated. Air flows into the engine  12  through an intake manifold  20  and is combusted with fuel in the cylinders  18 . Accessories (not shown) such as a hydraulic pump, HVAC compressor, and/or alternator are driven by the engine  12 .  
         [0015]    The engine  12  includes fuel injectors  22  and valves  24  associated with each cylinder  18 . In a closed position, the valves  24  inhibit air flow from the intake manifold  20  into the associated cylinders  18 . In an open position, the valves  24  enable air flow from the intake manifold  20  into the associated cylinder  18 . The fuel injectors  22  communicate with a fuel supply system  26 . The fuel injectors  26  are selectively operated to inject a quantity of fuel into the respective cylinders  18 . Air and fuel are combined in the cylinders  18  and are combusted to produce driving power.  
         [0016]    The exhaust system  14  includes an exhaust manifold  28  and an exhaust treatment device  30 . The combustion gases from each cylinder  18  flow to the exhaust manifold  28  and through the exhaust treatment device  30  to atmosphere. The exhaust treatment device  30  can be a filter, an oxidization catalytic converter, an NO x  catalytic converter or another type of exhaust treatment device  30  known in the art. The exhaust treatment device  30  reduces exhaust emissions to desired levels. For optimum efficiency, the exhaust treatment device  30  operates above a threshold temperature. The exhausted combustion gases heat the exhaust treatment device  30 .  
         [0017]    A controller  32  communicates with the engine  12  and various sensors discussed herein. More particularly, the controller  32  outputs control signals to the engine  12  to control operating modes of the engine. An engine speed sensor  34  generates a signal based on engine speed. An intake manifold temperature sensor  36  generates a signal based on intake manifold temperature. An intake manifold pressure sensor  38  generates a signal based on a vacuum pressure of the intake manifold  20 . An exhaust temperature sensor  40  generates a signal based on exhaust temperature. The controller  32  communicates with the fuel system  26  and the valves  24 .  
         [0018]    The diesel engine  12  has improved thermal efficiency over gasoline engines. Thus, the exhaust temperature of the diesel engine  12  is lower than that of gasoline engines. As a result, the exhaust temperature is not always sufficient to heat the exhaust treatment device  30 . According to the present invention, the controller  32  selectively deactivates cylinders  18  to increase the exhaust temperature of the diesel engine  12 .  
         [0019]    Deactivation can only occur during periods of light engine load to ensure that the cylinders  18  that remain active produce sufficient driving torque. The controller  32  determines the engine load based on the signals of the various sensors. If the exhaust temperature is below the threshold and the engine load is sufficiently light, the controller  32  deactivates a number of cylinders  18  and increases the torque output of the active cylinders  18  by increasing fuel supplied thereto. As a result, the exhaust temperature of the active cylinders  18  is increased. Cylinder deactivation is achieved by the controller sending output signals that direct the engine  12  to close particular intake valves  24  and cease fueling through particular fuel injectors  22 .  
         [0020]    Referring now to FIG. 2, the exhaust temperature control of the present invention is described in detail. In step  100 , control determines whether the exhaust temperature is less than the threshold temperature. If not, control loops back. Otherwise control continues in step  102 . In step  102 , control determines whether the engine load is sufficiently light for cylinder deactivation. If not, control loops back. Otherwise, control continues in step  104 .  
         [0021]    Control deactivates the selected cylinders  18  by closing the associated intake valves  24  and ceasing fuel supply to the selected cylinders  18  in steps  104  and  106 , respectively. In step  108 , control increases the fuel supply to the active cylinders  18 . The increased fuel provides an a lower air-to-fuel ratio within the cylinders  18  resulting in increased exhaust temperature. The exhaust subsequently heats the exhaust treatment device  30  to a sufficient temperature to enable treatment within the exhaust treatment device in step  110 .  
         [0022]    Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the present invention can be implemented in a variety of forms. Therefore, while this invention has been described in connection with particular examples thereof, the true scope of the invention should not be so limited since other modifications will become apparent to the skilled practitioner upon a study of the drawings, the specification and the following claims.