Abstract:
A turbocharger control system is disclosed. The control system may have an engine and a fuel system configured to regulate fuel flow into the engine. The control system may further have an air induction system configured to regulate air flow into the engine and a sensor situated to sense a speed value of the air induction system. The controller may also have a controller configured to receive the speed value and regulate fuel flow into the engine as a function of the speed value.

Description:
TECHNICAL FIELD 
     The present disclosure relates generally to a control system and, more particularly, to a control system that limits the speed of a turbocharger by controlling the rate of fuel flowing into an associated engine. 
     BACKGROUND 
     Internal combustion engines such as, for example, diesel engines, gasoline engines, and gaseous fuel powered engines, combust a mixture of air and fuel to produce power. The amount of air and fuel, and the ratio of air-to-fuel introduced into a combustion chamber of the engine can affect power output, efficiency, and exhaust emissions of the engine. Typically, the amount of air introduced into the engine and the ratio of air-to-fuel is controlled by a number of different fluid handling components located in both the air induction and exhaust systems of the engine. 
     An engine often includes a turbocharger to increase a power density of the engine. A turbocharger includes a turbine, driven by exhaust of the engine, to rotate a compressor and pressurize air directed into the engine. Depending on an internal geometry setting of the turbine and/or compressor, more or less air will be compressed to a higher or lower pressure for a given rotation. A variable geometry turbocharger (VGT), often used with diesel engines, is capable of altering the direction of exhaust flow to optimize turbine response. A VGT includes adjustable vanes within the turbine to adjustably direct exhaust flow radially inward toward turbine blades. It is common for a control system to command an actuator to change the angle of the vanes to optimize operation of the turbine. Changing the angle of air flow increases or decreases the speed of the turbocharger with a given amount of exhaust flow. Although this system can be successfully implemented, failure of the turbocharger due to excessive turbo speed my occur when the actuator is slow to adjust the movable vanes into a position that will decrease turbocharger speed. Hence, turbocharger failure may be caused by excessive energy passing through the turbocharger in response to a slow reaction by the actuator. 
     One attempt to minimize the likelihood of turbocharger failure has been described in U.S. Pat. No. 6,192,867 (the &#39;867 patent) to Fenchel et al. The &#39;867 patent describes a method and device for protecting a turbo-supercharger by determining a limit value for the fuel quantity metered to the engine from an intake air pressure, as derived from a program map. Determination of the intake air pressure does not require a sensor, because it is derived from a program map based on a function of charging pressures, engine speed, and a fuel quantity preset corresponding to an accelerator position. Reducing the fuel quantity decreases the overall energy in the exhaust conduit prevailing on the turbine of the turbocharger. As a result, the &#39;867 patent is able to prevent the turbocharger from reaching a critical turbocharger speed. 
     Although the &#39;867 patent may help reduce the likelihood of turbocharger failure due to excessive turbine speed, it may be overly complex and limited. The &#39;867 patent is complex because the intake air pressure must be determined based on numerous input values. That is, it may be possible for the air pressure to be low and yet turbo speeds to be excessive. The &#39;867 patent&#39;s derivation of intake air pressure may not accurately correspond to the actual speed of the turbocharger. The &#39;867 patent is limited because it does not consider the effects of turbocharger failure when using a variable geometry turbocharger that includes an exhaust flow control device. That is, the &#39;867 may be inapplicable to a turbocharger including a VGT. 
     The disclosed control system is directed to overcoming one or more of the problems set forth above. 
     SUMMARY OF THE INVENTION 
     In one aspect, the present disclosure is directed to a turbocharger control system. The control system may include an engine and a fuel system configured to regulate fuel flow into the engine. The control system may further include an air induction system configured to regulate air flow into the engine, and a sensor situated to sense a speed value of the air induction system. The controller may also include a controller configured to receive the speed value and regulate fuel flow into the engine as a function of the speed value. 
     In another aspect, the present disclosure is directed to a method of limiting turbo speed. The method may include sensing a turbo speed value. The method may further include comparing the turbo speed value to a turbo speed limit value. The method may also include regulating fuel flow into an engine based on the comparison. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a schematic illustration of an exemplary disclosed control system; 
         FIG. 2  is a schematic illustration of a variable geometry turbocharger with vanes in a substantially closed position for use with the control system of  FIG. 1 ; 
         FIG. 3  is a schematic illustration of a variable geometry turbocharger with vanes in a substantially open position for use with the control system of  FIG. 1 ; and 
         FIG. 4  is a flow diagram illustrating a method of limiting turbo speed by controlling engine fuel. 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  illustrates a control system  10  for limiting turbo speed by controlling engine fuel. Control system  10  may control operation of a power source  12 , a fuel system  14 , and an air induction system  16 . Power source  12  may embody an engine having multiple components that cooperate to combust a fuel/air mixture and produce a power output. For example, power source  12  may be a diesel engine, a gasoline engine, or a gaseous fuel-powered engine having an engine block  18  that at least partially defines a plurality of cylinders  19 , a piston (not shown) slidably disposed within each cylinder, and a cylinder head associated with each cylinder  19 . The cylinder  19 , piston, and cylinder head may form a combustion chamber (not shown). Power source  12  may draw the fuel/air mixture into each cylinder  19 , compress the mixture with the piston, and ignite the mixture to produce a combination of power, heat, and exhaust. The heated exhaust may be used to pressurize air induction system  16 . 
     Fuel system  14  may include a fuel tank  20 , a fuel pump  22 , and a fuel regulator  24 . Fuel tank  20  may hold a supply of fuel. Fuel may be drawn from fuel tank  20  by fuel pump  22  via a fuel line  26 . After exiting fuel pump  22 , fuel may be discharged to fuel regulator  24  via a fuel line  28 . Fuel regulator  24  may regulate the amount of fuel permitted to enter power source  12  via fuel line  30 . 
     Fuel pump  22  may be any type of pump capable of imparting fuel flow from fuel tank  20  through fuel system  14 . For example, fuel pump  22  may be a fixed displacement/variable delivery pump, a variable displacement pump, or a fixed delivery pump. Fuel pump  22  may be operably connected to and mechanically driven by power source  12 . Alternatively, fuel pump  22  may be driven electronically, hydraulically, pneumatically, or in any other known manner. 
     Fuel regulator  24  may control fuel flow entering power source  12  and, more specifically may control fuel flow into each combustion chamber of power source  12 . As shown in  FIG. 1 , fuel regulator may embody a valve located outside engine block  18 . Alternatively, fuel regulator  24  may embody a fuel injector system (not shown) including fuel injectors that may be disposed within engine block  18  to inject a regulated amount of pressurized fuel into each cylinder. It is contemplated that fuel regulator  24  may be operated hydraulically, mechanically, electrically, pneumatically, or in any other known manner. 
     Air induction system  16  may increase the power output of power source  12  by compressing air flowing into power source  12  with a turbocharger  32 . Turbocharger  32  may include a turbine  34  mechanically connected on a shared axis to a compressor  36  via a shaft  38 . Turbocharger  32  may include a bearing housing including a bearing (not shown) for supporting shaft  38  and improving efficiency and reducing wear of turbocharger  32 . It is contemplated that the bearing may be a rotary bearing and more specifically, a fluid bearing. Alternatively, the bearing may be any type of bearing sufficient to reduce wear of turbocharger  32 . 
     Power source  12  may include an exhaust manifold  40  used to direct exhaust flow from cylinders  19  of engine block  18  following combustion of the air/fuel mixture. Turbine  34  may be connected to exhaust manifold  40  by an exhaust line  42 . Compressor  36  may be connected to an air inlet manifold  44  of power source  12  via an air inlet line  46 . It is contemplated that an air cooler  48  may be inserted between compressor  36  and air inlet manifold  44  to cool the pressurized air before the air enters power source  12 , if desired. 
     Turbine  34  may include a plurality of turbine blades  50  (shown in  FIGS. 2 and 3 ) mounted to a turbine wheel  52 . Turbine wheel  52  may be connected to shaft  38 . As exhaust flows from exhaust manifold  40  into turbine  34 , exhaust flow my cause turbine blades  50  to spin shaft  38  and thereby drive compressor  36 . Exhaust flow may exit turbine  34  via an exhaust exit port  58 . 
     The amount of exhaust flow passing through turbine  34  may affect the speed of the compressor  36 . For example, an increase in exhaust flow and/or exhaust heat from power source  12  may cause turbine blades  50  to spin shaft  38  and drive compressor  36  at a higher rotational speed. Likewise, a reduction in exhaust flow and/or exhaust heat from power source  12  may cause turbine blades  50  to spin shaft  38  and drive compressor at a slower rotational speed. 
     Compressor  36  may include a plurality of compressor blades  54  mounted to a compressor wheel  56 . Compressor wheel  56  may be connected to shaft  38 . Rotational force from turbine  34  may be transferred to compressor  36  via shaft  38  and thereby spin compressor blades  54  to pressurize ambient air that may enter compressor  36  via an ambient air inlet port  59 . Therefore, rotation of compressor blades  54  within compressor  36  may pressurize ambient air entering power source  12 . 
     Air induction system  16  may include at least one exhaust flow control device for altering exhaust flow, for example, a wastegate  60  and/or one or more adjustable vanes  62  (shown in  FIGS. 2 and 3 ). The exhaust flow control devices, either used individually or in combination, may control the speed of turbocharger  32  by regulating the amount or the angle of exhaust flow from power source  12  into turbine  34 . Turbo speed may be defined as the rotational speed of turbocharger  32 , and more specifically, the speed of rotational components (e.g., shaft  38 , turbine wheel  52 , and compressor wheel  56 ) within turbocharger  32 . 
     Wastegate  60  may include a valve (not shown) located near an exhaust inlet port  64  of turbine  34  that regulates turbo speed by selectively directing excessive exhaust flow to bypass turbine blades  50 . Wastegate  60  may include an open position, at which the wastegate valve is fully open and exhaust flow is free to bypass turbine  34  and thereby may decrease the speed of turbocharger  32 . Wastegate  60  may also include a closed position, at which the wastegate valve is fully closed and exhaust flow is free to enter turbine  34  and thereby may increase the speed of turbocharger  32 . It is contemplated that the wastegate valve may adjust to various positions between the open and closed positions to precisely control exhaust flow in or around turbine  34  to thereby target a desired speed and/or intake air pressure. Wastegate  60  may include any known valve capable of regulating exhaust flow in or around turbine  34 . For example, wastegate  60  may include a butterfly or flapper-type valve. Alternatively or in addition to using wastegate  60 , turbine  34  may include one or more adjustable vanes  62  to control turbo speed and/or the intake air pressure (i.e., turbocharger  32  may be a variable geometry turbine (VGT)). 
       FIGS. 2 and 3  illustrate a VGT with adjustable vanes  62  in a substantially closed position and a substantially open position, respectively. A VGT may control turbo speed and intake air pressure by adjusting vanes  62  to alter exhaust flow within housing  66  toward or around turbine blades  50  to vary a force of impact on turbine blades  50 . It is contemplated that the configuration of vanes  62  may be adjusted by any known manner to control exhaust flow through turbine  34 . Each adjustable vane  62  may be pivoted about an axis  68  by an actuator  70  to alter exhaust flow within turbine  34 . For example, at low engine speeds, actuator  70  may cause vanes  62  to be partially closed (shown in  FIG. 2 ), which may accelerate exhaust flow toward the turbine blades  50  and thereby cause turbine  34  to spin faster and compressor  36  to compress more air to a higher level. Alternatively, at high engine speeds, exhaust flow may already be sufficiently strong. Therefore, actuator  70  may open vanes  62  (shown in  FIG. 2 ) to reduce the relative exhaust flow force on turbine blades  50 . 
     Actuator  70  may adjust the position of vanes  62 . Actuator  70  may be a hydraulic actuator. For example, actuator  70  may be connected to turbine  34  by a hydraulic line  72 . Alternatively, actuator  70  may be an electrical, pneumatic, or any other known actuator capable of controlling the position of vanes  62 . It is contemplated that actuator  70  may also actuate wastegate  60  or that an additional actuator may control operation of wastegate  60 . 
     Control system  10  may regulate operation of power source  12 , fuel system  14 , and air induction system  16  using a controller  74 . Controller  74  may communicate with a speed sensor  76  associated with power source  12  to monitor a speed of power source  12  via a communication line  86 . Controller  74  may further communicate with a flow sensor  78  associated with fuel system  14  to monitor and regulate fuel flow via a communication line  88 . Controller  74  may also communicate with a position sensor  80  associated with wastegate  60  to monitor and control movement of the position of the wastegate valve via a communication line  90 . Additionally, controller  74  may communicate with a speed sensor  82  associated with a turbocharger  32  to monitor speed of turbocharger  32  via a communication line  92 . Controller  74  may further communicate with actuator  70  to control movement of vanes  62  via a communication line  94 . It is contemplated that turbine  34  may include a position sensor  84  (shown in  FIGS. 2 and 3 ) to communicate the position of vanes  62  to controller  74  via a communication line  96 . Further, it is contemplated that an intake air pressure sensor (not shown) may be implemented, if desired. 
     Controller  74  may embody a single microprocessor or multiple microprocessors. It is contemplated that controller  74  could be a general power source processor capable of controlling numerous power source functions. Controller may include all of the components (not shown) required to run an application such as, for example, a memory device, a secondary storage device, and a processor. Controller  74  may transmit and receive communication from various sensors and power source devices, for example, sensors  76 ,  78 ,  80 ,  82 , and  84 . Controller  74  may analyze communications received from the various sensors and power source devices using stored instructions to determine whether action is required. For example, controller  74  may receive turbo speed data from turbo speed sensor  82  and compare the turbo speed data to a turbo speed limit stored in the memory device of controller  74 , and, based on the results of the comparison, controller  74  may transmit signals to one ore more components to cause adjustments thereto. 
     Controller  74  may access stored data for operation of power source  12 , fuel system  14 , and air induction system  16  from lookup tables  98  stored in memory. For example, controller  74  may access a first lookup table to store a turbo speed limit value and a second lookup table to store an engine derate value. While it may be possible for controller  74  to perform calculations for a turbo speed limit value and an engine derate value, it may be faster and more efficient for controller to access the values from lookup tables stored in memory. 
     Sensors  76 ,  78 ,  80 ,  82  and  84  may be any known sensor capable of sensing operating conditions of power source  12 , fuel system  14 , or air induction system  16 . For example, speed sensor  76  may be an engine speed sensor located in or near engine block  18  to monitor a rotational speed of an associated crankshaft. Flow sensor  78 , may be a fuel flow sensor located in or near the fuel system  14  to monitor a flow rate of fuel being sprayed into the combustion chambers of power source  12 . Position sensor  80  may detect a position of a valve within wastegate  60 . Speed sensor  82  may be a rotational speed sensor located in or near turbine  34  to measure the speed of turbine blades  50 , compressor blades  54 , and shaft  38 . More specifically, speed sensor  82  may be located in or near a bearing housing (not shown) of turbine  34 . Position sensor  84  may be an angle sensor located in or near turbine housing  66  to detect a position of vanes  62 . 
     Controller  74  may regulate operation of wastegate  60  and vanes  62  based on air pressure. Hence, as intake air pressure changes, controller  74  may continuously regulate operation of wastegate  60  and vanes  62 . Controller  74  may limit fuel flow based on sensed turbo speed. Hence, when sensed turbo speed exceeds a predetermined turbo speed limit, controller  74  may periodically limit fuel flow until the sensed turbo speed drops below the turbo speed limit. 
       FIG. 4  shows a flow-diagram illustrating a method of limiting turbo speed.  FIG. 4  will be discussed in detail in the following section. 
     INDUSTRIAL APPLICABILITY 
     The disclosed control system may be used in any system where excessive turbo speed is a concern. The disclosed control system may regulate turbo speed and air intake pressure continuously and then limit excessive turbospeed to prevent turbocharger failure. Operation of control system  10  will now be described. 
     Turbo speed and/or intake air pressure are typically regulated by bypassing exhaust flow around turbine  34  via a wastegate  60  or by adjusting the angle of exhaust flow within turbine  34 . When it is desirable to regulate turbo speed, wastegate  60  may adjust the amount of exhaust flow into or bypassing turbine  34  via the wastegate valve. For example, when turbocharger  32  experiences high turbo speed, controller  74  may bypass at least a portion of the exhaust flow around turbine  34  via wastegate  60 . When it is desired to increase turbo speed, the wastegate valve may be positioned to allow a greater amount of exhaust flow to enter turbine  34 . Optionally or in addition to wastegate control, vane control may also be used to regulate turbo speed and/or intake air pressure. Controller  74  may signal actuator  70  to adjust the position of vanes  62  and thereby adjust the angle of exhaust flow within turbine  34 . More specifically, actuator  70  may pivot vanes  62  from a first position to a second position to regulate the angle and force of exhaust flow that may impact turbine blades  50 . 
     A problem may arise that limits the reaction time of actuator  70  and/or wastegate  60 . For example, actuator  70  may not react with sufficient speed to adjust vanes  62  to prevent or reduce excessive exhaust flow from causing turbo speed to reach or exceed a predetermined turbo speed limit. More specifically, hydraulic actuators may be prone to sticking or slow movement, especially at low oil temperatures. Sudden changes in engine speed and engine load (i.e., downshifts) may outpace the reaction time of actuator  70 . Therefore, in addition to regulating turbo speed via exhaust flow control, it may be desirable to limit turbo speed via fuel flow control. Engine speed may be regulated by controlling a rate of fuel flow into power source  12 . It is contemplated that under certain adverse conditions, for example, low oil temperatures, high altitude, or sudden changes in engine speed or engine load, turbo speed may be controlled by regulating fuel flow as an alternative to managing a bypass or an angle of exhaust flow. More specifically, regulating fuel to limit turbo speed may be desirable when operation of an exhaust flow control device or an associated actuator  70  is insufficient to maintain the speed of turbocharger  32  below a predetermined speed limit. 
     With regard to  FIG. 4 , speed sensor  82  may detect a turbo speed value (TS) of turbocharger  32  and transmit the turbo speed value to controller  74  via communication line  92  (step  100 ). In response to receiving the turbo speed value, controller  74  may be instructed to access a turbo speed limit value (TL) from a first stored look-up table (step  102 ). Controller  74  may calculate a turbo speed error value (TE) by subtracting the turbo speed limit value from the sensed turbo speed value (step  104 ). Speed sensor  76  may detect an engine speed value (ES) of power source  12  and transmit the engine speed value to controller  74  via communication line  86  (step  106 ). Controller  74  may utilize the calculated turbo speed error value and the sensed engine speed value to access an engine derate value (ED) from a second stored look-up table (step  108 ). More specifically, the engine derate value may be expressed as a percent initialized to zero and determined from a map look-up, whereby engine derate may be increased or decreased. For example, the engine derate value may increase if the turbo speed error value is positive and the engine derate value may decrease if the turbo speed error value is negative, whereby the engine derate value may be applied by summing the increases and decreases in the turbo speed error values over time. Hence, as the turbo speed error value remains positive, the engine derate value may continue to increase, and when the turbo speed error rate is negative, the engine derate value may decrease until it reaches zero. Controller  74  may determine a change in fuel flow into power source  12  based on the engine derate value. Controller  74  may send a signal to fuel regulator  24  via communication line  88  to limit the amount of fuel flow from fuel system  14  into power source  12  and thereby limit engine speed (step  110 ). 
     Exhaust flow control, by wastegate and/or vane operation, may be continuously implemented as needed to selectively regulate turbo speed and/or intake air pressure. However, when exhaust flow control is insufficient to maintain a sensed turbo speed below a predetermined limit, then fuel flow regulation may be implemented in addition to or as an alternative to exhaust flow control. Hence, fuel flow control and exhaust flow control may be simultaneously or separately implemented to limit excessive turbo speed when the turbo speed value exceeds the turbo speed limit value. Once the sensed turbo speed is below the predetermined turbo speed limit, fuel flow regulation may cease until the sensed turbo speed again exceeds the predetermined turbo speed limit. 
     Because control system  10  may derate power source operation via engine fuel limiting, in addition to or as an alternative to exhaust flow control, responsiveness may be improved. Improvement may be particularly noticeable at low oil temperatures, high altitude, or during sudden engine speed or load changes. Engine speed or load changes can more quickly change turbine operation, as compared to merely implementing exhaust flow control. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed control system without departing from the scope of the disclosure. Other embodiments of the control system will be apparent to those skilled in the art from consideration of the specification and practice of the control system disclosed herein. It is intended that the specification and examples be considered as exemplary only, with a true scope of the disclosure being indicated by the following claims and their equivalents.