System and method for controlling fuel injections

A system and method for controlling fuel delivery from a fuel injector includes determining engine speed, determining a proposed pilot pulse width time based on engine speed, determining injection pressure, determining a proposed first quantity of fuel to be delivered by the fuel injector based on the proposed pilot pulse width time and injection pressure and determining a desired engine torque output. A desired total quantity of fuel to be delivered by the fuel injector is determined based on the desired engine torque output and engine speed. The proposed first quantity of fuel is compared with the desired total quantity of fuel. A desired first quantity of fuel to be delivered by the fuel injector is determined based on the desired engine torque output and engine speed if the proposed first quantity of fuel is greater than the desired total quantity of fuel. A desired pilot pulse width time is determined based on the desired first quantity of fuel and the injection pressure. A desired second quantity of fuel to be delivered by the fuel injector is determined by subtracting the proposed first quantity of fuel from the desired total quantity of fuel if the proposed first quantity of fuel is less than or equal to the desired first quantity of fuel. A main pulse width time is determined based on the desired second quantity of fuel and the injection pressure.

TECHNICAL FIELD 
The invention relates to a system and method for controlling fuel injection 
of fuel injectors in an internal combustion engine. 
BACKGROUND ART 
A prior fuel injection system includes a common fuel rail and a plurality 
of fuel injectors in communication with the fuel rail for injecting fuel 
into a plurality of cylinders of an internal combustion engine. Each of 
the fuel injectors has an electronic control valve or solenoid for 
controlling fuel injection into a particular cylinder. An electronic 
control unit, or controller, is used to control the electronic control 
valves, as well as other aspects of the fuel injection system. The 
controller may include volatile and non-volatile memory, input and output 
driver circuitry, and a processor capable of executing one or more stored 
instruction sets. In operation, the controller determines an excitation or 
energizing duration for each control valve corresponding to current engine 
conditions. Energizing of a particular control valve causes the valve to 
open, which allows fuel injection to occur. However, imprecise 
determination of energizing durations may result in operating problems 
such as engine noise and excessive engine emissions. 
A prior method for determining energizing durations by a controller 
involves determining a desired injection pressure and a raw injection 
duration, or raw pulse width, from two separate but interdependent look-up 
tables that each reference desired engine torque and engine speed. The raw 
injection duration is not based on time units, however, but rather is 
based on angular displacement of the engine crankshaft measured in 
degrees. The raw injection duration is then adjusted to establish a final 
injection duration based on injection pressure error, which is a function 
of desired injection pressure and observed or actual injection pressure. 
Finally, the final injection duration is converted from degrees to time to 
establish an energizing duration, and a corresponding control signal is 
sent to a particular fuel injector. 
Because this method involves interdependent look-up tables for determining 
desired injection pressure and raw injection duration, calibration of the 
look-up tables and associated controller is difficult and time-consuming. 
Furthermore, desired injection pressure values, which are used to control 
a fuel pump, cannot be independently varied so as to optimally adapt 
injection pressure to variable operating conditions such as air 
temperature. 
Several methods have been proposed to enhance fuel injection capabilities. 
One such method is known as split injection. Split injection consists of a 
first injection, called the pilot injection, followed by a delay, and then 
a second injection, referred to as the main injection. When performing 
split injection, precise determination of energizing durations for both 
the pilot injection and the main injection is essential. Many times, 
operating conditions at which split injection may be performed are 
restricted to lower engine speeds due to difficulties in establishing 
precise energizing durations. 
Another method for determining pilot and main energizing durations is 
similar to the method previously described. The method involves 
determining a desired injection pressure based on a desired engine torque 
output and engine speed; determining a raw pilot injection duration, or 
raw pilot pulse width, based on a desired pilot engine torque output and 
engine speed; and determining a raw main injection duration, or raw main 
pulse width, based on a desired main engine torque output and engine 
speed. As in the above method, the raw injection durations are not based 
on time units, but rather are represented in degrees of rotation of the 
crankshaft. Furthermore, the desired injection pressure and the raw 
injection durations are determined in parallel from separate, but 
interdependent, look-up tables. The raw pilot injection duration and the 
raw main injection duration are then adjusted to establish a final pilot 
injection duration and a final main injection duration, respectively, 
based on injection pressure error. Next, the final pilot injection 
duration and the final main injection duration are converted from degrees 
to time to establish a pilot energizing duration and a main energizing 
duration, respectively, and corresponding control signals are sent to a 
particular fuel injector. 
DISCLOSURE OF THE INVENTION 
It is therefore an object of the invention to provide a method and system 
for controlling fuel delivery from a fuel injector based on pulse widths 
that are more precisely determined as compared with prior methods and 
systems. 
Another object of the invention is to provide a method and system for 
determining pulse widths in time units independently of angular 
measurements associated with an engine crankshaft. 
In carrying out the above objects and other objects and features of the 
invention, a method for controlling fuel delivery from a fuel injector 
includes determining a proposed first pulse width time; determining a 
proposed first quantity of fuel to be delivered by the fuel injector based 
on the proposed first pulse width time; determining a desired total 
quantity of fuel to be delivered by the fuel injector; comparing the 
proposed first quantity of fuel with the desired total quantity of fuel; 
and utilizing the proposed first pulse width time for controlling the fuel 
injector if the proposed first quantity of fuel is less than or equal to 
the desired total quantity of fuel. 
Preferably, the proposed first pulse width time is based on engine speed, 
the proposed first quantity of fuel is further based on injection 
pressure, and the desired total quantity of fuel is based on engine speed 
and desired engine torque output. 
In addition, the method preferably includes determining a desired second 
quantity of fuel to be delivered by the fuel injector if the proposed 
first quantity of fuel is less than the desired total quantity of fuel. A 
second pulse width time is then determined based on the desired second 
quantity of fuel. 
If the proposed first quantity of fuel is greater than the desired total 
quantity of fuel, then the method preferably further includes determining 
a desired first pulse width time based on the desired total quantity of 
fuel, and utilizing the desired first pulse width time to control the fuel 
injector. 
According to a feature of the invention, the method may also include 
determining a desired injection pressure independently of determining the 
proposed pulse width time, and controlling a fuel pump system for 
supplying fuel to the fuel injector based on the difference between the 
desired injection pressure and actual injection pressure. Preferably, the 
desired injection pressure may be altered independently of the proposed 
pulse width time based on dynamic engine operating parameters. As a 
result, the fuel pump system may be effectively controlled to optimize 
fuel pressure to thereby optimize engine operation. 
More specifically, a method according to the invention for controlling fuel 
delivery from a fuel injector includes determining engine speed; 
determining a proposed pilot pulse width time based on engine speed; 
determining injection pressure; determining a proposed first quantity of 
fuel to be delivered by the fuel injector based on the proposed pilot 
pulse width time and injection pressure; determining a desired engine 
torque output; determining a desired total quantity of fuel to be 
delivered by the fuel injector based on the desired engine torque output 
and engine speed; comparing the proposed first quantity of fuel with the 
desired total quantity of fuel; determining a desired first quantity of 
fuel to be delivered by the fuel injector based on the desired engine 
torque output and engine speed if the proposed first quantity of fuel is 
greater than the desired total quantity of fuel; determining a desired 
pilot pulse width time based on the desired first quantity of fuel and the 
injection pressure; determining a desired second quantity of fuel to be 
delivered by the fuel injector by subtracting the proposed first quantity 
of fuel from the desired total quantity of fuel if the proposed first 
quantity of fuel is less than or equal to the desired first quantity of 
fuel; and determining a main pulse width time based on the desired second 
quantity of fuel and the injection pressure. 
A system is also provided for controlling fuel delivery from a fuel 
injector having an electronic control valve, wherein the fuel injector is 
in communication with a fuel rail. The system comprises an accelerator 
pedal sensor for sensing pedal position, a crankshaft sensor for sensing 
rotational speed of the crankshaft, and a fuel pressure sensor for 
measuring fuel pressure in the fuel rail. The system further includes a 
controller in communication with the accelerator pedal sensor, the 
crankshaft sensor, the fuel pressure sensor and the electronic control 
valve. The controller includes instructions for determining a desired 
engine torque output based on the pedal position, instructions for 
determining engine speed based on the rotational speed of the crankshaft, 
instructions for determining a proposed first pulse width time, 
instructions for determining a proposed first quantity of fuel to be 
delivered by the fuel injector based on the proposed first pulse width 
time, instructions for determining a desired total quantity of fuel to be 
delivered by the fuel injector, instructions for comparing the proposed 
first quantity of fuel with the desired total quantity of fuel, and 
instructions for utilizing the proposed first pulse width time for 
controlling the fuel injector if the proposed first quantity of fuel is 
less than or equal to the desired total quantity of fuel.

BEST MODE FOR CARRYING OUT THE INVENTION 
Referring now to FIG. 1, a system for controlling fuel delivery according 
to the present invention is shown. The system, generally indicated by 
reference numeral 10, includes an engine 12 having a plurality of 
cylinders, each of which is fed by one of a plurality of fuel injectors 
14. In a preferred embodiment, engine 12 is a compression-ignition 
internal combustion engine, such as a four, six, eight, twelve, sixteen, 
twenty, or twenty-four-cylinder diesel engine. Each of the fuel injectors 
14 preferably has an electronic control valve 16 (such as a solenoid, for 
example) for controlling injection into a particular cylinder. The fuel 
injectors 14 receive pressurized fuel from a common rail 18, which is 
connected to one or more high or low pressure fuel pumps, such as fuel 
pump 19, as is well known in the art. Alternatively, embodiments of the 
present invention may employ a plurality of unit pumps (not shown), each 
pump supplying fuel to one of the injectors 14. 
The system 10 further includes an accelerator pedal sensor 20 for sensing 
pedal or throttle position, a temperature sensor 22 for sensing engine 
temperature, a crankshaft sensor 24 for sensing rotational speed of the 
crankshaft (not shown), and a fuel pressure sensor 26 for sensing fuel 
pressure in the rail 18. The system 10 may also include various other 
sensors 28 for generating signals indicative of corresponding operating 
conditions or parameters of engine 12, a vehicle transmission (not shown), 
and/or other vehicular components. For example, the sensors 28 may 
generate signals corresponding to such parameters as battery voltage, fuel 
temperature, ambient air temperature, and ambient air pressure. The 
sensors 20-28 are in electrical communication with a controller 30 via 
input ports 32. The controller 30 preferably includes a microprocessor 34 
in communication with various computer readable storage media 36 via data 
and control bus 38. The computer readable storage media 36 may include any 
of a number of known devices which function as a read-only memory (ROM) 
40, random access memory (RAM) 42, keep-alive memory (KAM) 44, and the 
like. The computer readable storage media 30 may be implemented by any of 
a number of known physical devices capable of storing data representing 
instructions executable via a computer such as controller 30. Known 
devices may include, but are not limited to, PROM, EPROM, EEPROM, flash 
memory, and the like in addition to magnetic, optical, and combination 
media capable of temporary or permanent data storage. 
The computer readable storage media 36 include data representing program 
instructions (software), calibrations, operating variables and the like 
that are used in conjunction with associated hardware to effect control of 
various systems and subsystems of the vehicle, such as the engine 12, 
vehicle transmission, and the like. With respect to fuel delivery, the 
controller 30 receives signals from sensors 20-28 via input ports 32, and 
generates output signals that may be provided to various actuators and/or 
components, such as the electronic control valves 16 and pump 19, via 
output ports 46. Signals may also be provided to a display device 48, 
which may include various indicators such as lights 50 to communicate 
information relative to system operation to the operator of the vehicle. 
Of course, alphanumeric, audio, video, or other displays or indicators may 
be utilized if desired. 
A data, diagnostics, and programming interface 52 may also be selectively 
connected to controller 30 via a plug 54 to exchange various information 
therebetween. Interface 52 may be used to change values within the 
computer readable storage media 36, such as configuration settings, 
calibration variables including adjustment factor look-up tables, control 
logic, temperature thresholds for enabling or disabling split injection, 
and the like. 
In operation, controller 30 receives signals from sensors 20-28 and 
executes or implements control logic embedded in hardware and/or software 
to control fuel delivery to the engine 12 by controlling fuel pressure in 
the rail 18 and actuation of the electronic control valves 16. 
Furthermore, the controller 22 preferably implements control logic to 
determine the injection mode, such as split injection or single injection, 
depending on user preferences and/or current operating conditions. Split 
injection involves a first injection, known as a pilot injection, followed 
by a delay, and then a second injection, known as a main injection. 
Controller 22 is preferably capable of smooth transitions between 
injection modes under various operating conditions. The control logic is 
preferably implemented by the microprocessor 34 as described below in 
further detail. However, various alternative hardware and/or software may 
be used to implement the control logic without departing from the spirit 
or scope of the invention. In a preferred embodiment, the controller 30 is 
a Detroit Diesel Electronic Controller (DDEC) available from Detroit 
Diesel Corporation, Detroit, Mich. 
FIG. 2 is a flow chart illustrating operation of a method or system, such 
as system 10, for controlling fuel delivery according to the present 
invention. As will be appreciated by one of ordinary skill in the art, the 
flow chart represents control logic which may be effected or implemented 
by hardware, software, or a combination of hardware and software. The 
various functions are preferably implemented by a programmed 
microprocessor such as included in the DDEC controller. Alternatively, one 
or more of the functions may be implemented by dedicated electric, 
electronic, or integrated circuits. As will also be appreciated, the 
control logic may be implemented using any one of a number of known 
programming and processing techniques or strategies and is not limited to 
the order or sequence illustrated here for convenience only. For example, 
interrupt or event driven processing is typically employed in real-time 
control applications, such as control of a vehicle engine or transmission. 
Likewise, parallel processing or multi-tasking systems and methods may be 
used to accomplish the objects, features, and advantages of the present 
invention. The present invention is independent of the particular 
programming language, operating system, or processor used to implement the 
control logic illustrated. 
At step 100 of FIG. 2, a proposed pilot pulse width time (PPPWT) is 
determined based on one or more operating conditions, such as engine speed 
measured in revolutions per minute (RPM) of the crankshaft. The PPPWT is 
determined in time units and is not dependent on angular displacement of 
the crankshaft. Preferably, the PPPWT is found in a look-up table that 
references engine RPM. Alternatively, PPPWT may be a fixed value. 
At step 102, a proposed first or pilot quantity of fuel to be delivered 
during the pilot injection, or proposed pilot fuel per cycle (PPFPC), is 
determined based on the PPPWT and one or more engine operating parameters 
such as observed or actual fuel pressure in, for example, rail 18 (shown 
in FIG. 1). The actual fuel pressure is also referred to as actual 
injection pressure. Preferably, the PPFPC is found in a look-up table that 
references PPPWT and actual fuel pressure. 
At step 104, a desired engine governing torque (EGT) is determined based on 
various operating conditions such as throttle position and/or transmission 
gear ratio. Alternatively, EGT may be determined by a variable speed 
governor. Next, a desired total quantity of fuel to be delivered during 
both the pilot and main injections, or total fuel per cycle (TFPC) is 
determined at step 106. The TFPC is determined based on EGT and one or 
more engine operating parameters such as engine RPM. Preferably, the TFPC 
is found in a look-up table that references EGT and engine RPM, and the 
look-up table is preferably calibrated to correspond to the fuel 
efficiency of the engine 12. 
At step 108, PPFPC is compared with TFPC. If PPFPC is less than or equal to 
TFPC, as represented at step 110, then PPPWT is utilized to control the 
pilot injection of a particular fuel injector 14, shown in FIG. 1, as 
described below in greater detail. 
At step 112, a desired second or main quantity of fuel to be delivered 
during the main injection, or main fuel per cycle (MFPC) is determined by 
subtracting the PPFPC from the TFPC. Next, a main pulse width time (MPWT) 
is determined at step 114 based on the MFPC and one or more engine 
operating parameters such as actual fuel pressure in, for example, the 
rail 18 (shown in FIG. 1). Advantageously, the MPWT is determined in time 
units and is not dependent on angular displacement of the crankshaft. The 
MPWT is preferably found in a look-up table that references MFPC and 
actual injection pressure. Furthermore, this look-up table is preferably 
calibrated for a particular fuel injector 14. 
Under this scenario, i.e., PPFPC less than or equal to TFPC, pilot and main 
injections are controlled, such as by the controller 30 shown in FIG. 1, 
based on the PPPWT and the MPWT. Control logic may be applied to the PPPWT 
and/or the MPWT to adjust these values, as represented in FIG. 2 at step 
116 based on engine operating parameters such as fuel pressure, engine 
temperature, ambient air temperature and ambient air pressure. Next, a 
pilot output signal and a main output signal are generated at step 118 
based on the PPPWT and the MPWT, respectively. The output signals 
represent energizing durations and are used to energize a particular 
electronic control valve 16, show in FIG. 1, in order to deliver the PPFPC 
during the pilot injection, and the MFPC during the main injection. The 
output signals may also be generated based on additional factors such as 
actuation latency of the electronic control valves 16, and delay in 
lifting of associated spray tip needles. Furthermore, an inter-pulse gap 
between the pilot injection and the main injection is also determined. 
Additional details regarding fuel injection timing may be found in 
application Ser. No. 09/156,246, U.S. Pat. No. 6,032,642, which is 
assigned to the assignee of the present invention and is hereby 
incorporated by reference. It should be noted that although the time 
periods (PPPWT, MPWT and related energizing durations) associated with the 
pilot and main injections are determined in time units, initiation of 
these time periods is still preferably dependent on crankshaft orientation 
so that the injections may be completed at the appropriate time relative 
to piston position. 
If PPFPC is greater than TFPC, then the PPPWT is not utilized to control 
fuel injection from a particular fuel injector 14. Instead, a desired 
quantity of fuel to be delivered during the pilot injection, or desired 
pilot fuel per cycle (DPFPC) is determined at step 120. The DPFPC is 
determined based on EGT and one or more engine operating parameters such 
as engine RPM. Preferably, the DPFPC is found in a look-up table that 
references EGT and engine RPM, and the look-up table is preferably 
calibrated to correspond to the fuel efficiency of the engine 12. 
Next, a desired pilot pulse width time (DPPWT) is determined at step 122. 
The DPPWT is based on DPFPC and one or more engine operating parameters 
such as actual fuel pressure in, for example, the rail 18. Advantageously, 
the DPPWT is determined in time units and is not dependent on angular 
displacement of the crankshaft. The DPPWT is preferably found in a look-up 
table that references DPFPC and actual fuel pressure, and the look-up 
table is preferably calibrated for a particular fuel injector 14. Similar 
to the process described above with respect to the PPPWT and the MPWT, 
control logic may be applied to the DPPWT to adjust this value, as 
represented in FIG. 2 at step 124, based on engine operating parameters 
such as fuel pressure, engine temperature, ambient air temperature and 
ambient air pressure. Next, a pilot output signal is generated at step 126 
based on the DPPWT. The pilot output signal represents an energizing 
duration and is used to energize a particular electronic control valve 16, 
show in FIG. 1, in order to deliver the DPFPC during the pilot injection. 
Under this scenario, i.e., PPFPC greater than DTFPC, preferably only a 
single or pilot injection will occur, and the main injection duration is 
reduced to zero. 
If the particular fuel injector 14 is operating in single injection mode 
only, then steps 100, 102 and 106-118 may be omitted. Instead, a DPFPC, 
DPPWT and corresponding output signal may be determined as previously 
described. The output signal represents an energizing duration and is used 
to energize a particular electronic control valve 16, show in FIG. 1, in 
order to deliver the DPFPC during the single injection. 
Because pulse width times are determined in time units under the present 
invention, the pulse width times are more precise than prior pulse widths 
that are based on angular displacement of the engine crankshaft when the 
injection pressure is provided by a common rail. As a result, fuel 
injection may be precisely controlled so as to optimize engine operation. 
Furthermore, because the quantities of fuel per injection cycle are 
determined independently of angular displacement of the engine crankshaft, 
estimated fuel consumption may be determined more precisely than prior 
methods. 
The system and method of the present invention also provide optimum control 
of fuel injection arrangements that are capable of detecting injector 
response time. Because the PPPWT is a proposed value, it can be 
established as a sufficiently large value to ensure that enough time is 
available for accurate detection of injector response time. Consequently, 
injector latencies can be accurately measured and compensated for using 
the method and system according to the invention. 
Advantageously, each of the look-up tables mentioned above is preferably 
independently calibrated. In other words, the look-up tables are not 
mapped against each other. Consequently, each of the look-up tables may be 
recalibrated as needed without affecting the other look-up tables. 
Another aspect of controlling fuel delivery involves controlling fuel 
pressure. This is preferably accomplished by controlling a fuel pump 
system, such as fuel pump 19 shown in FIG. 1, based on desired injection 
pressure. At step 128 of FIG. 2, a desired injection pressure (DIP) is 
preferably determined independently of the previously described pulse 
width times based on EGT and one or more engine operating parameters, such 
as engine RPM. For a common rail system, the DIP is the desired fuel 
pressure in the rail. Preferably, the DIP is located in a look-up table 
referenced by EGT and engine RPM. Furthermore, the look-up table is 
preferably based on steady-state engine operation. At step 130, a pump 
output signal is generated for controlling the fuel pump 19, or other fuel 
pump system, and the pump output signal is based on the difference between 
the DIP and observed or actual fuel pressure. Additional details regarding 
controlling fuel pressure based on desired injection pressure may be found 
in U.S. patent application Ser. No. 08/867,695, now U.S. Pat. No. 
6,016,791, which is assigned to the assignee of the present invention and 
is hereby incorporated by reference. 
Advantageously, because the DIP is preferably determined independently of 
the previously described pulse width times, the DIP may be adjusted 
independently to account for dynamic engine operating parameters such as 
engine acceleration mode, engine temperature, boost pressure associated 
with a turbo-charger, ambient air temperature, and ambient air pressure. 
For example, during a rapid acceleration mode, the air to fuel ratio may 
be too low (not enough air) to achieve optimal engine efficiency. 
Consequently, it may be desirable to lower the DIP in order to lower the 
actual injection pressure. As another example, for cold starting 
conditions, it may be desirable to again lower the DIP in order to lower 
the actual injection pressure so as to avoid excessive lowering of 
cylinder pressure caused by fuel evaporation. 
One method for adjusting the DIP is shown in FIG. 3. At step 130, a desired 
maximum injection pressure (DMIP) is determined based on EGT and one or 
more engine operating parameters, such as engine RPM. For a common rail 
system, the DMIP is the desired maximum fuel pressure in the rail. At step 
132, a suitable adjustment factor is then applied to the DIP to determine 
an adjusted DIP that is limited by the DMIP and is based on dynamic engine 
operating parameters. For example, the adjustment factor may be used to 
interpolate between the DIP and the DMIP in order to determine the 
adjusted DIP. For certain engine operating parameters, such as high engine 
temperature, the adjustment factor may also trigger a discrete value for 
the adjusted DIP for engine protection purposes, failure mode recovery, 
and the like. Alternatively, the DIP may be adjusted in any suitable 
manner to account for dynamic engine operating parameters. Next, a pump 
output signal is generated at step 134 for controlling the fuel pump 19, 
or other fuel pump system, and the pump output signal is based on the 
difference between the adjusted DIP and the actual fuel pressure 
Because desired injection pressures can be adjusted based on dynamic engine 
operating parameters, control of a fuel pump system can be optimized so as 
to provide optimal fuel pressure. Consequently, engine performance and 
efficiency are improved, and exhaust emissions are reduced compared with 
prior systems and methods. 
While embodiments of the invention have been illustrated and described, it 
is not intended that these embodiments illustrate and describe all 
possible forms of the invention. Rather, the words used in the 
specification are words of description rather than limitation, and it is 
understood that various changes may be made without departing from the 
spirit and scope of the invention.