Patent Publication Number: US-7900606-B2

Title: Systems and methods for purging air of a fuel injection system

Description:
FIELD 
     The present disclosure relates to vehicle control systems for internal combustion engines, and more particularly to fuel injection control systems. 
     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. 
     Spark ignition direct injection (SIDI) systems are currently used by many engine manufacturers. In a SIDI system, highly pressurized gasoline is injected directly into cylinders of an engine. This is different than port fuel injection where fuel is injected into an intake manifold or port upstream from an intake valve of a cylinder. 
     SIDI technology enables stratified fuel-charged combustion for improved fuel efficiency and reduced emissions at low load. The stratified fuel charge allows for a lean burn and improves fuel efficiency and power output. 
     SIDI engines may be configured with a low-pressure fuel pump and a high-pressure fuel pump, which are used for pressurizing respectively a low-pressure fuel line and an injector fuel rail. A pressure sensor is attached to the fuel rail and generates a fuel rail pressure signal for feed back control of fuel rail pressure. 
     SUMMARY 
     Accordingly, a system includes an initialization module that generates an initialization signal. The initialization signal is generated based on a crankshaft speed signal and at least one of an initial purge value and an assembly-line monitoring value. A purge control module generates a purge signal to purge air from a fuel injection system of an engine when the crankshaft speed signal indicates that a crankshaft of the engine is stationary and based on the initialization signal. 
     In other features, a system includes an initialization module that generates an initialization signal. The initialization signal is generated based on a fuel rail pressure signal and at least one of an initial purge value and an assembly-line monitoring value. A purge control module generates a purge signal to purge air from a fuel injection system of an engine when the fuel rail pressure signal is less than a predetermined value and based on the initialization signal. 
     In other features, a method of purging air from a fuel injection system is provided. The method includes generating an initialization signal based on a crankshaft speed signal, a fuel rail pressure signal, and at least one of an initial purge value and an assembly-line monitoring value. A purge signal is generated when the crankshaft speed signal is zero and the fuel rail pressure signal is less than a predetermined value and based on the initialization signal. 
     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 engine system in accordance with an embodiment of the present disclosure; 
         FIG. 2  is a functional block diagram of a fuel injection system in accordance with an embodiment of the present disclosure; 
         FIG. 3  is a functional block diagram of the fuel injection system of  FIG. 2  illustrating a purge control system in accordance with another embodiment of the present disclosure; and 
         FIG. 4  illustrates a method of purging a fuel injection system in accordance with an embodiment of 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. 
     In addition, although the following embodiments are described primarily with respect to a SIDI engine, the embodiments of the present disclosure may apply to other types of engines. For example, the present invention may apply to compression ignition, spark ignition, spark ignition direct injection, homogenous spark ignition, homogeneous charge compression ignition, stratified spark ignition, diesel, and spark assisted compression ignition engines. 
     After a vehicle is built at a manufacturing facility, the engine of the vehicle is started near the end of an assembly process. The starting of the engine includes cranking of the engine and activating ignition and fuel injection systems. Prior to a first engine start, the fuel injection system is primed. 
     During the prime of the fuel injection system, the low-pressure fuel pump may be activated to pump fuel into and/or through components of the fuel injection system and to provide a predetermined pressure in the fuel injection system. The engine may need to be cranked for an extended period of time in order to purge the air from the fuel injection system. The air in the fuel injection system may cause the engine to not start or start erratically. 
     The embodiments of the present disclosure provide injector purge systems and methods for removing air within a fuel injection system after manufacturing of a vehicle and before starting of an engine of the vehicle. The injector purge systems and methods reduce engine crank times after vehicle assembly is complete. 
     Referring now to  FIG. 1 , an exemplary engine control system  10  of a vehicle is schematically illustrated in accordance with the present disclosure. The engine control system  10  includes an engine  12  and a fuel injection system  14 . The fuel injection system  14  includes an engine control module  16  with an injector purge control system  18 . The injector purge control system  18  controls purging of the fuel injection system  14  upon manufacture of a vehicle to remove trapped air from the fuel injection system  14 . Examples of the engine control module  16  and the purge control system  18  are shown in  FIGS. 2 and 3 . 
     The engine  12  includes an intake manifold  20 , the fuel injection system  14  with fuel rails  22 ,  24 , a transmission  26 , a cylinder  30 , and a piston  32 . The exemplary engine  12  includes eight cylinders  30  configured in adjacent cylinder banks  34 ,  36  in a V-type layout. Although  FIG. 1  depicts eight cylinders (N=8), it can be appreciated that the engine  12  may include any number of cylinders  30 . It is also anticipated that the engine  12  can have an inline-type cylinder configuration. While a gasoline powered internal combustion engine utilizing direct injection is shown, the embodiments disclosed herein apply to diesel or alternative fuel sourced engines. 
     During engine operation, air is drawn into the intake manifold  20  by an inlet vacuum created by intake strokes of the engine  12 . Fuel is directly injected by the fuel injection system  14  into the cylinders  30 . The air and fuel mixes in the cylinders  30  and heat from the compression and/or electrical energy ignites the air and fuel mixture. The piston  32  in the cylinder  30  drives a crankshaft  38  of the engine  12  to produce drive torque. Combustion exhaust within the cylinder  30  is forced out through exhaust conduits  40 . 
     The engine control module  16  may control the fuel injection system  14  based on speed of the crankshaft  38 . Speed and/or rotation of the crankshaft  38  may be detected by a crankshaft sensor  42 . The engine control module  16  may control injector timing based on a crankshaft speed signal CS generated by the crankshaft sensor  42 . A crankshaft speed signal of, for example, zero indicates that the crankshaft  38  of the engine  12  is not rotating or is stationary. A crankshaft speed signal of, for example, greater than zero indicates that the crankshaft  38  is rotating or is not stationary. 
     Referring now also to  FIG. 2 , the fuel injection system  14  is shown. The fuel injection system  14  includes the engine control module  16 , a low-pressure fuel line  100 , a high-pressure fuel line  102  that is connected to the fuel rails  22 ,  24 , and fuel injectors  104 ,  105 . The fuel lines  100 ,  102  receive fuel by a respective one of a low-pressure fuel pump  106  and a high-pressure fuel pump  108 . The low-pressure pump  106  may operate off of an electrical power source, such as a battery. The high-pressure pump  108  may operate off of the engine  12 . The low-pressure pump  106  may provide a fuel pressure of, for example, 400 kilopascal (kPa=10 3  Pa)+/−50 kPa. The high-pressure pump  108  may provide a fuel pressure of, for example, 15 megapascal (mPa=10 6  Pa)+/−5 mPa. 
     In use, the engine control module  16  generates a low-pressure control signal LowP  110  to pump fuel from a fuel tank  112  to the low-pressure fuel line  100  via the low-pressure fuel pump  106 . The engine control module  16  generates a high-pressure control signal HighP  114  to pump fuel into the cylinders  30 . The high-pressure fuel pump  108  is used to increase pressure of the fuel received from the low-pressure fuel line  100 . High-pressured fuel is provided to the high-pressure fuel line  102  and the fuel rails  22 ,  24 . The high-pressured fuel is injected into the cylinders  30  via the fuel injectors  104 ,  105 . Timing of the fuel injectors  104 ,  105  is controlled by the engine control module  16 . Although a particular number of fuel rails and fuel injectors per fuel rail are shown, any number of fuel rails and corresponding fuel injectors may be included. 
     The engine control module  16  controls the fuel pumps  106 ,  108  in response to various sensor inputs, such as a fuel rail pressure signal FR  116  from a fuel rail pressure sensor  118 . Fuel rail pressure sensors may be connected to and detect pressure in one or more of the fuel rails  22 ,  24 ,  102 . The fuel rail pressure sensor  118  is shown as one example. The engine control module  16  may generate various control signals, such as the low-pressure control signal  110 , the high-pressure control signal  114 , and a fuel injector control signal FI  120 . The fuel injector control signal  120  may be used to control the opening and closing of the fuel injectors  104 ,  105 . The low-pressure control signal  110  may be used to control operation of the low-pressure fuel pump  106 . The high-pressure control signal  114  may be used to control operation of the high-pressure fuel pump  108 . 
     Referring now also to  FIG. 3 , the fuel injection system  14  is shown illustrating the purge control system  18  and may be associated with a particular vehicle. The purge control system  18  includes an initialization module  200 , a purge control module  202 , a fuel pump module  204 , and a fuel injection control module  206 . 
     The initialization module  200  receives signals from sensors  208  via hardware input/output (HWIO) devices  210  to generate an initialization signal. The sensors  208  may include the crankshaft sensor  42 , the fuel rail pressure sensor  118 , and other sensors  212 . The other sensors  212  may include, but are not limited to, an intake air temperature (IAT) sensor, a humidity IAT sensor, and/or an oxygen sensor. The initialization signal is generated based on the crankshaft speed signal CS, the fuel rail pressure signal FR, and one or more stored vehicle and/or engine status values. The vehicle and/or engine status values may be stored in memory  220  and may include an initial purge value  214  and an assembly-line monitoring value  218 . 
     The initial purge value  214  indicates whether the fuel injection system  14  has been primed and the fuel injectors  104 , 105  have been purged since the manufacturing of the vehicle. An initial purge value of, for example, FALSE may indicate that a purge event has not been performed. An initial purge value of, for example, TRUE may indicate the fuel injection system  14  has been purged. 
     The assembly-line monitoring value  218  indicates whether a fuel system prime request is received and/or a prime is being performed. The prime is to put fuel into the fuel injection system  14  before starting the engine  12  to insure a sufficiently rich fuel/air mixture at the start. The fuel system prime request may be triggered in an assembly plant by a test tool or by a predetermined pedal stomp sequence. The pedal stomp sequence may include the actuating of, for example, brake and gas pedals. An assembly-line monitoring value of, for example, FALSE may indicate that the fuel system prime request is not received and/or a prime is not being performed. An assembly-line monitoring value of, for example, TRUE may indicate that fuel system prime request is received and/or a prime is being performed. The values  214 ,  218  may be accessed via the HWIO devices  210 . 
     The HWIO devices  210  may include an interface control module  222  and hardware interfaces/drivers  224 . The interface control module  222  provides an interface between the purge control module  202 , the fuel pump module  204 , the fuel injection control module  206 , and the hardware interfaces/drivers  224 . The hardware interfaces/drivers  224  control operation of, for example, fuel injectors  104 ,  105 , fuel pumps  106 ,  108 , and other engine system devices. The other engine system devices may include, but are not limited to, ignition coils, spark plugs, throttle valves, solenoids, etc. The hardware interface/drivers  224  also receive sensor signals, which are communicated to the respective control modules. The sensor signals may include the crankshaft speed signal CS and the fuel rail pressure signal FR. 
     The HWIO devices  210  may also include a boosting control module  228 . When the purge control module  202  receives the initialization signal, the boosting control module  228  determines whether the hardware drivers  224  for the fuel injectors  104 ,  105  are ready for operation. The boosting control module  228  controls the hardware drivers  224  for the fuel injectors  104 ,  105  to ensure the drivers are charged sufficiently to operate opening of the fuel injectors  104 ,  105 . When the boosting control module  228  enables the drivers, the purge control module  202  may generate a purge signal to initiate purging of the fuel injection system  14 . The purge control module  202  may transmit the purge signal to the fuel pump module  204 , the fuel injection control module  206 , and an injection period timer  230 . 
     When the fuel pump module  204  receives the purge signal, the fuel pump module  204  activates the actuators  226  via the HWIO devices  210 . The fuel pump module  204  activates the low-pressure fuel pump  106  for purging of the fuel injection system  14 . 
     When the fuel injection control module  206  receives the purge signal, the fuel injection control module  206  activates one or more of the fuel injectors  104 ,  105  via the HWIO devices  210 . The fuel injection control module  206  may activate the fuel injectors  104 ,  105  based on the pulse width of the purge signal. The fuel injectors  104 ,  105  may be opened and closed sequentially and for a predetermined period to remove air from the fuel injection system  14 . 
     The fuel injectors  104 ,  105 , and the low-pressure fuel pump  106  may be deactivated based on at least one of a purge completion signal, the crankshaft speed signal, and the fuel rail pressure signal. The purge completion signal is generated by the purge control module  202  based on a counter  232 . The injection period timer  230  may include the counter  232 . The counter  232  may be incremented by one after completion of a purge event for M of N fuel injectors, where M is an integer and N is an integer greater than zero. M may correspond to a selected number of the fuel injectors  104 ,  105 . N may correspond to a total number of the fuel injectors  104 ,  105 . The purge completion signal indicates that the M of the N injectors has been opened and closed at least once for purging of the fuel injection system  14 . When the counter is less than or equal to M, purging of the fuel injection system  14  continues by opening the next one of the M fuel injectors. When the counter is greater than or equal to M, the purge control module  202  generates the purge completion signal. Purging of the fuel injection system  14  may be ceased based on the purge completion signal. 
     Additionally, the injection period timer  230  accesses a system clock  234  via the HWIO devices  210  to receive an initial timestamp of, for example, when the M of the N fuel injectors  104 ,  105  is initially opened. The injection period timer  230  compares the initial timestamp with a current timestamp, which may also be received from the system clock  234 . When the difference between the timestamps is greater than a predetermined period, the purge completion signal is provided to the purge control module  202  to deactivate the M of the N fuel injectors  104 ,  105 . The purge completion signal indicates that the predetermined period has lapsed. This may also be used to cease purging of the fuel injection system  14 . 
     The purge control module  202  ceases purging of the fuel injection system  14  based on the crankshaft speed signal and/or the fuel rail pressure signal. When the crankshaft speed signal indicates that the crankshaft  38  is rotating or not stationary, the purge control module  202  may signal the fuel pump module  204  to deactivate the low-pressure fuel pump  106  and the fuel injection control module  206  to deactivate the M of the N fuel injectors  104 ,  105 . 
     When the fuel rail pressure signal indicates that the fuel rail pressure is greater than a predetermined threshold, the purge control module  202  may signal the fuel pump module  204  to deactivate the low-pressure fuel pump  106  and the fuel injection control module  206  to deactivate the M of the N fuel injectors  104 ,  105 . 
     Referring now also to  FIG. 4 , a method of purging a fuel injection system, such as the fuel injection system  14 , is shown. Although the following steps are primarily described with respect to the embodiments of  FIGS. 1-3 , the steps may be modified to apply to other embodiments of the present invention. 
     The method may begin at step  400 . In step  402 , signals from the sensors  208  and values in the memory  220  may be received and/or generated. The signals include the crankshaft speed signal CS and the fuel rail pressure signal FR. The values include the vehicle and/or engine status values, such as the initial purge value  214  and the assembly-line monitoring value  218 . The values may be transmitted to modules, such as the initialization module  200 , the purge control module  202 , the fuel pump module  204 , the fuel injection control module  206 , and the injection period timer  230 , via the HWIO devices  210 . 
     In step  404 , when the crankshaft speed signal CS indicates that the crankshaft  38  is not rotating, control may proceed to step  406 . When the crankshaft speed signal CS is greater than zero and/or indicates that the crankshaft  38  is rotating, control may return to step  402 . 
     In step  406 , when the fuel rail pressure signal FR indicates that a fuel rail pressure is less than or equal to a predetermined threshold, control may proceed to step  408 . Control may return to step  402  when the fuel rail pressure is greater than the predetermined threshold. 
     In step  408 , when the initial purge value  214  indicates that a purge event has not been performed since the manufacturing of a corresponding vehicle, control may proceed to step  410 . Otherwise, control may return to step  402 . 
     In step  412 , when the assembly-line monitoring value  218  stored in the memory  220  indicates that the vehicle is at an end of an assembly line, control may proceed to step  414 . Otherwise, control may return to step  402 . 
     In step  414 , the boosting control module  228  may determine whether the hardware interfaces/drivers  224  are charged to operate opening and closing of the fuel injectors  104 ,  105 . When the hardware drivers  224  are ready, control may proceed to step  416 . Otherwise, control may return to step  402 . 
     In step  416 , the purge control module  202  generates a purge signal and transmits the purge signal to the fuel pump module  204 , the fuel injection control module  206 , and the injection period timer  230 . In step  418 , the fuel pump module  204  activates the low-pressure fuel pump  106  for an initial prime and refrains from activating the high-pressure fuel pump  108 . The high-pressure fuel pump  108  performs as a pass-through when deactivated. 
     In step  419 , the purge control module  202  selects the M of the N fuel injectors  104 ,  105 . M may vary depending on a configuration type of the engine  12 . The fuel injectors at higher elevation points on the engine  12  may be selected, opened, and purged, as air in a fuel injection system tends to be located at the highest points. This selection reduces purge time. For example, when the fuel injectors  104  are at a higher elevation level than the fuel injectors  105 , the fuel injectors  104  may be selected, opened, and purged. The fuel injectors  105  may not be selected, opened, and purged. Each of the selected injectors may remain open for a predetermined period. In one embodiment, each injector is purged once. 
     In step  420 , the fuel injection control module  206  sequentially activates the fuel injectors  104 ,  105  by sending a predetermined pulse width. The fuel injection control module  206  opens a first one of the selected M of the N fuel injectors  104 ,  105 , or injector M(I) via HWIO devices  210  for a calibrated time period determined by the purge control module  202  using calibration software  236  in the memory  220 . I is an index of M. The fuel injection control module  206  deactivates the first one of the selected M of the N fuel injectors  104 ,  105  before activating a second one of the selected M of the N fuel injectors  104 ,  105 . 
     In step  422 , when the fuel rail pressure signal FR exceeds a predetermined value, control may proceed to step  434 . Otherwise, control may proceed to step  424 . The predetermined value may, for example, be calibrated and set at approximately 600 kPa+/−200 kPa. 
     In step  424 , when the crankshaft speed signal CS indicates that the crankshaft  38  is rotating, control may proceed to step  434 . Otherwise, control may proceed to step  426 . 
     In step  426 , when one or more of the selected fuel injectors  104 ,  105  are open longer than the predetermined period, control may proceed to step  428 . Otherwise, control may proceed to step  439 . In step  439 , the injection period timer  230  increases time spent for purging of the injector M(I), then control may proceed to step  422 . An injection period timer value  231  of the injection period timer  230  may be incremented. For example, the injection period timer  230  accesses a system clock  234  via the HWIO devices  210  to receive an initial timestamp of when the injector M(I) is initially opened. The injection period timer  230  compares the initial timestamp with a current timestamp, which may also be received from the system clock  234 . The difference between the timestamps may be the injection period timer value  231 . 
     Steps  422  and  426  aid in preventing a hydrolock situation of the engine  12 . The amount of fuel pumped into a fuel injection system may be estimated by the ON time of and the pressure provided by the low-pressure fuel pump  106 . Step  422  also prevents the purging of the fuel injection system  14 , for example, by a system developer or a dealership when fuel rail pressure is higher than the predetermined value. 
     In step  428 , the fuel injection control module  206  deactivates the M of the N fuel injectors  104 ,  105 , to prevent a hydrolock state of injected fuel into one or more of the cylinders  30 . In step  430 , the counter  232  increments the index I by one. In step  440 , the injection period timer  230  is reset to 0. 
     In step  432 , when I is less than M, control may proceed to step  420 . When I is greater than or equal to M, control may proceed to  434 . In step  434 , the selected fuel injectors are closed. In step  436 , the fuel pump module  204  deactivates the low-pressure fuel pump  106 , and the purge control module  202  may cease purging of the fuel injection system  14 . Then, control may end at step  438 . 
     The above described steps are meant to be illustrative examples; the steps may be performed sequentially, synchronously, simultaneously, continuously, during overlapping time periods or in a different order depending upon the application. 
     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.