Patent Publication Number: US-7900594-B2

Title: System and method for injecting fuel into a direct injection engine

Description:
FIELD 
     The present disclosure relates to a direct injection internal combustion engine. More particularly, the invention relates to a system and method for injecting fuel into a direct injection internal combustion engine at a specified time and for a specified duration. 
     BACKGROUND 
     A typical internal combustion engine in a motor vehicle operates by combusting a mixture of a vaporized fuel (i.e. gasoline) and air in a cylinder or combustion chamber. Generally, the combustion chamber includes a piston that is forced to translate or move up and down as a result of the combustion of the fuel/air mixture. The piston is rotatably secured to a crankshaft. The movement of the piston rotates the crankshaft which ultimately rotates the drive wheels of the vehicle. 
     Many internal combustion engines have four-stages of operation. These stages, also referred to as strokes, relate to the position of the piston within the combustion chamber. For example, a typical four-stage operation includes an intake stroke, a compression stroke, an expansion stroke, and an exhaust stroke. During each stroke the piston moves from one end of the combustion chamber to the other end of the chamber and the crankshaft rotates 180 degrees. During the intake stroke the fuel mixture is drawn into the combustion chamber. During the compression stroke the fuel mixture is compressed and then ignited. During the expansion stroke the piston is forced toward the bottom of the combustion chamber by the combustion process. Finally, during the exhaust stroke the combustion gases are expelled from the combustion chamber. 
     Fuel is delivered to the combustion chamber using a fuel delivery system. Conventional fuel delivery systems include, for example, a fuel tank, a low pressure pump, a high pressure pump, a plurality of fuel lines, a fuel rail, a pressure sensor, and a fuel injector. The low pressure fuel pump pumps the fuel out of the fuel tank and pressurizes the fuel to a first pressure. The low pressure pump is typically electrically driven by the vehicle&#39;s battery. The high pressure pump pumps the fuel into the fuel rail at a second pressure that is higher than the first pressure. The high pressure pump is typically mechanically driven by the engine. The pressure sensor transmits a signal indicative of the pressure sensed in the fuel rail to a control device, such as a microcontroller. The fuel rail distributes the fuel to the fuel injectors which inject fuel into the cylinders of the engine. 
     Conventional fuel delivery systems inject fuel into the combustion chamber during the intake stroke and during the compression stroke. However, this method of injection is not sufficient to supply the required amount of fuel to the fuel injector during certain engine operating conditions, such as a cold start condition. This may result from, for instance, the pressure in the fuel rail being insufficient during the cold start condition because the high pressure fuel pump is unable to supply the necessary flow. This typically occurs because the engine is operating at a low speed during the cold start condition prior to reaching a steady state condition. As such, vehicles started under a cold start condition generally need more fuel than what the high pressure fuel pump is capable of delivering due to the low operating speed of the engine. Accordingly, during cold start conditions these engines mostly rely on the low pressure fuel pump. 
     Therefore, there is a need for an improved system and method for delivering fuel to a direct injection engine to overcome the limitations of the conventional fuel delivery system during, for example, cold start conditions. 
     SUMMARY 
     The present invention provides a method for controlling the operation of at least one fuel injector in a direct injection four stroke internal combustion engine. The method includes the steps of initiating fuel injection into a combustion chamber during an expansion stroke of the engine, injecting fuel into the combustion chamber during an exhaust stroke of the engine, injecting fuel into the combustion chamber during an intake stroke of the engine, and terminating fuel injection into the combustion chamber during a compression stroke of the engine. 
     In one aspect of the present invention, the step of initiating fuel injection into the combustion chamber further includes initiating fuel injection during a first half of the expansion stroke of the direct injection internal combustion engine. 
     In another aspect of the present invention, the step of initiating fuel injection into the combustion chamber further includes initiating fuel injection during a second half of the expansion stroke of the direct injection internal combustion engine. 
     In yet another aspect of the present invention, the step of initiating fuel injection into the combustion chamber further includes initiating fuel injection between 620° to 660° of crankshaft rotation of the engine, wherein 0° of crankshaft rotation is the end of the compression stroke. 
     In still another aspect of the present invention, the step of terminating fuel injection into the combustion chamber further includes terminating fuel injection during a first half of the compression stroke of the direct injection internal combustion engine. 
     In still another aspect of the present invention, the step of terminating fuel injection into the combustion chamber further includes terminating fuel injection during a second half of the compression stroke of the direct injection internal combustion engine. 
     In still another aspect of the present invention, the step of terminating fuel injection into the combustion chamber further comprises terminating fuel injection between 40° to 80° of crankshaft rotation of the engine, wherein 0° of crankshaft rotation is the end of the compression stroke. 
     The present invention also provides a system for controlling the operation of at least one fuel injector in a direct injection four stroke internal combustion engine. The system includes a pressure sensor configured to sense the pressure in a fuel rail and transmit a signal indicative of the pressure. A microcontroller communicates with the pressure sensor for receiving the pressure signal. The microcontroller includes control logic for controlling the operation of the at least one fuel injector in response to the received pressure signal. The control logic includes a first control logic for initiating fuel injection into a combustion chamber during an expansion stroke of the engine, a second control logic for injecting fuel into the combustion chamber during an exhaust stroke of the engine, a third control logic for injecting fuel into the combustion chamber during an intake stroke of the engine, and a fourth control logic for terminating fuel injection into the combustion chamber during a compression stroke of the engine. 
     In one aspect of the present invention, the first control logic further comprises initiating fuel injection during a first half of the expansion stroke of the direct injection internal combustion engine. 
     In another aspect of the present invention, the first control logic further comprises initiating fuel injection during a second half of the expansion stroke of the direct injection internal combustion engine. 
     In yet another aspect of the present invention, the first control logic further comprises initiating fuel injection between 620° to 660° of crankshaft rotation of the engine, wherein 0° of crankshaft rotation is the end of the compression stroke. 
     In still another aspect of the present invention, the fourth control logic further comprises terminating fuel injection during a first half of the compression stroke of the direct injection internal combustion engine. 
     In still another aspect of the present invention, the fourth control logic further comprises terminating fuel injection during a second half of the compression stroke of the direct injection internal combustion engine. 
     In still another aspect of the present invention, the fourth control logic further comprises terminating fuel injection between 40° to 80° of crankshaft rotation of the engine, wherein 0° of crankshaft rotation is the end of the compression stroke. 
     Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. 
    
    
     
       DRAWINGS 
       The drawings described herein are for illustration purposes only and are not intended to limit the scope of the present disclosure in any way. 
         FIG. 1  is a schematic view of a system for injecting fuel in an internal combustion engine in accordance with an embodiment of the present invention; 
         FIG. 2  is a method for increasing the operating time of a fuel injector to inject fuel into the internal combustion engine shown in  FIG. 1 ; and 
         FIG. 3  is a diagram illustrating the operating time of a fuel injector from start of injection to end of injection relative to four cycles of the internal combustion engine shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     Referring now to  FIG. 1 , a system for injecting fuel into a direct injection internal combustion engine is generally indicated by reference number  10 . The system  10  includes an internal combustion engine  20 , a fuel system  30 , and a control system  50 . The fuel system  30  is operable to provide fuel to the internal combustion engine  20  and is controlled by the control system  50 . 
     The engine  20  generally includes a cylinder  21  defined by an engine block  23 . The cylinder  21  is capped at an end thereof by a cylinder head  24 . While in the particular example provided the engine  20  includes only one cylinder  21 , it should be appreciated that the engine  20  may have any number of cylinders, arranged in various configurations, without departing from the scope of the present invention. The engine  20  further includes a piston  22  located within the cylinder  21 . The piston  22  is configured to translate within the cylinder  21  between a top dead center (“TDC”) position and a bottom dead center (“BDC”) position. The TDC position is defined as the position of the piston  22  when it is closest to the cylinder head  24 , indicated by reference number  25 . The BDC position is defined as the position of the piston  22  when it is farthest from the cylinder head  24 , indicated by reference number  27 . The piston  22  is coupled to a crankshaft  29 . The crankshaft  29  is actuated or rotated by the translation of the piston  22 . The piston  22  and the cylinder head  24  define a combustion chamber  26  within the cylinder  21 . The engine  20  also includes a spark plug  28 . The spark plug  28  extends through the cylinder head  24  and into the combustion chamber  26 . It should be appreciated that the orientation and configuration of the spark plug  28  may vary from what is shown in  FIG. 1  without departing from the scope of the present invention. The spark plug  28  ignites a fuel/air mixture  31  present in the combustion chamber  26 , as will be described in greater detail below. 
     The fuel system  30  includes a fuel tank  32 , a low pressure fuel pump  34 , a high pressure fuel pump  38 , a first fuel line  36 , a second fuel line  40 , a fuel rail  42 , and a fuel injector  44 . The fuel tank  32  contains a combustible fuel, such as gasoline. The low pressure fuel pump  34  is connected to the fuel tank  32  and is operable to pump the fuel out of the fuel tank  32  at a first fuel pressure to a first fuel line  36 . While in the particular example shown the low pressure fuel pump  34  is located within the fuel tank  32 , it should be appreciated that the low pressure fuel pump  34  may be located external to the fuel tank  32  without departing from the scope of the present invention. The low pressure fuel pump  34  of this example may be activated or operated electrically, mechanically, hydraulically, or by any other means). The high pressure fuel pump  38  is connected to and receives fuel from the low pressure fuel pump  34  via the first fuel line  36 . The high pressure fuel pump  38  of this example is driven by the engine  20  and is configured to pump fuel at a second fuel pressure that is greater than the first fuel pressure to the fuel rail  42  via the second fuel line  40 . The fuel rail  42  is connected to the fuel injector  44  and is operable to distribute the fuel to the fuel injector  44 . The fuel injector  44  is arranged centrally within the cylinder head  24  in the example provided and is configured to inject fuel into the combustion chamber  26 . It should be appreciated that any number of fuel injectors  44 , corresponding, for example, to the number of cylinders  21  within the engine  20 , may be employed without departing from the scope of the present invention. 
     The control system  50  includes a pressure sensor  52 , a crankshaft position sensor  53 , and a microcontroller  54 . The pressure sensor  52  is configured to sense the pressure in the fuel rail  42  and send a signal indicative of the pressure to the microcontroller  54 . The crankshaft position sensor  53  is configured to sense the rotational position of the crankshaft  29 . The microcontroller  54  is, for example, an electronic device having a preprogrammed digital computer or processor, control logic, memory used to store data, and at least one I/O peripheral. However, other types of microcontrollers may be employed without departing from the scope of the present invention. The control logic includes a plurality of logic routines for monitoring, manipulating, and generating data. The microcontroller  54  may be part of an engine control module for the motor vehicle or a separate module. The microcontroller  54  also is operable to determine a current operating state of the motor vehicle, for example, whether the motor vehicle is in a cold start condition defined as when the engine  20  has not been running for a period of time prior to ignition. 
     Turning to  FIGS. 2 and 3 , and with continued reference to  FIG. 1 , a method for increasing the operating time of the fuel injector  44  during certain operating conditions will now be described. In  FIG. 2 , the method for increasing the operating time of the fuel injector is illustrated in a flow chart indicated by reference number  56 .  FIG. 3  illustrates the operating time of the fuel injector  44 , indicated by reference number  102 , relative to the angle of rotation of the crankshaft  29  and the location of the piston  22  through the four cycles or stages of the engine  20 . The operating time of the expansion stroke is indicated by reference number  104 , the operating time of the exhaust stroke is indicated by reference number  106 , the operating time of the intake stroke is indicated by reference number  108 , and the operating time of the compression stroke is indicated by reference number  110 . For explanatory purposes, the start of expansion stroke is defined herein as 720° of crankshaft rotation, indicated by reference number  112 . And the end of the compression stroke is defined herein as 0° of crankshaft rotation, indicated by reference number  114 . Fuel injection begins at a start of injection (“SOI”) event  116  and terminates at an end of injection (“EOI”) event  118 . In the example provided, the method  56  is operable to increase the operating time of the fuel injector  44  and introduce more fuel into the cylinder  21  during, for example, a cold start condition. 
     The method  56  is initiated at step  58 . At step  60 , the pressure sensor  52  senses the pressure of the fuel in the fuel rail  42  and sends a signal indicative of the fuel pressure to the microcontroller  54 . At step  62 , the microcontroller  54  determines the current operating condition of the vehicle. For example, the microcontroller  54  determines whether a normal operating condition exists or whether a condition exists that requires increased injector  44  operating time, such as during a cold start condition. At step  64 , the microcontroller  54  determines whether to increase the operating time of the fuel injector  44  based upon the current operating condition determined in step  62 . In the particular example shown, if the microcontroller  54  determines at step  62  that the motor vehicle is operating in a cold start condition, then the operating time of the fuel injector  44  will be increased and the method  56  advances to step  66 . Otherwise the method returns to step  58  and steps  60 ,  62 , and  64  are repeated. 
     At step  66 , the fuel injectors  44  are activated during an expansion stroke of the piston  22 . As shown in  FIG. 3 , the expansion stroke of the piston  22  begins when the piston  22  is positioned at the TDC position or 720° of crankshaft rotation. During the expansion stroke the piston  22  travels downward to the BDC position or 540° of crankshaft rotation. In one embodiment of the present invention, the fuel injector  44  is activated during a first half of the expansion stroke of the piston  22 , or between about 720° to 630° of crankshaft rotation. In another embodiment of the present invention, the fuel injector  44  is activated during a second half of the expansion stroke of the piston  22 , or between about 630° to 540° of crankshaft rotation. In still another embodiment of the present invention, the fuel injector  44  is preferably activated at between 620 to 660° of crankshaft rotation. The fuel injector  44  continues to operate throughout the remainder of the expansion stroke and inject fuel into the combustion chamber  26 . 
     At step  68 , the piston  22  is at the start of an exhaust stroke and positioned at BDC, or 540° of crankshaft rotation as illustrated in  FIG. 3 . During the exhaust stroke the piston  22  travels upward from the BDC position to the TDC position, or 360° of crankshaft rotation. The fuel injector  44  continues to operate throughout the exhaust stroke and more specifically from 540° to 360° of crankshaft rotation. 
     At step  70 , the piston  22  is at the start of the intake stroke and positioned at the TDC position, or 360° of crankshaft rotation as illustrated in  FIG. 3 . During the intake stroke the piston  22  travels downward from the TDC position to the BDC position, or 180° of crankshaft rotation. The fuel injector  44  continues to operate throughout the intake stroke and more specifically from 360° to 180° of crankshaft rotation. 
     At step  72 , the piston  22  is at the start of the compression stroke and positioned at the BDC position, or 180° of crankshaft rotation as illustrated in  FIG. 3 . During the compression stroke the piston  22  travels upward from the BDC position to the TDC or 0° of crankshaft rotation. The fuel injector  44  continues to operate from the start of the compression stroke, or at 180° of crankshaft rotation, until the end of injection (“EOI”)  118  where the fuel injector  44  is deactivated and fuel injection terminates. Generally, fuel injection terminates prior to the pressure in the combustion chamber  26  reaching the pressure generated in the fuel rail  42  by the low pressure pump  34 . In one embodiment of the present invention, the fuel injector  44  is deactivated during a first half of the compression stroke of the piston  22 , or between about 180° to 90° of crankshaft rotation. In another embodiment of the present invention, the fuel injector  44  is deactivated during a second half of the compression stroke of the piston  22 , or between about 180° to 0° of crankshaft rotation. In still another embodiment of the present invention, the fuel injector  44  is deactivated at between 80° to 40° of crankshaft rotation. 
     In conclusion, the present invention has many advantages and benefits over the prior art. For example, the method provides the ability to start direct injection internal combustion engines with various fuels i.e. Ethanol, Methanol, and gasoline without resealing (enlarging) current hardware to handle cold starts. 
     The description of the invention is merely exemplary in nature and variations that do not depart from the gist of the invention are intended to be within the scope of the invention. Such variations are not to be regarded as a departure from the spirit and scope of the invention.