Abstract:
A method is described for operating a gasoline engine having at least one throttle valve controlling a combustion air supply for at least two cylinders, the at least one throttle valve being opened completely and a power output of the gasoline engine being controlled by deactivating at least one of the at least two cylinders.

Description:
FIELD OF THE INVENTION 
       [0001]    The present invention relates to a method for operating a gasoline engine having at least one throttle valve controlling a combustion air supply for at least two cylinders as well as a gasoline engine. 
       BACKGROUND INFORMATION 
       [0002]    In the case of gasoline engines, it may be provided to reset the throttle valve to a basic position for emergency operation in the event of an electrical or mechanical malfunction. Such a basic position may conform to a lower power requirement, which is normally adequate for moving a vehicle driven by the gasoline engine. This type of emergency operation is unsuitable, in particular for high availability applications such as those encountered, for example, in watercraft and aircraft. For example, marine and flight applications exist in which engine power above a certain threshold of the rated power must be ensured. 
         [0003]    It is therefore desirable to provide a possibility for emergency operation which is also suitable for high availability applications. 
       SUMMARY 
       [0004]    According to the present invention, a method for operating a gasoline engine having at least one throttle valve controlling a combustion air supply for at least two cylinders as well as a gasoline engine are provided. 
         [0005]    The present invention is based on the measure of completely opening a throttle valve controlling the combustion air supply for at least two cylinders, in particular in the event of a malfunction of this throttle valve, and influencing a power output of the gasoline engine by deactivating at least one of the at least two cylinders. This provides the possibility of influencing the power output of a gasoline engine within certain limits, even in the event of a completely open throttle valve, the number of power stages resulting from the number of cylinders. 
         [0006]    Only a complete opening of the throttle in the event of an error would not solve the problem, since the operation then occurring at continuous full power would not be manageable. The result of this is a complete loss of power control (LOPC). 
         [0007]    A complete opening of the throttle valve supplies the maximum possible quantity of air to the at least two cylinders, for which reason they are basically only able to deliver the maximum possible power or no power. In most operating modes, the quantity of gasoline must namely be adapted to the instantaneous quantity of air in order to achieve combustion. As a function of the power request by a vehicle driver (e.g., driver or pilot), it is then possible to fire only individual cylinders and thus adapt the power output gradually. 
         [0008]    The throttle valve is preferably a normally open or currentlessly open throttle valve. A complete opening of the throttle valve in the event of a malfunction, for example, in the case of a defective actuator or a signal error, may, for example, be caused by a spring which pulls the throttle valve in the “open” direction and against which the actuator acts. Such throttle valves are in fact known for diesel engines; however, they are not used for gasoline engines. 
         [0009]    Preferably, the at least one cylinder is deactivated on an alternating basis. This may protect the mechanics of the gasoline engine, since cylinders are fired on an alternating basis (e.g., known strategy of half-engine operation). 
         [0010]    If the gasoline engine has more than one throttle valve, for example, in the case of multiple cylinder banks, one of the multiple throttle valves may be opened completely, at least one of the cylinders supplied with combustion air by the completely open throttle valve being deactivated or not fired. Another of the multiple throttle valves is operated in the conventional manner, in order to thus adapt the power output of the gasoline engine to the power request by the vehicle driver. This operating mode may be assumed in the event of a malfunction of a throttle valve; however, it may nonetheless also be assumed in the event of functioning throttle valves, for operating one in a completely open state and thus avoiding throttle losses. This has a positive impact on fuel consumption and on the associated environmental pollution. This approach might also be used for downsizing; an appropriate mechanical design of the engine would make it possible to deactivate individual cylinders. 
         [0011]    In the event of a faulty throttle valve, the bank having the open throttle valve is used for the basic power; the bank having the functioning throttle valve is used for the fine tuning. In order to avoid throttle losses in the event of functioning throttle valves, one of the throttle valves is deliberately opened further or is opened completely, and individual cylinders are deactivated simultaneously. 
         [0012]    For deactivating cylinders, the fuel supply may be interrupted to the cylinder or cylinders to be deactivated, for example, an entire engine bank. For reactivating the cylinder or cylinders or the entire engine bank, the fuel supply is resumed. Here, the so-called engine bank injection cutoff (MBEA) may be used in which only the injection into the cylinder or cylinders to be deactivated is interrupted (cut off); the valve-train assembly itself is not switched off. 
         [0013]    The present invention is in particular suitable for applications, such as aircraft engines, in which a minimum power and a change of power must be possible simultaneously. For example, in the event of a throttle valve malfunction in an eight-cylinder gasoline engine having only one throttle valve, the cylinders are fired in such a way that the power may be set in steps of 12.5%. This lies, for example, below a typical LOPC threshold of 15%. This simplifies the software strategy for activating the individual cylinders. 
         [0014]    An arithmetic unit according to the present invention, for example, a control unit of a gasoline engine, is, in particular, programmed for carrying out a method according to the present invention. 
         [0015]    The implementation of the method in the form of software is also advantageous, since it entails very low costs, in particular when an executing control unit is also used for other tasks and is therefore present anyway. Suitable data media for providing the computer program are, in particular, diskettes, hard drives, flash memories, EEPROMs, CD-ROMs, DVDs, etc. A download of a program via computer networks (Internet, Intranet, etc.) is also possible. 
         [0016]    Additional advantages and embodiments of the present invention arise from the description and the accompanying drawing. 
         [0017]    It is understood that the features stated above and the features still to be explained below are usable not only in the particular combination specified but also in other combinations or alone without departing from the scope of the present invention. 
         [0018]    The present invention is depicted schematically in the drawing based on an exemplary embodiment and is described in greater detail below with reference to the drawing. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         [0019]      FIG. 1  schematically shows a gasoline engine according to the present invention having two cylinder banks, each having a throttle valve, which may be operated according to a preferred specific embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0020]      FIG. 1  shows a gasoline engine designed, for example, as an aircraft engine in a highly schematic partial representation and is generally denoted by reference numeral  10 . Aircraft engine  10  may be operated with the aid of a method according to the present invention. 
         [0021]    Aircraft engine  10  has two cylinder or engine banks  1 ,  2 . Cylinders  11  through  13  (engine bank  1 ) and  21  through  23  (engine bank  2 ) are provided in each of engine banks  1 ,  2 . An intake manifold system  14  and  24 , which is equipped for supplying fresh air (combustion air) is assigned to each cylinder bank  1 ,  2 . A throttle valve  15  is provided in intake manifold system  14 ; a throttle valve  25  is provided in intake manifold system  24 . With the aid of throttle valves  15  and  25  it is possible to throttle the fresh air stream used to supply engine banks  1 ,  2 . With the aid of intake valves  16  and  27 , fresh air may be admitted into cylinders  11  through  13  (engine bank  1 ) and cylinders  21  through  23  (engine bank  2 ); via exhaust valves  17  and  26 , a combusted air-fuel mixture or uncombusted fresh air (in the case of deactivated cylinders) may be expelled from cylinders  11  through  13  (engine bank  1 ) and cylinders  21  through  23  (engine bank  2 ) into corresponding exhaust manifolds  19  and  29 ). 
         [0022]    Using injectors, fuel may be supplied to cylinders  11  through  13  (engine bank  1 ) and cylinders  21  through  23  (engine bank  2 ) via fuel lines  18  and  28  assigned to each of engine banks  1  through  2 . As explained, the method includes single cylinder injection cut off during partial engine operation, so that due to the injection interruption, i.e., interruption of the fuel supply to certain cylinders, a fuel input into these cylinders is suppressed. 
         [0023]    A control unit  30  is provided, which is able to influence a position of throttle valves  15  and  25  via signal lines (not shown) with the aid of control signals  31 . Control unit  30  is programmed for operating aircraft engine  10  according to the present invention. 
         [0024]    Aircraft engine  10  may be operated in an operating mode in which one of the throttle valves, for example, throttle valve  15 , is completely open. This operating mode may be assumed in particular when throttle valve  15  is defective and it is no longer possible to regulate the position of the throttle valve. However, this operating mode may be assumed alternatively in order to avoid throttle losses. For the complete opening of throttle valve  15 , a spring is provided which pretensions throttle valve  15  into the open position. 
         [0025]    If throttle valve  15  is completely open, it is possible to influence the power output generated by engine bank  1  by deactivating one or multiple of cylinders  11 ,  12 ,  13 . In this way, it is possible to set the power output of engine bank  1  in steps of (1/6)*100% of the total power output. In the event of a completely open throttle valve  15 , it is thus possible to set the power output of engine bank  1  gradually from (0/6)*100% through (3/6)*100% of the total power output. 
         [0026]    With the aid of a conventional, regulated operation of throttle valve  25 , it is thus possible to set the power output of engine bank  2  continuously from (0/6)*100% through (3/6)*100% of the total power output.