Abstract:
A system includes a fuel detection module, a misfire detection module, and a fuel control module. The fuel detection module detects when a fuel supplied to an engine having C cylinders has a high drivability index (HIDI), where C is an integer greater than 1. The misfire detection module detects whether M of the C cylinders misfire when the fuel has the HIDI, where M is an integer, and 1≦M&lt;C. The fuel control module injects a first amount of the fuel into the M of the C cylinders when M is less than or equal to D, where D is an integer less than C, and where the first amount is greater than a first predetermined amount.

Description:
FIELD 
     The present disclosure relates to fuel systems, and more particularly to systems and methods for controlling fuel injected into cylinders of an internal combustion engine. 
     BACKGROUND 
     The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. 
     An internal combustion engine compresses and ignites a mixture of air and fuel in one or more cylinders to produce engine power. If the mixture fails to ignite and/or completely burn, an incomplete combustion results in a cylinder misfiring. Misfiring of cylinders can damage engine components, produce unwanted emissions, and/or impact fuel economy. 
     Cylinders can misfire when the mixture is lean. The mixture may be lean due to various reasons. For example, the mixture may be lean when fuel injectors are partially clogged and/or when the fuel has a high drivability index (HIDI). The HIDI affects fuel combustion as follows. 
     Fuel is commonly characterized by fuel distillation curves. The fuel distillation curves plot percentages of fuel vaporization as a function of fuel temperature. Normally, X % of fuel may evaporate at a temperature T. Accordingly, Y amount of fuel may yield an air-to-fuel ratio of R at temperature T. However, when the drivability index of the fuel is high, a temperature greater than T is required to evaporate X % of the fuel having the HIDI. Accordingly, when the drivability index of the fuel is high, more than Y amount of fuel is required to obtain the air-to-fuel ratio of R at temperature T. 
     SUMMARY 
     A system comprises a fuel detection module, a misfire detection module, and a fuel control module. The fuel detection module detects when a fuel supplied to an engine having C cylinders has a high drivability index (HIDI), where C is an integer greater than 1. The misfire detection module detects whether M of the C cylinders misfire when the fuel has the HIDI, where M is an integer, and 1≦M&lt;C. The fuel control module injects a first amount of the fuel into the M of the C cylinders when M is less than or equal to D, where D is an integer less than C, and where the first amount is greater than a first predetermined amount. 
     The fuel control module injects the first amount of the fuel into each one of the C cylinders when M is greater than D. The fuel control module increases the first amount until the first amount is equal to a second predetermined amount that is greater than the first predetermined amount. When the first amount is greater than or equal to the second predetermined amount, the fuel control module stops injecting the first amount of the fuel into the M of the C cylinders if at least one of the C cylinders misfire. 
     A method comprises detecting when a fuel supplied to an engine having C cylinders has a high drivability index (HIDI), where C is an integer greater than 1. The method further comprises detecting whether M of the C cylinders misfire when the fuel has the HIDI, where M is an integer, and 1≦M&lt;C. The method further comprises injecting a first amount of the fuel into the M of the C cylinders when M is less than or equal to D, where D is an integer less than C, and where the first amount is greater than a first predetermined amount. 
     The method further comprises injecting the first amount of the fuel into each one of the C cylinders when M is greater than D. The method further comprises increasing the first amount until the first amount is equal to a second predetermined amount that is greater than the first predetermined amount. The method further comprises stopping injecting the first amount of the fuel into the M of the C cylinders when the first amount is greater than or equal to the second predetermined amount and when at least one of the C cylinders misfire. 
     Further areas of applicability of the present disclosure will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the disclosure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present disclosure will become more fully understood from the detailed description and the accompanying drawings, wherein: 
         FIG. 1  is a functional block diagram of an exemplary engine control system according to the present disclosure; 
         FIG. 2  is a functional block diagram of an exemplary engine control module of the engine control system of  FIG. 1  according to the present disclosure; and 
         FIG. 3  depicts a flowchart of exemplary steps executed by the engine control module of  FIG. 2  according to the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     The following description is merely exemplary in nature and is in no way intended to limit the disclosure, 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, the phrase at least one of A, B, and C should be construed to mean a logical (A or B or C), using a non-exclusive logical or. It should be understood that steps within a method may be executed in different order without altering the principles of the present disclosure. 
     As used herein, the term module refers to an Application Specific Integrated Circuit (ASIC), an electronic circuit, a processor (shared, dedicated, or group) and memory that execute one or more software or firmware programs, a combinational logic circuit, and/or other suitable components that provide the described functionality. 
     Misfiring of cylinders caused by lean air and fuel mixtures can be prevented by selectively injecting additional fuel only into cylinders that misfire. Selectively injecting additional fuel only into the cylinders that misfire and not into cylinders that perform optimally can improve the longevity, emissions, and/or the fuel economy of internal combustion engines. 
     Referring now to  FIG. 1 , a functional block diagram of an exemplary engine control system  100  is shown. The engine control system  100  comprises an engine  102 , an intake module (IM)  104 , a throttle  106 , cylinders  108 , a fuel system  110 , an ignition system  112 , pistons  114 , an engine control module  116 , and sensors  120 . 
     Air is drawn into the intake module  104  through the throttle  106  and distributed into the cylinders  108  of the engine  102 . The fuel system  110  injects fuel into the cylinders  108 . The air mixes with the fuel in the cylinders  108  to form an air/fuel mixture that is compressed and ignited by the ignition system  112  to drive the pistons  114 . The pistons  114  drive a crankshaft (not shown) of the engine  102  to provide a drive torque output. 
     The engine control module  116  controls the operation of the engine control system  100  based on various operating parameters detected by one or more sensors  120 . The operating parameters may include, for example, humidity, temperature, and/or air pressure. The sensors  120  generate one or more signals based on the operating parameters. The engine control module  116  controls the engine  102  and the fuel system  110  based on the signals generated by the sensors  120 . 
     Referring now to  FIG. 2 , a functional block diagram of an exemplary engine control module  116  is shown. The engine control module  116  includes a high drivability index (HIDI) fuel detection module  202 , a misfire detection module  204 , and a fuel control module  206 . The HIDI fuel detection module detects whether the fuel supplied to the engine  102  has the HIDI. When the fuel has the HIDI, the misfire detection module  204  detects cylinders that misfire. When the misfired cylinders are detected, the fuel control module  206  selectively injects additional fuel only into the misfiring cylinders. 
     The HIDI fuel detection module  202  determines the drivability index of the fuel when the engine  102  is cranked on. The HIDI fuel detection module  202  receives an engine status signal and an engine torque signal from the engine  102 . One or more of the sensors  120  may generate the engine status signal and the engine torque signal when the engine  102  is cranked on. Additionally, the HIDI fuel detection module  202  receives an engine speed signal from one of the sensors  120  when the engine  102  is cranked on. The engine speed signal may indicate the engine speed in revolutions-per-minute (RPM). 
     The engine status signal includes an engine start signal that is received when the engine  102  is started (i.e., when the engine  102  is cranked on). One or more of the sensors  120  may generate the engine start signal. The engine start signal may be asserted for a predetermined period of time. For example, the predetermined period of time may be 1-5 minutes. The predetermined period of time may be determined based on various ambient parameters. For example, the ambient parameters may include outdoor humidity and outdoor temperature. The HIDI fuel detection module  202  is enabled when the engine status signal includes the engine start signal. 
     When enabled, the HIDI fuel detection module  202  determines whether the fuel has the HIDI based on the RPM and the engine torque signals. For example only, HIDI fuel detection module  202  may determine that the fuel has the HIDI when the product of a delta RPM ratio and an engine torque ratio is greater than a predetermined value. When the fuel has the HIDI, the HIDI fuel detection module  202  enables the misfire detection module  204 . 
     When enabled, the misfire detection module  204  determines if any of the cylinders  108  has misfired. The commonly assigned U.S. patent application Ser. No. 11/390,974 titled “Misfire Detection Apparatus for Internal Combustion Engine Based on Piston Speed” filed on Mar. 28, 2006 discloses systems and methods for detecting misfiring cylinders. The application is incorporated herein by reference in its entirety. 
     The misfire detection module  204  detects the number of cylinders  108  that misfire (hereinafter misfiring cylinders). For example, the misfire detection module  204  may count a number of times any of the cylinders  108  misfires (i.e., a misfire count). The misfire detection module  204  generates a control signal for each of the misfiring cylinders when the misfire count for any of the misfiring cylinders is greater than zero (i.e., when the cylinder misfires). The misfire detection module  204  may reset the misfire counts of the misfiring cylinders after a predetermined number of engine cycles (e.g., 100 engine cycles). 
     The fuel control module  206  receives information that includes the number of misfiring cylinders, the misfire counts for the misfiring cylinders, and the control signals from the misfire detection module  204 . Based on the information and the control signals, the fuel control module  206  determines whether the number of misfiring cylinders is greater than or equal to a predetermined number. When the number of misfiring cylinders is greater than the predetermined number, the fuel control module  206  determines that a majority of the cylinders  108  are misfiring. 
     When the majority of the cylinders  108  are misfiring, the fuel control module  206  generates a first fuel control signal. The fuel system  110  enriches (i.e., injects more fuel into) all of the cylinders  108  when the fuel system  110  receives the first fuel control signal. When the number of misfiring cylinders is less than the predetermined value, the fuel control module  206  generates a second fuel control signal. The fuel system  1   10  enriches only the cylinders  108  that misfire when the fuel system  110  receives the second fuel control signal. 
     When the majority of the cylinders  108  misfire, the fuel system  110  enriches or injects a predetermined amount of fuel into all of the cylinders  108 . When less than the majority of the cylinders  108  misfire, the fuel system  110  enriches or injects the predetermined amount of fuel into only the cylinders  108  that misfire (i.e., the misfiring cylinders). 
     When the fuel system  110  enriches all or only the misfiring cylinders, the fuel control module  206  determines a total amount of enrichment (i.e., a cumulative or total amount of fuel) used to enrich the cylinders. A maximum enrichment is a predetermined maximum amount of fuel that may be used to enrich the cylinders. When the total enrichment is greater than or equal to the maximum enrichment, the misfire detection module  204  determines whether any of the cylinders being enriched are still misfiring. If any of the cylinders being enriched continue to misfire despite the maximum enrichment, the fuel control module  206  aborts enriching the cylinders. The enrichment is aborted since the enrichment does not prevent, correct, and or reduce the misfiring. 
     Referring now to  FIG. 3 , a flowchart depicting exemplary steps performed by the engine control module  116  is shown. Control begins in step  302 . Control determines in step  304  whether the engine is running. Control ends in step  306  if the result of step  304  is false. Control proceeds to step  308  if the result of step  306  is true. 
     In step  308 , control determines the RPM and the engine torque. In step  312 , control determines the fuel quality based on the RPM and the engine torque. In step  314 , control determines whether the fuel has the HIDI. Control ends in step  306  if the result of step  314  is false. Control proceeds to step  316  if the result of step  314  is true. 
     In step  316 , control determines the number of misfired cylinders. In step  320 , control determines total enrichment. In step  322 , control determines whether the total enrichment is greater than or equal to the maximum enrichment and whether the number of misfired cylinders is not decreasing. Control ends in step  306  if the result of step  322  is true. Control proceeds to step  324  if the result of step  320  is false. 
     In step  324 , control determines if the number of misfired cylinders is greater than or equal to a predetermined number. Control proceeds to step  326  if the result of step  324  is false. Control proceeds to step  328  if the result of step  324  if true. Control enriches only the misfiring cylinders in step  326 . Control enriches all of the cylinders  108  in step  328 . At the end of step  326  or  328 , control returns to step  316 . 
     Those skilled in the art can now appreciate from the foregoing description that the broad teachings of the disclosure can be implemented in a variety of forms. Therefore, while this disclosure includes particular examples, the true scope of the disclosure 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.