BACKGROUND OF THE INVENTION
1. Field of the Invention
[0001] This invention relates to a fuel injection amount control device and method for an
internal combustion engine of a vehicle.
2. Description of the Related Art
[0002] An ECU (Electronic Control Unit) for an engine of a vehicle, such as an automobile,
is available that learns a change in injection amount due to the degradation of an
injector over time. Learned values are stored in a control memory in the ECU. When
a failure occurs in the ECU, the ECU is removed and a new ECU is installed. In this
case, while the injector stays in a condition degraded over time, the learned values
of the injection amount of the injector that has been degraded over time is not stored
in the control memory in the new ECU after the replacement. Therefore, it takes a
while for the new ECU after the replacement to learn an appropriate injection amount
of the injector degraded over time. Thus, it is difficult to make the injection amount
of the injector optimum during the period (until the learning of the injection amount
is completed).
[0003] Japanese Patent Application Publication No.
2001-65399 (
JP-A-2001-65399) describes that when the ECU is replaced, the learned values stored in the control
memory in the old ECU before the replacement is read out to a terminal, and the read
learned value is written or stored into a control memory in a new ECU after the replacement.
[0004] Further, in an ECU system for a vehicle described in Japanese Patent Application
Publication No.
2003-56398 (
JP-A-2003-56398), a gateway ECU and several other ECUs are installed in the vehicle, and the gateway
ECU writes a copy of data into the other ECUs in advance. When the gateway ECU is
replaced, the new gateway ECU after the replacement requests the copy of data written
by the old gateway ECU before the replacement from the other ECUs, and the other ECUs
send the copy of data to the new gateway ECU after the replacement. By doing so, the
new gateway ECU after the replacement can obtain the information same as that held
by the old gateway ECU before replacement.
[0005] Japanese Patent Application Publication No.
2001-349259 (
JP-A-2001-349259) describes an injection device including a piezoelectric element for an actuator.
This injection device stores aging characteristics of the piezoelectric element as
a function.
[0006] Japanese Patent Application Publication No.
2005-36788 (
JP-A-2005-36788) describes a learning control device of a fuel injection quantity in a diesel engine.
In this learning control device, a single injection with a small amount of fuel is
performed during a no-injection period in which a command injection quantity to an
injector is zero or under, and a torque proportional quantity is calculated by multiplying
a change amount of the engine speed increased by the single injection, by the engine
speed at the time when the single injection is performed (engine speed before being
increased by the single injection). In the diesel engine, because the injection quantity
is proportional to the generation torque, an actual injection quantity can be estimated
from the generation torque calculated from the torque proportional quantity. As a
result, the difference between the estimated actual injection quantity and the command
fuel injection quantity is detected as a deviation in the injection quantity, and
the fuel injection quantity of the injector is corrected based on the deviation in
injection quantity.
[0007] In the method described in
JP-A-2001-65399, if the control memory in the old ECU before the replacement is broken, the learned
values cannot be read out from the control memory in the old ECU before the replacement.
In this case, the learned values stored in the control memory in the old ECU cannot
be carried over to the control memory in the new ECU after the replacement.
[0008] In the ECU system for a vehicle described in
JP-A-2003-56398, if a failure or the like occurs in the other ECUs and the other ECUs must be replaced
together with the gateway ECU, the new gateway ECU after the replacement cannot request
the copy of data from the other ECUs.
SUMMARY OF THE INVENTION
[0009] The present invention provides a fuel injection amount control device and method
that quickly recover from a serious degradation of the fuel injection amount of the
fuel injection valve that has been degraded over time, even if, when the ECU (a fuel
injection amount control device) for a vehicle is replaced, the learned values regarding
the fuel injection amount of the fuel injection valve stored in a memory in an ECU
(a fuel injection amount control device) for a vehicle before the replacement is not
carried over to a memory in an ECU for the vehicle after the replacement.
[0010] A first aspect of the present invention provides a fuel injection amount control
device that includes: learning means for learning a secular change in an injection
amount of a fuel injection valve to acquire a learned value; correcting means for
correcting the injection amount of the fuel injection valve based on the learned value
acquired by the learning means; and temporary learned value calculating means for
calculating a temporary learned value of the injection amount of the fuel injection
valve based on an input travel distance of a vehicle and an estimated secular change
information indicating the secular change in the injection amount of the fuel injection
valve estimated per travel distance of the vehicle. The correcting means corrects
the injection amount of the fuel injection valve based on the temporary learned value
calculated by the temporary learned value calculating means instead of the learned
value until the learning means completes an acquisition of the learned value after
the travel distance is input.
[0011] According to the first aspect of the present invention, for example, when a failure
etc. occurs in the fuel injection amount control device and the fuel injection amount
control device is replaced, the fuel injection amount control device after the replacement
corrects the fuel injection amount of the fuel injection valve based on the temporary
learned value after the replacement until the learning means completes the acquisition
of the learned value. The estimated secular change information may be, for example,
a mean value of empirically acquired secular changes in the injection amount of the
fuel injection valve per travel distance, and such estimated secular change information
may be stored in storage means in advance. By doing so, the degradation in the fuel
injection amount of the fuel injection valve degraded over time can be reduced during
the time period from the replacement of the fuel injection amount control device to
the completion of acquisition of the learned value by the learning means in many cases.
[0012] The fuel injection amount control device may further include fuel injection valve
learning priority means for performing the learning by the learning means in priority
to other learning after a command to enter a fuel injection valve learning priority
mode is input until the learning by the learning means is completed and the learned
value is acquired. The other learning here means learning other than the learning
performed by the learning means, and is performed by learning control that shares
an operation resource (CPU etc.) with the fuel injection amount control device. The
command to enter a fuel injection valve learning priority mode may be the input of
the travel distance.
[0013] According to this construction, the time period in which the temporary learned value
is used for correcting the fuel injection amount of the fuel injection valve is reduced,
compared to the case where no entry into the fuel injection valve learning priority
mode exists. As a result, the fuel injection valve can quickly recover the most appropriate
injection state.
[0014] A second aspect of the present invention provides a fuel injection amount control
device that includes learning means for learning a secular change in an injection
amount of a fuel injection valve to acquire a learned value; and correcting means
for correcting the injection amount of the fuel injection valve based on the learned
value acquired by the learning means. The fuel injection amount control device further
includes fuel injection valve learning priority means for performing the learning
by the learning means in priority to other learning after a command to enter a fuel
injection valve learning priority mode is input until the learning by the learning
means is completed and the learned value is acquired.
[0015] According to the second aspect of the present invention, the time period in which
a default value is used for correcting the fuel injection amount of the fuel injection
valve is reduced, compared to the case where no entry into the fuel injection valve
learning priority mode exists. As a result, the fuel injection valve can quickly recover
the most appropriate injection state.
[0016] A third aspect of the present invention provides a fuel injection amount control
method. A secular change in an injection amount of a fuel injection valve is learned
to acquire a learned value. The injection amount of the fuel injection valve is corrected
based on the acquired learned value. A travel distance of a vehicle is input. A temporary
learned value of the injection amount of the fuel injection valve is calculated based
on the input travel distance and an estimated secular change information indicating
the secular change in the injection amount of the fuel injection valve estimated per
travel distance of the vehicle. The injection amount of the fuel injection valve is
corrected based on the calculated temporary learned value instead of the learned value
until the acquisition of the learned value is completed after the travel distance
is input. According to the third aspect of the present invention, the effect similar
to that of the first aspect of the present invention may be obtained.
[0017] A fourth aspect of the present invention provides a fuel injection amount control
method. in the method, a secular change in an injection amount of a fuel injection
valve is learned to acquire a learned value. The injection amount of the fuel injection
valve is corrected based on the acquired learned value. A command to enter a fuel
injection valve learning priority mode is input. The learning of the secular change
is performed in priority to other learning after the command to enter the fuel injection
valve learning priority mode is input until the learning of the secular change is
completed and the learned value is acquired. According to the fourth aspect of the
present invention, the effect similar to that of the second aspect of the present
invention may be obtained.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The foregoing and further objects, features and advantages of the invention will
become apparent from the following description of example embodiments with reference
to the accompanying drawings, wherein like numerals are used to represent like elements
and wherein:
FIG 1 is a configuration diagram illustrating a fuel injection system of a diesel
engine according to an embodiment of the present invention;
FIG. 2 is a diagram showing an example of a pilot injection amount setting map;
FIG 3 is a flowchart showing a pilot injection amount learning control operation;
FIG 4 is a diagram showing an example of a deviation of the pilot injection amount
of the injector of a specific cylinder with a specific rail pressure;
FIG 5 is a diagram showing an integrated value of learned deviation and a deviation
of the pilot injection amount of an injector when no correction has been performed;
FIG 6 is a diagram showing an example of a degradation trend map;
FIG 7 is a flowchart showing a control operation of the ECU according to the first
embodiment of the present invention;
FIG 8 is a diagram showing an integrated value of learned deviation and a temporary
learned value of the ECU according to the first embodiment of the present invention,
and in particular, showing an example of a case where the ECU is replaced when the
vehicle travel distance is 2800km;
FIG 9 is a flowchart showing a control operation of the ECU according to a second
embodiment of the present invention;
FIG 10 is a diagram showing an integrated value of learned deviation and a temporary
learned value of the ECU according to the second embodiment of the present invention,
and in particular, showing an example of a case where the ECU is replaced when the
vehicle travel distance is 2800km;
FIG 11 is a flowchart showing a control operation of the ECU according to a third
embodiment of the present invention; and
FIG 12 is a diagram showing an integrated value of learned deviation and a temporary
learned value of the ECU according to the third embodiment of the present invention,
and in particular, showing an example of a case where the ECU is replaced when the
vehicle travel distance is 2800km.
DETAILED DESCRIPTION OF EMBODIMENTS
[0019] A fuel injection amount control device according to a first embodiment of the present
invention will be described hereinafter. In the embodiment, a fuel injection amount
control device that is installed in a common-rail diesel engine (internal combustion
engine) and performs learning control of a pilot injection amount (injection amount
of a fuel injection valve), and a fuel injection system including the fuel injection
amount control device are described as an example.
[0020] FIG. 1 is a configuration diagram illustrating a fuel injection system of a diesel
engine 1 according to the embodiment. The fuel injection system shown in FIG 1 is
applied to a four-cylinder diesel engine 1, for example. The fuel injection system
includes a common rail 2 serving as an accumulator that stores high-pressure fuel,
a high-pressure fuel pump 4 that pressurizes fuel pumped out by a feed pump 10 from
a fuel tank 3 and supplies the pressurized fuel to the common rail 2, an injector
(fuel injection valve) 5 that injects the high-pressure fuel supplied from the common
rail 2 into a cylinder (combustion chamber 1a) in the engine 1, and an electronic
control unit 6 (hereinafter, referred to as an "ECU 6"), serving as a fuel injection
amount control device that controls this fuel injection system.
[0021] The ECU 6 sets a target fuel pressure, and the common rail 2 accumulates the high-pressure
fuel supplied from the high-pressure fuel pump 4 at the target fuel pressure. A pressure
sensor 7 that detects an accumulated fuel pressure (hereinafter, referred to as a
"rail pressure") and outputs the detected rail pressure to the ECU 6, and a pressure
limiter 8 that limits the rail pressure so as not to exceed a preset upper limit are
attached to the common rail 2. When the rail pressure exceeds the upper limit, the
pressure limiter 8 opens to vent the excess pressure to the fuel tank 3.
[0022] The high-pressure fuel pump 4 is provided with a plunger 12 and a solenoid regulator
valve 14. The plunger 12 reciprocates in a cylinder 11 in synchronization with the
rotation of a camshaft 9 that is rotated by the drive force from a crankshaft of the
engine 1. The solenoid regulator valve 14 regulates or adjusts the fuel amount drawn
into a compression chamber 13 in the cylinder 11 from the feed pump 10. In the high-pressure
fuel pump 4, when the plunger 12 moves in the cylinder 11 from the top dead point
to the bottom dead point, the solenoid regulator valve 14 regulates the fuel pumped
out from the feed pump 10, and the fuel pushes open an inlet valve 15 to be drawn
into the compression chamber 13. Then, when the plunger 12 moves in the cylinder 11
from the bottom dead point to the top dead point, the plunger 12 pressurizes the fuel
in the compression chamber 13, and the pressurized fuel pushes open a discharge valve
16 to be pumped into the common rail 2. The solenoid regulator valve 14 is controlled
by a control signal from the ECU 6 to vary the (cross-sectional) passage area of a
fuel supply passage. By varying the passage area, the solenoid regulator valve 14
regulates or adjusts the amount of fuel introduced into the compression chamber 13
to adjust the discharge pressure of the fuel from the high-pressure fuel pump 4, thereby
adjusting the rail pressure. More specifically, when fuel is not injected (during
a fuel cut operation), such as when an accelerator angle is equal to "0," the solenoid
regulator valve 14 is fully closed. On the other hand, the solenoid regulator valve
14 is widely opened to increase the rail pressure.
[0023] Each cylinder in the engine 1 is provided with an injector 5. The injector 5 is connected
to the common rail 2 via a high-pressure pipe 17. The injector 5 includes a solenoid
valve 5a that is operated based on a command from the ECU 6, and a nozzle 5b that
injects a fuel when the solenoid valve 5a is energized. The solenoid valve 5a opens
and closes a low-pressure passage that connects between a pressure chamber to which
the high fuel pressure in the common rail 2 is applied and a low-pressure side. When
the solenoid valve is energized, the low-pressure passage is opened. When the solenoid
valve is de-energized, the low-pressure passage is closed.
[0024] The nozzle 5b includes a needle that opens and closes a nozzle hole. The fuel pressure
in the pressure chamber biases the needle in the valve closing direction (direction
to close the nozzle hole). Therefore, when the low-pressure passage is opened by energizing
the solenoid valve 5a and thereby the fuel pressure in the pressure chamber is reduced,
the needle moves upward in the nozzle 5b to open the valve (open the nozzle hole)
and the high-pressure fuel supplied from the common rail 2 is injected into the cylinder
through the nozzle hole. On the other hand, when the low-pressure passage is closed
by de-energizing the solenoid valve 5a, and thereby the fuel pressure in the pressure
chamber is increased, the needle moves downward in the nozzle 5b to close the valve
(close nozzle hole) and the injection ends.
[0025] An engine speed sensor 18 (for example, an electromagnetic pick up), an accelerator
angle sensor 19, a pressure sensor 7 and the like are connected to the ECU 6. The
engine speed sensor 18 outputs a pulse signal to calculate an engine speed. The accelerator
angle sensor 19 detects an accelerator angle (an engine load). The pressure sensor
7 detects the rail pressure. The ECU 6 calculates a target rail pressure of the common
rail 2 and an injection timing, injection amount, or the like appropriate for the
operating condition of the engine 1 based on the information detected by the sensors
18, 19 and 7. Then, the ECU 6 electronically controls the solenoid regulator valve
14 of the high-pressure fuel pump 4 and the solenoid valve 5a of the injector 5 in
accordance with the calculation result.
[0026] Further, a neutral switch 20 sends (inputs) a neutral signal to the ECU 6 when the
shift position of the transmission is N (neutral) position. Also, a clutch-off sensor
21 sends (inputs) a clutch-off signal to the ECU 6 when a vehicle driver depresses
a clutch pedal. The ECU 6 further includes an interface to connect to a terminal device
22, and predetermined information (such as a vehicle travel distance described later)
is input to the ECU 6 through the terminal device 22.
[0027] In the fuel injection control performed by the ECU 6, a pilot injection with a very
small amount of fuel is performed prior to the main injection performed at the beginning
of an expansion stroke, and pilot injection amount learning control is performed to
acquire an appropriate amount of the pilot injection. By performing the pilot injection
with a very small amount of fuel prior to the main injection, the temperature in the
combustion chamber 1a is lowered, fuel diffusion is enhanced during the main injection,
and an ignition lag from fuel injection to ignition is shortened. As a result, combustion
noises are reduced and NOx emission is reduced.
[0028] The ECU 6 stores a pilot injection amount setting map as shown in FIG. 2 in a ROM.
The pilot injection amount setting map defines relationships between a pilot injection
amount and an energization time (valve opening time) respectively for multiple levels
(six levels in FIG. 2) of common rail pressure (a - f in FIG 2 that are set such that,
for example, a = 32MPa, b = 48MPa, c = 64MPa, d = 80MPa, e = 96MPa, f = 112MPa). The
energization time of the injector appropriate for a certain common rail pressure is
acquired in accordance with the pilot injection amount setting map, such that a command
pilot injection amount, which is determined in accordance with an engine speed or
the like, is acquired or achieved.
[0029] Next, a pilot injection amount learning control operation will be described with
reference to the flowchart shown in FIG. 3. In the pilot injection amount learning
control, a secular change in pilot injection amount of the injector 5 is learned,
and the pilot injection amount of the injector 5 is corrected based on the learned
value of the secular change.
[0030] In step ST1, the ECU 6 determines whether a learning condition to perform pilot injection
amount learning control during an operation of the engine 1 is satisfied. More specifically,
the learning condition is satisfied if all of the following three conditions (1) -
(3) are satisfied. (1) The accelerator angle is equal to "0." (2) The shift position
of the transmission is N (neutral) position or the clutch is off (disconnected). (3)
A predetermined rail pressure is maintained.
[0031] The ECU 6 determines the above-described conditions based on the outputs of the accelerator
angle sensor 19, the neutral switch 20, the clutch-off sensor 21 and the pressure
sensor 7. Note that the learning conditions for the pilot injection amount learning
control are not limited to the above conditions, but may be set any other appropriate
conditions.
[0032] If the determination in step ST1 is negative, this control routine is once ended.
On the other hand, if the determination in step ST1 is affirmative, the process proceeds
to step ST2.
[0033] In step ST2, a single injection with a very small amount of fuel (an amount same
as the pilot injection amount, for example) is performed as a learning injection into
a particular cylinder (a cylinder in which a piston is positioned near the top dead
point). Then, in step ST3, the change in engine speed due to the single injection
is detected. The change in engine speed is detected based on the output signal from
the engine speed sensor 18.
[0034] In step ST4, the ECU 6 calculates the difference between a command fuel injection
amount (a target injection amount determined by the ECU 6) and an actual fuel injection
amount by the single injection. The difference (hereinafter, sometimes referred to
as "deviation") between the command fuel injection amount and the actual fuel injection
amount is set as a learned deviation (learned value). Further, the pilot injection
amount of the injector 5 is corrected based on the learned deviation. In other words,
the ECU 6 compares the change in engine speed when a single injection with the command
fuel injection amount is assumed to be performed (this change is stored in the memory
in the ECU 6 in advance) with the change in actual engine speed corresponding to the
actual fuel injection amount, and calculates the learned deviation (learned value)
of the fuel injection amount from the difference in the engine speed. Then, the pilot
injection amount setting map (see FIG 2) described above is corrected based on the
calculated learned deviation. Preferably, multiple single injections may be performed
(for example, 10 times) for each combination of a rail pressure and a cylinder to
acquire multiple deviations between the command fuel injection amount and the actual
fuel injection amount, and an average of the multiple deviations may be set as the
learned deviation related to the combination of the rail pressure and the cylinder.
[0035] The above-described pilot injection amount learning control is performed per cylinder
per rail pressure. When the steps ST1 to ST4 are performed for all cylinders and for
all rail pressures (six rail pressures shown in FIG 2), the pilot injection amount
learning control ends. Thereafter, the pilot injection amount learning control is
preformed at appropriate times, and the deviation (secular change) of the pilot injection
amount due to the degradation of the injector 5 over time is appropriately calculated.
[0036] The above-described pilot injection amount learning control is performed at such
a frequency that the deviation in the pilot injection amount of the injector 5 does
not exceed a predetermined injection amount correction accuracy line (for example,
0.2mm
3). In FIG. 4, the horizontal axis indicates a vehicle travel distance, and the vertical
axis indicates a deviation in the pilot injection amount of the injector 5. The zigzag
line L1 indicates a deviation in the pilot injection amount of the injector 5 of a
specific cylinder with a specific rail pressure. This zigzag line L1 indicates a case
in which the pilot injection amount learning control is performed at an appropriate
timing, that is, when the difference amount matches the injection amount correction
accuracy line L2. Thus, the pilot injection amount is corrected such that the deviation
is equal to zero at the vehicle travel distances 100km, 600km, 1600km and 3600km.
[0037] In FIG 5, the horizontal line indicates a vehicle travel distance, and the vertical
line indicates the deviation and a learned deviation of the pilot injection amount
of the injector 5. More specifically, the curve L3 indicates an example of a deviation
of the pilot injection amount of the injector 5 when the pilot injection amount learning
control has never been performed. The line L4 indicates an integrated value of learned
deviation shown in FIG 4. As shown in line L4, when the vehicle travel distances are
100km, 600km, 1600km and 3600km, the deviation of 0.2 mm
3 is calculated as the learned deviation. In this case, the integrated value of the
learned deviation at 100km, 600km, 1600km and 3600km are respectively 0.2mm
3, 0.4mm
3, 0.6mm
3 and 0.8mm
3.
[0038] Pilot injection amount correction control of the injector 5 when the ECU is replaced
will be described hereinafter.
[0039] The ECU 6 stores a degradation trend map L5 shown by a solid line in FIG 6 in the
ROM. The degradation trend map L5 indicates a mean value of deviations (secular changes)
in the pilot injection amount of the injector 5 estimated per vehicle travel distance
when the pilot injection amount learning control has never been performed. Thus, the
degradation trend map L5 indicates a relationship between the estimated secular change
and the vehicle travel distance. The degradation trend map L5 may sometimes be referred
to as an "estimated secular change information," hereinafter. The curve L6 shows the
fastest secular change in the pilot injection amount, and the curve L7 shows the slowest
secular change in the pilot injection amount. Therefore, the deviation of the pilot
injection amount of the injector 5 when the pilot injection amount has never been
corrected by the pilot injection amount learning control falls between the curve L6
and the curve L7 in most cases, and results in a value close to the curve (degradation
trend map) L5 with high probability. The curves L5 to L7 can be acquired in advance
through experiments, or the like.
[0040] Hereinafter, an example when the secular change in the pilot injection amount progresses
the most rapidly (the case of curve L6) will be described. In addition, in the following
description, it is assumed that the curve L3 shown in FIG 5 indicates the case where
the secular change in the pilot injection amount progresses the most rapidly.
[0041] It is assumed that, when a failure occurs in the ECU 6 installed on a vehicle and
the ECU 6 is replaced, the vehicle travel distance is, for example, 2800km. In this
case, as shown in FIG. 5, in the memory in the ECU 6 before the replacement, 0.6mm
3 is stored as an integrated value of learned deviation. However, in the memory of
the ECU 6 after the replacement, an initial value (0mm
3) is stored as the integrated value of learned deviation. Therefore, if nothing is
done, the deviation of the pilot injection amount of the degraded injector 5 is large
and therefore a good pilot injection cannot be performed. In other words, because
the pilot injection is performed according to a default pilot injection amount setting
map corresponding to a new injector 5, the deviation increases and good pilot injection
cannot be performed.
[0042] Therefore, the ECU 6 after the replacement calculates a temporary learned value of
the pilot injection amount of the injector 5 in accordance with the degradation trend
map L5 and a vehicle travel distance input from the terminal device 22, and corrects
the pilot injection amount of the injector 5 using the temporary learned value instead
of the default value until the first pilot injection amount learning control is completed
after the replacement of the ECU 6. The operation for correcting the pilot injection
amount will be described hereinafter with reference to FIG. 7.
[0043] In step ST11, the ECU 6 after the replacement (hereinafter, simply referred to as
"ECU 6") determines whether a vehicle travel distance is input from the terminal device
22. If the determination in step ST11 is affirmative, the control process proceeds
to step ST12. On the other hand, if the determination in step ST11 is negative, this
control routine is once ended.
[0044] In step ST12, the ECU 6 calculates a temporary learned value of the pilot injection
amount of the injector 5 (temporary integrated value of learned deviation) based on
the input vehicle travel distance and the degradation trend map (estimated secular
change information) L5. In other words, the ECU 6 acquires the value (deviation) on
the degradation trend map L5 shown in FIG 6 corresponding to the input vehicle travel
distance, as the temporary learned value.
[0045] In step ST13, the ECU 6 sets the calculated temporary learned value as the integrated
value of the learned deviation (learned value) to be used in the correction of the
pilot injection amount of the injector 5, and corrects the pilot injection amount
of the injector 5 based on the temporary learned value. In other words, the ECU 6
corrects the pilot injection amount setting map (see FIG 2) using the temporary learned
value as the integrated value of learned deviation. The correction of the pilot injection
amount using the temporary learned value continues until the first pilot injection
amount learning control is completed and the learned deviation is acquired through
the first pilot injection amount leaning control. Incidentally, when the first pilot
injection amount learning control is completed after the replacement of the ECU, the
integrated value of the learned deviation used to correct the pilot injection amount
is updated from the temporary learned value to the learned value newly acquired by
the first pilot injection amount learning control.
[0046] According to the ECU 6 described above, as shown in FIG 8, the temporary learned
value F is used as the integrated value of the learned deviation to correct the pilot
injection amount until the first pilot injection amount learning control is completed
after the ECU is replaced. Thus, during this period, the deviation of the pilot injection
amount of the injector 5 is difference "a" between the value on the curve L6 and the
temporary learned value F. Compared to the conventional case in which the deviation
of the pilot injection amount of the injector 5 after replacement of the ECU is difference
"b" between the value on the curve L6 and the default value, the accuracy of the pilot
injection amount improves significantly.
[0047] In the meantime, if the deviation of the pilot injection amount of the injector 5
changes over time along the curve L7, the deviation in the pilot injection amount
of the injector 5 after the correction is difference "c" between the value on the
curve L7 and the temporary learned value F. In this case, the deviation of the conventional
way is difference "d" between the value on the curve L7 and the default value. Therefore,
the accuracy of the pilot injection amount does not much improve. However, because
the degradation trend map L5 indicates the mean value of the estimated deviations
of the pilot injection amount of the injector 5 (for each vehicle travel distance)
when the pilot injection amount learning control has never been performed, the temporary
learned value F calculated based on the degradation trend map L5 and the input vehicle
travel distance is highly likely to be the value close to the integrated value of
the learned deviation stored in the ECU before the replacement. Therefore, according
to the ECU 6, in many cases, the degradation in accuracy of the pilot injection amount
after the replacement of the ECU, which conventionally occurred, can be avoided.
[0048] A second embodiment of the present invention will be described. In the second embodiment,
the difference between the first embodiment and the second embodiment will be mainly
described. Like elements are denoted by the like reference numerals in the drawings,
and the description thereof will be omitted hereinafter.
[0049] The ECU 6 in the first embodiment is different from the ECU 6A in the second embodiment
in a portion of the pilot injection amount correction control operation performed
when the ECU is replaced. The difference is described with reference to the flowchart
shown in FIG 9.
[0050] In step ST21, the ECU 6A after replacement (hereinafter, simply referred to as "ECU
6A") determines whether a vehicle travel distance is input from the terminal device
22. If the determination in step ST21 is affirmative, the process proceeds to step
ST22. On the other hand, if the determination in step ST21 is negative, this control
routine is once ended.
[0051] In step ST22, the ECU 6A enters an injector learning priority mode. In the injector
learning priority mode, the ECU 6A executes the pilot injection amount learning control
described with reference to FIG. 3 in priority to other learning processes, and execution
frequency of the pilot injection amount learning control increases than before entering
the injector learning priority mode. The other leaning processes means learning processes
other than the pilot injection amount learning control operation, but shares an operation
resource (ECU etc.) with the pilot injection amount learning control operation. Incidentally,
in this embodiment, the input of the vehicle travel distance from the terminal device
22 in step ST21 is used as an input of a command to enter the injector learning priority
mode. However, the command to enter the injector learning priority mode may be input
independently from the input of vehicle travel distance.
[0052] Step ST23 is an operation similar to that of step ST12, and step ST24 is an operation
similar to that of step ST13. Therefore, description thereof will be omitted here.
[0053] In step ST25, the ECU 6A determines whether the first pilot injection amount learning
control after replacement of the ECU is completed. If the determination in step ST25
is affirmative, the process proceeds to step ST26. On the contrary, if the determination
in step ST25 is negative, the determination in step ST25 is performed repeatedly.
[0054] In step ST26, the ECU 6A cancels (ends) the injector learning priority mode and ends
this control routine.
[0055] According to the ECU 6A, as shown in FIG 10, the time period T2 in which the temporary
learned value is used to correct the pilot injection amount is reduced, compared to
the same time period T1 in the case where the ECU does not enter the injector learning
priority mode. Therefore, the injector 5 can recover the most suitable injection state
quickly after the replacement of the ECU.
[0056] A third embodiment of the present invention will be described hereinafter. In the
following description, the difference between the first embodiment and the third embodiment
will be mainly described. In the drawings, like elements will be denoted by like reference
numerals, and the description thereof will be omitted.
[0057] The ECU 6 in the first embodiment is different from the ECU 6B in the third embodiment
in the pilot injection amount correction control operation when the ECU is replaced.
The difference is described with reference to the flowchart shown in FIG. 11.
[0058] In step ST31, the ECU 6B determines whether a predetermined command (command to enter
the injector learning priority mode) is input from the terminal device 22. If the
determination in step ST31 is affirmative, the process proceeds to step ST32. On the
contrary, if the determination in step ST31 is negative, this control routine is once
ended.
[0059] In step ST32, the ECU 6B enters the injector learning priority mode. In the injector
learning priority mode, the ECU 6B executes the pilot injection amount learning control
described above with reference to FIG. 3 in priority to other learning processes,
and the execution frequency of the pilot injection amount learning control increases
than before entering the injector learning priority mode.
[0060] Then, when the first pilot injection amount learning control after replacement of
ECU is completed (step ST33:YES), the injector learning priority mode is canceled
in step ST34, and this control routine ends.
[0061] According to the ECU 6B, as shown in FIG. 12, the time period T3 in which the default
value (0) is used to correct the pilot injection amount is reduced, compared to the
same time period T1 in the case where the ECU does not enter the injector learning
priority mode. Therefore, the injector 5 can recover the most suitable injection state
quickly after the replacement of the ECU.
[0062] In the above-described first to third embodiments, in-cylinder direct fuel injection
engine in which fuel is directly injected into a combustion chamber from an injector
is described as an example. However, an engine (a port-injection engine) in which
fuel is injected into an intake pipe may be used, instead. In addition, an engine
in which fuel is injected into both a combustion chamber and an intake pipe may be
used. Further, the present invention is not limited to a diesel engine; rather the
present invention may be applied to the fuel injection in an in-cylinder direct injection
gasoline engine or a port-injection gasoline engine.
[0063] Furthermore, in the above-described first to third embodiments, the injection amount
learning control is performed for pilot injection. However, the present invention
is not limited to the pilot injection. Rather, the injection amount learning control
may be performed for main injection or after injection, which is performed after the
main injection.
[0064] In addition, the command to enter the injector learning priority mode may not be
input from the terminal device 22. For example, switches may be connected to the ECU
6A or 6B, and a predetermined switch signal input from the switches may be used as
the command to enter the injector learning priority mode.
[0065] The present invention may be used, for example, in a fuel injection amount control
apparatus that performs learning control to correct secular change in a pilot injection
amount of a diesel engine.
[0066] While some embodiments of the invention have been illustrated above, it is to be
understood that the invention is not limited to details of the illustrated embodiments,
but may be embodied with various changes, modifications or improvements, which may
occur to those skilled in the art, without departing from the spirit and scope of
the invention.