BACKGROUND OF THE INVENTION
1 Technical Field of the Invention
[0001] The present invention relates generally to a fuel injection apparatus for diesel
engines, and more particularly to such a fuel injection apparatus designed to diagnose
a failure in injecting fuel into each cylinder of a diesel engine.
2 Background Art
[0002] There are known fuel injection apparatuses designed to diagnose whether a failure
has occurred in injecting fuel into each cylinder of an automotive diesel engine.
Typical ones of such fuel injection apparatuses include an injector drive unit and
a control unit. The injector drive unit works to actuate injectors which inject fuel
into cylinders of the engine, respectively. The control unit connects with the injector
drive unit through a diagnostic signal line and works to control an operation of the
injector drive unit. When the control unit directs the injector drive unit to drive
the injectors, the injector drive unit outputs a pulse signal to the diagnostic signal
line. The control unit monitors the pulse signal appearing on the diagnostic signal
line and diagnoses whether the injectors have been driven to complete injection of
fuel into the cylinders of the engine or not.
[0003] In recent years, in order to meet strengthened exhaust emission regulations, injection
systems have been employed which work to perform additional injection of fuel in a
combustion cycle of each cylinder of the diesel engine for reducing or burning particulates
contained in exhaust emissions. This results in an increased total number of injections
of fuel into each cylinder of the diesel engine, which leads to a difficulty in securing
the time required for diagnosing the failure of the fuel injection. In order to alleviate
this drawback, an approach may be proposed to perform parallel diagnoses using pairs
of diagnostic signal lines and diagnostic units. This, however, results in complexity
of the system and increased production costs thereof. The diagnoses may be suspended
when fuel injections are being performed for the purpose of reducing or burning out
particulates contained in exhaust gasses of the engine. This is, however, unuseful
because it may result in an increased period of time during which the diagnoses are
suspended, thus requiring much time for activating a diesel particulate filter to
burn out the particulates trapped therein.
SUMMARY OF THE INVENTION
[0004] It is therefore a principal object of the invention to avoid the disadvantages of
the prior art.
[0005] It is another object of the invention to provide a fuel injection apparatus which
is designed to ensure accurate diagnosis of a failure in injecting fuel into each
cylinder of a diesel engine.
[0006] According to one aspect of the invention, there is provided a fuel injection apparatus
for diesel engines which is designed to diagnose a failure in injecting fuel into
each cylinder of the engine. The fuel injection apparatus comprises: (a) injectors
designed to inject fuel into cylinders of a diesel engine, respectively; (b) an injector
controller working to control the injectors to perform a plurality of injections of
the fuel into each of the cylinders of the engine in each combustion cycle thereof;
(c) a single diagnostic signal line to which a diagnostic signal is provided which
indicates whether the injection of fuel into each of the cylinders has been completed
or not; and (d) an injection failure diagnosing circuit working to select one of the
cylinders that is to be diagnosed, inhibit the injectors from injecting the fuel into
others of the cylinders when the injectors are required by the injector controller
to inject the fuel into the others of the cylinders, and monitor the diagnostic signal
appearing on the diagnostic signal line to make an injection failure diagnosis of
whether a failure in injecting the fuel into the selected one of the cylinders has
occurred or not. This ensures accurate diagnoses of whether the failure has occurred
in injecting the fuel into each of the cylinders of the engine or not in a case where
the engine is so controlled that a plurality of injections of fuel into each of the
cylinders every combustion cycle thereof.
[0007] In the preferred mode of the invention, the injection failure diagnosing circuit
sets a diagnosis time during which the injection failure diagnosis is to be performed
on the selected one of the cylinders and a non-injection time during which no injection
of fuel into the others of the cylinders is to be performed and which coincides with
the diagnosis time. The injection failure diagnosing circuit permits the injection
of fuel into the selected one of the cylinders to be performed during the diagnosis
time and inhibits the injection of fuel into each of the others of the cylinders during
the non-injection time when it is required to inject the fuel into the each of the
others of the cylinders.
[0008] The injection failure diagnosing circuit may work to select one of the cylinders
to be diagnosed in sequence.
[0009] Upon completion of a determination of whether the injection of fuel into the selected
one of the cylinders has been completed or not, the injection failure diagnosing circuit
determines whether each of the cylinders is to be diagnosed subsequently or not.
[0010] The injection failure diagnosing circuit suspends the injection failure diagnosis
of each of the cylinders of the engine for a given period of time after completion
of one or a given number of times of the injection failure diagnoses of the selected
one of the cylinders.
[0011] The apparatus may further comprise injection failure counters, one for each of the
cylinders of the engine, each of which counts an event that no injection of fuel has
been performed in a corresponding one of the cylinders of the engine for the diagnosis
time. The injection failure diagnosing circuit works to make the injection failure
diagnosis of each of the cylinders of the engine a plurality of times. When a count
value of each of the injection failure counters exceeds a preselected value, the injection
failure diagnosing circuit determines that the failure has occurred in injecting the
fuel into a corresponding one of the cylinders.
[0012] The injection failure diagnosing circuit performs the injection failure diagnosis
for a period of time between completion of all injections of the fuel into the selected
one of the cylinders in the combustion cycle and a time when the fuel is to start
to be injected into a subsequent one of the cylinders. The preselected value may be
two or more.
[0013] When the fuel has been injected into the selected one of the cylinders at least one
time during the diagnosis time, the injection failure diagnosing circuit resets a
corresponding one of the injection failure counters.
[0014] When each of the injectors has injected the fuel into one of the cylinders, the injector
controller outputs the diagnostic signal in the form of a pulse signal to the diagnostic
signal line. The apparatus also includes injection counters, one for each of the cylinders,
which count the number of times the injectors have performed the injections of fuel
into the cylinders during the diagnosis time, respectively. The injection failure
diagnosing circuit monitors the injection counters to know the number of times each
of the injectors has completed the injection of fuel into a corresponding one of the
cylinders.
[0015] The injection failure diagnosing circuit resets each of the injection counters when
a corresponding one of the cylinders is placed in the non-injection time.
[0016] The plurality of injections of the fuel into each of the cylinders of the engine
every combustion cycle include an injection of the fuel serving to produce torque
in the diesel engine and an injection of the fuel serving to produce no torque in
the diesel engine. The injection of fuel inhibited from being performed by the injection
failure diagnosing circuit during the non-injection time is the injection of the fuel
serving to produce no torque in the diesel engine.
[0017] The diesel engine is connected to a trapping device working to trap particulates
contained in exhaust emissions of the diesel engine. The injection of the fuel serving
to produce no torque in the diesel engine works to burn the particulates trapped in
the trapping device.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The present invention will be understood more fully from the detailed description
given hereinbelow and from the accompanying drawings of the preferred embodiments
of the invention, which, however, should not be taken to limit the invention to the
specific embodiments but are for the purpose of explanation and understanding only.
[0019] In the drawings:
Fig. 1 is a block diagram which shows a fuel injection system according to the invention;
Fig. 2 is a timechart which demonstrates a relation among an injector drive signal,
an injector drive current, and an injection failure diagnostic signal;
Fig. 3 is a timechart which demonstrates a sequence of fuel injections performed in
each cylinder of a diesel engine, injector drive signals, and count value indicating
the number of the fuel injections;
Fig. 4 is a flowchart of a program to perform post injection of fuel into each cylinder
of a diesel engine;
Fig. 5 is a flowchart of a program to control operations of injection counters which
count the number of injections of fuel into cylinders of a diesel engine, respectively;
Fig. 6 is a flowchart of a program to diagnose a failure in injecting fuel into each
cylinder of a diesel engine; and
Fig. 7 is a flowchart of a program to determine whether an injection failure diagnosis
should be continued or suspended.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0020] Referring to the drawings, wherein like reference numbers refer to like parts in
several views, particularly to Fig. 1, there is shown a fuel injection system 1 according
to the invention which is designed to control injection of fuel into a diesel engine
2 mounted in an automotive vehicle. An exhaust emission purification device 3 is joined
to an exhaust pipe extending from the engine 2 to purify potentially polluting exhaust
gasses.
[0021] The structure and operation of the exhaust emission purification device 3 will first
be described below.
[0022] The exhaust emission purification device 3 works to suck in exhaust gasses discharged
from the engine 2 and capture or trap particulates contained in the exhaust gasses
through a diesel particulate filter (not shown) to clean up the exhaust gasses, which
are, in turn, discharged outside the vehicle. The exhaust emission purification device
3 has disposed therein an oxidation catalyst (not shown) which reacts with fuel (HC)
to produce heat to burn out the trapped particulates. The exhaust emission purification
device 3 is equipped with a pressure difference sensor 31, an inlet temperature sensor
32, and an outlet temperature sensor 33. The pressure difference sensor 31 works to
measure a difference in pressure between the exhaust gases entering and going out
of the exhaust emission purification device 3. The inlet temperature sensor 32 works
to measure the temperature of the exhaust gasses entering the exhaust emission purification
device 3. The outlet temperature sensor works to measure the temperature of the exhaust
gasses discharged from the exhaust emission purification device 3. The sensors 31,
32, and 33 provide sensor outputs to the fuel injection system 1.
[0023] The fuel injection system 1 consists essentially of a high-pressure fuel pump 11,
a common rail 12, injectors 13, 14, 15, and 16, and an injection control ECU 17.
[0024] The high-pressure fuel pump 11 is implemented by a typical automotive supply pump
which works to draw the fuel from a fuel tank (not shown) installed in the vehicle
and pressurize it up to a target pressure (e.g., 135 to 180 MPa) to produce a high-pressure
fuel which is, in turn, supplied to the common rail 12. The high-pressure fuel pump
11 is so designed that the target pressure may be changed selectively.
[0025] The common rail 12 works as an accumulator which accumulates therein the high-pressure
fuel supplied from the high-pressure fuel pump 11 and delivers it to the injectors
13 to 16 selectively. The common rail 12 is equipped with a pressure sensor (not shown)
which measures the pressure of fuel in the common rail 12 and outputs a signal indicative
thereof to the injection control ECU 17.
[0026] Each of the injectors 13 to 16 is equipped with a solenoid-operated fuel injection
valve (not shown) which is energized by a drive current supplied from the injection
control ECU 17 to inject the fuel into a corresponding one of first to fourth cylinders
21, 22, 23, and 24 of the engine 2.
[0027] The injection control ECU 17 consists of an injector drive unit 18 and a microcomputer
19. The microcomputer 19 works to direct the injector drive unit 18 to output the
drive current to each of the injectors 13 to 16 to control the injection of fuel into
a corresponding one of the cylinders 21 to 24 of the engine 2. The injection control
ECU 17 also includes drive signal lines 1A to 1D through which the microcomputer 19
transmits drive signals to the injector drive unit 18 to output the drive currents
to the injectors 13 to 16, respectively, and a single diagnostic signal line 1E through
which the injector drive unit 18 outputs a diagnostic signal in the form of a pulse
signal to the microcomputer 19 which indicates completion of supply of the drive currents
to the injectors 13 to 16.
[0028] The injector drive unit 18 is equipped with a drive current output circuit 1F and
a drive current detector 1G. When the drive signal in a high level is outputted from
the microcomputer 19 to one of the drive signal lines 1A to 1D, the injector drive
unit 18 activates the drive current output circuit 1F to output the drive current
to a corresponding one of the injectors 13 to 16. The drive current detector 1 G works
to detect the output of the drive current from the drive current output circuit 1F
and output the diagnostic signal in a high level to the diagnostic signal line 1E.
When the drive current reaches a peak, the drive current detector 1G outputs the diagnostic
signal in a low level to the diagnostic signal line 1E. Additionally, when no drive
signal is outputted from the drive current output signal 1F, the drive current detector
1G outputs the diagnostic signal in the low level to the diagnostic signal line 1E.
Fig. 2 demonstrates examples of the drive signal outputted to each of the drive signal
lines 1A to 1D, the drive current produced by the injector drive unit 18, and the
diagnostic signal outputted to the diagnostic signal line 1E.
[0029] The microcomputer 19 has a typical structure and receives an output of an accelerator
sensor (not shown) indicating a stroke or an effort on an accelerator pedal of the
vehicle, an output of a speed sensor (not shown) indicating the speed of the engine
2, and an output of a crankshaft position sensor (not shown) indicating an angular
position of a crank shaft of the engine 2 to direct the injector drive unit 18 to
produce the drive signals for the injectors 13 to 16, respectively.
[0030] Fig. 3 demonstrates an example of operation of the microcomputer 19. Specifically,
the microcomputer 19 analyzes the outputs of the above sensors and calculates times
(i.e., the injection timings) when the fuel is to be injected three times during every
compression stroke of each of the cylinders 21 to 24 of the engine 2, a time when
the fuel is to be injected one time during every combustion stroke of each of the
cylinders 21 to 24, and the quantities of fuel to be injected into the engine 2. The
microcomputer 19 monitors the output of the crankshaft position sensor and determines
whether each of the cylinders 21 to 24 has reached the injection timing or not. When
it is determined that one of the cylinders 21 to 24 has reached the injection timing
thereof, the microcomputer 19 outputs the drive signal in the high level to one of
the drive signal lines 1A to 1D for activating a corresponding one of the injectors
13 to 16 to inject the fuel into the one of the cylinders 21 to 24 for a period of
time corresponding to the injection quantity of fuel calculated. The injector drive
unit 18 then outputs the drive current to energize the one of the injectors 13 to
16. The engine 2 is, as described above, a diesel engine, so that the fuel is burned
right after injection thereof in the combustion stroke of each of the cylinders 21
to 24. In this embodiment, the microcomputer 19 works to perform three injections
(i.e., pilot- and pre-injections) of fuel into each of the cylinders 21 to 24 of the
engine 2 in each compression stroke thereof in order to reduce exhaust emissions or
mechanical engine vibrations and one injection (i.e., a main-injection) of fuel into
each of the cylinders 21 to 24 in each combustion stroke (also called an expansion
stroke) thereof in order to produce an engine torque.
[0031] When the amount of particulates trapped in the exhaust emission purification device
3 reaches a given level, and the temperature of exhaust gas discharged from the engine
2 is lower than a given value, the microcomputer 19 directs the injector drive unit
18 to initiate an additional injection, called post injection, of fuel in an exhaust
stroke of each of the cylinders 21 to 24 in order to burn out the particulates in
the exhaust emission purification device 3.
[0032] Specifically, when the output of the pressure difference sensor 31 is less than a
preselected value, and outputs of the inlet and outlet temperature sensors 32 and
33 are also less than a preselected value, the microcomputer 19 decides that the post
injection should be performed and determines a timing of the post injection and the
quantity of fuel to be injected into the engine 2. The microcomputer 19 monitors the
output of the crankshaft position sensor and determines whether each of the cylinders
21 to 24 has reached the timing of the post injection or not. If one of the cylinders
21 to 24 is determined to have reached the timing of the post injection, the microcomputer
19 outputs the drive signal in the high level to one of the drive signal lines 1A
to 1D for a corresponding one of the injectors 13 to 16 that is to inject the fuel
into the one of the cylinders 21 to 24 for a period of time corresponding to the injection
quantity of fuel calculated. The injector drive unit 18 then outputs the drive current
to activate the one of the injectors 13 to 16. Note that the post injection is the
injection of fuel not serving to produce drive torque in the engine 2.
[0033] The engine 2 is so designed that the pistons of the cylinders 21 to 24 experience,
in sequence, the intake, exhaust, combustion, and compression strokes, respectively.
For instance, when the first cylinder 21 is on the intake stroke, the second cylinder
22, the third cylinder 23, and the fourth cylinder 24 are on the exhaust, combustion,
and compression strokes, respectively. The microcomputer 19 directs the injector drive
unit 18 to perform fuel injections, in sequence, on the cylinders 21 to 24 of the
engine 2. The microcomputer 19 also works to calculate a target pressure using outputs
of the speed sensor indicating the speed of the engine 2 and the pressure sensor indicating
the pressure of fuel in the common rail 12 and controls the high-pressure pump 11
to bring an output thereof into agreement with the target pressure. The microcomputer
19 also outputs control signals to a supercharger, an exhaust gas recirculation (EGR)
system, an intake throttle valve, a radiator fan relay, etc.
[0034] The microcomputer 19 is also equipped with injection counters 51, 52, 53, and 54
and injection failure counters 61, 62, 63, and 64. Each of the injection counters
51 to 54 works to count the number of times the fuel has been injected into a corresponding
one of the cylinders 21 to 24. Each of the injection failure counters 61 to 64 works
to count the number of times a corresponding one of the cylinders 21 to 24 has experienced
a failure in injecting the fuel thereinto. The microcomputer 19 also operates in four
post injection inhibit modes
A, B, C, and
D to inhibit the fuel from being injected into the cylinders 21, 22, 23, and 24, respectively.
Each time the piston of each of the cylinders 21 to 24 experiences a given number
of rotations, the microcomputer 19 starts to diagnose whether the failure in fuel
injection has occurred in a selected one of the cylinders 21 to 24 or not. For example,
the microcomputer 19 may start to diagnose each of the cylinders 21 to 24 after a
given number of revolutions of the engine 4 following completion of diagnosis of a
preceding one of the cylinders 21 to 24 or a sequence of diagnoses of others of the
cylinders 21 to 24. The post injection inhibit modes
A, B, C, and
D are each entered only when requirements to perform such injection failure diagnosis
and the post injection are met. For instance, when it is required to perform the post
injection to burn out the particulates trapped in the exhaust emission purification
device 3 and to diagnose the first cylinder 21, the microcomputer 19 enters the post
injection mode
D to inhibit the post injection of fuel into the fourth cylinder 24.
[0035] The microcomputer 19 performs the injection failure diagnosis of each of the cylinders
21 to 24 in the following manner. First, the microcomputer 19 selects one of the cylinders
21 to 24 to be diagnosed and sets as a diagnosis time a time interval between completion
of a sequence of injections (not including the post injection) of fuel into one of
the cylinders 21 to 24 preceding the selected one and a time when the injection of
fuel into one of the cylinders 21 to 24 following the selected one is to be started.
For instance, when the third cylinder 23 is selected to be diagnosed, a time interval
between completion of a sequence of injections of fuel into the second cylinder 22
and a time when the injection of fuel into the fourth cylinder 24 is to be started
is determined as the diagnosis time. The microcomputer 19 also sets a non-injection
time coinciding with the diagnosis time during which the others of the cylinders 21
to 24 undergo no injection of fuel thereinto.
[0036] Next, immediately after the one of the cylinders 21 to 24 of the engine 2 selected
to be diagnosed enters the compression stroke, the microcomputer 19 determines whether
it is required to initiate the post injection of fuel into each of the cylinders 21
to 24 or not. When such post injection requirement is met, the microcomputer 19 commences
post injection initialization and enters one of the post injection inhibit modes
A,
B,
C, and
D which inhibits the post injection of fuel into one of the cylinders 21 to 24 preceding
one thereof selected to be diagnosed. This causes the post injection of fuel not to
be performed to ones of the cylinders 21 to 24 not selected to be diagnosed during
the diagnosis time and permits the fuel to be injected only into the one of the cylinders
21 to 24 selected to be diagnosed. Specifically, in the example as illustrated in
Fig. 3, when the first cylinder 21 is placed in the diagnosis time, the second cylinder
22 is in a time range of the suction stroke to the compression stroke within which
the injection of fuel is not to be performed. The third cylinder 23 is in a time range
of the exhaust stroke to the suction stroke within which the injection of fuel is
not to be performed. The fourth cylinder 24 is in a time range of the combustion stroke
to the exhaust stroke within which the post injection of fuel, as indicated by a broken
line, is to be performed. Therefore, the microcomputer 19 enters the post injection
inhibit mode
D to inhibit the fuel from being injected into the fourth cylinder 24, thereby placing
all ones of the cylinders 21 to 24 not selected to be diagnosed, that is, the second
to fourth cylinders 22 to 24 in a condition where they do not undergo the injection
of fuel thereinto at all. In a case where the engine 2 is so controlled that two of
the cylinders 21 to 24 undergo the post injections sequentially during the diagnosis
time of another of the cylinders 21 to 24, the microcomputer 19 works to enter two
of the post injection inhibit modes
A,
B,
C, and
D to inhibit the fuel from being injected into the two of the cylinders 21 to 24. Alternatively,
when the post injection requirement is not met, the microcomputer 19 proceeds to steps,
as described below, without entering any of the post injection inhibit modes
A,
B,
C, and
D.
[0037] The microcomputer 19 analyzes inputs from the sensors, as described above, and directs
the injection drive unit 18 to initiate a sequence of injections of fuel into the
one of the cylinders 21 to 24 as selected to be diagnosed. Afterwards, when the diagnostic
signal on the diagnostic signal line 1E is changed from the high to low level, the
microcomputer 19 determines that a corresponding one of the injectors 13 to 16 has
been successful in injecting the fuel into the selected one of the cylinders 21 to
24, increments the count value of a corresponding one of the injection counters 51
to 54 by one (1) through interruption handling, and resets the count values of others
of the injection counters 51 to 54. Alternatively, when the diagnostic signal on the
diagnostic signal line 1E remains unchanged to the low level, that is, it is kept
at the high level, the microcomputer 19 determines that the selected one of the cylinders
21 to 24 has undergone no injection of fuel thereinto and holds the count value of
the corresponding one of the injection counters 51 to 54 as it is.
[0038] Upon expiry of a period of time during which a total of four injections of fuel into
the one of the cylinders 21 to 24 as selected to be diagnosed are to be performed
in the compression and combustion strokes thereof, the microcomputer 19 diagnoses
whether a corresponding one of the injectors 13 to 16 has failed to inject the fuel
into the selected one of the cylinders 21 to 24 or not during a period of time until
start of injection of fuel into a subsequent one of the cylinders 21 to 24, which
will also be referred to a non-injection period. Specifically, the microcomputer 19
samples the count value from one of the injection counters 51 to 54 corresponding
to the selected one of the cylinders 21 to 24. When the count value is zero (0), the
microcomputer 19 increments a corresponding one of the injection failure counters
61 to 64 by one (1). When a resulting value of the one of the injection failure counters
61 to 64 indicates two (2), the microcomputer 19 determines that the corresponding
one of the injectors 13 to 16 has failed to inject the fuel into the selected one
of the cylinders 21 to 24 and turn on a warning lamp. Alternatively, when the resulting
value of the one of the injection failure counters 61 to 64 is less than or equal
to one (1), the microcomputer 19 remains the warning lamp off. When the resulting
value of the one of the injection failure counters 61 to 64 is more than or equal
to one (1), the microcomputer 19 resets it to zero (0).
[0039] After expiry of the diagnosis time and completion of the diagnosis of whether the
corresponding one of the injectors 13 to 16 has failed to inject the fuel into the
selected one of the cylinders 21 to 24 or not, the microcomputer 19 determines whether
all the cylinders 21 to 24 have been diagnosed or not and suspends the injection failure
diagnosis until the engine 2 rotates a given number of times.
[0040] Fig. 4 is a flowchart of a sequence of logical steps or program executed by the microcomputer
19 of the fuel injection system 1 to control the post injection of fuel into each
of the cylinders 21 to 24 when it is required to diagnose the failure in injecting
the fuel into each of the cylinders 21 to 24 of the engine. The program is initiated
at the beginning of the compression stroke in each of the cylinders 21 to 24 of the
engine 2.
[0041] After entering the program, the routine proceeds to step 401 wherein it is determined
whether the requirements to perform the post injection of fuel into each of the cylinders
21 to 24 of the engine 2 have been met or not using outputs of the pressure difference
sensor 31, the inlet temperature sensor 32, and the output temperature sensor 33.
If a NO answer is obtained, the routine terminates. Alternatively, if a YES answer
is obtained, then the routine proceeds to step 402 wherein it is determined whether
the post injection has already been performed or not. If a NO answer is obtained,
then the routine proceeds to step 403 wherein the microcomputer 19 performs initialization
to select one of the post injection inhibit modes
A,
B,
C, and
D to inhibit the post injection of fuel into one of the cylinders 21 to 24 preceding
one thereof as selected to be diagnosed and starts to operate in the selected one
of the post injection inhibit modes
A, B, C, and
D. Alternatively, if a YES answer is obtained, then the routine proceeds to step 404
wherein the microcomputer 19 alters a selected one of the post injection inhibit modes
A, B, C, and
D to one that inhibits the post injection of fuel into one of the cylinders 21 to 24
preceding one thereof as selected to be diagnosed.
[0042] In step 405, the post injection quantity and post injection timing for one of the
cylinders 21 to 24, as selected to be diagnosed, are determined. The routine proceeds
to step 406 wherein the microcomputer 19 directs the injector drive unit 18 to perform
the post injection to the selected one of the cylinders 21 to 24 in one of the post
injection inhibit modes
A, B, C, and
D, as set in step 403 or 404.
[0043] For example, when the first cylinder 21 is selected to be diagnosed, the microcomputer
19 selects the post injection inhibit mode
D to inhibit the post injection of fuel into the fourth cylinder 24 and is allowed
to initiate a sequence of injections of fuel only into the first cylinder 21 during
the diagnosis time.
[0044] Fig. 5 is a flowchart of a program to be executed by the microcomputer 19 to count
the number of times the fuel has been injected into one of the cylinders 21 to 24,
which is selected to be diagnosed, during the diagnosis time. The program is initiated
each time the diagnostic signal appearing in the form of a pulse signal on the diagnostic
signal line 1E is changed from the high to low level.
[0045] After entering the program, the routine proceeds to step 501 to interrupt input of
any signals to the diagnostic signal line E1 in order to avoid an error in the following
counting operation of the microcomputer 19 arising from chattering or electrical noises.
[0046] The routine proceeds to step 502 wherein it is determined which of the cylinders
21 to 24 is selected to be diagnosed. If the first cylinder 21 is selected, then the
routine proceeds to step 503. If the second cylinder 22 is selected, then the routine
proceeds to step 505. If the third cylinder 23 is selected, then the routine proceeds
to step 507. If the fourth cylinder 24 is selected, then the routine proceeds to step
509.
[0047] In step 503, the count value of the injection counter 51 is incremented by one (1).
Similarly, in steps 505, 507, 509, the count values of the injection counters 52,
53, and 54 are incremented by one (1), respectively. After steps 503, 505, 507, and
509, the routine proceeds to steps 504, 506, 508, and 510, respectively.
[0048] In step 504, the injection counters 52, 53, and 54 are reset to zero (0). In step
506, the injection counters 51, 53, and 54 are reset to zero (0). In step 507, the
injection counters 51, 52, and 54 are reset to zero (0). In step 510, the injection
counters 51, 52, and 53 are reset to zero (0).
[0049] After step 504, 506, 508, or 510, the routine proceeds to step 511 wherein the interruption
of input of signals into the diagnostic signal line 1E is released and then terminates.
[0050] The program of Fig. 5 works to ensure counting of the number of times the fuel has
been injected into each of the cylinders 21 to 24 during the diagnosis time and avoid
errors in incrementing the count values of ones of the counters 51 to 54 for ones
of the cylinders 21 to 24 not being diagnosed.
[0051] Fig. 6 is a flowchart of a program to be executed by the microcomputer 19 to diagnose
whether a failure in injecting the fuel into each of the cylinders 21 to 24 of the
engine 2 has occurred or not. This program is initiated during the non-injection period
defined between completion of a sequence of four injections of fuel into each of the
cylinders 21 to 24 and start of injection of fuel into a following one of the cylinders
21 to 24.
[0052] After entering the program, the routine proceeds to step 601 wherein each of the
cylinders 21 to 24 is checked to determine whether it has been selected as an object
that should be diagnosed or not by monitoring a currently selected one of the post
injection inhibit modes
A, B, C, and
D. If a NO answer is obtained, then the routine terminates. Alternatively, if a YES
answer is obtained, then the routine proceeds to step 602. For the brevity of disclosure,
it is assumed in the following discussion that the first cylinder 21 is determined
in step 601 to have been selected as the object to be diagnosed. In step 602, the
count value is read out from a corresponding one of the injection counters 51 to 54,
i.e., the injection counter 51. The routine proceed to step 603 wherein it is determined
whether the count value, as derived in step 602, is zero (0) or not. If a NO answer
is obtained meaning that the count value is not zero (0), that is, that the fuel has
been injected into the first cylinder 21 at least one time, then the routine proceeds
to step 604 wherein it is determined that the injection of fuel into the first cylinder
21 has been completed correctly, and the injection failure counter 61 is reset to
zero (0). The routine then terminates. Alternatively, if a NO answer is obtained in
step 603 meaning that no injection of fuel into the first cylinder 21 has been performed,
then the routine proceeds to step 605.
[0053] In step 605, the count value of the injection failure counter 61 corresponding to
the first cylinder 21, as selected to be diagnosed, is incremented by one (1). The
routine proceeds to step 606 wherein it is determined whether the count value, as
incremented in step 605, is two (2) or more, that is, whether the event that the first
cylinder 21 has undergone no injection of fuel thereinto during the diagnosis time
has occurred in sequence two times or not. This is for avoiding an accidental error
in determining that the injector 13 has failed to inject the fuel into the first cylinder
21. If a YES answer is obtained in step 606 meaning that the count value is more than
or equal to two (2), then the routine proceeds to step 607 wherein a warning lamp
is turned on to inform the drive of the vehicle of the event of failure in the fuel
injection.
[0054] The program of Fig. 6 is executed during the non-injection period within the diagnosis
time in order to minimize an error in determining the failure in injection of fuel
into one of the cylinders 21 to 24 as selected to be diagnosed.
[0055] Fig. 7 is a flowchart of a program to be executed by the microcomputer 19 to determine
whether the injection failure diagnosis should continue or not. The program is initiated
immediately after expiry of the diagnosis time for each of the cylinders 21 to 24.
[0056] After entering the program, the routine proceeds to step 701 wherein the injection
failure diagnosis has been completed a preselected number of times or not, that is,
whether all the cylinders 21 to 24 have been diagnosed or not. If a NO answer is obtained,
then the routine proceeds to step 702 wherein one of the cylinders 21 to 24 is selected
which is to be diagnosed subsequently.
[0057] The routine proceeds to step 703 wherein the diagnosis time is determined for the
one of the cylinders 21 to 24 selected in step 702. The non-injection time coinciding
with the diagnosis time is also set for others of the cylinders 21 to 24, thereby
prohibiting the fuel from being injected into the others of the cylinders 21 to 24.
The routine then terminates.
[0058] If a YES answer is obtained in step 701 meaning that all the cylinders 21 to 24 have
been diagnosed, then the routine proceeds to step 704 wherein the post injection modes
A, B, C, and
D are released to place the microcomputer 19 out of the post injection modes
A,
B,
C, and
D. The routine then terminates. After completion of the injection failure diagnosis
of each of the cylinders 21 to 24 of the engine 2, when the microcomputer 19 monitors
outputs of the pressure difference sensor 31, the inlet temperature sensor 32, and
the outlet temperature sensor 33 and determines that a need has arisen for the post
injection of fuel into one of the cylinders 21 to 24, the microcomputer 19 commences
the post injection of fuel into the one of the cylinders 21 to 24.
[0059] The microcomputer 19 does not perform the injection failure diagnosis of one of the
cylinders 21 to 24 until the injection failure diagnosis of a preceding one of the
cylinders 21 to 24 has been completed, and the cylinders 21 to 24 have experienced
a given number of rotations. This is because the frequent injection failure diagnoses
will cause the cylinders 21 to 24 to be prohibited from undergoing the post injection,
thus requiring much time for burning out particulates trapped in the exhaust emission
purification device 3.
[0060] As apparent from the above discussion, the microcomputer 19 works to select one of
the cylinders 21 to 24, in sequence, as an object to be diagnosed each time the cylinders
21 to 24 rotate a given number of times and also select one of the post injection
modes
A, B, C, and
D which prohibits a preceding one of the cylinders 21 to 24 from undergoing the post
injection, thereby enabling a determination to be made as to whether the fuel has
been injected into the selected one of the cylinders 21 to 24 correctly or not by
monitoring the diagnostic signal appearing on the diagnostic signal line 1E. This
ensures the injection failure diagnosis of each of the cylinders 21 to 24 even in
a case where many injections of fuel are to be performed every combustion cycle of
each of the cylinders 21 to 24.
[0061] The injection control ECU 17, as described above, works to determine that the post
injection of fuel into each of the cylinders 21 to 24 should be performed when the
pressure indicated by an output of the pressure difference sensor 31 is greater than
a given value, and temperatures indicated by outputs of the inlet temperature sensor
32 and the outlet temperature sensor 33 are lower than a given value and calculate
the post injection quantity and post injection timing, but however, it may alternatively
be designed to perform the post injection of fuel into the cylinders 21 to 24 at all
times when the injection failure diagnosis is not carried out.
[0062] The injection control ECU 17, as described above, works to activate each of the injectors
13 to 16 to perform a total of five injections (including the post injection) of fuel
into one of the cylinders 21 to 24 in each combustion cycle (i.e., each sequence of
four strokes) of the engine 2, but however, it may be designed to perform a total
of more or less than five injections of fuel into each of the cylinders 21 to 24.
The injection control ECU 17 may also be designed to perform a plurality of post injections
sequentially.
[0063] The injection control ECU 17, as described above, works to switch between the post
injection modes
A, B, C, and
D to inhibit the post injection of fuel into one of the cylinders 21 to 24 preceding
one thereof selected as an object to be diagnosed in order to diagnose whether the
fuel has been injected completely into the selected one of the cylinders 21 to 24
or not by monitoring the diagnostic signal appearing on the diagnostic signal line
1E. The engine 2, however, may be designed according to required specifications so
that the post injections of fuel into more than one of the cylinders 21 to 24 other
than one thereof as selected to be diagnosed are performed at the same time. In this
case, the injection control ECU 17 is designed to establish a post injection inhibit
mode to inhibit the more than one of the cylinders 21 to 24 from undergoing the post
injection during the injection failure diagnosis of the one of the cylinders 21 to
24 selected to be diagnosed.
[0064] The engine 4 has the four cylinders 21 to 24. The fuel injection system 1 works to
inject fuel into and diagnose the injection failures in the cylinders 21 to 24. The
engine 4, however, may alternatively be designed to have six, eight, or twelve cylinders.
In this case, the injection control ECU 17 is, like the above, designed to establish
a post injection inhibit mode to inhibit more than one of the cylinders from undergoing
the post injection during the injection failure diagnosis of one of the cylinders
selected to be diagnosed.
[0065] The fuel injection system 1 may also be employed for diesel engines installed in
trains, boats, or ships, but is most effective to be used for automotive diesel engines.
[0066] While the present invention has been disclosed in terms of the preferred embodiments
in order to facilitate better understanding thereof, it should be appreciated that
the invention can be embodied in various ways without departing from the principle
of the invention. Therefore, the invention should be understood to include all possible
embodiments and modifications to the shown embodiments which can be embodied without
departing from the principle of the invention as set forth in the appended claims.
1. A fuel injection apparatus for a diesel engine comprising:
injectors designed to inject fuel into cylinders of a diesel engine, respectively;
an injector controller working to control said injectors to perform a plurality of
injections of the fuel into each of the cylinders of the engine in each combustion
cycle thereof;
a single diagnostic signal line to which a diagnostic signal is provided which indicates
whether the injection of fuel into each of the cylinders has been completed or not;
and
an injection failure diagnosing circuit working to select one of the cylinders that
is to be diagnosed, inhibit said injectors from injecting the fuel into others of
the cylinders when said injectors are required by said injector controller to inject
the fuel into the others of the cylinders, and monitor the diagnostic signal appearing
on said diagnostic signal line to make an injection failure diagnosis of whether a
failure in injecting the fuel into the selected one of the cylinders has occurred
or not.
2. A fuel injection apparatus as set forth in claim 1, wherein said injection failure
diagnosing circuit sets a diagnosis time during which the injection failure diagnosis
is to be performed on the selected one of the cylinders and a non-injection time during
which no injection of fuel into the others of the cylinders is to be performed and
which coincides with the diagnosis time, and wherein said injection failure diagnosing
circuit permits the injection of fuel into the selected one of the cylinders to be
performed during the diagnosis time and inhibits the injection of fuel into each of
the others of the cylinders during the non-injection time when it is required to inject
the fuel into the each of the others of the cylinders.
3. A fuel injection apparatus as set forth in claim 1 or 2, wherein said injection failure
diagnosing circuit works to select one of the cylinders to be diagnosed in sequence.
4. A fuel injection apparatus as set forth in any one of claims 1 to 3, wherein upon
completion of a determination of whether the injection of fuel into the selected one
of the cylinders has been completed or not, said injection failure diagnosing circuit
determines whether each of the cylinders is to be diagnosed subsequently or not.
5. A fuel injection apparatus as set forth in any one of claims 1 to 4, wherein said
injection failure diagnosing circuit suspends the injection failure diagnosis of each
of the cylinders of the engine for a given period of time after completion of one
or a given number of times of the injection failure diagnoses of the selected one
of the cylinders.
6. A fuel injection apparatus as set forth in any one of claims 2 to 5, further comprising
injection failure counters, one for each of the cylinders of the engine, each of which
counts an event that no injection of fuel has been performed in a corresponding one
of the cylinders of the engine for the diagnosis time, and wherein said injection
failure diagnosing circuit works to make the injection failure diagnosis of each of
the cylinders of the engine a plurality of times, when a count value of each of the
injection failure counters exceeds a preselected value, said injection failure diagnosing
circuit determining that the failure has occurred in injecting the fuel into a corresponding
one of the cylinders.
7. A fuel injection apparatus as set forth in claim 6, wherein said injection failure
diagnosing circuit performs the injection failure diagnosis for a period of time between
completion of all injections of the fuel into the selected one of the cylinders in
the combustion cycle and a time when the fuel is to start to be injected into a subsequent
one of the cylinders.
8. A fuel injection apparatus as set forth in claim 6 or 7, wherein the preselected value
is two or more.
9. A fuel injection apparatus as set forth in any one of claims 6 to 8, wherein when
the fuel has been injected into the selected one of the cylinders at least one time
during the diagnosis time, said injection failure diagnosing circuit resets a corresponding
one of the injection failure counters.
10. A fuel injection apparatus as set forth in any one of claims 6 to 9, wherein when
each of the injectors has injected the fuel into one of the cylinders, said injector
controller outputs the diagnostic signal in the form of a pulse signal to the diagnostic
signal line, further comprising injection counters, one for each of the cylinders,
which count the number of times said injectors have performed the injections of fuel
into the cylinders during the diagnosis time, respectively, and wherein said injection
failure diagnosing circuit monitors the injection counters to know the number of times
each of the injectors has completed the injection of fuel into a corresponding one
of the cylinders.
11. A fuel injection apparatus as set forth in claim 10, wherein said injection failure
diagnosing circuit resets each of the injection counters when a corresponding one
of the cylinders is placed in the non-injection time.
12. A fuel injection apparatus as set forth in any one of claims 2 to 11, wherein the
plurality of injections of the fuel into each of the cylinders of the engine every
combustion cycle include an injection of the fuel serving to produce torque in the
diesel engine and an injection of the fuel serving to produce no torque in the diesel
engine, and wherein the injection of fuel inhibited from being performed by said injection
failure diagnosing circuit during the non-injection time is the injection of the fuel
serving to produce no torque in the diesel engine.
13. A fuel injection apparatus as set forth in claim 12, wherein the diesel engine is
connected to a trapping device working to trap particulates contained in exhaust emissions
of the diesel engine, and wherein the injection of the fuel serving to produce no
torque in the diesel engine works to burn the particulates trapped in the trapping
device.